1 ABSTRACT One of the most popular techniques to control robotic arm is by making it emulate the movements of the human arm. One of the advantages of the robotic arm is that it simplifies computational complexities. An arrangement of sensors attached to the human arm is used for tracking down hand movement. The arrangement consists of two accelerometers, a potentiometer and an IR receiver- transmitter pair. The Robotic Arm has Five degree of freedom where each joint is controlled by a servo motor that are capable of producing a movement of 180 degrees. In this project we have proposed an algorithm based on correction and prediction for the purpose of swift synchronization of human hand and Robotic Arm. Successful implementation of the algorithm was achieved on the robotic arm.
Transcript
1
ABSTRACT
One of the most popular techniques to control robotic arm is by making it emulate the movements
of the human arm One of the advantages of the robotic arm is that it simplifies computational
complexities An arrangement of sensors attached to the human arm is used for tracking down hand
movement The arrangement consists of two accelerometers a potentiometer and an IR receiver-
transmitter pair The Robotic Arm has Five degree of freedom where each joint is controlled by a
servo motor that are capable of producing a movement of 180 degrees In this project we have
proposed an algorithm based on correction and prediction for the purpose of swift synchronization
of human hand and Robotic Arm Successful implementation of the algorithm was achieved on the
robotic arm
2
CONTENTS
Title Page no
CERTIFICATE i
ACKNOWLEDGEMENT ii
ABSTRACT iii
1 INTRODUCTION 1-7
11 KINEMATICS AND DYNAMICS OF ROBOTIC ARM helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 3-5
12 CALCULATING THE DESIGN PARAMETERS helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 5-7
32 IR SENSORhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip13-14
34 AT MEGA 32 helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 17-18
4 METHODOLOGY 19-22
41 SETUP USED amp SCHEMATIChelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 22
Fig1 GUROO- The Robotic Arm helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip2
Fig2 Two-link Robot Arm helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip3
Fig3 Two solution to robot inverse kinematics problem helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip4
Fig4 Example of Gripper helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip7
Fig5 Steps for gesture control by image processing helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip9
Fig6 An Accelerometer helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip10
Fig7 Schematic of an accelerometer helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip11
Fig8 Circuit diagram of An IR sensor helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip14
Fig9 Controlling of Servo helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip15
Fig11 Pin Configuration of Atmega 16 helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip18
Fig121 Flow chart of First Accelerometer helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip19
Fig122 Flow chart of Second Accelerometer helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip19
Fig123 Flow chart for Ir sensor helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip20
Fig124 Flow chart for Potentiometer helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip20
Fig13 Schematic of the component used helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip22
Fig14 Setup used helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip23
Fig151 Linear prediction for wrist movement 1 helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip24
Fig152 Linear prediction for wrist movement 2 helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip25
Fig153 Linear prediction for elbow movement 1 helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip25
4
Fig154 Linear prediction for elbow movement 2 helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip26
5
CHAPTER 1 INTRODUCTION
Robotic arms have been in use by industries and alike for decades now However the precision
they provide along with the accuracy is still unparalleled anywhere in the whole realm of robotics
However to program these machining marvels to execute a predefined set of movements takes
time which is essentially a luxury that we fall short of at times Now imagine controlling an arm
thatrsquos as good a robotic arm as it can get and still it doesnrsquot needs to be programmed Yes the
answer lies with gesture controlled robotics By making a robotic arm replicate the movements of a
real-time human arm we not only save ourselves from seemingly endless sessions of coding but
also make it virtually alive The robotic arm presented here has currently six degrees of freedom
along with swift movements and quick response time The arm is currently maneuvered by DC
Servo Motors that are controlled by precisely controlled pulses generated by the widely used micro-
controller At Mega 16 The arm is able to follow real time hand gestures made by a human being
For real-time gesture recognition 3 three-axis accelerometers have been used which are strapped to
the arm of the controller at pre-defined positions These accelerometers detect the change in any of
the three axes viz X Y and Z and produce a differential voltage output accordingly The voltages
generated are then sent to the micro-controller where they are further converted to the digital form
by an inbuilt on-chip ADC converter
Thus the algorithm is able to sense the change in the position vectors of the human arm and
correspondingly generates electrical pulses to control the servo motors Servo motors are specially
designed to rotate through a given angle on each pulse that is sent to them Thus the servos of the
robotic arm are able to follow or trace back the gestures made by the human arm controller in real-
time Thatrsquos like having a chauffeur stand by your side while you teach him how to serve you
These kind of robotic arms are currently in immense demand especially in surgical and military
affairs For instance a cardiologist can perform a bypass surgery without being present physically
anywhere near the patient and that too with the same life-saving precision In the battle-zone and
modern urban warfare such arms can be used to detect and defuse IEDs and such explosive devices
without risking the life of any soldier Virtually such arms are as good as having an extra human
arm at places where we wonrsquot want or canrsquot have a real human Itrsquos only our gestures and
imagination that can set limits to the true potential of such robotic wonders Why even think why
not make a gesture beside that arm and see how it replicates you learning from you bit by bit
gesture by gesture
6
FIGURE 1 GUROO- THE ROBOTIC ARM
7
11 KINEMATICS AND DYNAMICS OF ROBOTIC ARM
Robotic arms are commonplace in todays world They are used to weld automobile bodies
employed to locate merchandise in computerized warehouses and used by the Space Shuttle to
retrieve satellites from orbit They are reliable and accurate This reliability and accuracy is due to
the computer a robot arm uses in determining where and how it should move This control
computer is programmed with some basic mathematics In this section we will look at the
mathematics behind robot arms
We will study the two-link robot arm shown in Figure 1 Most robot arms are more complicated
than this using three links and a moveable hand but with these complications come much more
difficult mathematics Operation of the two-link arm is simple The first link (length L1) pivots
around the origin of an XY Cartesian coordinate system while the second link (length L2) pivots
about the connection between the two links The two pivot points are drawn as circles The angle
the first link makes with the horizontal (X) axis is designated A while the angle the second link
makes with the first link is designated B The end of the second link is the position of the robot arm
(X Y)
There are three basic problems in robotics The first problem is that of kinematics This problem
asks the question given the angles A and B what is the arm position (X Y) This is simple
trigonometry The second problem is inverse kinematics Here we want to ask given the position
(X Y) what angles A and B yield this position This is a more difficult problem Lastly we need
to look at the problem of trajectory planning In trajectory planning we ask given our current
position (X Y) and some desired new position how do we change the angles A and B to arrive at
this new position We examine each of these problems separately using the two-link robot arm
8
Figure2 Two-link robot arm
111 Robot Arm Kinematics
The kinematics problem requires computation of the robot arm Cartesian position (X Y) knowing
the two link angles A and B Referring to Figure 1 we can see the position of the end of the first
link (X1 Y1) is given by
X1 = L1cos(A)
Y1 = L1sin(A)
Then the end of the second link (X Y) is simply
X = X1 + L2cos(A + B)
Y = Y1 + L2sin(A + B)
Combining these two sets of equations provides the solution to the kinematics problem
X = L1cos(A) + L2cos(A + B)
Y = L1sin(A) + L2sin(A + B)
An interesting question at this point is if we cycle A and B through all possible combinations (-180
degrees lt A lt 180 degrees -180 degrees lt B lt 180 degrees) what would the region of coverage
look like If L1 and L2 are equal the region would be a circle (radius L1 + L2) If L1 and L2 are not
equal the region would be armular (like a donut) This coverage region becomes important in the
inverse kinematics problem where we need to know if its possible to reach a given point by
adjusting the link angles
9
Figure 3Two solutions to robot inverse kinematics problem
112 Robot Arm Inverse Kinematics
The kinematics problem is seen to be fairly easy to solve The inverse problem that of finding A
and B knowing (X Y) is not nearly as simple Lets see why Using the kinematics equations if we
know X and Y we need to solve the following for A and B
L1cos(A) + L2cos(A + B) = X
L1sin(A) + L2sin(A + B) = Y
This is a nonlinear problem There are two possible solution approaches algebraic and geometric
The algebraic approach (solving the equations directly) is tedious and involved For the two-link
robot arm the geometric approach is more straightforward We will outline the steps of the
algebraic approach to illustrate some salient points of the inverse kinematics problem Also by
outlining these steps we allow the more industrious reader to see if heshe can solve the problem
algebraically After this outline we will develop the solution to the problem with a geometric
approach
12 CALCULATING THE DESIGN PARAMETERS
121 Motor torque
The point of doing force calculations is for motor selection We must make sure that the motor we
choose can not only support the weight of the robot arm but also what the robot arm will carry (the
blue ball in the image below)
The first step is to label your FBD with the robot arm stretched out to its maximum length
10
Choose these parameters
weight of each linkage
weight of each joint
weight of object to lift
length of each linkage
Next you do a moment arm calculation multiplying downward force times the linkage lengths This
calculation must be done for each lifting actuator This particular design has just two DOF that
requires lifting and the center of mass of each linkage is assumed to be Length2
For each DOF you add the math gets more complicated and the joint weights get heavier We will
also find that shorter arm lengths allow for smaller torque requirements
The above equations only deal with the case where the robot arm is being held horizontally (not in
motion) This is not necessarily the worst case scenario For the arm to move from a rest position
acceleration is required To solve for this added torque it is known that the sum of torques acting at
a pivot point is equal to the moment of inertia (I) multiplied by the angular acceleration (alpha)
T=Ixα
To calculate the extra torque required to move (ie create an angular acceleration) you would
calculate the moment of inertia of the part from the end to the pivot using the equation (or an
equation similar to)
11
I=mr^22
Note this equation calculates the moment of inertia about the center of mass In the case of a robotic
arm the moment of inertia must take into consideration that the part is being rotated about a pivot
point located a distance away from the center of mass and a second term ( +MR2 ) needs to be
added For each joint the moment of inertia is calculated by adding the products of each individual
mass (mi) by the square of its respective length from the pivot (ri) Note that the equation for
calculating the moment of inertia to consider for actuator N omits the mass of the actuator at the
pivot
122 GRIPPER
Jaw torque is the other critical factor when specifying a gripper There are two sources of this
torque torque generated by the gripper on itself and torque generated by the acceleration and
weight of the part These can be addressed separately
Torque from the robotic gripper
Long Jaws are often required Either the part is bulky like an engine block or the part must be held
at a distance to fit in a machine In either case the longer the jaw the greater the torque the gripper
imposes on itself Therefore the torque from the grippers is GRIPPER TORQUE=Gripper Force x
Jaw Length (where jaw length is measured from the face of the gripper to the center of gravity of
the part)
12
Figure 4 Example of Gripper
Gripper Example
If we put 6rdquo long jaws on a gripper with 100 pounds of closing force gripper the jaws will see
Jaw Torque= 100 Pounds x 6rdquo= 600 in-pounds
The rating on the gripper is 840 in-pounds We used the majority of this rating without even
gripping a part because of the length of the jaws
Thus we can see that the length of the jaws plays a major factor in specifying a gripper The next
task is to determine the torque the gripper will experience from the part
CHAPTER 2 GESTURE
21 GESTURE CONTROLLED SYSTEM
Humans naturally use gesture to communicate It has been demonstrated that young children can
readily learn to communicate with gesture before they learn to talk A gesture is non-verbal
communication made with a part of the body We use gesture instead of or in combination with
verbal communication Using this process human can interface with the machine without any
mechanical devices Human movements are typically analyzed by segmenting them into shorter and
understandable format The movements vary person to person It can be used as a command to
control different devices of daily activities mobility etc So our natural or intuitive body
movements or gestures can be used as command or interface to operate machines communicate
with intelligent environments to control home appliances smart home telecare systems etc In this
paper we also review the different types of technologies of gesture controlled system
212 TYPES OF GESTURES
Most of the researches are based on hand gestures Direct control via hand posture is immediate but
limited in the number of Choices There are researches about body gesture finger point movement
In the early stage researchers used gloves with microcontroller and connected with the device
through a wire Head gesture and gesture with voice were also in the research but hand gesture was
the most dominant part of gesture control system
A primary goal of gesture control is to create a system which can identify specific human gestures
and use them to convey information or for device control Gesture recognition can be achieved by
various methods in which popular two are
13
1 Gesture control using any particular sensor
2 Gesture control using image processing
1 Gesture control using any particular sensor
This includes interpreting the human gestures by the use of any particular sensors The most widely
used sensor are accelerometer and gyroscope
We just need to wear a small transmitting device in your hand which included an acceleration
meter(either accelerometer or gyroscope) This will transmit an appropriate command to the robot
so that it can do whatever we want
2 Gesture control using any image processing
This includes following processes or steps
14
Figure 5-(steps for gesture control by image processing)
In our project we our deploying the first method ie gesture control using an
accelerometer sensor
CHAPTER 3 HARDWARE IMPLEMENTATION
31 Accelerometer
An accelerometer is a sensor that measures the physical acceleration experienced by an object due
to inertial forces or due to mechanical excitation In aerospace applications accelerometers are used
along with gyroscopes for navigation guidance and flight control Conceptually an accelerometer
behaves as a damped mass on a spring When the accelerometer experiences acceleration the mass
is displaced and the displacement is then measured to give the acceleration
In these devices piezoelectric piezoresistive and capacitive techniques are commonly used to
convert the mechanical motion into an electrical signal Piezoelectric accelerometers rely on
piezoceramics (eg lead zirconate titanate) or single crystals (eg quartz tourmaline) They are
unmatched in terms of their upper frequency range low packaged weight and high temperature
range Piezoresistive accelerometers are preferred in high shock applications Capacitive
accelerometers performance is superior in low frequency range and they can be operated in servo
mode to achieve high stability and linearity
15
Figure 6 An accelerometer
311 Working principle of accelerometer
16
Figure 7(schematic of an accelerometer)
The principle of working of an accelerometer can be explained by a simple mass (m) attached to a
spring of stiffness (k) that in turn is attached to a casing as illustrated in figure3 The mass used in
accelerometers is often called the seismic-mass or proof-mass In most cases the system also
includes a dashpot to provide a desirable damping effect
The dashpot with damping coefficient (c) is normally attached to the mass in parallel with the
spring When the spring mass system is subjected to linear acceleration a force equal to mass times
acceleration acts on the proof-mass causing it to deflect This deflection is sensed by a suitable
means and converted into an equivalent electrical signal Some form of damping is required
otherwise the system would not stabilize quickly under applied acceleration
To derive the motion equation of the system Newton‟s second law is used where all real forces
acting on the proof-mass are equal to the inertia force on the proof-mass Accordingly a dynamic
problem can be treated as a problem of static equilibrium and the equation of motion can be
obtained by direct formulation of the equations of equilibrium This damped mass-spring system
with applied force constitutes a classical second order mechanical system
312Accelerometer as Gesture Control Sensor
The accelerometer can be used in gesture controlled application As seen the accelerometer sensor measures the physical acceleration experienced by an object due to inertial forces or due to
mechanical excitationSo this means it will give different values for different gestures when
mounted on human handThis can be used as an advantage ieit can be interfaced with any of the
microcontroller or other device and can be used to control any robot or any oher device
313 Key factors while selecting an accelerometer
Some of the Key factors while selecting an accelerometer are
1Analog vs digital Depending on the interface to which you will be connecting the accelerometer
you need to select analog or digital output accelerometer
2Output Accelerometer comes with different outputs-Charge output IEPE output Voltage
output current output
17
3Number of axis Depending on your requirement you need to select single double or tri axis
accelerometer The 3 axis accelerometer will measure acceleration in all directions
4Acceleration range Acceleration Range is measured in units of g 1g is equal to the earths
gravity at sea level
5Sensitivity is the ratio of change in acceleration (input) to change in the output signal Sensitivity
is specified at a particular supply voltage and is typically expressed in units of mVg
314 Applications of Accelerometers
Used in cars to study shock and vibrations
Camcorders use accelerometers for image stabilization
Still cameras use accelerometers for anti-blur capturing
Used in mobile phones for multiple functions including tilt detection motion detectionetc
32 IR SENSOR
The InfraRed receiver transmitter pair is to use be worn around the fingers and controls the opening
and closing of the end effector
321 Introduction
An infrared sensor is an electronic instrument that is used to sense certain characteristics of its
surroundings by either emitting andor detecting infrared radiation It is also capable of measuring
heat of an object and detecting motion Infrared waves are not visible to the human eye
In the electromagnetic spectrum infrared radiation is the region having wavelengths longer than
visible light wavelengths but shorter than microwaves The infrared region is approximately
demarcated from 075 to 1000microm The wavelength region from 075 to 3microm is termed as near
infrared the region from 3 to 6microm is termed mid-infrared and the region higher than 6microm is termed
as far infrared
18
Infrared technology is found in many of our everyday products For example TV has an IR detector
for interpreting the signal from the remote control Key benefits of infrared sensors include low
power requirements simple circuitry and their portable feature
322 Working Principle
A typical system for detecting infrared radiation using infrared sensors includes the infrared source
such as blackbody radiators tungsten lamps and silicon carbide In case of active IR sensors the
sources are infrared lasers and LEDs of specific IR wavelengths Next is the transmission medium
used for infrared transmission which includes vacuum the atmosphere and optical fibers
Thirdly optical components such as optical lenses made from quartz CaF2 Ge and Si polyethylene
Fresnel lenses and Al or Au mirrors are used to converge or focus infrared radiation Likewise to
limit spectral response band-pass filters are ideal
Finally the infrared detector completes the system for detecting infrared radiation The output from
the detector is usually very small and hence pre-amplifiers coupled with circuitry are added to
further process the received signals
Figure 8 Circuit Diagram Of An IR Sensor
19
323 Applications
The following are the key application areas of infrared sensors
Tracking and art history
Climatology meteorology and astronomy
Thermography communications and alcohol testing
Heating hyperspectral imaging and night vision
Biological systems photobiomodulation and plant health
Gas detectorsgas leak detection
Water and steel analysis flame detection
Anesthesiology testing and spectroscopy
Petroleum exploration and underground solution
Rail safety
33 SERVO MOTORS
A servomotor is a rotary actuator that allows for precise control of angular position velocity and
acceleration It consists of a suitable motor coupled to a sensor for position feedback It also requires
a relatively sophisticated controller often a dedicated module designed specifically for use with
servomotors
331 Controlling Of A Servo Motor
Servos are controlled by sending an electrical pulse of variable width or pulse width
modulation (PWM) through the control wire There is a minimum pulse a maximum pulse and a
repetition rate A servo motor can usually only turn 90 degrees in either direction for a total of 180
degree movement The motors neutral position is defined as the position where the servo has the
same amount of potential rotation in the both the clockwise or counter-clockwise direction The
PWM sent to the motor determines position of the shaft and based on the duration of the pulse sent
via the control wire the rotor will turn to the desired position The servo motor expects to see a
pulse every 20 milliseconds (ms) and the length of the pulse will determine how far the motor turns
For example a 15ms pulse will make the motor turn to the 90-degree position Shorter than 15ms
moves it to 0 degrees and any longer than 15ms will turn the servo to 180 degrees as diagramed
below
20
Figure 9 Controlling an servo
332 Types of Servo Motors
There are two types of servo motors - AC and DC AC servo can handle higher current surges and
tend to be used in industrial machinery DC servos are not designed for high current surges and are
usually better suited for smaller applications Generally speaking DC motors are less expensive
than their AC counterparts These are also servo motors that have been built specifically
for continuous rotation making it an easy way to get your robot moving They feature two ball
bearings on the output shaft for reduced friction and easy access to the rest-point
adjustment potentiometer
333Servo Motor Applications
Servos are used in radio-controlled airplanes to position control surfaces like elevators rudders
walking a robot or operating grippers Servo motors are small have built-in control circuitry and
have good power for their size
In food services and pharmaceuticals the tools are designed to be used in harsher environments
where the potential for corrosion is high due to being washed at high pressures and temperatures
repeatedly to maintain strict hygiene standards Servos are also used in in-line manufacturing
where high repetition yet precise work is necessary
21
Of course you dont have to know how a servo works to use one but as with most electronics the
more you understand the more doors open for expanded projects and projects capabilities Whether
youre a hobbyist building robots an engineer designing industrial systems or just constantly
curious where will servo motors take you
334 Specifications
It is highly desirable to control or to maintain a certain location of motor rotor in a robotic arm not
only to determine its precise motion and position but also to control it in desired fashion most of the
industrial robotic arm contains pneumatic hydraulic and stepper motor to actuates they have very
high payload capacity but GuRoo is a low powered high degree of freedom robotic arm we uses
servo motor due their easy availability and high weight to torque ratio
HS-645mg standard deluxe high torque servo
Figure 10HS-475-SERVO
Detailed Specifications of above shown servo
Motor Type 3 Pole
Bearing Type Top Ball Bearing
22
Speed 023 018 sec 60 deg
Torque 44 55 kgcm
Size 3880 x 1980 x 3600mm
Weight 4000g
34 ATMega32
A microcontroller is the brain of the robot The main features of this controller are
Advanced RISC Architecture
Up to 16 MIPS Throughput at 16 MHz
16K Bytes of In-System Self-Programmable Flash
512 Bytes EEPROM
1K Byte Internal SRAM
32 Programmable IO Lines
In-System Programming by On-chip Boot Program
8-channel 10-bit ADC
Two 8-bit TimerCounters with Separate Prescalers and Compare Modes
One 16-bit TimerCounter with Separate Prescaler Compare Mode and Capture
Four PWM Channels
Programmable Serial USART
MasterSlave SPI Serial Interface
Byte-oriented Two-wire Serial Interface
Programmable Watchdog Timer with Separate On-chip Oscillator
External and Internal Interrupt Sources
23
Figure 11 - Pin configuration
CHAPTER 4 METHODOLOGY
The setup consists of a robotic arm having 5 degrees of freedom and 6 servo motors
The movements of the joints are controlled using servo motors that can move a fixed angle ranging from 0 to
180 degrees
Accelerometer 1
ADC of Microcontroller
Servo for wrist movement
24
IR sensor
Microcontroller
Servomotor for gripping
mechanism
Figure121 Flowchart for First Accelerometer
Figure122 Flowchart for second Accelerometer
Figure123 Flowchart for IR sensor
Accelerometer 2
ADC of Microcontroller
Servomotor for elbow
movement
25
Figure124 Flowchart for POTENTIOMETER
Potentiometer
ADC of microcontroller
servomotor for base movement
26
Figure 125 Complete Flow Chart
Complete flow chart depicting each sensor interfaced with microcontroller and the
movement of each and every servos (ie robotic arm)
27
41 SETUP USED amp SCHEMATIC
A setup consisting of
1 IR sensors
2 Two accelerometers and
3 A potentiometer is to be worn around the human hand for sensing the gesture
movements
The InfraRed receiver transmitter pair is to be worn around the fingers and controls the
opening and closing of the end effector
2 accelerometers are used for sensing the movement of the forearm and the wrist movement
A potentiometer is used to track the elbow movement
Figure13 Schematic of the components used
28
Figure 14 Setup Used
29
Figure 151 Linear prediction for wrist movement 1
CHAPTER 5 ALGORITHIM USED
(PREDICTION AND CORRECTION ALGORITHM)
An algorithm has been devised to make the robotic arm replicate the motions of the human arm
The robotic arm does not exactly have an idea of the exact movement of the human arm and takes
input from noisy sensors
The algorithm consists of the following parts
1 LINEAR PREDICTION
The values of the sensors and motors for every joint have been stored for certain predefined
positions for each joint movement The position of the robotic arm is predicted linearly using the
given formulae
119823119851119838119837119842119836119853119838119837 119852119838119851119855119848 119855119834119845119854119838 = (119846120784 minus 119846120783) lowast119842119847119849119854119853 119852119838119847119852119848119851 119855119834119845119854119838 minus 119852120783
(119852120784 minus 119852120783)
-
30
Figure 152 Linear prediction for wrist movement 2
Figure 153 Linear prediction for elbow movement 1
31
Figure 154 Linear prediction for elbow movement 2
m2- predefined value of the servo motor for the next known position
m1- predefined value of the servo motor for the previous known position
s1- predefined sensor value for the last known position
s2- predefined sensor value for the next known position
2) CORRECTION
The predicted value is then compared to the present value and the difference between the two
32 IR SENSORhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip13-14
34 AT MEGA 32 helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 17-18
4 METHODOLOGY 19-22
41 SETUP USED amp SCHEMATIChelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip 22
Fig1 GUROO- The Robotic Arm helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip2
Fig2 Two-link Robot Arm helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip3
Fig3 Two solution to robot inverse kinematics problem helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip4
Fig4 Example of Gripper helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip7
Fig5 Steps for gesture control by image processing helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip9
Fig6 An Accelerometer helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip10
Fig7 Schematic of an accelerometer helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip11
Fig8 Circuit diagram of An IR sensor helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip14
Fig9 Controlling of Servo helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip15
Fig11 Pin Configuration of Atmega 16 helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip18
Fig121 Flow chart of First Accelerometer helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip19
Fig122 Flow chart of Second Accelerometer helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip19
Fig123 Flow chart for Ir sensor helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip20
Fig124 Flow chart for Potentiometer helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip20
Fig13 Schematic of the component used helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip22
Fig14 Setup used helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip23
Fig151 Linear prediction for wrist movement 1 helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip24
Fig152 Linear prediction for wrist movement 2 helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip25
Fig153 Linear prediction for elbow movement 1 helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip25
4
Fig154 Linear prediction for elbow movement 2 helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip26
5
CHAPTER 1 INTRODUCTION
Robotic arms have been in use by industries and alike for decades now However the precision
they provide along with the accuracy is still unparalleled anywhere in the whole realm of robotics
However to program these machining marvels to execute a predefined set of movements takes
time which is essentially a luxury that we fall short of at times Now imagine controlling an arm
thatrsquos as good a robotic arm as it can get and still it doesnrsquot needs to be programmed Yes the
answer lies with gesture controlled robotics By making a robotic arm replicate the movements of a
real-time human arm we not only save ourselves from seemingly endless sessions of coding but
also make it virtually alive The robotic arm presented here has currently six degrees of freedom
along with swift movements and quick response time The arm is currently maneuvered by DC
Servo Motors that are controlled by precisely controlled pulses generated by the widely used micro-
controller At Mega 16 The arm is able to follow real time hand gestures made by a human being
For real-time gesture recognition 3 three-axis accelerometers have been used which are strapped to
the arm of the controller at pre-defined positions These accelerometers detect the change in any of
the three axes viz X Y and Z and produce a differential voltage output accordingly The voltages
generated are then sent to the micro-controller where they are further converted to the digital form
by an inbuilt on-chip ADC converter
Thus the algorithm is able to sense the change in the position vectors of the human arm and
correspondingly generates electrical pulses to control the servo motors Servo motors are specially
designed to rotate through a given angle on each pulse that is sent to them Thus the servos of the
robotic arm are able to follow or trace back the gestures made by the human arm controller in real-
time Thatrsquos like having a chauffeur stand by your side while you teach him how to serve you
These kind of robotic arms are currently in immense demand especially in surgical and military
affairs For instance a cardiologist can perform a bypass surgery without being present physically
anywhere near the patient and that too with the same life-saving precision In the battle-zone and
modern urban warfare such arms can be used to detect and defuse IEDs and such explosive devices
without risking the life of any soldier Virtually such arms are as good as having an extra human
arm at places where we wonrsquot want or canrsquot have a real human Itrsquos only our gestures and
imagination that can set limits to the true potential of such robotic wonders Why even think why
not make a gesture beside that arm and see how it replicates you learning from you bit by bit
gesture by gesture
6
FIGURE 1 GUROO- THE ROBOTIC ARM
7
11 KINEMATICS AND DYNAMICS OF ROBOTIC ARM
Robotic arms are commonplace in todays world They are used to weld automobile bodies
employed to locate merchandise in computerized warehouses and used by the Space Shuttle to
retrieve satellites from orbit They are reliable and accurate This reliability and accuracy is due to
the computer a robot arm uses in determining where and how it should move This control
computer is programmed with some basic mathematics In this section we will look at the
mathematics behind robot arms
We will study the two-link robot arm shown in Figure 1 Most robot arms are more complicated
than this using three links and a moveable hand but with these complications come much more
difficult mathematics Operation of the two-link arm is simple The first link (length L1) pivots
around the origin of an XY Cartesian coordinate system while the second link (length L2) pivots
about the connection between the two links The two pivot points are drawn as circles The angle
the first link makes with the horizontal (X) axis is designated A while the angle the second link
makes with the first link is designated B The end of the second link is the position of the robot arm
(X Y)
There are three basic problems in robotics The first problem is that of kinematics This problem
asks the question given the angles A and B what is the arm position (X Y) This is simple
trigonometry The second problem is inverse kinematics Here we want to ask given the position
(X Y) what angles A and B yield this position This is a more difficult problem Lastly we need
to look at the problem of trajectory planning In trajectory planning we ask given our current
position (X Y) and some desired new position how do we change the angles A and B to arrive at
this new position We examine each of these problems separately using the two-link robot arm
8
Figure2 Two-link robot arm
111 Robot Arm Kinematics
The kinematics problem requires computation of the robot arm Cartesian position (X Y) knowing
the two link angles A and B Referring to Figure 1 we can see the position of the end of the first
link (X1 Y1) is given by
X1 = L1cos(A)
Y1 = L1sin(A)
Then the end of the second link (X Y) is simply
X = X1 + L2cos(A + B)
Y = Y1 + L2sin(A + B)
Combining these two sets of equations provides the solution to the kinematics problem
X = L1cos(A) + L2cos(A + B)
Y = L1sin(A) + L2sin(A + B)
An interesting question at this point is if we cycle A and B through all possible combinations (-180
degrees lt A lt 180 degrees -180 degrees lt B lt 180 degrees) what would the region of coverage
look like If L1 and L2 are equal the region would be a circle (radius L1 + L2) If L1 and L2 are not
equal the region would be armular (like a donut) This coverage region becomes important in the
inverse kinematics problem where we need to know if its possible to reach a given point by
adjusting the link angles
9
Figure 3Two solutions to robot inverse kinematics problem
112 Robot Arm Inverse Kinematics
The kinematics problem is seen to be fairly easy to solve The inverse problem that of finding A
and B knowing (X Y) is not nearly as simple Lets see why Using the kinematics equations if we
know X and Y we need to solve the following for A and B
L1cos(A) + L2cos(A + B) = X
L1sin(A) + L2sin(A + B) = Y
This is a nonlinear problem There are two possible solution approaches algebraic and geometric
The algebraic approach (solving the equations directly) is tedious and involved For the two-link
robot arm the geometric approach is more straightforward We will outline the steps of the
algebraic approach to illustrate some salient points of the inverse kinematics problem Also by
outlining these steps we allow the more industrious reader to see if heshe can solve the problem
algebraically After this outline we will develop the solution to the problem with a geometric
approach
12 CALCULATING THE DESIGN PARAMETERS
121 Motor torque
The point of doing force calculations is for motor selection We must make sure that the motor we
choose can not only support the weight of the robot arm but also what the robot arm will carry (the
blue ball in the image below)
The first step is to label your FBD with the robot arm stretched out to its maximum length
10
Choose these parameters
weight of each linkage
weight of each joint
weight of object to lift
length of each linkage
Next you do a moment arm calculation multiplying downward force times the linkage lengths This
calculation must be done for each lifting actuator This particular design has just two DOF that
requires lifting and the center of mass of each linkage is assumed to be Length2
For each DOF you add the math gets more complicated and the joint weights get heavier We will
also find that shorter arm lengths allow for smaller torque requirements
The above equations only deal with the case where the robot arm is being held horizontally (not in
motion) This is not necessarily the worst case scenario For the arm to move from a rest position
acceleration is required To solve for this added torque it is known that the sum of torques acting at
a pivot point is equal to the moment of inertia (I) multiplied by the angular acceleration (alpha)
T=Ixα
To calculate the extra torque required to move (ie create an angular acceleration) you would
calculate the moment of inertia of the part from the end to the pivot using the equation (or an
equation similar to)
11
I=mr^22
Note this equation calculates the moment of inertia about the center of mass In the case of a robotic
arm the moment of inertia must take into consideration that the part is being rotated about a pivot
point located a distance away from the center of mass and a second term ( +MR2 ) needs to be
added For each joint the moment of inertia is calculated by adding the products of each individual
mass (mi) by the square of its respective length from the pivot (ri) Note that the equation for
calculating the moment of inertia to consider for actuator N omits the mass of the actuator at the
pivot
122 GRIPPER
Jaw torque is the other critical factor when specifying a gripper There are two sources of this
torque torque generated by the gripper on itself and torque generated by the acceleration and
weight of the part These can be addressed separately
Torque from the robotic gripper
Long Jaws are often required Either the part is bulky like an engine block or the part must be held
at a distance to fit in a machine In either case the longer the jaw the greater the torque the gripper
imposes on itself Therefore the torque from the grippers is GRIPPER TORQUE=Gripper Force x
Jaw Length (where jaw length is measured from the face of the gripper to the center of gravity of
the part)
12
Figure 4 Example of Gripper
Gripper Example
If we put 6rdquo long jaws on a gripper with 100 pounds of closing force gripper the jaws will see
Jaw Torque= 100 Pounds x 6rdquo= 600 in-pounds
The rating on the gripper is 840 in-pounds We used the majority of this rating without even
gripping a part because of the length of the jaws
Thus we can see that the length of the jaws plays a major factor in specifying a gripper The next
task is to determine the torque the gripper will experience from the part
CHAPTER 2 GESTURE
21 GESTURE CONTROLLED SYSTEM
Humans naturally use gesture to communicate It has been demonstrated that young children can
readily learn to communicate with gesture before they learn to talk A gesture is non-verbal
communication made with a part of the body We use gesture instead of or in combination with
verbal communication Using this process human can interface with the machine without any
mechanical devices Human movements are typically analyzed by segmenting them into shorter and
understandable format The movements vary person to person It can be used as a command to
control different devices of daily activities mobility etc So our natural or intuitive body
movements or gestures can be used as command or interface to operate machines communicate
with intelligent environments to control home appliances smart home telecare systems etc In this
paper we also review the different types of technologies of gesture controlled system
212 TYPES OF GESTURES
Most of the researches are based on hand gestures Direct control via hand posture is immediate but
limited in the number of Choices There are researches about body gesture finger point movement
In the early stage researchers used gloves with microcontroller and connected with the device
through a wire Head gesture and gesture with voice were also in the research but hand gesture was
the most dominant part of gesture control system
A primary goal of gesture control is to create a system which can identify specific human gestures
and use them to convey information or for device control Gesture recognition can be achieved by
various methods in which popular two are
13
1 Gesture control using any particular sensor
2 Gesture control using image processing
1 Gesture control using any particular sensor
This includes interpreting the human gestures by the use of any particular sensors The most widely
used sensor are accelerometer and gyroscope
We just need to wear a small transmitting device in your hand which included an acceleration
meter(either accelerometer or gyroscope) This will transmit an appropriate command to the robot
so that it can do whatever we want
2 Gesture control using any image processing
This includes following processes or steps
14
Figure 5-(steps for gesture control by image processing)
In our project we our deploying the first method ie gesture control using an
accelerometer sensor
CHAPTER 3 HARDWARE IMPLEMENTATION
31 Accelerometer
An accelerometer is a sensor that measures the physical acceleration experienced by an object due
to inertial forces or due to mechanical excitation In aerospace applications accelerometers are used
along with gyroscopes for navigation guidance and flight control Conceptually an accelerometer
behaves as a damped mass on a spring When the accelerometer experiences acceleration the mass
is displaced and the displacement is then measured to give the acceleration
In these devices piezoelectric piezoresistive and capacitive techniques are commonly used to
convert the mechanical motion into an electrical signal Piezoelectric accelerometers rely on
piezoceramics (eg lead zirconate titanate) or single crystals (eg quartz tourmaline) They are
unmatched in terms of their upper frequency range low packaged weight and high temperature
range Piezoresistive accelerometers are preferred in high shock applications Capacitive
accelerometers performance is superior in low frequency range and they can be operated in servo
mode to achieve high stability and linearity
15
Figure 6 An accelerometer
311 Working principle of accelerometer
16
Figure 7(schematic of an accelerometer)
The principle of working of an accelerometer can be explained by a simple mass (m) attached to a
spring of stiffness (k) that in turn is attached to a casing as illustrated in figure3 The mass used in
accelerometers is often called the seismic-mass or proof-mass In most cases the system also
includes a dashpot to provide a desirable damping effect
The dashpot with damping coefficient (c) is normally attached to the mass in parallel with the
spring When the spring mass system is subjected to linear acceleration a force equal to mass times
acceleration acts on the proof-mass causing it to deflect This deflection is sensed by a suitable
means and converted into an equivalent electrical signal Some form of damping is required
otherwise the system would not stabilize quickly under applied acceleration
To derive the motion equation of the system Newton‟s second law is used where all real forces
acting on the proof-mass are equal to the inertia force on the proof-mass Accordingly a dynamic
problem can be treated as a problem of static equilibrium and the equation of motion can be
obtained by direct formulation of the equations of equilibrium This damped mass-spring system
with applied force constitutes a classical second order mechanical system
312Accelerometer as Gesture Control Sensor
The accelerometer can be used in gesture controlled application As seen the accelerometer sensor measures the physical acceleration experienced by an object due to inertial forces or due to
mechanical excitationSo this means it will give different values for different gestures when
mounted on human handThis can be used as an advantage ieit can be interfaced with any of the
microcontroller or other device and can be used to control any robot or any oher device
313 Key factors while selecting an accelerometer
Some of the Key factors while selecting an accelerometer are
1Analog vs digital Depending on the interface to which you will be connecting the accelerometer
you need to select analog or digital output accelerometer
2Output Accelerometer comes with different outputs-Charge output IEPE output Voltage
output current output
17
3Number of axis Depending on your requirement you need to select single double or tri axis
accelerometer The 3 axis accelerometer will measure acceleration in all directions
4Acceleration range Acceleration Range is measured in units of g 1g is equal to the earths
gravity at sea level
5Sensitivity is the ratio of change in acceleration (input) to change in the output signal Sensitivity
is specified at a particular supply voltage and is typically expressed in units of mVg
314 Applications of Accelerometers
Used in cars to study shock and vibrations
Camcorders use accelerometers for image stabilization
Still cameras use accelerometers for anti-blur capturing
Used in mobile phones for multiple functions including tilt detection motion detectionetc
32 IR SENSOR
The InfraRed receiver transmitter pair is to use be worn around the fingers and controls the opening
and closing of the end effector
321 Introduction
An infrared sensor is an electronic instrument that is used to sense certain characteristics of its
surroundings by either emitting andor detecting infrared radiation It is also capable of measuring
heat of an object and detecting motion Infrared waves are not visible to the human eye
In the electromagnetic spectrum infrared radiation is the region having wavelengths longer than
visible light wavelengths but shorter than microwaves The infrared region is approximately
demarcated from 075 to 1000microm The wavelength region from 075 to 3microm is termed as near
infrared the region from 3 to 6microm is termed mid-infrared and the region higher than 6microm is termed
as far infrared
18
Infrared technology is found in many of our everyday products For example TV has an IR detector
for interpreting the signal from the remote control Key benefits of infrared sensors include low
power requirements simple circuitry and their portable feature
322 Working Principle
A typical system for detecting infrared radiation using infrared sensors includes the infrared source
such as blackbody radiators tungsten lamps and silicon carbide In case of active IR sensors the
sources are infrared lasers and LEDs of specific IR wavelengths Next is the transmission medium
used for infrared transmission which includes vacuum the atmosphere and optical fibers
Thirdly optical components such as optical lenses made from quartz CaF2 Ge and Si polyethylene
Fresnel lenses and Al or Au mirrors are used to converge or focus infrared radiation Likewise to
limit spectral response band-pass filters are ideal
Finally the infrared detector completes the system for detecting infrared radiation The output from
the detector is usually very small and hence pre-amplifiers coupled with circuitry are added to
further process the received signals
Figure 8 Circuit Diagram Of An IR Sensor
19
323 Applications
The following are the key application areas of infrared sensors
Tracking and art history
Climatology meteorology and astronomy
Thermography communications and alcohol testing
Heating hyperspectral imaging and night vision
Biological systems photobiomodulation and plant health
Gas detectorsgas leak detection
Water and steel analysis flame detection
Anesthesiology testing and spectroscopy
Petroleum exploration and underground solution
Rail safety
33 SERVO MOTORS
A servomotor is a rotary actuator that allows for precise control of angular position velocity and
acceleration It consists of a suitable motor coupled to a sensor for position feedback It also requires
a relatively sophisticated controller often a dedicated module designed specifically for use with
servomotors
331 Controlling Of A Servo Motor
Servos are controlled by sending an electrical pulse of variable width or pulse width
modulation (PWM) through the control wire There is a minimum pulse a maximum pulse and a
repetition rate A servo motor can usually only turn 90 degrees in either direction for a total of 180
degree movement The motors neutral position is defined as the position where the servo has the
same amount of potential rotation in the both the clockwise or counter-clockwise direction The
PWM sent to the motor determines position of the shaft and based on the duration of the pulse sent
via the control wire the rotor will turn to the desired position The servo motor expects to see a
pulse every 20 milliseconds (ms) and the length of the pulse will determine how far the motor turns
For example a 15ms pulse will make the motor turn to the 90-degree position Shorter than 15ms
moves it to 0 degrees and any longer than 15ms will turn the servo to 180 degrees as diagramed
below
20
Figure 9 Controlling an servo
332 Types of Servo Motors
There are two types of servo motors - AC and DC AC servo can handle higher current surges and
tend to be used in industrial machinery DC servos are not designed for high current surges and are
usually better suited for smaller applications Generally speaking DC motors are less expensive
than their AC counterparts These are also servo motors that have been built specifically
for continuous rotation making it an easy way to get your robot moving They feature two ball
bearings on the output shaft for reduced friction and easy access to the rest-point
adjustment potentiometer
333Servo Motor Applications
Servos are used in radio-controlled airplanes to position control surfaces like elevators rudders
walking a robot or operating grippers Servo motors are small have built-in control circuitry and
have good power for their size
In food services and pharmaceuticals the tools are designed to be used in harsher environments
where the potential for corrosion is high due to being washed at high pressures and temperatures
repeatedly to maintain strict hygiene standards Servos are also used in in-line manufacturing
where high repetition yet precise work is necessary
21
Of course you dont have to know how a servo works to use one but as with most electronics the
more you understand the more doors open for expanded projects and projects capabilities Whether
youre a hobbyist building robots an engineer designing industrial systems or just constantly
curious where will servo motors take you
334 Specifications
It is highly desirable to control or to maintain a certain location of motor rotor in a robotic arm not
only to determine its precise motion and position but also to control it in desired fashion most of the
industrial robotic arm contains pneumatic hydraulic and stepper motor to actuates they have very
high payload capacity but GuRoo is a low powered high degree of freedom robotic arm we uses
servo motor due their easy availability and high weight to torque ratio
HS-645mg standard deluxe high torque servo
Figure 10HS-475-SERVO
Detailed Specifications of above shown servo
Motor Type 3 Pole
Bearing Type Top Ball Bearing
22
Speed 023 018 sec 60 deg
Torque 44 55 kgcm
Size 3880 x 1980 x 3600mm
Weight 4000g
34 ATMega32
A microcontroller is the brain of the robot The main features of this controller are
Advanced RISC Architecture
Up to 16 MIPS Throughput at 16 MHz
16K Bytes of In-System Self-Programmable Flash
512 Bytes EEPROM
1K Byte Internal SRAM
32 Programmable IO Lines
In-System Programming by On-chip Boot Program
8-channel 10-bit ADC
Two 8-bit TimerCounters with Separate Prescalers and Compare Modes
One 16-bit TimerCounter with Separate Prescaler Compare Mode and Capture
Four PWM Channels
Programmable Serial USART
MasterSlave SPI Serial Interface
Byte-oriented Two-wire Serial Interface
Programmable Watchdog Timer with Separate On-chip Oscillator
External and Internal Interrupt Sources
23
Figure 11 - Pin configuration
CHAPTER 4 METHODOLOGY
The setup consists of a robotic arm having 5 degrees of freedom and 6 servo motors
The movements of the joints are controlled using servo motors that can move a fixed angle ranging from 0 to
180 degrees
Accelerometer 1
ADC of Microcontroller
Servo for wrist movement
24
IR sensor
Microcontroller
Servomotor for gripping
mechanism
Figure121 Flowchart for First Accelerometer
Figure122 Flowchart for second Accelerometer
Figure123 Flowchart for IR sensor
Accelerometer 2
ADC of Microcontroller
Servomotor for elbow
movement
25
Figure124 Flowchart for POTENTIOMETER
Potentiometer
ADC of microcontroller
servomotor for base movement
26
Figure 125 Complete Flow Chart
Complete flow chart depicting each sensor interfaced with microcontroller and the
movement of each and every servos (ie robotic arm)
27
41 SETUP USED amp SCHEMATIC
A setup consisting of
1 IR sensors
2 Two accelerometers and
3 A potentiometer is to be worn around the human hand for sensing the gesture
movements
The InfraRed receiver transmitter pair is to be worn around the fingers and controls the
opening and closing of the end effector
2 accelerometers are used for sensing the movement of the forearm and the wrist movement
A potentiometer is used to track the elbow movement
Figure13 Schematic of the components used
28
Figure 14 Setup Used
29
Figure 151 Linear prediction for wrist movement 1
CHAPTER 5 ALGORITHIM USED
(PREDICTION AND CORRECTION ALGORITHM)
An algorithm has been devised to make the robotic arm replicate the motions of the human arm
The robotic arm does not exactly have an idea of the exact movement of the human arm and takes
input from noisy sensors
The algorithm consists of the following parts
1 LINEAR PREDICTION
The values of the sensors and motors for every joint have been stored for certain predefined
positions for each joint movement The position of the robotic arm is predicted linearly using the
given formulae
119823119851119838119837119842119836119853119838119837 119852119838119851119855119848 119855119834119845119854119838 = (119846120784 minus 119846120783) lowast119842119847119849119854119853 119852119838119847119852119848119851 119855119834119845119854119838 minus 119852120783
(119852120784 minus 119852120783)
-
30
Figure 152 Linear prediction for wrist movement 2
Figure 153 Linear prediction for elbow movement 1
31
Figure 154 Linear prediction for elbow movement 2
m2- predefined value of the servo motor for the next known position
m1- predefined value of the servo motor for the previous known position
s1- predefined sensor value for the last known position
s2- predefined sensor value for the next known position
2) CORRECTION
The predicted value is then compared to the present value and the difference between the two
120782 119838119851119851119848119851 ge 119853119841119851119838119852119841119848119845119837
33
CHAPTER 6 APPLICATIONS
1) Industrial Applications
Such arms may prove handy in such sectors where the precision has to be adjusted from
time to time
Such arms make the job of the controller easier and have the capability of being operated at
faster speed than the traditional robotic arms used in the industries
A combination of the traditional and gesture controlled robotic arm may prove to be very
handy providing the arm both flexibility as well as accuracy
Disposing off radioactive wastes or any other hazardous chemical that may be dangerous
for human beings
Can be used in mines and space where human intervention is not possible
2) Defense
It Can be used for bomb disposal offering as much accuracy as a human arm and also
saving a human life
3) Medical Uses
Can be used by doctors to perform surgical operations at distant places
Such a technology can prove to be helping hand to physically disabled people or extremely
old people
34
CHAPTER 7 CONCLUSION AND FUTURE PROSPRCTS
71 CONCLUSION
As the error can be both positive and negative hence the robotic arm becomes less susceptible to
vibrations as when the human arm vibrates the error would eventually cancel itself or become small
in magnitude than the threshold value and at the same time it can detect small changes made in the
human arm because the error adds up to cross the threshold
In the paper an algorithm is proposed to control a gesture based robotic arm The position of each
motor is predicted based on the sensory input later the position is corrected while comparing it to
the actual position of the motor This algorithm is helpful in reducing the effects of vibrations that
may take place in a human arm and hence it can find great use in the area of medical surgery
72 FUTURE PROSPECTS
Modern robot systems provide graphical simulation and virtual environment for programming of
robots Our system can be enhanced to include these facilities Vision is one of the most important
features of the industrial robot systems present today For this purpose a pair of cameras can be
attached to the robotic arm which will allow robot to automatically identify and grasp the objects
Imitation based learning capability can be added to the robotic arm which will allow path tracking
by a different technique The instruction set for the language and the teach pendant can be enhanced
to include vision forces torques imitation etc The communication from the host can be made
wireless this will allow programming and teaching from a remote location and would create a lot of
other applications for this robotic arm A robotic arm with remotely located control A wearable
robotic arm (exoskeleton) with high force reflection capability
35
CHAPTER 8 REFRENCES
[1] Cyber Technology in Automation Control and Intelligent Systems (CYBER) 2012 IEEE
International Conference on Mechatronics(ICOM)
[2] Matthias Rehm Nikolaus Bee Elisabeth Andreacute Wave Like an Egyptian - Accelerometer
Based Gesture Recognition for Culture Specific InteractionsBritish Computer Society
2007
[3] Pavlovic V Sharma R amp Huang T (1997) Visual interpretation of hand gestures for
human- computer Interaction A review (IEEE Trans Pattern Analysis and Machine
Intelligence July 1997 Vol 19(7) pp 677 -695
[4] Micro Electro Mechanical Systems (MEMS) START Selected Topics in Assurance
Related Technologies) volume 8 number 1
[5] Wong Guan Hao Yap Yee Leck and Lim Chot Hunldquo6-DOFPC-Based robotic arm (PC-
robo arm) with efficient trajectory lanning and speed controlrdquo 2011 4th International
Conference on Mechatronics (ICOM) 17-19 May 2011 Kuala Lumpur Malaysia
3
LIST OF FIGURE
S No Figure Name Page No
Fig1 GUROO- The Robotic Arm helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip2
Fig2 Two-link Robot Arm helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip3
Fig3 Two solution to robot inverse kinematics problem helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip4
Fig4 Example of Gripper helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip7
Fig5 Steps for gesture control by image processing helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip9
Fig6 An Accelerometer helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip10
Fig7 Schematic of an accelerometer helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip11
Fig8 Circuit diagram of An IR sensor helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip14
Fig9 Controlling of Servo helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip15
Fig11 Pin Configuration of Atmega 16 helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip18
Fig121 Flow chart of First Accelerometer helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip19
Fig122 Flow chart of Second Accelerometer helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip19
Fig123 Flow chart for Ir sensor helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip20
Fig124 Flow chart for Potentiometer helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip20
Fig13 Schematic of the component used helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip22
Fig14 Setup used helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip23
Fig151 Linear prediction for wrist movement 1 helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip24
Fig152 Linear prediction for wrist movement 2 helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip25
Fig153 Linear prediction for elbow movement 1 helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip25
4
Fig154 Linear prediction for elbow movement 2 helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellip26
5
CHAPTER 1 INTRODUCTION
Robotic arms have been in use by industries and alike for decades now However the precision
they provide along with the accuracy is still unparalleled anywhere in the whole realm of robotics
However to program these machining marvels to execute a predefined set of movements takes
time which is essentially a luxury that we fall short of at times Now imagine controlling an arm
thatrsquos as good a robotic arm as it can get and still it doesnrsquot needs to be programmed Yes the
answer lies with gesture controlled robotics By making a robotic arm replicate the movements of a
real-time human arm we not only save ourselves from seemingly endless sessions of coding but
also make it virtually alive The robotic arm presented here has currently six degrees of freedom
along with swift movements and quick response time The arm is currently maneuvered by DC
Servo Motors that are controlled by precisely controlled pulses generated by the widely used micro-
controller At Mega 16 The arm is able to follow real time hand gestures made by a human being
For real-time gesture recognition 3 three-axis accelerometers have been used which are strapped to
the arm of the controller at pre-defined positions These accelerometers detect the change in any of
the three axes viz X Y and Z and produce a differential voltage output accordingly The voltages
generated are then sent to the micro-controller where they are further converted to the digital form
by an inbuilt on-chip ADC converter
Thus the algorithm is able to sense the change in the position vectors of the human arm and
correspondingly generates electrical pulses to control the servo motors Servo motors are specially
designed to rotate through a given angle on each pulse that is sent to them Thus the servos of the
robotic arm are able to follow or trace back the gestures made by the human arm controller in real-
time Thatrsquos like having a chauffeur stand by your side while you teach him how to serve you
These kind of robotic arms are currently in immense demand especially in surgical and military
affairs For instance a cardiologist can perform a bypass surgery without being present physically
anywhere near the patient and that too with the same life-saving precision In the battle-zone and
modern urban warfare such arms can be used to detect and defuse IEDs and such explosive devices
without risking the life of any soldier Virtually such arms are as good as having an extra human
arm at places where we wonrsquot want or canrsquot have a real human Itrsquos only our gestures and
imagination that can set limits to the true potential of such robotic wonders Why even think why
not make a gesture beside that arm and see how it replicates you learning from you bit by bit
gesture by gesture
6
FIGURE 1 GUROO- THE ROBOTIC ARM
7
11 KINEMATICS AND DYNAMICS OF ROBOTIC ARM
Robotic arms are commonplace in todays world They are used to weld automobile bodies
employed to locate merchandise in computerized warehouses and used by the Space Shuttle to
retrieve satellites from orbit They are reliable and accurate This reliability and accuracy is due to
the computer a robot arm uses in determining where and how it should move This control
computer is programmed with some basic mathematics In this section we will look at the
mathematics behind robot arms
We will study the two-link robot arm shown in Figure 1 Most robot arms are more complicated
than this using three links and a moveable hand but with these complications come much more
difficult mathematics Operation of the two-link arm is simple The first link (length L1) pivots
around the origin of an XY Cartesian coordinate system while the second link (length L2) pivots
about the connection between the two links The two pivot points are drawn as circles The angle
the first link makes with the horizontal (X) axis is designated A while the angle the second link
makes with the first link is designated B The end of the second link is the position of the robot arm
(X Y)
There are three basic problems in robotics The first problem is that of kinematics This problem
asks the question given the angles A and B what is the arm position (X Y) This is simple
trigonometry The second problem is inverse kinematics Here we want to ask given the position
(X Y) what angles A and B yield this position This is a more difficult problem Lastly we need
to look at the problem of trajectory planning In trajectory planning we ask given our current
position (X Y) and some desired new position how do we change the angles A and B to arrive at
this new position We examine each of these problems separately using the two-link robot arm
8
Figure2 Two-link robot arm
111 Robot Arm Kinematics
The kinematics problem requires computation of the robot arm Cartesian position (X Y) knowing
the two link angles A and B Referring to Figure 1 we can see the position of the end of the first
link (X1 Y1) is given by
X1 = L1cos(A)
Y1 = L1sin(A)
Then the end of the second link (X Y) is simply
X = X1 + L2cos(A + B)
Y = Y1 + L2sin(A + B)
Combining these two sets of equations provides the solution to the kinematics problem
X = L1cos(A) + L2cos(A + B)
Y = L1sin(A) + L2sin(A + B)
An interesting question at this point is if we cycle A and B through all possible combinations (-180
degrees lt A lt 180 degrees -180 degrees lt B lt 180 degrees) what would the region of coverage
look like If L1 and L2 are equal the region would be a circle (radius L1 + L2) If L1 and L2 are not
equal the region would be armular (like a donut) This coverage region becomes important in the
inverse kinematics problem where we need to know if its possible to reach a given point by
adjusting the link angles
9
Figure 3Two solutions to robot inverse kinematics problem
112 Robot Arm Inverse Kinematics
The kinematics problem is seen to be fairly easy to solve The inverse problem that of finding A
and B knowing (X Y) is not nearly as simple Lets see why Using the kinematics equations if we
know X and Y we need to solve the following for A and B
L1cos(A) + L2cos(A + B) = X
L1sin(A) + L2sin(A + B) = Y
This is a nonlinear problem There are two possible solution approaches algebraic and geometric
The algebraic approach (solving the equations directly) is tedious and involved For the two-link
robot arm the geometric approach is more straightforward We will outline the steps of the
algebraic approach to illustrate some salient points of the inverse kinematics problem Also by
outlining these steps we allow the more industrious reader to see if heshe can solve the problem
algebraically After this outline we will develop the solution to the problem with a geometric
approach
12 CALCULATING THE DESIGN PARAMETERS
121 Motor torque
The point of doing force calculations is for motor selection We must make sure that the motor we
choose can not only support the weight of the robot arm but also what the robot arm will carry (the
blue ball in the image below)
The first step is to label your FBD with the robot arm stretched out to its maximum length
10
Choose these parameters
weight of each linkage
weight of each joint
weight of object to lift
length of each linkage
Next you do a moment arm calculation multiplying downward force times the linkage lengths This
calculation must be done for each lifting actuator This particular design has just two DOF that
requires lifting and the center of mass of each linkage is assumed to be Length2
For each DOF you add the math gets more complicated and the joint weights get heavier We will
also find that shorter arm lengths allow for smaller torque requirements
The above equations only deal with the case where the robot arm is being held horizontally (not in
motion) This is not necessarily the worst case scenario For the arm to move from a rest position
acceleration is required To solve for this added torque it is known that the sum of torques acting at
a pivot point is equal to the moment of inertia (I) multiplied by the angular acceleration (alpha)
T=Ixα
To calculate the extra torque required to move (ie create an angular acceleration) you would
calculate the moment of inertia of the part from the end to the pivot using the equation (or an
equation similar to)
11
I=mr^22
Note this equation calculates the moment of inertia about the center of mass In the case of a robotic
arm the moment of inertia must take into consideration that the part is being rotated about a pivot
point located a distance away from the center of mass and a second term ( +MR2 ) needs to be
added For each joint the moment of inertia is calculated by adding the products of each individual
mass (mi) by the square of its respective length from the pivot (ri) Note that the equation for
calculating the moment of inertia to consider for actuator N omits the mass of the actuator at the
pivot
122 GRIPPER
Jaw torque is the other critical factor when specifying a gripper There are two sources of this
torque torque generated by the gripper on itself and torque generated by the acceleration and
weight of the part These can be addressed separately
Torque from the robotic gripper
Long Jaws are often required Either the part is bulky like an engine block or the part must be held
at a distance to fit in a machine In either case the longer the jaw the greater the torque the gripper
imposes on itself Therefore the torque from the grippers is GRIPPER TORQUE=Gripper Force x
Jaw Length (where jaw length is measured from the face of the gripper to the center of gravity of
the part)
12
Figure 4 Example of Gripper
Gripper Example
If we put 6rdquo long jaws on a gripper with 100 pounds of closing force gripper the jaws will see
Jaw Torque= 100 Pounds x 6rdquo= 600 in-pounds
The rating on the gripper is 840 in-pounds We used the majority of this rating without even
gripping a part because of the length of the jaws
Thus we can see that the length of the jaws plays a major factor in specifying a gripper The next
task is to determine the torque the gripper will experience from the part
CHAPTER 2 GESTURE
21 GESTURE CONTROLLED SYSTEM
Humans naturally use gesture to communicate It has been demonstrated that young children can
readily learn to communicate with gesture before they learn to talk A gesture is non-verbal
communication made with a part of the body We use gesture instead of or in combination with
verbal communication Using this process human can interface with the machine without any
mechanical devices Human movements are typically analyzed by segmenting them into shorter and
understandable format The movements vary person to person It can be used as a command to
control different devices of daily activities mobility etc So our natural or intuitive body
movements or gestures can be used as command or interface to operate machines communicate
with intelligent environments to control home appliances smart home telecare systems etc In this
paper we also review the different types of technologies of gesture controlled system
212 TYPES OF GESTURES
Most of the researches are based on hand gestures Direct control via hand posture is immediate but
limited in the number of Choices There are researches about body gesture finger point movement
In the early stage researchers used gloves with microcontroller and connected with the device
through a wire Head gesture and gesture with voice were also in the research but hand gesture was
the most dominant part of gesture control system
A primary goal of gesture control is to create a system which can identify specific human gestures
and use them to convey information or for device control Gesture recognition can be achieved by
various methods in which popular two are
13
1 Gesture control using any particular sensor
2 Gesture control using image processing
1 Gesture control using any particular sensor
This includes interpreting the human gestures by the use of any particular sensors The most widely
used sensor are accelerometer and gyroscope
We just need to wear a small transmitting device in your hand which included an acceleration
meter(either accelerometer or gyroscope) This will transmit an appropriate command to the robot
so that it can do whatever we want
2 Gesture control using any image processing
This includes following processes or steps
14
Figure 5-(steps for gesture control by image processing)
In our project we our deploying the first method ie gesture control using an
accelerometer sensor
CHAPTER 3 HARDWARE IMPLEMENTATION
31 Accelerometer
An accelerometer is a sensor that measures the physical acceleration experienced by an object due
to inertial forces or due to mechanical excitation In aerospace applications accelerometers are used
along with gyroscopes for navigation guidance and flight control Conceptually an accelerometer
behaves as a damped mass on a spring When the accelerometer experiences acceleration the mass
is displaced and the displacement is then measured to give the acceleration
In these devices piezoelectric piezoresistive and capacitive techniques are commonly used to
convert the mechanical motion into an electrical signal Piezoelectric accelerometers rely on
piezoceramics (eg lead zirconate titanate) or single crystals (eg quartz tourmaline) They are
unmatched in terms of their upper frequency range low packaged weight and high temperature
range Piezoresistive accelerometers are preferred in high shock applications Capacitive
accelerometers performance is superior in low frequency range and they can be operated in servo
mode to achieve high stability and linearity
15
Figure 6 An accelerometer
311 Working principle of accelerometer
16
Figure 7(schematic of an accelerometer)
The principle of working of an accelerometer can be explained by a simple mass (m) attached to a
spring of stiffness (k) that in turn is attached to a casing as illustrated in figure3 The mass used in
accelerometers is often called the seismic-mass or proof-mass In most cases the system also
includes a dashpot to provide a desirable damping effect
The dashpot with damping coefficient (c) is normally attached to the mass in parallel with the
spring When the spring mass system is subjected to linear acceleration a force equal to mass times
acceleration acts on the proof-mass causing it to deflect This deflection is sensed by a suitable
means and converted into an equivalent electrical signal Some form of damping is required
otherwise the system would not stabilize quickly under applied acceleration
To derive the motion equation of the system Newton‟s second law is used where all real forces
acting on the proof-mass are equal to the inertia force on the proof-mass Accordingly a dynamic
problem can be treated as a problem of static equilibrium and the equation of motion can be
obtained by direct formulation of the equations of equilibrium This damped mass-spring system
with applied force constitutes a classical second order mechanical system
312Accelerometer as Gesture Control Sensor
The accelerometer can be used in gesture controlled application As seen the accelerometer sensor measures the physical acceleration experienced by an object due to inertial forces or due to
mechanical excitationSo this means it will give different values for different gestures when
mounted on human handThis can be used as an advantage ieit can be interfaced with any of the
microcontroller or other device and can be used to control any robot or any oher device
313 Key factors while selecting an accelerometer
Some of the Key factors while selecting an accelerometer are
1Analog vs digital Depending on the interface to which you will be connecting the accelerometer
you need to select analog or digital output accelerometer
2Output Accelerometer comes with different outputs-Charge output IEPE output Voltage
output current output
17
3Number of axis Depending on your requirement you need to select single double or tri axis
accelerometer The 3 axis accelerometer will measure acceleration in all directions
4Acceleration range Acceleration Range is measured in units of g 1g is equal to the earths
gravity at sea level
5Sensitivity is the ratio of change in acceleration (input) to change in the output signal Sensitivity
is specified at a particular supply voltage and is typically expressed in units of mVg
314 Applications of Accelerometers
Used in cars to study shock and vibrations
Camcorders use accelerometers for image stabilization
Still cameras use accelerometers for anti-blur capturing
Used in mobile phones for multiple functions including tilt detection motion detectionetc
32 IR SENSOR
The InfraRed receiver transmitter pair is to use be worn around the fingers and controls the opening
and closing of the end effector
321 Introduction
An infrared sensor is an electronic instrument that is used to sense certain characteristics of its
surroundings by either emitting andor detecting infrared radiation It is also capable of measuring
heat of an object and detecting motion Infrared waves are not visible to the human eye
In the electromagnetic spectrum infrared radiation is the region having wavelengths longer than
visible light wavelengths but shorter than microwaves The infrared region is approximately
demarcated from 075 to 1000microm The wavelength region from 075 to 3microm is termed as near
infrared the region from 3 to 6microm is termed mid-infrared and the region higher than 6microm is termed
as far infrared
18
Infrared technology is found in many of our everyday products For example TV has an IR detector
for interpreting the signal from the remote control Key benefits of infrared sensors include low
power requirements simple circuitry and their portable feature
322 Working Principle
A typical system for detecting infrared radiation using infrared sensors includes the infrared source
such as blackbody radiators tungsten lamps and silicon carbide In case of active IR sensors the
sources are infrared lasers and LEDs of specific IR wavelengths Next is the transmission medium
used for infrared transmission which includes vacuum the atmosphere and optical fibers
Thirdly optical components such as optical lenses made from quartz CaF2 Ge and Si polyethylene
Fresnel lenses and Al or Au mirrors are used to converge or focus infrared radiation Likewise to
limit spectral response band-pass filters are ideal
Finally the infrared detector completes the system for detecting infrared radiation The output from
the detector is usually very small and hence pre-amplifiers coupled with circuitry are added to
further process the received signals
Figure 8 Circuit Diagram Of An IR Sensor
19
323 Applications
The following are the key application areas of infrared sensors
Tracking and art history
Climatology meteorology and astronomy
Thermography communications and alcohol testing
Heating hyperspectral imaging and night vision
Biological systems photobiomodulation and plant health
Gas detectorsgas leak detection
Water and steel analysis flame detection
Anesthesiology testing and spectroscopy
Petroleum exploration and underground solution
Rail safety
33 SERVO MOTORS
A servomotor is a rotary actuator that allows for precise control of angular position velocity and
acceleration It consists of a suitable motor coupled to a sensor for position feedback It also requires
a relatively sophisticated controller often a dedicated module designed specifically for use with
servomotors
331 Controlling Of A Servo Motor
Servos are controlled by sending an electrical pulse of variable width or pulse width
modulation (PWM) through the control wire There is a minimum pulse a maximum pulse and a
repetition rate A servo motor can usually only turn 90 degrees in either direction for a total of 180
degree movement The motors neutral position is defined as the position where the servo has the
same amount of potential rotation in the both the clockwise or counter-clockwise direction The
PWM sent to the motor determines position of the shaft and based on the duration of the pulse sent
via the control wire the rotor will turn to the desired position The servo motor expects to see a
pulse every 20 milliseconds (ms) and the length of the pulse will determine how far the motor turns
For example a 15ms pulse will make the motor turn to the 90-degree position Shorter than 15ms
moves it to 0 degrees and any longer than 15ms will turn the servo to 180 degrees as diagramed
below
20
Figure 9 Controlling an servo
332 Types of Servo Motors
There are two types of servo motors - AC and DC AC servo can handle higher current surges and
tend to be used in industrial machinery DC servos are not designed for high current surges and are
usually better suited for smaller applications Generally speaking DC motors are less expensive
than their AC counterparts These are also servo motors that have been built specifically
for continuous rotation making it an easy way to get your robot moving They feature two ball
bearings on the output shaft for reduced friction and easy access to the rest-point
adjustment potentiometer
333Servo Motor Applications
Servos are used in radio-controlled airplanes to position control surfaces like elevators rudders
walking a robot or operating grippers Servo motors are small have built-in control circuitry and
have good power for their size
In food services and pharmaceuticals the tools are designed to be used in harsher environments
where the potential for corrosion is high due to being washed at high pressures and temperatures
repeatedly to maintain strict hygiene standards Servos are also used in in-line manufacturing
where high repetition yet precise work is necessary
21
Of course you dont have to know how a servo works to use one but as with most electronics the
more you understand the more doors open for expanded projects and projects capabilities Whether
youre a hobbyist building robots an engineer designing industrial systems or just constantly
curious where will servo motors take you
334 Specifications
It is highly desirable to control or to maintain a certain location of motor rotor in a robotic arm not
only to determine its precise motion and position but also to control it in desired fashion most of the
industrial robotic arm contains pneumatic hydraulic and stepper motor to actuates they have very
high payload capacity but GuRoo is a low powered high degree of freedom robotic arm we uses
servo motor due their easy availability and high weight to torque ratio
HS-645mg standard deluxe high torque servo
Figure 10HS-475-SERVO
Detailed Specifications of above shown servo
Motor Type 3 Pole
Bearing Type Top Ball Bearing
22
Speed 023 018 sec 60 deg
Torque 44 55 kgcm
Size 3880 x 1980 x 3600mm
Weight 4000g
34 ATMega32
A microcontroller is the brain of the robot The main features of this controller are
Advanced RISC Architecture
Up to 16 MIPS Throughput at 16 MHz
16K Bytes of In-System Self-Programmable Flash
512 Bytes EEPROM
1K Byte Internal SRAM
32 Programmable IO Lines
In-System Programming by On-chip Boot Program
8-channel 10-bit ADC
Two 8-bit TimerCounters with Separate Prescalers and Compare Modes
One 16-bit TimerCounter with Separate Prescaler Compare Mode and Capture
Four PWM Channels
Programmable Serial USART
MasterSlave SPI Serial Interface
Byte-oriented Two-wire Serial Interface
Programmable Watchdog Timer with Separate On-chip Oscillator
External and Internal Interrupt Sources
23
Figure 11 - Pin configuration
CHAPTER 4 METHODOLOGY
The setup consists of a robotic arm having 5 degrees of freedom and 6 servo motors
The movements of the joints are controlled using servo motors that can move a fixed angle ranging from 0 to
180 degrees
Accelerometer 1
ADC of Microcontroller
Servo for wrist movement
24
IR sensor
Microcontroller
Servomotor for gripping
mechanism
Figure121 Flowchart for First Accelerometer
Figure122 Flowchart for second Accelerometer
Figure123 Flowchart for IR sensor
Accelerometer 2
ADC of Microcontroller
Servomotor for elbow
movement
25
Figure124 Flowchart for POTENTIOMETER
Potentiometer
ADC of microcontroller
servomotor for base movement
26
Figure 125 Complete Flow Chart
Complete flow chart depicting each sensor interfaced with microcontroller and the
movement of each and every servos (ie robotic arm)
27
41 SETUP USED amp SCHEMATIC
A setup consisting of
1 IR sensors
2 Two accelerometers and
3 A potentiometer is to be worn around the human hand for sensing the gesture
movements
The InfraRed receiver transmitter pair is to be worn around the fingers and controls the
opening and closing of the end effector
2 accelerometers are used for sensing the movement of the forearm and the wrist movement
A potentiometer is used to track the elbow movement
Figure13 Schematic of the components used
28
Figure 14 Setup Used
29
Figure 151 Linear prediction for wrist movement 1
CHAPTER 5 ALGORITHIM USED
(PREDICTION AND CORRECTION ALGORITHM)
An algorithm has been devised to make the robotic arm replicate the motions of the human arm
The robotic arm does not exactly have an idea of the exact movement of the human arm and takes
input from noisy sensors
The algorithm consists of the following parts
1 LINEAR PREDICTION
The values of the sensors and motors for every joint have been stored for certain predefined
positions for each joint movement The position of the robotic arm is predicted linearly using the
given formulae
119823119851119838119837119842119836119853119838119837 119852119838119851119855119848 119855119834119845119854119838 = (119846120784 minus 119846120783) lowast119842119847119849119854119853 119852119838119847119852119848119851 119855119834119845119854119838 minus 119852120783
(119852120784 minus 119852120783)
-
30
Figure 152 Linear prediction for wrist movement 2
Figure 153 Linear prediction for elbow movement 1
31
Figure 154 Linear prediction for elbow movement 2
m2- predefined value of the servo motor for the next known position
m1- predefined value of the servo motor for the previous known position
s1- predefined sensor value for the last known position
s2- predefined sensor value for the next known position
2) CORRECTION
The predicted value is then compared to the present value and the difference between the two
For each DOF you add the math gets more complicated and the joint weights get heavier We will
also find that shorter arm lengths allow for smaller torque requirements
The above equations only deal with the case where the robot arm is being held horizontally (not in
motion) This is not necessarily the worst case scenario For the arm to move from a rest position
acceleration is required To solve for this added torque it is known that the sum of torques acting at
a pivot point is equal to the moment of inertia (I) multiplied by the angular acceleration (alpha)
T=Ixα
To calculate the extra torque required to move (ie create an angular acceleration) you would
calculate the moment of inertia of the part from the end to the pivot using the equation (or an
equation similar to)
11
I=mr^22
Note this equation calculates the moment of inertia about the center of mass In the case of a robotic
arm the moment of inertia must take into consideration that the part is being rotated about a pivot
point located a distance away from the center of mass and a second term ( +MR2 ) needs to be
added For each joint the moment of inertia is calculated by adding the products of each individual
mass (mi) by the square of its respective length from the pivot (ri) Note that the equation for
calculating the moment of inertia to consider for actuator N omits the mass of the actuator at the
pivot
122 GRIPPER
Jaw torque is the other critical factor when specifying a gripper There are two sources of this
torque torque generated by the gripper on itself and torque generated by the acceleration and
weight of the part These can be addressed separately
Torque from the robotic gripper
Long Jaws are often required Either the part is bulky like an engine block or the part must be held
at a distance to fit in a machine In either case the longer the jaw the greater the torque the gripper
imposes on itself Therefore the torque from the grippers is GRIPPER TORQUE=Gripper Force x
Jaw Length (where jaw length is measured from the face of the gripper to the center of gravity of
the part)
12
Figure 4 Example of Gripper
Gripper Example
If we put 6rdquo long jaws on a gripper with 100 pounds of closing force gripper the jaws will see
Jaw Torque= 100 Pounds x 6rdquo= 600 in-pounds
The rating on the gripper is 840 in-pounds We used the majority of this rating without even
gripping a part because of the length of the jaws
Thus we can see that the length of the jaws plays a major factor in specifying a gripper The next
task is to determine the torque the gripper will experience from the part
CHAPTER 2 GESTURE
21 GESTURE CONTROLLED SYSTEM
Humans naturally use gesture to communicate It has been demonstrated that young children can
readily learn to communicate with gesture before they learn to talk A gesture is non-verbal
communication made with a part of the body We use gesture instead of or in combination with
verbal communication Using this process human can interface with the machine without any
mechanical devices Human movements are typically analyzed by segmenting them into shorter and
understandable format The movements vary person to person It can be used as a command to
control different devices of daily activities mobility etc So our natural or intuitive body
movements or gestures can be used as command or interface to operate machines communicate
with intelligent environments to control home appliances smart home telecare systems etc In this
paper we also review the different types of technologies of gesture controlled system
212 TYPES OF GESTURES
Most of the researches are based on hand gestures Direct control via hand posture is immediate but
limited in the number of Choices There are researches about body gesture finger point movement
In the early stage researchers used gloves with microcontroller and connected with the device
through a wire Head gesture and gesture with voice were also in the research but hand gesture was
the most dominant part of gesture control system
A primary goal of gesture control is to create a system which can identify specific human gestures
and use them to convey information or for device control Gesture recognition can be achieved by
various methods in which popular two are
13
1 Gesture control using any particular sensor
2 Gesture control using image processing
1 Gesture control using any particular sensor
This includes interpreting the human gestures by the use of any particular sensors The most widely
used sensor are accelerometer and gyroscope
We just need to wear a small transmitting device in your hand which included an acceleration
meter(either accelerometer or gyroscope) This will transmit an appropriate command to the robot
so that it can do whatever we want
2 Gesture control using any image processing
This includes following processes or steps
14
Figure 5-(steps for gesture control by image processing)
In our project we our deploying the first method ie gesture control using an
accelerometer sensor
CHAPTER 3 HARDWARE IMPLEMENTATION
31 Accelerometer
An accelerometer is a sensor that measures the physical acceleration experienced by an object due
to inertial forces or due to mechanical excitation In aerospace applications accelerometers are used
along with gyroscopes for navigation guidance and flight control Conceptually an accelerometer
behaves as a damped mass on a spring When the accelerometer experiences acceleration the mass
is displaced and the displacement is then measured to give the acceleration
In these devices piezoelectric piezoresistive and capacitive techniques are commonly used to
convert the mechanical motion into an electrical signal Piezoelectric accelerometers rely on
piezoceramics (eg lead zirconate titanate) or single crystals (eg quartz tourmaline) They are
unmatched in terms of their upper frequency range low packaged weight and high temperature
range Piezoresistive accelerometers are preferred in high shock applications Capacitive
accelerometers performance is superior in low frequency range and they can be operated in servo
mode to achieve high stability and linearity
15
Figure 6 An accelerometer
311 Working principle of accelerometer
16
Figure 7(schematic of an accelerometer)
The principle of working of an accelerometer can be explained by a simple mass (m) attached to a
spring of stiffness (k) that in turn is attached to a casing as illustrated in figure3 The mass used in
accelerometers is often called the seismic-mass or proof-mass In most cases the system also
includes a dashpot to provide a desirable damping effect
The dashpot with damping coefficient (c) is normally attached to the mass in parallel with the
spring When the spring mass system is subjected to linear acceleration a force equal to mass times
acceleration acts on the proof-mass causing it to deflect This deflection is sensed by a suitable
means and converted into an equivalent electrical signal Some form of damping is required
otherwise the system would not stabilize quickly under applied acceleration
To derive the motion equation of the system Newton‟s second law is used where all real forces
acting on the proof-mass are equal to the inertia force on the proof-mass Accordingly a dynamic
problem can be treated as a problem of static equilibrium and the equation of motion can be
obtained by direct formulation of the equations of equilibrium This damped mass-spring system
with applied force constitutes a classical second order mechanical system
312Accelerometer as Gesture Control Sensor
The accelerometer can be used in gesture controlled application As seen the accelerometer sensor measures the physical acceleration experienced by an object due to inertial forces or due to
mechanical excitationSo this means it will give different values for different gestures when
mounted on human handThis can be used as an advantage ieit can be interfaced with any of the
microcontroller or other device and can be used to control any robot or any oher device
313 Key factors while selecting an accelerometer
Some of the Key factors while selecting an accelerometer are
1Analog vs digital Depending on the interface to which you will be connecting the accelerometer
you need to select analog or digital output accelerometer
2Output Accelerometer comes with different outputs-Charge output IEPE output Voltage
output current output
17
3Number of axis Depending on your requirement you need to select single double or tri axis
accelerometer The 3 axis accelerometer will measure acceleration in all directions
4Acceleration range Acceleration Range is measured in units of g 1g is equal to the earths
gravity at sea level
5Sensitivity is the ratio of change in acceleration (input) to change in the output signal Sensitivity
is specified at a particular supply voltage and is typically expressed in units of mVg
314 Applications of Accelerometers
Used in cars to study shock and vibrations
Camcorders use accelerometers for image stabilization
Still cameras use accelerometers for anti-blur capturing
Used in mobile phones for multiple functions including tilt detection motion detectionetc
32 IR SENSOR
The InfraRed receiver transmitter pair is to use be worn around the fingers and controls the opening
and closing of the end effector
321 Introduction
An infrared sensor is an electronic instrument that is used to sense certain characteristics of its
surroundings by either emitting andor detecting infrared radiation It is also capable of measuring
heat of an object and detecting motion Infrared waves are not visible to the human eye
In the electromagnetic spectrum infrared radiation is the region having wavelengths longer than
visible light wavelengths but shorter than microwaves The infrared region is approximately
demarcated from 075 to 1000microm The wavelength region from 075 to 3microm is termed as near
infrared the region from 3 to 6microm is termed mid-infrared and the region higher than 6microm is termed
as far infrared
18
Infrared technology is found in many of our everyday products For example TV has an IR detector
for interpreting the signal from the remote control Key benefits of infrared sensors include low
power requirements simple circuitry and their portable feature
322 Working Principle
A typical system for detecting infrared radiation using infrared sensors includes the infrared source
such as blackbody radiators tungsten lamps and silicon carbide In case of active IR sensors the
sources are infrared lasers and LEDs of specific IR wavelengths Next is the transmission medium
used for infrared transmission which includes vacuum the atmosphere and optical fibers
Thirdly optical components such as optical lenses made from quartz CaF2 Ge and Si polyethylene
Fresnel lenses and Al or Au mirrors are used to converge or focus infrared radiation Likewise to
limit spectral response band-pass filters are ideal
Finally the infrared detector completes the system for detecting infrared radiation The output from
the detector is usually very small and hence pre-amplifiers coupled with circuitry are added to
further process the received signals
Figure 8 Circuit Diagram Of An IR Sensor
19
323 Applications
The following are the key application areas of infrared sensors
Tracking and art history
Climatology meteorology and astronomy
Thermography communications and alcohol testing
Heating hyperspectral imaging and night vision
Biological systems photobiomodulation and plant health
Gas detectorsgas leak detection
Water and steel analysis flame detection
Anesthesiology testing and spectroscopy
Petroleum exploration and underground solution
Rail safety
33 SERVO MOTORS
A servomotor is a rotary actuator that allows for precise control of angular position velocity and
acceleration It consists of a suitable motor coupled to a sensor for position feedback It also requires
a relatively sophisticated controller often a dedicated module designed specifically for use with
servomotors
331 Controlling Of A Servo Motor
Servos are controlled by sending an electrical pulse of variable width or pulse width
modulation (PWM) through the control wire There is a minimum pulse a maximum pulse and a
repetition rate A servo motor can usually only turn 90 degrees in either direction for a total of 180
degree movement The motors neutral position is defined as the position where the servo has the
same amount of potential rotation in the both the clockwise or counter-clockwise direction The
PWM sent to the motor determines position of the shaft and based on the duration of the pulse sent
via the control wire the rotor will turn to the desired position The servo motor expects to see a
pulse every 20 milliseconds (ms) and the length of the pulse will determine how far the motor turns
For example a 15ms pulse will make the motor turn to the 90-degree position Shorter than 15ms
moves it to 0 degrees and any longer than 15ms will turn the servo to 180 degrees as diagramed
below
20
Figure 9 Controlling an servo
332 Types of Servo Motors
There are two types of servo motors - AC and DC AC servo can handle higher current surges and
tend to be used in industrial machinery DC servos are not designed for high current surges and are
usually better suited for smaller applications Generally speaking DC motors are less expensive
than their AC counterparts These are also servo motors that have been built specifically
for continuous rotation making it an easy way to get your robot moving They feature two ball
bearings on the output shaft for reduced friction and easy access to the rest-point
adjustment potentiometer
333Servo Motor Applications
Servos are used in radio-controlled airplanes to position control surfaces like elevators rudders
walking a robot or operating grippers Servo motors are small have built-in control circuitry and
have good power for their size
In food services and pharmaceuticals the tools are designed to be used in harsher environments
where the potential for corrosion is high due to being washed at high pressures and temperatures
repeatedly to maintain strict hygiene standards Servos are also used in in-line manufacturing
where high repetition yet precise work is necessary
21
Of course you dont have to know how a servo works to use one but as with most electronics the
more you understand the more doors open for expanded projects and projects capabilities Whether
youre a hobbyist building robots an engineer designing industrial systems or just constantly
curious where will servo motors take you
334 Specifications
It is highly desirable to control or to maintain a certain location of motor rotor in a robotic arm not
only to determine its precise motion and position but also to control it in desired fashion most of the
industrial robotic arm contains pneumatic hydraulic and stepper motor to actuates they have very
high payload capacity but GuRoo is a low powered high degree of freedom robotic arm we uses
servo motor due their easy availability and high weight to torque ratio
HS-645mg standard deluxe high torque servo
Figure 10HS-475-SERVO
Detailed Specifications of above shown servo
Motor Type 3 Pole
Bearing Type Top Ball Bearing
22
Speed 023 018 sec 60 deg
Torque 44 55 kgcm
Size 3880 x 1980 x 3600mm
Weight 4000g
34 ATMega32
A microcontroller is the brain of the robot The main features of this controller are
Advanced RISC Architecture
Up to 16 MIPS Throughput at 16 MHz
16K Bytes of In-System Self-Programmable Flash
512 Bytes EEPROM
1K Byte Internal SRAM
32 Programmable IO Lines
In-System Programming by On-chip Boot Program
8-channel 10-bit ADC
Two 8-bit TimerCounters with Separate Prescalers and Compare Modes
One 16-bit TimerCounter with Separate Prescaler Compare Mode and Capture
Four PWM Channels
Programmable Serial USART
MasterSlave SPI Serial Interface
Byte-oriented Two-wire Serial Interface
Programmable Watchdog Timer with Separate On-chip Oscillator
External and Internal Interrupt Sources
23
Figure 11 - Pin configuration
CHAPTER 4 METHODOLOGY
The setup consists of a robotic arm having 5 degrees of freedom and 6 servo motors
The movements of the joints are controlled using servo motors that can move a fixed angle ranging from 0 to
180 degrees
Accelerometer 1
ADC of Microcontroller
Servo for wrist movement
24
IR sensor
Microcontroller
Servomotor for gripping
mechanism
Figure121 Flowchart for First Accelerometer
Figure122 Flowchart for second Accelerometer
Figure123 Flowchart for IR sensor
Accelerometer 2
ADC of Microcontroller
Servomotor for elbow
movement
25
Figure124 Flowchart for POTENTIOMETER
Potentiometer
ADC of microcontroller
servomotor for base movement
26
Figure 125 Complete Flow Chart
Complete flow chart depicting each sensor interfaced with microcontroller and the
movement of each and every servos (ie robotic arm)
27
41 SETUP USED amp SCHEMATIC
A setup consisting of
1 IR sensors
2 Two accelerometers and
3 A potentiometer is to be worn around the human hand for sensing the gesture
movements
The InfraRed receiver transmitter pair is to be worn around the fingers and controls the
opening and closing of the end effector
2 accelerometers are used for sensing the movement of the forearm and the wrist movement
A potentiometer is used to track the elbow movement
Figure13 Schematic of the components used
28
Figure 14 Setup Used
29
Figure 151 Linear prediction for wrist movement 1
CHAPTER 5 ALGORITHIM USED
(PREDICTION AND CORRECTION ALGORITHM)
An algorithm has been devised to make the robotic arm replicate the motions of the human arm
The robotic arm does not exactly have an idea of the exact movement of the human arm and takes
input from noisy sensors
The algorithm consists of the following parts
1 LINEAR PREDICTION
The values of the sensors and motors for every joint have been stored for certain predefined
positions for each joint movement The position of the robotic arm is predicted linearly using the
given formulae
119823119851119838119837119842119836119853119838119837 119852119838119851119855119848 119855119834119845119854119838 = (119846120784 minus 119846120783) lowast119842119847119849119854119853 119852119838119847119852119848119851 119855119834119845119854119838 minus 119852120783
(119852120784 minus 119852120783)
-
30
Figure 152 Linear prediction for wrist movement 2
Figure 153 Linear prediction for elbow movement 1
31
Figure 154 Linear prediction for elbow movement 2
m2- predefined value of the servo motor for the next known position
m1- predefined value of the servo motor for the previous known position
s1- predefined sensor value for the last known position
s2- predefined sensor value for the next known position
2) CORRECTION
The predicted value is then compared to the present value and the difference between the two
For each DOF you add the math gets more complicated and the joint weights get heavier We will
also find that shorter arm lengths allow for smaller torque requirements
The above equations only deal with the case where the robot arm is being held horizontally (not in
motion) This is not necessarily the worst case scenario For the arm to move from a rest position
acceleration is required To solve for this added torque it is known that the sum of torques acting at
a pivot point is equal to the moment of inertia (I) multiplied by the angular acceleration (alpha)
T=Ixα
To calculate the extra torque required to move (ie create an angular acceleration) you would
calculate the moment of inertia of the part from the end to the pivot using the equation (or an
equation similar to)
11
I=mr^22
Note this equation calculates the moment of inertia about the center of mass In the case of a robotic
arm the moment of inertia must take into consideration that the part is being rotated about a pivot
point located a distance away from the center of mass and a second term ( +MR2 ) needs to be
added For each joint the moment of inertia is calculated by adding the products of each individual
mass (mi) by the square of its respective length from the pivot (ri) Note that the equation for
calculating the moment of inertia to consider for actuator N omits the mass of the actuator at the
pivot
122 GRIPPER
Jaw torque is the other critical factor when specifying a gripper There are two sources of this
torque torque generated by the gripper on itself and torque generated by the acceleration and
weight of the part These can be addressed separately
Torque from the robotic gripper
Long Jaws are often required Either the part is bulky like an engine block or the part must be held
at a distance to fit in a machine In either case the longer the jaw the greater the torque the gripper
imposes on itself Therefore the torque from the grippers is GRIPPER TORQUE=Gripper Force x
Jaw Length (where jaw length is measured from the face of the gripper to the center of gravity of
the part)
12
Figure 4 Example of Gripper
Gripper Example
If we put 6rdquo long jaws on a gripper with 100 pounds of closing force gripper the jaws will see
Jaw Torque= 100 Pounds x 6rdquo= 600 in-pounds
The rating on the gripper is 840 in-pounds We used the majority of this rating without even
gripping a part because of the length of the jaws
Thus we can see that the length of the jaws plays a major factor in specifying a gripper The next
task is to determine the torque the gripper will experience from the part
CHAPTER 2 GESTURE
21 GESTURE CONTROLLED SYSTEM
Humans naturally use gesture to communicate It has been demonstrated that young children can
readily learn to communicate with gesture before they learn to talk A gesture is non-verbal
communication made with a part of the body We use gesture instead of or in combination with
verbal communication Using this process human can interface with the machine without any
mechanical devices Human movements are typically analyzed by segmenting them into shorter and
understandable format The movements vary person to person It can be used as a command to
control different devices of daily activities mobility etc So our natural or intuitive body
movements or gestures can be used as command or interface to operate machines communicate
with intelligent environments to control home appliances smart home telecare systems etc In this
paper we also review the different types of technologies of gesture controlled system
212 TYPES OF GESTURES
Most of the researches are based on hand gestures Direct control via hand posture is immediate but
limited in the number of Choices There are researches about body gesture finger point movement
In the early stage researchers used gloves with microcontroller and connected with the device
through a wire Head gesture and gesture with voice were also in the research but hand gesture was
the most dominant part of gesture control system
A primary goal of gesture control is to create a system which can identify specific human gestures
and use them to convey information or for device control Gesture recognition can be achieved by
various methods in which popular two are
13
1 Gesture control using any particular sensor
2 Gesture control using image processing
1 Gesture control using any particular sensor
This includes interpreting the human gestures by the use of any particular sensors The most widely
used sensor are accelerometer and gyroscope
We just need to wear a small transmitting device in your hand which included an acceleration
meter(either accelerometer or gyroscope) This will transmit an appropriate command to the robot
so that it can do whatever we want
2 Gesture control using any image processing
This includes following processes or steps
14
Figure 5-(steps for gesture control by image processing)
In our project we our deploying the first method ie gesture control using an
accelerometer sensor
CHAPTER 3 HARDWARE IMPLEMENTATION
31 Accelerometer
An accelerometer is a sensor that measures the physical acceleration experienced by an object due
to inertial forces or due to mechanical excitation In aerospace applications accelerometers are used
along with gyroscopes for navigation guidance and flight control Conceptually an accelerometer
behaves as a damped mass on a spring When the accelerometer experiences acceleration the mass
is displaced and the displacement is then measured to give the acceleration
In these devices piezoelectric piezoresistive and capacitive techniques are commonly used to
convert the mechanical motion into an electrical signal Piezoelectric accelerometers rely on
piezoceramics (eg lead zirconate titanate) or single crystals (eg quartz tourmaline) They are
unmatched in terms of their upper frequency range low packaged weight and high temperature
range Piezoresistive accelerometers are preferred in high shock applications Capacitive
accelerometers performance is superior in low frequency range and they can be operated in servo
mode to achieve high stability and linearity
15
Figure 6 An accelerometer
311 Working principle of accelerometer
16
Figure 7(schematic of an accelerometer)
The principle of working of an accelerometer can be explained by a simple mass (m) attached to a
spring of stiffness (k) that in turn is attached to a casing as illustrated in figure3 The mass used in
accelerometers is often called the seismic-mass or proof-mass In most cases the system also
includes a dashpot to provide a desirable damping effect
The dashpot with damping coefficient (c) is normally attached to the mass in parallel with the
spring When the spring mass system is subjected to linear acceleration a force equal to mass times
acceleration acts on the proof-mass causing it to deflect This deflection is sensed by a suitable
means and converted into an equivalent electrical signal Some form of damping is required
otherwise the system would not stabilize quickly under applied acceleration
To derive the motion equation of the system Newton‟s second law is used where all real forces
acting on the proof-mass are equal to the inertia force on the proof-mass Accordingly a dynamic
problem can be treated as a problem of static equilibrium and the equation of motion can be
obtained by direct formulation of the equations of equilibrium This damped mass-spring system
with applied force constitutes a classical second order mechanical system
312Accelerometer as Gesture Control Sensor
The accelerometer can be used in gesture controlled application As seen the accelerometer sensor measures the physical acceleration experienced by an object due to inertial forces or due to
mechanical excitationSo this means it will give different values for different gestures when
mounted on human handThis can be used as an advantage ieit can be interfaced with any of the
microcontroller or other device and can be used to control any robot or any oher device
313 Key factors while selecting an accelerometer
Some of the Key factors while selecting an accelerometer are
1Analog vs digital Depending on the interface to which you will be connecting the accelerometer
you need to select analog or digital output accelerometer
2Output Accelerometer comes with different outputs-Charge output IEPE output Voltage
output current output
17
3Number of axis Depending on your requirement you need to select single double or tri axis
accelerometer The 3 axis accelerometer will measure acceleration in all directions
4Acceleration range Acceleration Range is measured in units of g 1g is equal to the earths
gravity at sea level
5Sensitivity is the ratio of change in acceleration (input) to change in the output signal Sensitivity
is specified at a particular supply voltage and is typically expressed in units of mVg
314 Applications of Accelerometers
Used in cars to study shock and vibrations
Camcorders use accelerometers for image stabilization
Still cameras use accelerometers for anti-blur capturing
Used in mobile phones for multiple functions including tilt detection motion detectionetc
32 IR SENSOR
The InfraRed receiver transmitter pair is to use be worn around the fingers and controls the opening
and closing of the end effector
321 Introduction
An infrared sensor is an electronic instrument that is used to sense certain characteristics of its
surroundings by either emitting andor detecting infrared radiation It is also capable of measuring
heat of an object and detecting motion Infrared waves are not visible to the human eye
In the electromagnetic spectrum infrared radiation is the region having wavelengths longer than
visible light wavelengths but shorter than microwaves The infrared region is approximately
demarcated from 075 to 1000microm The wavelength region from 075 to 3microm is termed as near
infrared the region from 3 to 6microm is termed mid-infrared and the region higher than 6microm is termed
as far infrared
18
Infrared technology is found in many of our everyday products For example TV has an IR detector
for interpreting the signal from the remote control Key benefits of infrared sensors include low
power requirements simple circuitry and their portable feature
322 Working Principle
A typical system for detecting infrared radiation using infrared sensors includes the infrared source
such as blackbody radiators tungsten lamps and silicon carbide In case of active IR sensors the
sources are infrared lasers and LEDs of specific IR wavelengths Next is the transmission medium
used for infrared transmission which includes vacuum the atmosphere and optical fibers
Thirdly optical components such as optical lenses made from quartz CaF2 Ge and Si polyethylene
Fresnel lenses and Al or Au mirrors are used to converge or focus infrared radiation Likewise to
limit spectral response band-pass filters are ideal
Finally the infrared detector completes the system for detecting infrared radiation The output from
the detector is usually very small and hence pre-amplifiers coupled with circuitry are added to
further process the received signals
Figure 8 Circuit Diagram Of An IR Sensor
19
323 Applications
The following are the key application areas of infrared sensors
Tracking and art history
Climatology meteorology and astronomy
Thermography communications and alcohol testing
Heating hyperspectral imaging and night vision
Biological systems photobiomodulation and plant health
Gas detectorsgas leak detection
Water and steel analysis flame detection
Anesthesiology testing and spectroscopy
Petroleum exploration and underground solution
Rail safety
33 SERVO MOTORS
A servomotor is a rotary actuator that allows for precise control of angular position velocity and
acceleration It consists of a suitable motor coupled to a sensor for position feedback It also requires
a relatively sophisticated controller often a dedicated module designed specifically for use with
servomotors
331 Controlling Of A Servo Motor
Servos are controlled by sending an electrical pulse of variable width or pulse width
modulation (PWM) through the control wire There is a minimum pulse a maximum pulse and a
repetition rate A servo motor can usually only turn 90 degrees in either direction for a total of 180
degree movement The motors neutral position is defined as the position where the servo has the
same amount of potential rotation in the both the clockwise or counter-clockwise direction The
PWM sent to the motor determines position of the shaft and based on the duration of the pulse sent
via the control wire the rotor will turn to the desired position The servo motor expects to see a
pulse every 20 milliseconds (ms) and the length of the pulse will determine how far the motor turns
For example a 15ms pulse will make the motor turn to the 90-degree position Shorter than 15ms
moves it to 0 degrees and any longer than 15ms will turn the servo to 180 degrees as diagramed
below
20
Figure 9 Controlling an servo
332 Types of Servo Motors
There are two types of servo motors - AC and DC AC servo can handle higher current surges and
tend to be used in industrial machinery DC servos are not designed for high current surges and are
usually better suited for smaller applications Generally speaking DC motors are less expensive
than their AC counterparts These are also servo motors that have been built specifically
for continuous rotation making it an easy way to get your robot moving They feature two ball
bearings on the output shaft for reduced friction and easy access to the rest-point
adjustment potentiometer
333Servo Motor Applications
Servos are used in radio-controlled airplanes to position control surfaces like elevators rudders
walking a robot or operating grippers Servo motors are small have built-in control circuitry and
have good power for their size
In food services and pharmaceuticals the tools are designed to be used in harsher environments
where the potential for corrosion is high due to being washed at high pressures and temperatures
repeatedly to maintain strict hygiene standards Servos are also used in in-line manufacturing
where high repetition yet precise work is necessary
21
Of course you dont have to know how a servo works to use one but as with most electronics the
more you understand the more doors open for expanded projects and projects capabilities Whether
youre a hobbyist building robots an engineer designing industrial systems or just constantly
curious where will servo motors take you
334 Specifications
It is highly desirable to control or to maintain a certain location of motor rotor in a robotic arm not
only to determine its precise motion and position but also to control it in desired fashion most of the
industrial robotic arm contains pneumatic hydraulic and stepper motor to actuates they have very
high payload capacity but GuRoo is a low powered high degree of freedom robotic arm we uses
servo motor due their easy availability and high weight to torque ratio
HS-645mg standard deluxe high torque servo
Figure 10HS-475-SERVO
Detailed Specifications of above shown servo
Motor Type 3 Pole
Bearing Type Top Ball Bearing
22
Speed 023 018 sec 60 deg
Torque 44 55 kgcm
Size 3880 x 1980 x 3600mm
Weight 4000g
34 ATMega32
A microcontroller is the brain of the robot The main features of this controller are
Advanced RISC Architecture
Up to 16 MIPS Throughput at 16 MHz
16K Bytes of In-System Self-Programmable Flash
512 Bytes EEPROM
1K Byte Internal SRAM
32 Programmable IO Lines
In-System Programming by On-chip Boot Program
8-channel 10-bit ADC
Two 8-bit TimerCounters with Separate Prescalers and Compare Modes
One 16-bit TimerCounter with Separate Prescaler Compare Mode and Capture
Four PWM Channels
Programmable Serial USART
MasterSlave SPI Serial Interface
Byte-oriented Two-wire Serial Interface
Programmable Watchdog Timer with Separate On-chip Oscillator
External and Internal Interrupt Sources
23
Figure 11 - Pin configuration
CHAPTER 4 METHODOLOGY
The setup consists of a robotic arm having 5 degrees of freedom and 6 servo motors
The movements of the joints are controlled using servo motors that can move a fixed angle ranging from 0 to
180 degrees
Accelerometer 1
ADC of Microcontroller
Servo for wrist movement
24
IR sensor
Microcontroller
Servomotor for gripping
mechanism
Figure121 Flowchart for First Accelerometer
Figure122 Flowchart for second Accelerometer
Figure123 Flowchart for IR sensor
Accelerometer 2
ADC of Microcontroller
Servomotor for elbow
movement
25
Figure124 Flowchart for POTENTIOMETER
Potentiometer
ADC of microcontroller
servomotor for base movement
26
Figure 125 Complete Flow Chart
Complete flow chart depicting each sensor interfaced with microcontroller and the
movement of each and every servos (ie robotic arm)
27
41 SETUP USED amp SCHEMATIC
A setup consisting of
1 IR sensors
2 Two accelerometers and
3 A potentiometer is to be worn around the human hand for sensing the gesture
movements
The InfraRed receiver transmitter pair is to be worn around the fingers and controls the
opening and closing of the end effector
2 accelerometers are used for sensing the movement of the forearm and the wrist movement
A potentiometer is used to track the elbow movement
Figure13 Schematic of the components used
28
Figure 14 Setup Used
29
Figure 151 Linear prediction for wrist movement 1
CHAPTER 5 ALGORITHIM USED
(PREDICTION AND CORRECTION ALGORITHM)
An algorithm has been devised to make the robotic arm replicate the motions of the human arm
The robotic arm does not exactly have an idea of the exact movement of the human arm and takes
input from noisy sensors
The algorithm consists of the following parts
1 LINEAR PREDICTION
The values of the sensors and motors for every joint have been stored for certain predefined
positions for each joint movement The position of the robotic arm is predicted linearly using the
given formulae
119823119851119838119837119842119836119853119838119837 119852119838119851119855119848 119855119834119845119854119838 = (119846120784 minus 119846120783) lowast119842119847119849119854119853 119852119838119847119852119848119851 119855119834119845119854119838 minus 119852120783
(119852120784 minus 119852120783)
-
30
Figure 152 Linear prediction for wrist movement 2
Figure 153 Linear prediction for elbow movement 1
31
Figure 154 Linear prediction for elbow movement 2
m2- predefined value of the servo motor for the next known position
m1- predefined value of the servo motor for the previous known position
s1- predefined sensor value for the last known position
s2- predefined sensor value for the next known position
2) CORRECTION
The predicted value is then compared to the present value and the difference between the two
For each DOF you add the math gets more complicated and the joint weights get heavier We will
also find that shorter arm lengths allow for smaller torque requirements
The above equations only deal with the case where the robot arm is being held horizontally (not in
motion) This is not necessarily the worst case scenario For the arm to move from a rest position
acceleration is required To solve for this added torque it is known that the sum of torques acting at
a pivot point is equal to the moment of inertia (I) multiplied by the angular acceleration (alpha)
T=Ixα
To calculate the extra torque required to move (ie create an angular acceleration) you would
calculate the moment of inertia of the part from the end to the pivot using the equation (or an
equation similar to)
11
I=mr^22
Note this equation calculates the moment of inertia about the center of mass In the case of a robotic
arm the moment of inertia must take into consideration that the part is being rotated about a pivot
point located a distance away from the center of mass and a second term ( +MR2 ) needs to be
added For each joint the moment of inertia is calculated by adding the products of each individual
mass (mi) by the square of its respective length from the pivot (ri) Note that the equation for
calculating the moment of inertia to consider for actuator N omits the mass of the actuator at the
pivot
122 GRIPPER
Jaw torque is the other critical factor when specifying a gripper There are two sources of this
torque torque generated by the gripper on itself and torque generated by the acceleration and
weight of the part These can be addressed separately
Torque from the robotic gripper
Long Jaws are often required Either the part is bulky like an engine block or the part must be held
at a distance to fit in a machine In either case the longer the jaw the greater the torque the gripper
imposes on itself Therefore the torque from the grippers is GRIPPER TORQUE=Gripper Force x
Jaw Length (where jaw length is measured from the face of the gripper to the center of gravity of
the part)
12
Figure 4 Example of Gripper
Gripper Example
If we put 6rdquo long jaws on a gripper with 100 pounds of closing force gripper the jaws will see
Jaw Torque= 100 Pounds x 6rdquo= 600 in-pounds
The rating on the gripper is 840 in-pounds We used the majority of this rating without even
gripping a part because of the length of the jaws
Thus we can see that the length of the jaws plays a major factor in specifying a gripper The next
task is to determine the torque the gripper will experience from the part
CHAPTER 2 GESTURE
21 GESTURE CONTROLLED SYSTEM
Humans naturally use gesture to communicate It has been demonstrated that young children can
readily learn to communicate with gesture before they learn to talk A gesture is non-verbal
communication made with a part of the body We use gesture instead of or in combination with
verbal communication Using this process human can interface with the machine without any
mechanical devices Human movements are typically analyzed by segmenting them into shorter and
understandable format The movements vary person to person It can be used as a command to
control different devices of daily activities mobility etc So our natural or intuitive body
movements or gestures can be used as command or interface to operate machines communicate
with intelligent environments to control home appliances smart home telecare systems etc In this
paper we also review the different types of technologies of gesture controlled system
212 TYPES OF GESTURES
Most of the researches are based on hand gestures Direct control via hand posture is immediate but
limited in the number of Choices There are researches about body gesture finger point movement
In the early stage researchers used gloves with microcontroller and connected with the device
through a wire Head gesture and gesture with voice were also in the research but hand gesture was
the most dominant part of gesture control system
A primary goal of gesture control is to create a system which can identify specific human gestures
and use them to convey information or for device control Gesture recognition can be achieved by
various methods in which popular two are
13
1 Gesture control using any particular sensor
2 Gesture control using image processing
1 Gesture control using any particular sensor
This includes interpreting the human gestures by the use of any particular sensors The most widely
used sensor are accelerometer and gyroscope
We just need to wear a small transmitting device in your hand which included an acceleration
meter(either accelerometer or gyroscope) This will transmit an appropriate command to the robot
so that it can do whatever we want
2 Gesture control using any image processing
This includes following processes or steps
14
Figure 5-(steps for gesture control by image processing)
In our project we our deploying the first method ie gesture control using an
accelerometer sensor
CHAPTER 3 HARDWARE IMPLEMENTATION
31 Accelerometer
An accelerometer is a sensor that measures the physical acceleration experienced by an object due
to inertial forces or due to mechanical excitation In aerospace applications accelerometers are used
along with gyroscopes for navigation guidance and flight control Conceptually an accelerometer
behaves as a damped mass on a spring When the accelerometer experiences acceleration the mass
is displaced and the displacement is then measured to give the acceleration
In these devices piezoelectric piezoresistive and capacitive techniques are commonly used to
convert the mechanical motion into an electrical signal Piezoelectric accelerometers rely on
piezoceramics (eg lead zirconate titanate) or single crystals (eg quartz tourmaline) They are
unmatched in terms of their upper frequency range low packaged weight and high temperature
range Piezoresistive accelerometers are preferred in high shock applications Capacitive
accelerometers performance is superior in low frequency range and they can be operated in servo
mode to achieve high stability and linearity
15
Figure 6 An accelerometer
311 Working principle of accelerometer
16
Figure 7(schematic of an accelerometer)
The principle of working of an accelerometer can be explained by a simple mass (m) attached to a
spring of stiffness (k) that in turn is attached to a casing as illustrated in figure3 The mass used in
accelerometers is often called the seismic-mass or proof-mass In most cases the system also
includes a dashpot to provide a desirable damping effect
The dashpot with damping coefficient (c) is normally attached to the mass in parallel with the
spring When the spring mass system is subjected to linear acceleration a force equal to mass times
acceleration acts on the proof-mass causing it to deflect This deflection is sensed by a suitable
means and converted into an equivalent electrical signal Some form of damping is required
otherwise the system would not stabilize quickly under applied acceleration
To derive the motion equation of the system Newton‟s second law is used where all real forces
acting on the proof-mass are equal to the inertia force on the proof-mass Accordingly a dynamic
problem can be treated as a problem of static equilibrium and the equation of motion can be
obtained by direct formulation of the equations of equilibrium This damped mass-spring system
with applied force constitutes a classical second order mechanical system
312Accelerometer as Gesture Control Sensor
The accelerometer can be used in gesture controlled application As seen the accelerometer sensor measures the physical acceleration experienced by an object due to inertial forces or due to
mechanical excitationSo this means it will give different values for different gestures when
mounted on human handThis can be used as an advantage ieit can be interfaced with any of the
microcontroller or other device and can be used to control any robot or any oher device
313 Key factors while selecting an accelerometer
Some of the Key factors while selecting an accelerometer are
1Analog vs digital Depending on the interface to which you will be connecting the accelerometer
you need to select analog or digital output accelerometer
2Output Accelerometer comes with different outputs-Charge output IEPE output Voltage
output current output
17
3Number of axis Depending on your requirement you need to select single double or tri axis
accelerometer The 3 axis accelerometer will measure acceleration in all directions
4Acceleration range Acceleration Range is measured in units of g 1g is equal to the earths
gravity at sea level
5Sensitivity is the ratio of change in acceleration (input) to change in the output signal Sensitivity
is specified at a particular supply voltage and is typically expressed in units of mVg
314 Applications of Accelerometers
Used in cars to study shock and vibrations
Camcorders use accelerometers for image stabilization
Still cameras use accelerometers for anti-blur capturing
Used in mobile phones for multiple functions including tilt detection motion detectionetc
32 IR SENSOR
The InfraRed receiver transmitter pair is to use be worn around the fingers and controls the opening
and closing of the end effector
321 Introduction
An infrared sensor is an electronic instrument that is used to sense certain characteristics of its
surroundings by either emitting andor detecting infrared radiation It is also capable of measuring
heat of an object and detecting motion Infrared waves are not visible to the human eye
In the electromagnetic spectrum infrared radiation is the region having wavelengths longer than
visible light wavelengths but shorter than microwaves The infrared region is approximately
demarcated from 075 to 1000microm The wavelength region from 075 to 3microm is termed as near
infrared the region from 3 to 6microm is termed mid-infrared and the region higher than 6microm is termed
as far infrared
18
Infrared technology is found in many of our everyday products For example TV has an IR detector
for interpreting the signal from the remote control Key benefits of infrared sensors include low
power requirements simple circuitry and their portable feature
322 Working Principle
A typical system for detecting infrared radiation using infrared sensors includes the infrared source
such as blackbody radiators tungsten lamps and silicon carbide In case of active IR sensors the
sources are infrared lasers and LEDs of specific IR wavelengths Next is the transmission medium
used for infrared transmission which includes vacuum the atmosphere and optical fibers
Thirdly optical components such as optical lenses made from quartz CaF2 Ge and Si polyethylene
Fresnel lenses and Al or Au mirrors are used to converge or focus infrared radiation Likewise to
limit spectral response band-pass filters are ideal
Finally the infrared detector completes the system for detecting infrared radiation The output from
the detector is usually very small and hence pre-amplifiers coupled with circuitry are added to
further process the received signals
Figure 8 Circuit Diagram Of An IR Sensor
19
323 Applications
The following are the key application areas of infrared sensors
Tracking and art history
Climatology meteorology and astronomy
Thermography communications and alcohol testing
Heating hyperspectral imaging and night vision
Biological systems photobiomodulation and plant health
Gas detectorsgas leak detection
Water and steel analysis flame detection
Anesthesiology testing and spectroscopy
Petroleum exploration and underground solution
Rail safety
33 SERVO MOTORS
A servomotor is a rotary actuator that allows for precise control of angular position velocity and
acceleration It consists of a suitable motor coupled to a sensor for position feedback It also requires
a relatively sophisticated controller often a dedicated module designed specifically for use with
servomotors
331 Controlling Of A Servo Motor
Servos are controlled by sending an electrical pulse of variable width or pulse width
modulation (PWM) through the control wire There is a minimum pulse a maximum pulse and a
repetition rate A servo motor can usually only turn 90 degrees in either direction for a total of 180
degree movement The motors neutral position is defined as the position where the servo has the
same amount of potential rotation in the both the clockwise or counter-clockwise direction The
PWM sent to the motor determines position of the shaft and based on the duration of the pulse sent
via the control wire the rotor will turn to the desired position The servo motor expects to see a
pulse every 20 milliseconds (ms) and the length of the pulse will determine how far the motor turns
For example a 15ms pulse will make the motor turn to the 90-degree position Shorter than 15ms
moves it to 0 degrees and any longer than 15ms will turn the servo to 180 degrees as diagramed
below
20
Figure 9 Controlling an servo
332 Types of Servo Motors
There are two types of servo motors - AC and DC AC servo can handle higher current surges and
tend to be used in industrial machinery DC servos are not designed for high current surges and are
usually better suited for smaller applications Generally speaking DC motors are less expensive
than their AC counterparts These are also servo motors that have been built specifically
for continuous rotation making it an easy way to get your robot moving They feature two ball
bearings on the output shaft for reduced friction and easy access to the rest-point
adjustment potentiometer
333Servo Motor Applications
Servos are used in radio-controlled airplanes to position control surfaces like elevators rudders
walking a robot or operating grippers Servo motors are small have built-in control circuitry and
have good power for their size
In food services and pharmaceuticals the tools are designed to be used in harsher environments
where the potential for corrosion is high due to being washed at high pressures and temperatures
repeatedly to maintain strict hygiene standards Servos are also used in in-line manufacturing
where high repetition yet precise work is necessary
21
Of course you dont have to know how a servo works to use one but as with most electronics the
more you understand the more doors open for expanded projects and projects capabilities Whether
youre a hobbyist building robots an engineer designing industrial systems or just constantly
curious where will servo motors take you
334 Specifications
It is highly desirable to control or to maintain a certain location of motor rotor in a robotic arm not
only to determine its precise motion and position but also to control it in desired fashion most of the
industrial robotic arm contains pneumatic hydraulic and stepper motor to actuates they have very
high payload capacity but GuRoo is a low powered high degree of freedom robotic arm we uses
servo motor due their easy availability and high weight to torque ratio
HS-645mg standard deluxe high torque servo
Figure 10HS-475-SERVO
Detailed Specifications of above shown servo
Motor Type 3 Pole
Bearing Type Top Ball Bearing
22
Speed 023 018 sec 60 deg
Torque 44 55 kgcm
Size 3880 x 1980 x 3600mm
Weight 4000g
34 ATMega32
A microcontroller is the brain of the robot The main features of this controller are
Advanced RISC Architecture
Up to 16 MIPS Throughput at 16 MHz
16K Bytes of In-System Self-Programmable Flash
512 Bytes EEPROM
1K Byte Internal SRAM
32 Programmable IO Lines
In-System Programming by On-chip Boot Program
8-channel 10-bit ADC
Two 8-bit TimerCounters with Separate Prescalers and Compare Modes
One 16-bit TimerCounter with Separate Prescaler Compare Mode and Capture
Four PWM Channels
Programmable Serial USART
MasterSlave SPI Serial Interface
Byte-oriented Two-wire Serial Interface
Programmable Watchdog Timer with Separate On-chip Oscillator
External and Internal Interrupt Sources
23
Figure 11 - Pin configuration
CHAPTER 4 METHODOLOGY
The setup consists of a robotic arm having 5 degrees of freedom and 6 servo motors
The movements of the joints are controlled using servo motors that can move a fixed angle ranging from 0 to
180 degrees
Accelerometer 1
ADC of Microcontroller
Servo for wrist movement
24
IR sensor
Microcontroller
Servomotor for gripping
mechanism
Figure121 Flowchart for First Accelerometer
Figure122 Flowchart for second Accelerometer
Figure123 Flowchart for IR sensor
Accelerometer 2
ADC of Microcontroller
Servomotor for elbow
movement
25
Figure124 Flowchart for POTENTIOMETER
Potentiometer
ADC of microcontroller
servomotor for base movement
26
Figure 125 Complete Flow Chart
Complete flow chart depicting each sensor interfaced with microcontroller and the
movement of each and every servos (ie robotic arm)
27
41 SETUP USED amp SCHEMATIC
A setup consisting of
1 IR sensors
2 Two accelerometers and
3 A potentiometer is to be worn around the human hand for sensing the gesture
movements
The InfraRed receiver transmitter pair is to be worn around the fingers and controls the
opening and closing of the end effector
2 accelerometers are used for sensing the movement of the forearm and the wrist movement
A potentiometer is used to track the elbow movement
Figure13 Schematic of the components used
28
Figure 14 Setup Used
29
Figure 151 Linear prediction for wrist movement 1
CHAPTER 5 ALGORITHIM USED
(PREDICTION AND CORRECTION ALGORITHM)
An algorithm has been devised to make the robotic arm replicate the motions of the human arm
The robotic arm does not exactly have an idea of the exact movement of the human arm and takes
input from noisy sensors
The algorithm consists of the following parts
1 LINEAR PREDICTION
The values of the sensors and motors for every joint have been stored for certain predefined
positions for each joint movement The position of the robotic arm is predicted linearly using the
given formulae
119823119851119838119837119842119836119853119838119837 119852119838119851119855119848 119855119834119845119854119838 = (119846120784 minus 119846120783) lowast119842119847119849119854119853 119852119838119847119852119848119851 119855119834119845119854119838 minus 119852120783
(119852120784 minus 119852120783)
-
30
Figure 152 Linear prediction for wrist movement 2
Figure 153 Linear prediction for elbow movement 1
31
Figure 154 Linear prediction for elbow movement 2
m2- predefined value of the servo motor for the next known position
m1- predefined value of the servo motor for the previous known position
s1- predefined sensor value for the last known position
s2- predefined sensor value for the next known position
2) CORRECTION
The predicted value is then compared to the present value and the difference between the two
For each DOF you add the math gets more complicated and the joint weights get heavier We will
also find that shorter arm lengths allow for smaller torque requirements
The above equations only deal with the case where the robot arm is being held horizontally (not in
motion) This is not necessarily the worst case scenario For the arm to move from a rest position
acceleration is required To solve for this added torque it is known that the sum of torques acting at
a pivot point is equal to the moment of inertia (I) multiplied by the angular acceleration (alpha)
T=Ixα
To calculate the extra torque required to move (ie create an angular acceleration) you would
calculate the moment of inertia of the part from the end to the pivot using the equation (or an
equation similar to)
11
I=mr^22
Note this equation calculates the moment of inertia about the center of mass In the case of a robotic
arm the moment of inertia must take into consideration that the part is being rotated about a pivot
point located a distance away from the center of mass and a second term ( +MR2 ) needs to be
added For each joint the moment of inertia is calculated by adding the products of each individual
mass (mi) by the square of its respective length from the pivot (ri) Note that the equation for
calculating the moment of inertia to consider for actuator N omits the mass of the actuator at the
pivot
122 GRIPPER
Jaw torque is the other critical factor when specifying a gripper There are two sources of this
torque torque generated by the gripper on itself and torque generated by the acceleration and
weight of the part These can be addressed separately
Torque from the robotic gripper
Long Jaws are often required Either the part is bulky like an engine block or the part must be held
at a distance to fit in a machine In either case the longer the jaw the greater the torque the gripper
imposes on itself Therefore the torque from the grippers is GRIPPER TORQUE=Gripper Force x
Jaw Length (where jaw length is measured from the face of the gripper to the center of gravity of
the part)
12
Figure 4 Example of Gripper
Gripper Example
If we put 6rdquo long jaws on a gripper with 100 pounds of closing force gripper the jaws will see
Jaw Torque= 100 Pounds x 6rdquo= 600 in-pounds
The rating on the gripper is 840 in-pounds We used the majority of this rating without even
gripping a part because of the length of the jaws
Thus we can see that the length of the jaws plays a major factor in specifying a gripper The next
task is to determine the torque the gripper will experience from the part
CHAPTER 2 GESTURE
21 GESTURE CONTROLLED SYSTEM
Humans naturally use gesture to communicate It has been demonstrated that young children can
readily learn to communicate with gesture before they learn to talk A gesture is non-verbal
communication made with a part of the body We use gesture instead of or in combination with
verbal communication Using this process human can interface with the machine without any
mechanical devices Human movements are typically analyzed by segmenting them into shorter and
understandable format The movements vary person to person It can be used as a command to
control different devices of daily activities mobility etc So our natural or intuitive body
movements or gestures can be used as command or interface to operate machines communicate
with intelligent environments to control home appliances smart home telecare systems etc In this
paper we also review the different types of technologies of gesture controlled system
212 TYPES OF GESTURES
Most of the researches are based on hand gestures Direct control via hand posture is immediate but
limited in the number of Choices There are researches about body gesture finger point movement
In the early stage researchers used gloves with microcontroller and connected with the device
through a wire Head gesture and gesture with voice were also in the research but hand gesture was
the most dominant part of gesture control system
A primary goal of gesture control is to create a system which can identify specific human gestures
and use them to convey information or for device control Gesture recognition can be achieved by
various methods in which popular two are
13
1 Gesture control using any particular sensor
2 Gesture control using image processing
1 Gesture control using any particular sensor
This includes interpreting the human gestures by the use of any particular sensors The most widely
used sensor are accelerometer and gyroscope
We just need to wear a small transmitting device in your hand which included an acceleration
meter(either accelerometer or gyroscope) This will transmit an appropriate command to the robot
so that it can do whatever we want
2 Gesture control using any image processing
This includes following processes or steps
14
Figure 5-(steps for gesture control by image processing)
In our project we our deploying the first method ie gesture control using an
accelerometer sensor
CHAPTER 3 HARDWARE IMPLEMENTATION
31 Accelerometer
An accelerometer is a sensor that measures the physical acceleration experienced by an object due
to inertial forces or due to mechanical excitation In aerospace applications accelerometers are used
along with gyroscopes for navigation guidance and flight control Conceptually an accelerometer
behaves as a damped mass on a spring When the accelerometer experiences acceleration the mass
is displaced and the displacement is then measured to give the acceleration
In these devices piezoelectric piezoresistive and capacitive techniques are commonly used to
convert the mechanical motion into an electrical signal Piezoelectric accelerometers rely on
piezoceramics (eg lead zirconate titanate) or single crystals (eg quartz tourmaline) They are
unmatched in terms of their upper frequency range low packaged weight and high temperature
range Piezoresistive accelerometers are preferred in high shock applications Capacitive
accelerometers performance is superior in low frequency range and they can be operated in servo
mode to achieve high stability and linearity
15
Figure 6 An accelerometer
311 Working principle of accelerometer
16
Figure 7(schematic of an accelerometer)
The principle of working of an accelerometer can be explained by a simple mass (m) attached to a
spring of stiffness (k) that in turn is attached to a casing as illustrated in figure3 The mass used in
accelerometers is often called the seismic-mass or proof-mass In most cases the system also
includes a dashpot to provide a desirable damping effect
The dashpot with damping coefficient (c) is normally attached to the mass in parallel with the
spring When the spring mass system is subjected to linear acceleration a force equal to mass times
acceleration acts on the proof-mass causing it to deflect This deflection is sensed by a suitable
means and converted into an equivalent electrical signal Some form of damping is required
otherwise the system would not stabilize quickly under applied acceleration
To derive the motion equation of the system Newton‟s second law is used where all real forces
acting on the proof-mass are equal to the inertia force on the proof-mass Accordingly a dynamic
problem can be treated as a problem of static equilibrium and the equation of motion can be
obtained by direct formulation of the equations of equilibrium This damped mass-spring system
with applied force constitutes a classical second order mechanical system
312Accelerometer as Gesture Control Sensor
The accelerometer can be used in gesture controlled application As seen the accelerometer sensor measures the physical acceleration experienced by an object due to inertial forces or due to
mechanical excitationSo this means it will give different values for different gestures when
mounted on human handThis can be used as an advantage ieit can be interfaced with any of the
microcontroller or other device and can be used to control any robot or any oher device
313 Key factors while selecting an accelerometer
Some of the Key factors while selecting an accelerometer are
1Analog vs digital Depending on the interface to which you will be connecting the accelerometer
you need to select analog or digital output accelerometer
2Output Accelerometer comes with different outputs-Charge output IEPE output Voltage
output current output
17
3Number of axis Depending on your requirement you need to select single double or tri axis
accelerometer The 3 axis accelerometer will measure acceleration in all directions
4Acceleration range Acceleration Range is measured in units of g 1g is equal to the earths
gravity at sea level
5Sensitivity is the ratio of change in acceleration (input) to change in the output signal Sensitivity
is specified at a particular supply voltage and is typically expressed in units of mVg
314 Applications of Accelerometers
Used in cars to study shock and vibrations
Camcorders use accelerometers for image stabilization
Still cameras use accelerometers for anti-blur capturing
Used in mobile phones for multiple functions including tilt detection motion detectionetc
32 IR SENSOR
The InfraRed receiver transmitter pair is to use be worn around the fingers and controls the opening
and closing of the end effector
321 Introduction
An infrared sensor is an electronic instrument that is used to sense certain characteristics of its
surroundings by either emitting andor detecting infrared radiation It is also capable of measuring
heat of an object and detecting motion Infrared waves are not visible to the human eye
In the electromagnetic spectrum infrared radiation is the region having wavelengths longer than
visible light wavelengths but shorter than microwaves The infrared region is approximately
demarcated from 075 to 1000microm The wavelength region from 075 to 3microm is termed as near
infrared the region from 3 to 6microm is termed mid-infrared and the region higher than 6microm is termed
as far infrared
18
Infrared technology is found in many of our everyday products For example TV has an IR detector
for interpreting the signal from the remote control Key benefits of infrared sensors include low
power requirements simple circuitry and their portable feature
322 Working Principle
A typical system for detecting infrared radiation using infrared sensors includes the infrared source
such as blackbody radiators tungsten lamps and silicon carbide In case of active IR sensors the
sources are infrared lasers and LEDs of specific IR wavelengths Next is the transmission medium
used for infrared transmission which includes vacuum the atmosphere and optical fibers
Thirdly optical components such as optical lenses made from quartz CaF2 Ge and Si polyethylene
Fresnel lenses and Al or Au mirrors are used to converge or focus infrared radiation Likewise to
limit spectral response band-pass filters are ideal
Finally the infrared detector completes the system for detecting infrared radiation The output from
the detector is usually very small and hence pre-amplifiers coupled with circuitry are added to
further process the received signals
Figure 8 Circuit Diagram Of An IR Sensor
19
323 Applications
The following are the key application areas of infrared sensors
Tracking and art history
Climatology meteorology and astronomy
Thermography communications and alcohol testing
Heating hyperspectral imaging and night vision
Biological systems photobiomodulation and plant health
Gas detectorsgas leak detection
Water and steel analysis flame detection
Anesthesiology testing and spectroscopy
Petroleum exploration and underground solution
Rail safety
33 SERVO MOTORS
A servomotor is a rotary actuator that allows for precise control of angular position velocity and
acceleration It consists of a suitable motor coupled to a sensor for position feedback It also requires
a relatively sophisticated controller often a dedicated module designed specifically for use with
servomotors
331 Controlling Of A Servo Motor
Servos are controlled by sending an electrical pulse of variable width or pulse width
modulation (PWM) through the control wire There is a minimum pulse a maximum pulse and a
repetition rate A servo motor can usually only turn 90 degrees in either direction for a total of 180
degree movement The motors neutral position is defined as the position where the servo has the
same amount of potential rotation in the both the clockwise or counter-clockwise direction The
PWM sent to the motor determines position of the shaft and based on the duration of the pulse sent
via the control wire the rotor will turn to the desired position The servo motor expects to see a
pulse every 20 milliseconds (ms) and the length of the pulse will determine how far the motor turns
For example a 15ms pulse will make the motor turn to the 90-degree position Shorter than 15ms
moves it to 0 degrees and any longer than 15ms will turn the servo to 180 degrees as diagramed
below
20
Figure 9 Controlling an servo
332 Types of Servo Motors
There are two types of servo motors - AC and DC AC servo can handle higher current surges and
tend to be used in industrial machinery DC servos are not designed for high current surges and are
usually better suited for smaller applications Generally speaking DC motors are less expensive
than their AC counterparts These are also servo motors that have been built specifically
for continuous rotation making it an easy way to get your robot moving They feature two ball
bearings on the output shaft for reduced friction and easy access to the rest-point
adjustment potentiometer
333Servo Motor Applications
Servos are used in radio-controlled airplanes to position control surfaces like elevators rudders
walking a robot or operating grippers Servo motors are small have built-in control circuitry and
have good power for their size
In food services and pharmaceuticals the tools are designed to be used in harsher environments
where the potential for corrosion is high due to being washed at high pressures and temperatures
repeatedly to maintain strict hygiene standards Servos are also used in in-line manufacturing
where high repetition yet precise work is necessary
21
Of course you dont have to know how a servo works to use one but as with most electronics the
more you understand the more doors open for expanded projects and projects capabilities Whether
youre a hobbyist building robots an engineer designing industrial systems or just constantly
curious where will servo motors take you
334 Specifications
It is highly desirable to control or to maintain a certain location of motor rotor in a robotic arm not
only to determine its precise motion and position but also to control it in desired fashion most of the
industrial robotic arm contains pneumatic hydraulic and stepper motor to actuates they have very
high payload capacity but GuRoo is a low powered high degree of freedom robotic arm we uses
servo motor due their easy availability and high weight to torque ratio
HS-645mg standard deluxe high torque servo
Figure 10HS-475-SERVO
Detailed Specifications of above shown servo
Motor Type 3 Pole
Bearing Type Top Ball Bearing
22
Speed 023 018 sec 60 deg
Torque 44 55 kgcm
Size 3880 x 1980 x 3600mm
Weight 4000g
34 ATMega32
A microcontroller is the brain of the robot The main features of this controller are
Advanced RISC Architecture
Up to 16 MIPS Throughput at 16 MHz
16K Bytes of In-System Self-Programmable Flash
512 Bytes EEPROM
1K Byte Internal SRAM
32 Programmable IO Lines
In-System Programming by On-chip Boot Program
8-channel 10-bit ADC
Two 8-bit TimerCounters with Separate Prescalers and Compare Modes
One 16-bit TimerCounter with Separate Prescaler Compare Mode and Capture
Four PWM Channels
Programmable Serial USART
MasterSlave SPI Serial Interface
Byte-oriented Two-wire Serial Interface
Programmable Watchdog Timer with Separate On-chip Oscillator
External and Internal Interrupt Sources
23
Figure 11 - Pin configuration
CHAPTER 4 METHODOLOGY
The setup consists of a robotic arm having 5 degrees of freedom and 6 servo motors
The movements of the joints are controlled using servo motors that can move a fixed angle ranging from 0 to
180 degrees
Accelerometer 1
ADC of Microcontroller
Servo for wrist movement
24
IR sensor
Microcontroller
Servomotor for gripping
mechanism
Figure121 Flowchart for First Accelerometer
Figure122 Flowchart for second Accelerometer
Figure123 Flowchart for IR sensor
Accelerometer 2
ADC of Microcontroller
Servomotor for elbow
movement
25
Figure124 Flowchart for POTENTIOMETER
Potentiometer
ADC of microcontroller
servomotor for base movement
26
Figure 125 Complete Flow Chart
Complete flow chart depicting each sensor interfaced with microcontroller and the
movement of each and every servos (ie robotic arm)
27
41 SETUP USED amp SCHEMATIC
A setup consisting of
1 IR sensors
2 Two accelerometers and
3 A potentiometer is to be worn around the human hand for sensing the gesture
movements
The InfraRed receiver transmitter pair is to be worn around the fingers and controls the
opening and closing of the end effector
2 accelerometers are used for sensing the movement of the forearm and the wrist movement
A potentiometer is used to track the elbow movement
Figure13 Schematic of the components used
28
Figure 14 Setup Used
29
Figure 151 Linear prediction for wrist movement 1
CHAPTER 5 ALGORITHIM USED
(PREDICTION AND CORRECTION ALGORITHM)
An algorithm has been devised to make the robotic arm replicate the motions of the human arm
The robotic arm does not exactly have an idea of the exact movement of the human arm and takes
input from noisy sensors
The algorithm consists of the following parts
1 LINEAR PREDICTION
The values of the sensors and motors for every joint have been stored for certain predefined
positions for each joint movement The position of the robotic arm is predicted linearly using the
given formulae
119823119851119838119837119842119836119853119838119837 119852119838119851119855119848 119855119834119845119854119838 = (119846120784 minus 119846120783) lowast119842119847119849119854119853 119852119838119847119852119848119851 119855119834119845119854119838 minus 119852120783
(119852120784 minus 119852120783)
-
30
Figure 152 Linear prediction for wrist movement 2
Figure 153 Linear prediction for elbow movement 1
31
Figure 154 Linear prediction for elbow movement 2
m2- predefined value of the servo motor for the next known position
m1- predefined value of the servo motor for the previous known position
s1- predefined sensor value for the last known position
s2- predefined sensor value for the next known position
2) CORRECTION
The predicted value is then compared to the present value and the difference between the two
For each DOF you add the math gets more complicated and the joint weights get heavier We will
also find that shorter arm lengths allow for smaller torque requirements
The above equations only deal with the case where the robot arm is being held horizontally (not in
motion) This is not necessarily the worst case scenario For the arm to move from a rest position
acceleration is required To solve for this added torque it is known that the sum of torques acting at
a pivot point is equal to the moment of inertia (I) multiplied by the angular acceleration (alpha)
T=Ixα
To calculate the extra torque required to move (ie create an angular acceleration) you would
calculate the moment of inertia of the part from the end to the pivot using the equation (or an
equation similar to)
11
I=mr^22
Note this equation calculates the moment of inertia about the center of mass In the case of a robotic
arm the moment of inertia must take into consideration that the part is being rotated about a pivot
point located a distance away from the center of mass and a second term ( +MR2 ) needs to be
added For each joint the moment of inertia is calculated by adding the products of each individual
mass (mi) by the square of its respective length from the pivot (ri) Note that the equation for
calculating the moment of inertia to consider for actuator N omits the mass of the actuator at the
pivot
122 GRIPPER
Jaw torque is the other critical factor when specifying a gripper There are two sources of this
torque torque generated by the gripper on itself and torque generated by the acceleration and
weight of the part These can be addressed separately
Torque from the robotic gripper
Long Jaws are often required Either the part is bulky like an engine block or the part must be held
at a distance to fit in a machine In either case the longer the jaw the greater the torque the gripper
imposes on itself Therefore the torque from the grippers is GRIPPER TORQUE=Gripper Force x
Jaw Length (where jaw length is measured from the face of the gripper to the center of gravity of
the part)
12
Figure 4 Example of Gripper
Gripper Example
If we put 6rdquo long jaws on a gripper with 100 pounds of closing force gripper the jaws will see
Jaw Torque= 100 Pounds x 6rdquo= 600 in-pounds
The rating on the gripper is 840 in-pounds We used the majority of this rating without even
gripping a part because of the length of the jaws
Thus we can see that the length of the jaws plays a major factor in specifying a gripper The next
task is to determine the torque the gripper will experience from the part
CHAPTER 2 GESTURE
21 GESTURE CONTROLLED SYSTEM
Humans naturally use gesture to communicate It has been demonstrated that young children can
readily learn to communicate with gesture before they learn to talk A gesture is non-verbal
communication made with a part of the body We use gesture instead of or in combination with
verbal communication Using this process human can interface with the machine without any
mechanical devices Human movements are typically analyzed by segmenting them into shorter and
understandable format The movements vary person to person It can be used as a command to
control different devices of daily activities mobility etc So our natural or intuitive body
movements or gestures can be used as command or interface to operate machines communicate
with intelligent environments to control home appliances smart home telecare systems etc In this
paper we also review the different types of technologies of gesture controlled system
212 TYPES OF GESTURES
Most of the researches are based on hand gestures Direct control via hand posture is immediate but
limited in the number of Choices There are researches about body gesture finger point movement
In the early stage researchers used gloves with microcontroller and connected with the device
through a wire Head gesture and gesture with voice were also in the research but hand gesture was
the most dominant part of gesture control system
A primary goal of gesture control is to create a system which can identify specific human gestures
and use them to convey information or for device control Gesture recognition can be achieved by
various methods in which popular two are
13
1 Gesture control using any particular sensor
2 Gesture control using image processing
1 Gesture control using any particular sensor
This includes interpreting the human gestures by the use of any particular sensors The most widely
used sensor are accelerometer and gyroscope
We just need to wear a small transmitting device in your hand which included an acceleration
meter(either accelerometer or gyroscope) This will transmit an appropriate command to the robot
so that it can do whatever we want
2 Gesture control using any image processing
This includes following processes or steps
14
Figure 5-(steps for gesture control by image processing)
In our project we our deploying the first method ie gesture control using an
accelerometer sensor
CHAPTER 3 HARDWARE IMPLEMENTATION
31 Accelerometer
An accelerometer is a sensor that measures the physical acceleration experienced by an object due
to inertial forces or due to mechanical excitation In aerospace applications accelerometers are used
along with gyroscopes for navigation guidance and flight control Conceptually an accelerometer
behaves as a damped mass on a spring When the accelerometer experiences acceleration the mass
is displaced and the displacement is then measured to give the acceleration
In these devices piezoelectric piezoresistive and capacitive techniques are commonly used to
convert the mechanical motion into an electrical signal Piezoelectric accelerometers rely on
piezoceramics (eg lead zirconate titanate) or single crystals (eg quartz tourmaline) They are
unmatched in terms of their upper frequency range low packaged weight and high temperature
range Piezoresistive accelerometers are preferred in high shock applications Capacitive
accelerometers performance is superior in low frequency range and they can be operated in servo
mode to achieve high stability and linearity
15
Figure 6 An accelerometer
311 Working principle of accelerometer
16
Figure 7(schematic of an accelerometer)
The principle of working of an accelerometer can be explained by a simple mass (m) attached to a
spring of stiffness (k) that in turn is attached to a casing as illustrated in figure3 The mass used in
accelerometers is often called the seismic-mass or proof-mass In most cases the system also
includes a dashpot to provide a desirable damping effect
The dashpot with damping coefficient (c) is normally attached to the mass in parallel with the
spring When the spring mass system is subjected to linear acceleration a force equal to mass times
acceleration acts on the proof-mass causing it to deflect This deflection is sensed by a suitable
means and converted into an equivalent electrical signal Some form of damping is required
otherwise the system would not stabilize quickly under applied acceleration
To derive the motion equation of the system Newton‟s second law is used where all real forces
acting on the proof-mass are equal to the inertia force on the proof-mass Accordingly a dynamic
problem can be treated as a problem of static equilibrium and the equation of motion can be
obtained by direct formulation of the equations of equilibrium This damped mass-spring system
with applied force constitutes a classical second order mechanical system
312Accelerometer as Gesture Control Sensor
The accelerometer can be used in gesture controlled application As seen the accelerometer sensor measures the physical acceleration experienced by an object due to inertial forces or due to
mechanical excitationSo this means it will give different values for different gestures when
mounted on human handThis can be used as an advantage ieit can be interfaced with any of the
microcontroller or other device and can be used to control any robot or any oher device
313 Key factors while selecting an accelerometer
Some of the Key factors while selecting an accelerometer are
1Analog vs digital Depending on the interface to which you will be connecting the accelerometer
you need to select analog or digital output accelerometer
2Output Accelerometer comes with different outputs-Charge output IEPE output Voltage
output current output
17
3Number of axis Depending on your requirement you need to select single double or tri axis
accelerometer The 3 axis accelerometer will measure acceleration in all directions
4Acceleration range Acceleration Range is measured in units of g 1g is equal to the earths
gravity at sea level
5Sensitivity is the ratio of change in acceleration (input) to change in the output signal Sensitivity
is specified at a particular supply voltage and is typically expressed in units of mVg
314 Applications of Accelerometers
Used in cars to study shock and vibrations
Camcorders use accelerometers for image stabilization
Still cameras use accelerometers for anti-blur capturing
Used in mobile phones for multiple functions including tilt detection motion detectionetc
32 IR SENSOR
The InfraRed receiver transmitter pair is to use be worn around the fingers and controls the opening
and closing of the end effector
321 Introduction
An infrared sensor is an electronic instrument that is used to sense certain characteristics of its
surroundings by either emitting andor detecting infrared radiation It is also capable of measuring
heat of an object and detecting motion Infrared waves are not visible to the human eye
In the electromagnetic spectrum infrared radiation is the region having wavelengths longer than
visible light wavelengths but shorter than microwaves The infrared region is approximately
demarcated from 075 to 1000microm The wavelength region from 075 to 3microm is termed as near
infrared the region from 3 to 6microm is termed mid-infrared and the region higher than 6microm is termed
as far infrared
18
Infrared technology is found in many of our everyday products For example TV has an IR detector
for interpreting the signal from the remote control Key benefits of infrared sensors include low
power requirements simple circuitry and their portable feature
322 Working Principle
A typical system for detecting infrared radiation using infrared sensors includes the infrared source
such as blackbody radiators tungsten lamps and silicon carbide In case of active IR sensors the
sources are infrared lasers and LEDs of specific IR wavelengths Next is the transmission medium
used for infrared transmission which includes vacuum the atmosphere and optical fibers
Thirdly optical components such as optical lenses made from quartz CaF2 Ge and Si polyethylene
Fresnel lenses and Al or Au mirrors are used to converge or focus infrared radiation Likewise to
limit spectral response band-pass filters are ideal
Finally the infrared detector completes the system for detecting infrared radiation The output from
the detector is usually very small and hence pre-amplifiers coupled with circuitry are added to
further process the received signals
Figure 8 Circuit Diagram Of An IR Sensor
19
323 Applications
The following are the key application areas of infrared sensors
Tracking and art history
Climatology meteorology and astronomy
Thermography communications and alcohol testing
Heating hyperspectral imaging and night vision
Biological systems photobiomodulation and plant health
Gas detectorsgas leak detection
Water and steel analysis flame detection
Anesthesiology testing and spectroscopy
Petroleum exploration and underground solution
Rail safety
33 SERVO MOTORS
A servomotor is a rotary actuator that allows for precise control of angular position velocity and
acceleration It consists of a suitable motor coupled to a sensor for position feedback It also requires
a relatively sophisticated controller often a dedicated module designed specifically for use with
servomotors
331 Controlling Of A Servo Motor
Servos are controlled by sending an electrical pulse of variable width or pulse width
modulation (PWM) through the control wire There is a minimum pulse a maximum pulse and a
repetition rate A servo motor can usually only turn 90 degrees in either direction for a total of 180
degree movement The motors neutral position is defined as the position where the servo has the
same amount of potential rotation in the both the clockwise or counter-clockwise direction The
PWM sent to the motor determines position of the shaft and based on the duration of the pulse sent
via the control wire the rotor will turn to the desired position The servo motor expects to see a
pulse every 20 milliseconds (ms) and the length of the pulse will determine how far the motor turns
For example a 15ms pulse will make the motor turn to the 90-degree position Shorter than 15ms
moves it to 0 degrees and any longer than 15ms will turn the servo to 180 degrees as diagramed
below
20
Figure 9 Controlling an servo
332 Types of Servo Motors
There are two types of servo motors - AC and DC AC servo can handle higher current surges and
tend to be used in industrial machinery DC servos are not designed for high current surges and are
usually better suited for smaller applications Generally speaking DC motors are less expensive
than their AC counterparts These are also servo motors that have been built specifically
for continuous rotation making it an easy way to get your robot moving They feature two ball
bearings on the output shaft for reduced friction and easy access to the rest-point
adjustment potentiometer
333Servo Motor Applications
Servos are used in radio-controlled airplanes to position control surfaces like elevators rudders
walking a robot or operating grippers Servo motors are small have built-in control circuitry and
have good power for their size
In food services and pharmaceuticals the tools are designed to be used in harsher environments
where the potential for corrosion is high due to being washed at high pressures and temperatures
repeatedly to maintain strict hygiene standards Servos are also used in in-line manufacturing
where high repetition yet precise work is necessary
21
Of course you dont have to know how a servo works to use one but as with most electronics the
more you understand the more doors open for expanded projects and projects capabilities Whether
youre a hobbyist building robots an engineer designing industrial systems or just constantly
curious where will servo motors take you
334 Specifications
It is highly desirable to control or to maintain a certain location of motor rotor in a robotic arm not
only to determine its precise motion and position but also to control it in desired fashion most of the
industrial robotic arm contains pneumatic hydraulic and stepper motor to actuates they have very
high payload capacity but GuRoo is a low powered high degree of freedom robotic arm we uses
servo motor due their easy availability and high weight to torque ratio
HS-645mg standard deluxe high torque servo
Figure 10HS-475-SERVO
Detailed Specifications of above shown servo
Motor Type 3 Pole
Bearing Type Top Ball Bearing
22
Speed 023 018 sec 60 deg
Torque 44 55 kgcm
Size 3880 x 1980 x 3600mm
Weight 4000g
34 ATMega32
A microcontroller is the brain of the robot The main features of this controller are
Advanced RISC Architecture
Up to 16 MIPS Throughput at 16 MHz
16K Bytes of In-System Self-Programmable Flash
512 Bytes EEPROM
1K Byte Internal SRAM
32 Programmable IO Lines
In-System Programming by On-chip Boot Program
8-channel 10-bit ADC
Two 8-bit TimerCounters with Separate Prescalers and Compare Modes
One 16-bit TimerCounter with Separate Prescaler Compare Mode and Capture
Four PWM Channels
Programmable Serial USART
MasterSlave SPI Serial Interface
Byte-oriented Two-wire Serial Interface
Programmable Watchdog Timer with Separate On-chip Oscillator
External and Internal Interrupt Sources
23
Figure 11 - Pin configuration
CHAPTER 4 METHODOLOGY
The setup consists of a robotic arm having 5 degrees of freedom and 6 servo motors
The movements of the joints are controlled using servo motors that can move a fixed angle ranging from 0 to
180 degrees
Accelerometer 1
ADC of Microcontroller
Servo for wrist movement
24
IR sensor
Microcontroller
Servomotor for gripping
mechanism
Figure121 Flowchart for First Accelerometer
Figure122 Flowchart for second Accelerometer
Figure123 Flowchart for IR sensor
Accelerometer 2
ADC of Microcontroller
Servomotor for elbow
movement
25
Figure124 Flowchart for POTENTIOMETER
Potentiometer
ADC of microcontroller
servomotor for base movement
26
Figure 125 Complete Flow Chart
Complete flow chart depicting each sensor interfaced with microcontroller and the
movement of each and every servos (ie robotic arm)
27
41 SETUP USED amp SCHEMATIC
A setup consisting of
1 IR sensors
2 Two accelerometers and
3 A potentiometer is to be worn around the human hand for sensing the gesture
movements
The InfraRed receiver transmitter pair is to be worn around the fingers and controls the
opening and closing of the end effector
2 accelerometers are used for sensing the movement of the forearm and the wrist movement
A potentiometer is used to track the elbow movement
Figure13 Schematic of the components used
28
Figure 14 Setup Used
29
Figure 151 Linear prediction for wrist movement 1
CHAPTER 5 ALGORITHIM USED
(PREDICTION AND CORRECTION ALGORITHM)
An algorithm has been devised to make the robotic arm replicate the motions of the human arm
The robotic arm does not exactly have an idea of the exact movement of the human arm and takes
input from noisy sensors
The algorithm consists of the following parts
1 LINEAR PREDICTION
The values of the sensors and motors for every joint have been stored for certain predefined
positions for each joint movement The position of the robotic arm is predicted linearly using the
given formulae
119823119851119838119837119842119836119853119838119837 119852119838119851119855119848 119855119834119845119854119838 = (119846120784 minus 119846120783) lowast119842119847119849119854119853 119852119838119847119852119848119851 119855119834119845119854119838 minus 119852120783
(119852120784 minus 119852120783)
-
30
Figure 152 Linear prediction for wrist movement 2
Figure 153 Linear prediction for elbow movement 1
31
Figure 154 Linear prediction for elbow movement 2
m2- predefined value of the servo motor for the next known position
m1- predefined value of the servo motor for the previous known position
s1- predefined sensor value for the last known position
s2- predefined sensor value for the next known position
2) CORRECTION
The predicted value is then compared to the present value and the difference between the two
For each DOF you add the math gets more complicated and the joint weights get heavier We will
also find that shorter arm lengths allow for smaller torque requirements
The above equations only deal with the case where the robot arm is being held horizontally (not in
motion) This is not necessarily the worst case scenario For the arm to move from a rest position
acceleration is required To solve for this added torque it is known that the sum of torques acting at
a pivot point is equal to the moment of inertia (I) multiplied by the angular acceleration (alpha)
T=Ixα
To calculate the extra torque required to move (ie create an angular acceleration) you would
calculate the moment of inertia of the part from the end to the pivot using the equation (or an
equation similar to)
11
I=mr^22
Note this equation calculates the moment of inertia about the center of mass In the case of a robotic
arm the moment of inertia must take into consideration that the part is being rotated about a pivot
point located a distance away from the center of mass and a second term ( +MR2 ) needs to be
added For each joint the moment of inertia is calculated by adding the products of each individual
mass (mi) by the square of its respective length from the pivot (ri) Note that the equation for
calculating the moment of inertia to consider for actuator N omits the mass of the actuator at the
pivot
122 GRIPPER
Jaw torque is the other critical factor when specifying a gripper There are two sources of this
torque torque generated by the gripper on itself and torque generated by the acceleration and
weight of the part These can be addressed separately
Torque from the robotic gripper
Long Jaws are often required Either the part is bulky like an engine block or the part must be held
at a distance to fit in a machine In either case the longer the jaw the greater the torque the gripper
imposes on itself Therefore the torque from the grippers is GRIPPER TORQUE=Gripper Force x
Jaw Length (where jaw length is measured from the face of the gripper to the center of gravity of
the part)
12
Figure 4 Example of Gripper
Gripper Example
If we put 6rdquo long jaws on a gripper with 100 pounds of closing force gripper the jaws will see
Jaw Torque= 100 Pounds x 6rdquo= 600 in-pounds
The rating on the gripper is 840 in-pounds We used the majority of this rating without even
gripping a part because of the length of the jaws
Thus we can see that the length of the jaws plays a major factor in specifying a gripper The next
task is to determine the torque the gripper will experience from the part
CHAPTER 2 GESTURE
21 GESTURE CONTROLLED SYSTEM
Humans naturally use gesture to communicate It has been demonstrated that young children can
readily learn to communicate with gesture before they learn to talk A gesture is non-verbal
communication made with a part of the body We use gesture instead of or in combination with
verbal communication Using this process human can interface with the machine without any
mechanical devices Human movements are typically analyzed by segmenting them into shorter and
understandable format The movements vary person to person It can be used as a command to
control different devices of daily activities mobility etc So our natural or intuitive body
movements or gestures can be used as command or interface to operate machines communicate
with intelligent environments to control home appliances smart home telecare systems etc In this
paper we also review the different types of technologies of gesture controlled system
212 TYPES OF GESTURES
Most of the researches are based on hand gestures Direct control via hand posture is immediate but
limited in the number of Choices There are researches about body gesture finger point movement
In the early stage researchers used gloves with microcontroller and connected with the device
through a wire Head gesture and gesture with voice were also in the research but hand gesture was
the most dominant part of gesture control system
A primary goal of gesture control is to create a system which can identify specific human gestures
and use them to convey information or for device control Gesture recognition can be achieved by
various methods in which popular two are
13
1 Gesture control using any particular sensor
2 Gesture control using image processing
1 Gesture control using any particular sensor
This includes interpreting the human gestures by the use of any particular sensors The most widely
used sensor are accelerometer and gyroscope
We just need to wear a small transmitting device in your hand which included an acceleration
meter(either accelerometer or gyroscope) This will transmit an appropriate command to the robot
so that it can do whatever we want
2 Gesture control using any image processing
This includes following processes or steps
14
Figure 5-(steps for gesture control by image processing)
In our project we our deploying the first method ie gesture control using an
accelerometer sensor
CHAPTER 3 HARDWARE IMPLEMENTATION
31 Accelerometer
An accelerometer is a sensor that measures the physical acceleration experienced by an object due
to inertial forces or due to mechanical excitation In aerospace applications accelerometers are used
along with gyroscopes for navigation guidance and flight control Conceptually an accelerometer
behaves as a damped mass on a spring When the accelerometer experiences acceleration the mass
is displaced and the displacement is then measured to give the acceleration
In these devices piezoelectric piezoresistive and capacitive techniques are commonly used to
convert the mechanical motion into an electrical signal Piezoelectric accelerometers rely on
piezoceramics (eg lead zirconate titanate) or single crystals (eg quartz tourmaline) They are
unmatched in terms of their upper frequency range low packaged weight and high temperature
range Piezoresistive accelerometers are preferred in high shock applications Capacitive
accelerometers performance is superior in low frequency range and they can be operated in servo
mode to achieve high stability and linearity
15
Figure 6 An accelerometer
311 Working principle of accelerometer
16
Figure 7(schematic of an accelerometer)
The principle of working of an accelerometer can be explained by a simple mass (m) attached to a
spring of stiffness (k) that in turn is attached to a casing as illustrated in figure3 The mass used in
accelerometers is often called the seismic-mass or proof-mass In most cases the system also
includes a dashpot to provide a desirable damping effect
The dashpot with damping coefficient (c) is normally attached to the mass in parallel with the
spring When the spring mass system is subjected to linear acceleration a force equal to mass times
acceleration acts on the proof-mass causing it to deflect This deflection is sensed by a suitable
means and converted into an equivalent electrical signal Some form of damping is required
otherwise the system would not stabilize quickly under applied acceleration
To derive the motion equation of the system Newton‟s second law is used where all real forces
acting on the proof-mass are equal to the inertia force on the proof-mass Accordingly a dynamic
problem can be treated as a problem of static equilibrium and the equation of motion can be
obtained by direct formulation of the equations of equilibrium This damped mass-spring system
with applied force constitutes a classical second order mechanical system
312Accelerometer as Gesture Control Sensor
The accelerometer can be used in gesture controlled application As seen the accelerometer sensor measures the physical acceleration experienced by an object due to inertial forces or due to
mechanical excitationSo this means it will give different values for different gestures when
mounted on human handThis can be used as an advantage ieit can be interfaced with any of the
microcontroller or other device and can be used to control any robot or any oher device
313 Key factors while selecting an accelerometer
Some of the Key factors while selecting an accelerometer are
1Analog vs digital Depending on the interface to which you will be connecting the accelerometer
you need to select analog or digital output accelerometer
2Output Accelerometer comes with different outputs-Charge output IEPE output Voltage
output current output
17
3Number of axis Depending on your requirement you need to select single double or tri axis
accelerometer The 3 axis accelerometer will measure acceleration in all directions
4Acceleration range Acceleration Range is measured in units of g 1g is equal to the earths
gravity at sea level
5Sensitivity is the ratio of change in acceleration (input) to change in the output signal Sensitivity
is specified at a particular supply voltage and is typically expressed in units of mVg
314 Applications of Accelerometers
Used in cars to study shock and vibrations
Camcorders use accelerometers for image stabilization
Still cameras use accelerometers for anti-blur capturing
Used in mobile phones for multiple functions including tilt detection motion detectionetc
32 IR SENSOR
The InfraRed receiver transmitter pair is to use be worn around the fingers and controls the opening
and closing of the end effector
321 Introduction
An infrared sensor is an electronic instrument that is used to sense certain characteristics of its
surroundings by either emitting andor detecting infrared radiation It is also capable of measuring
heat of an object and detecting motion Infrared waves are not visible to the human eye
In the electromagnetic spectrum infrared radiation is the region having wavelengths longer than
visible light wavelengths but shorter than microwaves The infrared region is approximately
demarcated from 075 to 1000microm The wavelength region from 075 to 3microm is termed as near
infrared the region from 3 to 6microm is termed mid-infrared and the region higher than 6microm is termed
as far infrared
18
Infrared technology is found in many of our everyday products For example TV has an IR detector
for interpreting the signal from the remote control Key benefits of infrared sensors include low
power requirements simple circuitry and their portable feature
322 Working Principle
A typical system for detecting infrared radiation using infrared sensors includes the infrared source
such as blackbody radiators tungsten lamps and silicon carbide In case of active IR sensors the
sources are infrared lasers and LEDs of specific IR wavelengths Next is the transmission medium
used for infrared transmission which includes vacuum the atmosphere and optical fibers
Thirdly optical components such as optical lenses made from quartz CaF2 Ge and Si polyethylene
Fresnel lenses and Al or Au mirrors are used to converge or focus infrared radiation Likewise to
limit spectral response band-pass filters are ideal
Finally the infrared detector completes the system for detecting infrared radiation The output from
the detector is usually very small and hence pre-amplifiers coupled with circuitry are added to
further process the received signals
Figure 8 Circuit Diagram Of An IR Sensor
19
323 Applications
The following are the key application areas of infrared sensors
Tracking and art history
Climatology meteorology and astronomy
Thermography communications and alcohol testing
Heating hyperspectral imaging and night vision
Biological systems photobiomodulation and plant health
Gas detectorsgas leak detection
Water and steel analysis flame detection
Anesthesiology testing and spectroscopy
Petroleum exploration and underground solution
Rail safety
33 SERVO MOTORS
A servomotor is a rotary actuator that allows for precise control of angular position velocity and
acceleration It consists of a suitable motor coupled to a sensor for position feedback It also requires
a relatively sophisticated controller often a dedicated module designed specifically for use with
servomotors
331 Controlling Of A Servo Motor
Servos are controlled by sending an electrical pulse of variable width or pulse width
modulation (PWM) through the control wire There is a minimum pulse a maximum pulse and a
repetition rate A servo motor can usually only turn 90 degrees in either direction for a total of 180
degree movement The motors neutral position is defined as the position where the servo has the
same amount of potential rotation in the both the clockwise or counter-clockwise direction The
PWM sent to the motor determines position of the shaft and based on the duration of the pulse sent
via the control wire the rotor will turn to the desired position The servo motor expects to see a
pulse every 20 milliseconds (ms) and the length of the pulse will determine how far the motor turns
For example a 15ms pulse will make the motor turn to the 90-degree position Shorter than 15ms
moves it to 0 degrees and any longer than 15ms will turn the servo to 180 degrees as diagramed
below
20
Figure 9 Controlling an servo
332 Types of Servo Motors
There are two types of servo motors - AC and DC AC servo can handle higher current surges and
tend to be used in industrial machinery DC servos are not designed for high current surges and are
usually better suited for smaller applications Generally speaking DC motors are less expensive
than their AC counterparts These are also servo motors that have been built specifically
for continuous rotation making it an easy way to get your robot moving They feature two ball
bearings on the output shaft for reduced friction and easy access to the rest-point
adjustment potentiometer
333Servo Motor Applications
Servos are used in radio-controlled airplanes to position control surfaces like elevators rudders
walking a robot or operating grippers Servo motors are small have built-in control circuitry and
have good power for their size
In food services and pharmaceuticals the tools are designed to be used in harsher environments
where the potential for corrosion is high due to being washed at high pressures and temperatures
repeatedly to maintain strict hygiene standards Servos are also used in in-line manufacturing
where high repetition yet precise work is necessary
21
Of course you dont have to know how a servo works to use one but as with most electronics the
more you understand the more doors open for expanded projects and projects capabilities Whether
youre a hobbyist building robots an engineer designing industrial systems or just constantly
curious where will servo motors take you
334 Specifications
It is highly desirable to control or to maintain a certain location of motor rotor in a robotic arm not
only to determine its precise motion and position but also to control it in desired fashion most of the
industrial robotic arm contains pneumatic hydraulic and stepper motor to actuates they have very
high payload capacity but GuRoo is a low powered high degree of freedom robotic arm we uses
servo motor due their easy availability and high weight to torque ratio
HS-645mg standard deluxe high torque servo
Figure 10HS-475-SERVO
Detailed Specifications of above shown servo
Motor Type 3 Pole
Bearing Type Top Ball Bearing
22
Speed 023 018 sec 60 deg
Torque 44 55 kgcm
Size 3880 x 1980 x 3600mm
Weight 4000g
34 ATMega32
A microcontroller is the brain of the robot The main features of this controller are
Advanced RISC Architecture
Up to 16 MIPS Throughput at 16 MHz
16K Bytes of In-System Self-Programmable Flash
512 Bytes EEPROM
1K Byte Internal SRAM
32 Programmable IO Lines
In-System Programming by On-chip Boot Program
8-channel 10-bit ADC
Two 8-bit TimerCounters with Separate Prescalers and Compare Modes
One 16-bit TimerCounter with Separate Prescaler Compare Mode and Capture
Four PWM Channels
Programmable Serial USART
MasterSlave SPI Serial Interface
Byte-oriented Two-wire Serial Interface
Programmable Watchdog Timer with Separate On-chip Oscillator
External and Internal Interrupt Sources
23
Figure 11 - Pin configuration
CHAPTER 4 METHODOLOGY
The setup consists of a robotic arm having 5 degrees of freedom and 6 servo motors
The movements of the joints are controlled using servo motors that can move a fixed angle ranging from 0 to
180 degrees
Accelerometer 1
ADC of Microcontroller
Servo for wrist movement
24
IR sensor
Microcontroller
Servomotor for gripping
mechanism
Figure121 Flowchart for First Accelerometer
Figure122 Flowchart for second Accelerometer
Figure123 Flowchart for IR sensor
Accelerometer 2
ADC of Microcontroller
Servomotor for elbow
movement
25
Figure124 Flowchart for POTENTIOMETER
Potentiometer
ADC of microcontroller
servomotor for base movement
26
Figure 125 Complete Flow Chart
Complete flow chart depicting each sensor interfaced with microcontroller and the
movement of each and every servos (ie robotic arm)
27
41 SETUP USED amp SCHEMATIC
A setup consisting of
1 IR sensors
2 Two accelerometers and
3 A potentiometer is to be worn around the human hand for sensing the gesture
movements
The InfraRed receiver transmitter pair is to be worn around the fingers and controls the
opening and closing of the end effector
2 accelerometers are used for sensing the movement of the forearm and the wrist movement
A potentiometer is used to track the elbow movement
Figure13 Schematic of the components used
28
Figure 14 Setup Used
29
Figure 151 Linear prediction for wrist movement 1
CHAPTER 5 ALGORITHIM USED
(PREDICTION AND CORRECTION ALGORITHM)
An algorithm has been devised to make the robotic arm replicate the motions of the human arm
The robotic arm does not exactly have an idea of the exact movement of the human arm and takes
input from noisy sensors
The algorithm consists of the following parts
1 LINEAR PREDICTION
The values of the sensors and motors for every joint have been stored for certain predefined
positions for each joint movement The position of the robotic arm is predicted linearly using the
given formulae
119823119851119838119837119842119836119853119838119837 119852119838119851119855119848 119855119834119845119854119838 = (119846120784 minus 119846120783) lowast119842119847119849119854119853 119852119838119847119852119848119851 119855119834119845119854119838 minus 119852120783
(119852120784 minus 119852120783)
-
30
Figure 152 Linear prediction for wrist movement 2
Figure 153 Linear prediction for elbow movement 1
31
Figure 154 Linear prediction for elbow movement 2
m2- predefined value of the servo motor for the next known position
m1- predefined value of the servo motor for the previous known position
s1- predefined sensor value for the last known position
s2- predefined sensor value for the next known position
2) CORRECTION
The predicted value is then compared to the present value and the difference between the two
For each DOF you add the math gets more complicated and the joint weights get heavier We will
also find that shorter arm lengths allow for smaller torque requirements
The above equations only deal with the case where the robot arm is being held horizontally (not in
motion) This is not necessarily the worst case scenario For the arm to move from a rest position
acceleration is required To solve for this added torque it is known that the sum of torques acting at
a pivot point is equal to the moment of inertia (I) multiplied by the angular acceleration (alpha)
T=Ixα
To calculate the extra torque required to move (ie create an angular acceleration) you would
calculate the moment of inertia of the part from the end to the pivot using the equation (or an
equation similar to)
11
I=mr^22
Note this equation calculates the moment of inertia about the center of mass In the case of a robotic
arm the moment of inertia must take into consideration that the part is being rotated about a pivot
point located a distance away from the center of mass and a second term ( +MR2 ) needs to be
added For each joint the moment of inertia is calculated by adding the products of each individual
mass (mi) by the square of its respective length from the pivot (ri) Note that the equation for
calculating the moment of inertia to consider for actuator N omits the mass of the actuator at the
pivot
122 GRIPPER
Jaw torque is the other critical factor when specifying a gripper There are two sources of this
torque torque generated by the gripper on itself and torque generated by the acceleration and
weight of the part These can be addressed separately
Torque from the robotic gripper
Long Jaws are often required Either the part is bulky like an engine block or the part must be held
at a distance to fit in a machine In either case the longer the jaw the greater the torque the gripper
imposes on itself Therefore the torque from the grippers is GRIPPER TORQUE=Gripper Force x
Jaw Length (where jaw length is measured from the face of the gripper to the center of gravity of
the part)
12
Figure 4 Example of Gripper
Gripper Example
If we put 6rdquo long jaws on a gripper with 100 pounds of closing force gripper the jaws will see
Jaw Torque= 100 Pounds x 6rdquo= 600 in-pounds
The rating on the gripper is 840 in-pounds We used the majority of this rating without even
gripping a part because of the length of the jaws
Thus we can see that the length of the jaws plays a major factor in specifying a gripper The next
task is to determine the torque the gripper will experience from the part
CHAPTER 2 GESTURE
21 GESTURE CONTROLLED SYSTEM
Humans naturally use gesture to communicate It has been demonstrated that young children can
readily learn to communicate with gesture before they learn to talk A gesture is non-verbal
communication made with a part of the body We use gesture instead of or in combination with
verbal communication Using this process human can interface with the machine without any
mechanical devices Human movements are typically analyzed by segmenting them into shorter and
understandable format The movements vary person to person It can be used as a command to
control different devices of daily activities mobility etc So our natural or intuitive body
movements or gestures can be used as command or interface to operate machines communicate
with intelligent environments to control home appliances smart home telecare systems etc In this
paper we also review the different types of technologies of gesture controlled system
212 TYPES OF GESTURES
Most of the researches are based on hand gestures Direct control via hand posture is immediate but
limited in the number of Choices There are researches about body gesture finger point movement
In the early stage researchers used gloves with microcontroller and connected with the device
through a wire Head gesture and gesture with voice were also in the research but hand gesture was
the most dominant part of gesture control system
A primary goal of gesture control is to create a system which can identify specific human gestures
and use them to convey information or for device control Gesture recognition can be achieved by
various methods in which popular two are
13
1 Gesture control using any particular sensor
2 Gesture control using image processing
1 Gesture control using any particular sensor
This includes interpreting the human gestures by the use of any particular sensors The most widely
used sensor are accelerometer and gyroscope
We just need to wear a small transmitting device in your hand which included an acceleration
meter(either accelerometer or gyroscope) This will transmit an appropriate command to the robot
so that it can do whatever we want
2 Gesture control using any image processing
This includes following processes or steps
14
Figure 5-(steps for gesture control by image processing)
In our project we our deploying the first method ie gesture control using an
accelerometer sensor
CHAPTER 3 HARDWARE IMPLEMENTATION
31 Accelerometer
An accelerometer is a sensor that measures the physical acceleration experienced by an object due
to inertial forces or due to mechanical excitation In aerospace applications accelerometers are used
along with gyroscopes for navigation guidance and flight control Conceptually an accelerometer
behaves as a damped mass on a spring When the accelerometer experiences acceleration the mass
is displaced and the displacement is then measured to give the acceleration
In these devices piezoelectric piezoresistive and capacitive techniques are commonly used to
convert the mechanical motion into an electrical signal Piezoelectric accelerometers rely on
piezoceramics (eg lead zirconate titanate) or single crystals (eg quartz tourmaline) They are
unmatched in terms of their upper frequency range low packaged weight and high temperature
range Piezoresistive accelerometers are preferred in high shock applications Capacitive
accelerometers performance is superior in low frequency range and they can be operated in servo
mode to achieve high stability and linearity
15
Figure 6 An accelerometer
311 Working principle of accelerometer
16
Figure 7(schematic of an accelerometer)
The principle of working of an accelerometer can be explained by a simple mass (m) attached to a
spring of stiffness (k) that in turn is attached to a casing as illustrated in figure3 The mass used in
accelerometers is often called the seismic-mass or proof-mass In most cases the system also
includes a dashpot to provide a desirable damping effect
The dashpot with damping coefficient (c) is normally attached to the mass in parallel with the
spring When the spring mass system is subjected to linear acceleration a force equal to mass times
acceleration acts on the proof-mass causing it to deflect This deflection is sensed by a suitable
means and converted into an equivalent electrical signal Some form of damping is required
otherwise the system would not stabilize quickly under applied acceleration
To derive the motion equation of the system Newton‟s second law is used where all real forces
acting on the proof-mass are equal to the inertia force on the proof-mass Accordingly a dynamic
problem can be treated as a problem of static equilibrium and the equation of motion can be
obtained by direct formulation of the equations of equilibrium This damped mass-spring system
with applied force constitutes a classical second order mechanical system
312Accelerometer as Gesture Control Sensor
The accelerometer can be used in gesture controlled application As seen the accelerometer sensor measures the physical acceleration experienced by an object due to inertial forces or due to
mechanical excitationSo this means it will give different values for different gestures when
mounted on human handThis can be used as an advantage ieit can be interfaced with any of the
microcontroller or other device and can be used to control any robot or any oher device
313 Key factors while selecting an accelerometer
Some of the Key factors while selecting an accelerometer are
1Analog vs digital Depending on the interface to which you will be connecting the accelerometer
you need to select analog or digital output accelerometer
2Output Accelerometer comes with different outputs-Charge output IEPE output Voltage
output current output
17
3Number of axis Depending on your requirement you need to select single double or tri axis
accelerometer The 3 axis accelerometer will measure acceleration in all directions
4Acceleration range Acceleration Range is measured in units of g 1g is equal to the earths
gravity at sea level
5Sensitivity is the ratio of change in acceleration (input) to change in the output signal Sensitivity
is specified at a particular supply voltage and is typically expressed in units of mVg
314 Applications of Accelerometers
Used in cars to study shock and vibrations
Camcorders use accelerometers for image stabilization
Still cameras use accelerometers for anti-blur capturing
Used in mobile phones for multiple functions including tilt detection motion detectionetc
32 IR SENSOR
The InfraRed receiver transmitter pair is to use be worn around the fingers and controls the opening
and closing of the end effector
321 Introduction
An infrared sensor is an electronic instrument that is used to sense certain characteristics of its
surroundings by either emitting andor detecting infrared radiation It is also capable of measuring
heat of an object and detecting motion Infrared waves are not visible to the human eye
In the electromagnetic spectrum infrared radiation is the region having wavelengths longer than
visible light wavelengths but shorter than microwaves The infrared region is approximately
demarcated from 075 to 1000microm The wavelength region from 075 to 3microm is termed as near
infrared the region from 3 to 6microm is termed mid-infrared and the region higher than 6microm is termed
as far infrared
18
Infrared technology is found in many of our everyday products For example TV has an IR detector
for interpreting the signal from the remote control Key benefits of infrared sensors include low
power requirements simple circuitry and their portable feature
322 Working Principle
A typical system for detecting infrared radiation using infrared sensors includes the infrared source
such as blackbody radiators tungsten lamps and silicon carbide In case of active IR sensors the
sources are infrared lasers and LEDs of specific IR wavelengths Next is the transmission medium
used for infrared transmission which includes vacuum the atmosphere and optical fibers
Thirdly optical components such as optical lenses made from quartz CaF2 Ge and Si polyethylene
Fresnel lenses and Al or Au mirrors are used to converge or focus infrared radiation Likewise to
limit spectral response band-pass filters are ideal
Finally the infrared detector completes the system for detecting infrared radiation The output from
the detector is usually very small and hence pre-amplifiers coupled with circuitry are added to
further process the received signals
Figure 8 Circuit Diagram Of An IR Sensor
19
323 Applications
The following are the key application areas of infrared sensors
Tracking and art history
Climatology meteorology and astronomy
Thermography communications and alcohol testing
Heating hyperspectral imaging and night vision
Biological systems photobiomodulation and plant health
Gas detectorsgas leak detection
Water and steel analysis flame detection
Anesthesiology testing and spectroscopy
Petroleum exploration and underground solution
Rail safety
33 SERVO MOTORS
A servomotor is a rotary actuator that allows for precise control of angular position velocity and
acceleration It consists of a suitable motor coupled to a sensor for position feedback It also requires
a relatively sophisticated controller often a dedicated module designed specifically for use with
servomotors
331 Controlling Of A Servo Motor
Servos are controlled by sending an electrical pulse of variable width or pulse width
modulation (PWM) through the control wire There is a minimum pulse a maximum pulse and a
repetition rate A servo motor can usually only turn 90 degrees in either direction for a total of 180
degree movement The motors neutral position is defined as the position where the servo has the
same amount of potential rotation in the both the clockwise or counter-clockwise direction The
PWM sent to the motor determines position of the shaft and based on the duration of the pulse sent
via the control wire the rotor will turn to the desired position The servo motor expects to see a
pulse every 20 milliseconds (ms) and the length of the pulse will determine how far the motor turns
For example a 15ms pulse will make the motor turn to the 90-degree position Shorter than 15ms
moves it to 0 degrees and any longer than 15ms will turn the servo to 180 degrees as diagramed
below
20
Figure 9 Controlling an servo
332 Types of Servo Motors
There are two types of servo motors - AC and DC AC servo can handle higher current surges and
tend to be used in industrial machinery DC servos are not designed for high current surges and are
usually better suited for smaller applications Generally speaking DC motors are less expensive
than their AC counterparts These are also servo motors that have been built specifically
for continuous rotation making it an easy way to get your robot moving They feature two ball
bearings on the output shaft for reduced friction and easy access to the rest-point
adjustment potentiometer
333Servo Motor Applications
Servos are used in radio-controlled airplanes to position control surfaces like elevators rudders
walking a robot or operating grippers Servo motors are small have built-in control circuitry and
have good power for their size
In food services and pharmaceuticals the tools are designed to be used in harsher environments
where the potential for corrosion is high due to being washed at high pressures and temperatures
repeatedly to maintain strict hygiene standards Servos are also used in in-line manufacturing
where high repetition yet precise work is necessary
21
Of course you dont have to know how a servo works to use one but as with most electronics the
more you understand the more doors open for expanded projects and projects capabilities Whether
youre a hobbyist building robots an engineer designing industrial systems or just constantly
curious where will servo motors take you
334 Specifications
It is highly desirable to control or to maintain a certain location of motor rotor in a robotic arm not
only to determine its precise motion and position but also to control it in desired fashion most of the
industrial robotic arm contains pneumatic hydraulic and stepper motor to actuates they have very
high payload capacity but GuRoo is a low powered high degree of freedom robotic arm we uses
servo motor due their easy availability and high weight to torque ratio
HS-645mg standard deluxe high torque servo
Figure 10HS-475-SERVO
Detailed Specifications of above shown servo
Motor Type 3 Pole
Bearing Type Top Ball Bearing
22
Speed 023 018 sec 60 deg
Torque 44 55 kgcm
Size 3880 x 1980 x 3600mm
Weight 4000g
34 ATMega32
A microcontroller is the brain of the robot The main features of this controller are
Advanced RISC Architecture
Up to 16 MIPS Throughput at 16 MHz
16K Bytes of In-System Self-Programmable Flash
512 Bytes EEPROM
1K Byte Internal SRAM
32 Programmable IO Lines
In-System Programming by On-chip Boot Program
8-channel 10-bit ADC
Two 8-bit TimerCounters with Separate Prescalers and Compare Modes
One 16-bit TimerCounter with Separate Prescaler Compare Mode and Capture
Four PWM Channels
Programmable Serial USART
MasterSlave SPI Serial Interface
Byte-oriented Two-wire Serial Interface
Programmable Watchdog Timer with Separate On-chip Oscillator
External and Internal Interrupt Sources
23
Figure 11 - Pin configuration
CHAPTER 4 METHODOLOGY
The setup consists of a robotic arm having 5 degrees of freedom and 6 servo motors
The movements of the joints are controlled using servo motors that can move a fixed angle ranging from 0 to
180 degrees
Accelerometer 1
ADC of Microcontroller
Servo for wrist movement
24
IR sensor
Microcontroller
Servomotor for gripping
mechanism
Figure121 Flowchart for First Accelerometer
Figure122 Flowchart for second Accelerometer
Figure123 Flowchart for IR sensor
Accelerometer 2
ADC of Microcontroller
Servomotor for elbow
movement
25
Figure124 Flowchart for POTENTIOMETER
Potentiometer
ADC of microcontroller
servomotor for base movement
26
Figure 125 Complete Flow Chart
Complete flow chart depicting each sensor interfaced with microcontroller and the
movement of each and every servos (ie robotic arm)
27
41 SETUP USED amp SCHEMATIC
A setup consisting of
1 IR sensors
2 Two accelerometers and
3 A potentiometer is to be worn around the human hand for sensing the gesture
movements
The InfraRed receiver transmitter pair is to be worn around the fingers and controls the
opening and closing of the end effector
2 accelerometers are used for sensing the movement of the forearm and the wrist movement
A potentiometer is used to track the elbow movement
Figure13 Schematic of the components used
28
Figure 14 Setup Used
29
Figure 151 Linear prediction for wrist movement 1
CHAPTER 5 ALGORITHIM USED
(PREDICTION AND CORRECTION ALGORITHM)
An algorithm has been devised to make the robotic arm replicate the motions of the human arm
The robotic arm does not exactly have an idea of the exact movement of the human arm and takes
input from noisy sensors
The algorithm consists of the following parts
1 LINEAR PREDICTION
The values of the sensors and motors for every joint have been stored for certain predefined
positions for each joint movement The position of the robotic arm is predicted linearly using the
given formulae
119823119851119838119837119842119836119853119838119837 119852119838119851119855119848 119855119834119845119854119838 = (119846120784 minus 119846120783) lowast119842119847119849119854119853 119852119838119847119852119848119851 119855119834119845119854119838 minus 119852120783
(119852120784 minus 119852120783)
-
30
Figure 152 Linear prediction for wrist movement 2
Figure 153 Linear prediction for elbow movement 1
31
Figure 154 Linear prediction for elbow movement 2
m2- predefined value of the servo motor for the next known position
m1- predefined value of the servo motor for the previous known position
s1- predefined sensor value for the last known position
s2- predefined sensor value for the next known position
2) CORRECTION
The predicted value is then compared to the present value and the difference between the two
120782 119838119851119851119848119851 ge 119853119841119851119838119852119841119848119845119837
33
CHAPTER 6 APPLICATIONS
1) Industrial Applications
Such arms may prove handy in such sectors where the precision has to be adjusted from
time to time
Such arms make the job of the controller easier and have the capability of being operated at
faster speed than the traditional robotic arms used in the industries
A combination of the traditional and gesture controlled robotic arm may prove to be very
handy providing the arm both flexibility as well as accuracy
Disposing off radioactive wastes or any other hazardous chemical that may be dangerous
for human beings
Can be used in mines and space where human intervention is not possible
2) Defense
It Can be used for bomb disposal offering as much accuracy as a human arm and also
saving a human life
3) Medical Uses
Can be used by doctors to perform surgical operations at distant places
Such a technology can prove to be helping hand to physically disabled people or extremely
old people
34
CHAPTER 7 CONCLUSION AND FUTURE PROSPRCTS
71 CONCLUSION
As the error can be both positive and negative hence the robotic arm becomes less susceptible to
vibrations as when the human arm vibrates the error would eventually cancel itself or become small
in magnitude than the threshold value and at the same time it can detect small changes made in the
human arm because the error adds up to cross the threshold
In the paper an algorithm is proposed to control a gesture based robotic arm The position of each
motor is predicted based on the sensory input later the position is corrected while comparing it to
the actual position of the motor This algorithm is helpful in reducing the effects of vibrations that
may take place in a human arm and hence it can find great use in the area of medical surgery
72 FUTURE PROSPECTS
Modern robot systems provide graphical simulation and virtual environment for programming of
robots Our system can be enhanced to include these facilities Vision is one of the most important
features of the industrial robot systems present today For this purpose a pair of cameras can be
attached to the robotic arm which will allow robot to automatically identify and grasp the objects
Imitation based learning capability can be added to the robotic arm which will allow path tracking
by a different technique The instruction set for the language and the teach pendant can be enhanced
to include vision forces torques imitation etc The communication from the host can be made
wireless this will allow programming and teaching from a remote location and would create a lot of
other applications for this robotic arm A robotic arm with remotely located control A wearable
robotic arm (exoskeleton) with high force reflection capability
35
CHAPTER 8 REFRENCES
[1] Cyber Technology in Automation Control and Intelligent Systems (CYBER) 2012 IEEE
International Conference on Mechatronics(ICOM)
[2] Matthias Rehm Nikolaus Bee Elisabeth Andreacute Wave Like an Egyptian - Accelerometer
Based Gesture Recognition for Culture Specific InteractionsBritish Computer Society
2007
[3] Pavlovic V Sharma R amp Huang T (1997) Visual interpretation of hand gestures for
human- computer Interaction A review (IEEE Trans Pattern Analysis and Machine
Intelligence July 1997 Vol 19(7) pp 677 -695
[4] Micro Electro Mechanical Systems (MEMS) START Selected Topics in Assurance
Related Technologies) volume 8 number 1
[5] Wong Guan Hao Yap Yee Leck and Lim Chot Hunldquo6-DOFPC-Based robotic arm (PC-
robo arm) with efficient trajectory lanning and speed controlrdquo 2011 4th International
Conference on Mechatronics (ICOM) 17-19 May 2011 Kuala Lumpur Malaysia
11
I=mr^22
Note this equation calculates the moment of inertia about the center of mass In the case of a robotic
arm the moment of inertia must take into consideration that the part is being rotated about a pivot
point located a distance away from the center of mass and a second term ( +MR2 ) needs to be
added For each joint the moment of inertia is calculated by adding the products of each individual
mass (mi) by the square of its respective length from the pivot (ri) Note that the equation for
calculating the moment of inertia to consider for actuator N omits the mass of the actuator at the
pivot
122 GRIPPER
Jaw torque is the other critical factor when specifying a gripper There are two sources of this
torque torque generated by the gripper on itself and torque generated by the acceleration and
weight of the part These can be addressed separately
Torque from the robotic gripper
Long Jaws are often required Either the part is bulky like an engine block or the part must be held
at a distance to fit in a machine In either case the longer the jaw the greater the torque the gripper
imposes on itself Therefore the torque from the grippers is GRIPPER TORQUE=Gripper Force x
Jaw Length (where jaw length is measured from the face of the gripper to the center of gravity of
the part)
12
Figure 4 Example of Gripper
Gripper Example
If we put 6rdquo long jaws on a gripper with 100 pounds of closing force gripper the jaws will see
Jaw Torque= 100 Pounds x 6rdquo= 600 in-pounds
The rating on the gripper is 840 in-pounds We used the majority of this rating without even
gripping a part because of the length of the jaws
Thus we can see that the length of the jaws plays a major factor in specifying a gripper The next
task is to determine the torque the gripper will experience from the part
CHAPTER 2 GESTURE
21 GESTURE CONTROLLED SYSTEM
Humans naturally use gesture to communicate It has been demonstrated that young children can
readily learn to communicate with gesture before they learn to talk A gesture is non-verbal
communication made with a part of the body We use gesture instead of or in combination with
verbal communication Using this process human can interface with the machine without any
mechanical devices Human movements are typically analyzed by segmenting them into shorter and
understandable format The movements vary person to person It can be used as a command to
control different devices of daily activities mobility etc So our natural or intuitive body
movements or gestures can be used as command or interface to operate machines communicate
with intelligent environments to control home appliances smart home telecare systems etc In this
paper we also review the different types of technologies of gesture controlled system
212 TYPES OF GESTURES
Most of the researches are based on hand gestures Direct control via hand posture is immediate but
limited in the number of Choices There are researches about body gesture finger point movement
In the early stage researchers used gloves with microcontroller and connected with the device
through a wire Head gesture and gesture with voice were also in the research but hand gesture was
the most dominant part of gesture control system
A primary goal of gesture control is to create a system which can identify specific human gestures
and use them to convey information or for device control Gesture recognition can be achieved by
various methods in which popular two are
13
1 Gesture control using any particular sensor
2 Gesture control using image processing
1 Gesture control using any particular sensor
This includes interpreting the human gestures by the use of any particular sensors The most widely
used sensor are accelerometer and gyroscope
We just need to wear a small transmitting device in your hand which included an acceleration
meter(either accelerometer or gyroscope) This will transmit an appropriate command to the robot
so that it can do whatever we want
2 Gesture control using any image processing
This includes following processes or steps
14
Figure 5-(steps for gesture control by image processing)
In our project we our deploying the first method ie gesture control using an
accelerometer sensor
CHAPTER 3 HARDWARE IMPLEMENTATION
31 Accelerometer
An accelerometer is a sensor that measures the physical acceleration experienced by an object due
to inertial forces or due to mechanical excitation In aerospace applications accelerometers are used
along with gyroscopes for navigation guidance and flight control Conceptually an accelerometer
behaves as a damped mass on a spring When the accelerometer experiences acceleration the mass
is displaced and the displacement is then measured to give the acceleration
In these devices piezoelectric piezoresistive and capacitive techniques are commonly used to
convert the mechanical motion into an electrical signal Piezoelectric accelerometers rely on
piezoceramics (eg lead zirconate titanate) or single crystals (eg quartz tourmaline) They are
unmatched in terms of their upper frequency range low packaged weight and high temperature
range Piezoresistive accelerometers are preferred in high shock applications Capacitive
accelerometers performance is superior in low frequency range and they can be operated in servo
mode to achieve high stability and linearity
15
Figure 6 An accelerometer
311 Working principle of accelerometer
16
Figure 7(schematic of an accelerometer)
The principle of working of an accelerometer can be explained by a simple mass (m) attached to a
spring of stiffness (k) that in turn is attached to a casing as illustrated in figure3 The mass used in
accelerometers is often called the seismic-mass or proof-mass In most cases the system also
includes a dashpot to provide a desirable damping effect
The dashpot with damping coefficient (c) is normally attached to the mass in parallel with the
spring When the spring mass system is subjected to linear acceleration a force equal to mass times
acceleration acts on the proof-mass causing it to deflect This deflection is sensed by a suitable
means and converted into an equivalent electrical signal Some form of damping is required
otherwise the system would not stabilize quickly under applied acceleration
To derive the motion equation of the system Newton‟s second law is used where all real forces
acting on the proof-mass are equal to the inertia force on the proof-mass Accordingly a dynamic
problem can be treated as a problem of static equilibrium and the equation of motion can be
obtained by direct formulation of the equations of equilibrium This damped mass-spring system
with applied force constitutes a classical second order mechanical system
312Accelerometer as Gesture Control Sensor
The accelerometer can be used in gesture controlled application As seen the accelerometer sensor measures the physical acceleration experienced by an object due to inertial forces or due to
mechanical excitationSo this means it will give different values for different gestures when
mounted on human handThis can be used as an advantage ieit can be interfaced with any of the
microcontroller or other device and can be used to control any robot or any oher device
313 Key factors while selecting an accelerometer
Some of the Key factors while selecting an accelerometer are
1Analog vs digital Depending on the interface to which you will be connecting the accelerometer
you need to select analog or digital output accelerometer
2Output Accelerometer comes with different outputs-Charge output IEPE output Voltage
output current output
17
3Number of axis Depending on your requirement you need to select single double or tri axis
accelerometer The 3 axis accelerometer will measure acceleration in all directions
4Acceleration range Acceleration Range is measured in units of g 1g is equal to the earths
gravity at sea level
5Sensitivity is the ratio of change in acceleration (input) to change in the output signal Sensitivity
is specified at a particular supply voltage and is typically expressed in units of mVg
314 Applications of Accelerometers
Used in cars to study shock and vibrations
Camcorders use accelerometers for image stabilization
Still cameras use accelerometers for anti-blur capturing
Used in mobile phones for multiple functions including tilt detection motion detectionetc
32 IR SENSOR
The InfraRed receiver transmitter pair is to use be worn around the fingers and controls the opening
and closing of the end effector
321 Introduction
An infrared sensor is an electronic instrument that is used to sense certain characteristics of its
surroundings by either emitting andor detecting infrared radiation It is also capable of measuring
heat of an object and detecting motion Infrared waves are not visible to the human eye
In the electromagnetic spectrum infrared radiation is the region having wavelengths longer than
visible light wavelengths but shorter than microwaves The infrared region is approximately
demarcated from 075 to 1000microm The wavelength region from 075 to 3microm is termed as near
infrared the region from 3 to 6microm is termed mid-infrared and the region higher than 6microm is termed
as far infrared
18
Infrared technology is found in many of our everyday products For example TV has an IR detector
for interpreting the signal from the remote control Key benefits of infrared sensors include low
power requirements simple circuitry and their portable feature
322 Working Principle
A typical system for detecting infrared radiation using infrared sensors includes the infrared source
such as blackbody radiators tungsten lamps and silicon carbide In case of active IR sensors the
sources are infrared lasers and LEDs of specific IR wavelengths Next is the transmission medium
used for infrared transmission which includes vacuum the atmosphere and optical fibers
Thirdly optical components such as optical lenses made from quartz CaF2 Ge and Si polyethylene
Fresnel lenses and Al or Au mirrors are used to converge or focus infrared radiation Likewise to
limit spectral response band-pass filters are ideal
Finally the infrared detector completes the system for detecting infrared radiation The output from
the detector is usually very small and hence pre-amplifiers coupled with circuitry are added to
further process the received signals
Figure 8 Circuit Diagram Of An IR Sensor
19
323 Applications
The following are the key application areas of infrared sensors
Tracking and art history
Climatology meteorology and astronomy
Thermography communications and alcohol testing
Heating hyperspectral imaging and night vision
Biological systems photobiomodulation and plant health
Gas detectorsgas leak detection
Water and steel analysis flame detection
Anesthesiology testing and spectroscopy
Petroleum exploration and underground solution
Rail safety
33 SERVO MOTORS
A servomotor is a rotary actuator that allows for precise control of angular position velocity and
acceleration It consists of a suitable motor coupled to a sensor for position feedback It also requires
a relatively sophisticated controller often a dedicated module designed specifically for use with
servomotors
331 Controlling Of A Servo Motor
Servos are controlled by sending an electrical pulse of variable width or pulse width
modulation (PWM) through the control wire There is a minimum pulse a maximum pulse and a
repetition rate A servo motor can usually only turn 90 degrees in either direction for a total of 180
degree movement The motors neutral position is defined as the position where the servo has the
same amount of potential rotation in the both the clockwise or counter-clockwise direction The
PWM sent to the motor determines position of the shaft and based on the duration of the pulse sent
via the control wire the rotor will turn to the desired position The servo motor expects to see a
pulse every 20 milliseconds (ms) and the length of the pulse will determine how far the motor turns
For example a 15ms pulse will make the motor turn to the 90-degree position Shorter than 15ms
moves it to 0 degrees and any longer than 15ms will turn the servo to 180 degrees as diagramed
below
20
Figure 9 Controlling an servo
332 Types of Servo Motors
There are two types of servo motors - AC and DC AC servo can handle higher current surges and
tend to be used in industrial machinery DC servos are not designed for high current surges and are
usually better suited for smaller applications Generally speaking DC motors are less expensive
than their AC counterparts These are also servo motors that have been built specifically
for continuous rotation making it an easy way to get your robot moving They feature two ball
bearings on the output shaft for reduced friction and easy access to the rest-point
adjustment potentiometer
333Servo Motor Applications
Servos are used in radio-controlled airplanes to position control surfaces like elevators rudders
walking a robot or operating grippers Servo motors are small have built-in control circuitry and
have good power for their size
In food services and pharmaceuticals the tools are designed to be used in harsher environments
where the potential for corrosion is high due to being washed at high pressures and temperatures
repeatedly to maintain strict hygiene standards Servos are also used in in-line manufacturing
where high repetition yet precise work is necessary
21
Of course you dont have to know how a servo works to use one but as with most electronics the
more you understand the more doors open for expanded projects and projects capabilities Whether
youre a hobbyist building robots an engineer designing industrial systems or just constantly
curious where will servo motors take you
334 Specifications
It is highly desirable to control or to maintain a certain location of motor rotor in a robotic arm not
only to determine its precise motion and position but also to control it in desired fashion most of the
industrial robotic arm contains pneumatic hydraulic and stepper motor to actuates they have very
high payload capacity but GuRoo is a low powered high degree of freedom robotic arm we uses
servo motor due their easy availability and high weight to torque ratio
HS-645mg standard deluxe high torque servo
Figure 10HS-475-SERVO
Detailed Specifications of above shown servo
Motor Type 3 Pole
Bearing Type Top Ball Bearing
22
Speed 023 018 sec 60 deg
Torque 44 55 kgcm
Size 3880 x 1980 x 3600mm
Weight 4000g
34 ATMega32
A microcontroller is the brain of the robot The main features of this controller are
Advanced RISC Architecture
Up to 16 MIPS Throughput at 16 MHz
16K Bytes of In-System Self-Programmable Flash
512 Bytes EEPROM
1K Byte Internal SRAM
32 Programmable IO Lines
In-System Programming by On-chip Boot Program
8-channel 10-bit ADC
Two 8-bit TimerCounters with Separate Prescalers and Compare Modes
One 16-bit TimerCounter with Separate Prescaler Compare Mode and Capture
Four PWM Channels
Programmable Serial USART
MasterSlave SPI Serial Interface
Byte-oriented Two-wire Serial Interface
Programmable Watchdog Timer with Separate On-chip Oscillator
External and Internal Interrupt Sources
23
Figure 11 - Pin configuration
CHAPTER 4 METHODOLOGY
The setup consists of a robotic arm having 5 degrees of freedom and 6 servo motors
The movements of the joints are controlled using servo motors that can move a fixed angle ranging from 0 to
180 degrees
Accelerometer 1
ADC of Microcontroller
Servo for wrist movement
24
IR sensor
Microcontroller
Servomotor for gripping
mechanism
Figure121 Flowchart for First Accelerometer
Figure122 Flowchart for second Accelerometer
Figure123 Flowchart for IR sensor
Accelerometer 2
ADC of Microcontroller
Servomotor for elbow
movement
25
Figure124 Flowchart for POTENTIOMETER
Potentiometer
ADC of microcontroller
servomotor for base movement
26
Figure 125 Complete Flow Chart
Complete flow chart depicting each sensor interfaced with microcontroller and the
movement of each and every servos (ie robotic arm)
27
41 SETUP USED amp SCHEMATIC
A setup consisting of
1 IR sensors
2 Two accelerometers and
3 A potentiometer is to be worn around the human hand for sensing the gesture
movements
The InfraRed receiver transmitter pair is to be worn around the fingers and controls the
opening and closing of the end effector
2 accelerometers are used for sensing the movement of the forearm and the wrist movement
A potentiometer is used to track the elbow movement
Figure13 Schematic of the components used
28
Figure 14 Setup Used
29
Figure 151 Linear prediction for wrist movement 1
CHAPTER 5 ALGORITHIM USED
(PREDICTION AND CORRECTION ALGORITHM)
An algorithm has been devised to make the robotic arm replicate the motions of the human arm
The robotic arm does not exactly have an idea of the exact movement of the human arm and takes
input from noisy sensors
The algorithm consists of the following parts
1 LINEAR PREDICTION
The values of the sensors and motors for every joint have been stored for certain predefined
positions for each joint movement The position of the robotic arm is predicted linearly using the
given formulae
119823119851119838119837119842119836119853119838119837 119852119838119851119855119848 119855119834119845119854119838 = (119846120784 minus 119846120783) lowast119842119847119849119854119853 119852119838119847119852119848119851 119855119834119845119854119838 minus 119852120783
(119852120784 minus 119852120783)
-
30
Figure 152 Linear prediction for wrist movement 2
Figure 153 Linear prediction for elbow movement 1
31
Figure 154 Linear prediction for elbow movement 2
m2- predefined value of the servo motor for the next known position
m1- predefined value of the servo motor for the previous known position
s1- predefined sensor value for the last known position
s2- predefined sensor value for the next known position
2) CORRECTION
The predicted value is then compared to the present value and the difference between the two
120782 119838119851119851119848119851 ge 119853119841119851119838119852119841119848119845119837
33
CHAPTER 6 APPLICATIONS
1) Industrial Applications
Such arms may prove handy in such sectors where the precision has to be adjusted from
time to time
Such arms make the job of the controller easier and have the capability of being operated at
faster speed than the traditional robotic arms used in the industries
A combination of the traditional and gesture controlled robotic arm may prove to be very
handy providing the arm both flexibility as well as accuracy
Disposing off radioactive wastes or any other hazardous chemical that may be dangerous
for human beings
Can be used in mines and space where human intervention is not possible
2) Defense
It Can be used for bomb disposal offering as much accuracy as a human arm and also
saving a human life
3) Medical Uses
Can be used by doctors to perform surgical operations at distant places
Such a technology can prove to be helping hand to physically disabled people or extremely
old people
34
CHAPTER 7 CONCLUSION AND FUTURE PROSPRCTS
71 CONCLUSION
As the error can be both positive and negative hence the robotic arm becomes less susceptible to
vibrations as when the human arm vibrates the error would eventually cancel itself or become small
in magnitude than the threshold value and at the same time it can detect small changes made in the
human arm because the error adds up to cross the threshold
In the paper an algorithm is proposed to control a gesture based robotic arm The position of each
motor is predicted based on the sensory input later the position is corrected while comparing it to
the actual position of the motor This algorithm is helpful in reducing the effects of vibrations that
may take place in a human arm and hence it can find great use in the area of medical surgery
72 FUTURE PROSPECTS
Modern robot systems provide graphical simulation and virtual environment for programming of
robots Our system can be enhanced to include these facilities Vision is one of the most important
features of the industrial robot systems present today For this purpose a pair of cameras can be
attached to the robotic arm which will allow robot to automatically identify and grasp the objects
Imitation based learning capability can be added to the robotic arm which will allow path tracking
by a different technique The instruction set for the language and the teach pendant can be enhanced
to include vision forces torques imitation etc The communication from the host can be made
wireless this will allow programming and teaching from a remote location and would create a lot of
other applications for this robotic arm A robotic arm with remotely located control A wearable
robotic arm (exoskeleton) with high force reflection capability
35
CHAPTER 8 REFRENCES
[1] Cyber Technology in Automation Control and Intelligent Systems (CYBER) 2012 IEEE
International Conference on Mechatronics(ICOM)
[2] Matthias Rehm Nikolaus Bee Elisabeth Andreacute Wave Like an Egyptian - Accelerometer
Based Gesture Recognition for Culture Specific InteractionsBritish Computer Society
2007
[3] Pavlovic V Sharma R amp Huang T (1997) Visual interpretation of hand gestures for
human- computer Interaction A review (IEEE Trans Pattern Analysis and Machine
Intelligence July 1997 Vol 19(7) pp 677 -695
[4] Micro Electro Mechanical Systems (MEMS) START Selected Topics in Assurance
Related Technologies) volume 8 number 1
[5] Wong Guan Hao Yap Yee Leck and Lim Chot Hunldquo6-DOFPC-Based robotic arm (PC-
robo arm) with efficient trajectory lanning and speed controlrdquo 2011 4th International
Conference on Mechatronics (ICOM) 17-19 May 2011 Kuala Lumpur Malaysia
12
Figure 4 Example of Gripper
Gripper Example
If we put 6rdquo long jaws on a gripper with 100 pounds of closing force gripper the jaws will see
Jaw Torque= 100 Pounds x 6rdquo= 600 in-pounds
The rating on the gripper is 840 in-pounds We used the majority of this rating without even
gripping a part because of the length of the jaws
Thus we can see that the length of the jaws plays a major factor in specifying a gripper The next
task is to determine the torque the gripper will experience from the part
CHAPTER 2 GESTURE
21 GESTURE CONTROLLED SYSTEM
Humans naturally use gesture to communicate It has been demonstrated that young children can
readily learn to communicate with gesture before they learn to talk A gesture is non-verbal
communication made with a part of the body We use gesture instead of or in combination with
verbal communication Using this process human can interface with the machine without any
mechanical devices Human movements are typically analyzed by segmenting them into shorter and
understandable format The movements vary person to person It can be used as a command to
control different devices of daily activities mobility etc So our natural or intuitive body
movements or gestures can be used as command or interface to operate machines communicate
with intelligent environments to control home appliances smart home telecare systems etc In this
paper we also review the different types of technologies of gesture controlled system
212 TYPES OF GESTURES
Most of the researches are based on hand gestures Direct control via hand posture is immediate but
limited in the number of Choices There are researches about body gesture finger point movement
In the early stage researchers used gloves with microcontroller and connected with the device
through a wire Head gesture and gesture with voice were also in the research but hand gesture was
the most dominant part of gesture control system
A primary goal of gesture control is to create a system which can identify specific human gestures
and use them to convey information or for device control Gesture recognition can be achieved by
various methods in which popular two are
13
1 Gesture control using any particular sensor
2 Gesture control using image processing
1 Gesture control using any particular sensor
This includes interpreting the human gestures by the use of any particular sensors The most widely
used sensor are accelerometer and gyroscope
We just need to wear a small transmitting device in your hand which included an acceleration
meter(either accelerometer or gyroscope) This will transmit an appropriate command to the robot
so that it can do whatever we want
2 Gesture control using any image processing
This includes following processes or steps
14
Figure 5-(steps for gesture control by image processing)
In our project we our deploying the first method ie gesture control using an
accelerometer sensor
CHAPTER 3 HARDWARE IMPLEMENTATION
31 Accelerometer
An accelerometer is a sensor that measures the physical acceleration experienced by an object due
to inertial forces or due to mechanical excitation In aerospace applications accelerometers are used
along with gyroscopes for navigation guidance and flight control Conceptually an accelerometer
behaves as a damped mass on a spring When the accelerometer experiences acceleration the mass
is displaced and the displacement is then measured to give the acceleration
In these devices piezoelectric piezoresistive and capacitive techniques are commonly used to
convert the mechanical motion into an electrical signal Piezoelectric accelerometers rely on
piezoceramics (eg lead zirconate titanate) or single crystals (eg quartz tourmaline) They are
unmatched in terms of their upper frequency range low packaged weight and high temperature
range Piezoresistive accelerometers are preferred in high shock applications Capacitive
accelerometers performance is superior in low frequency range and they can be operated in servo
mode to achieve high stability and linearity
15
Figure 6 An accelerometer
311 Working principle of accelerometer
16
Figure 7(schematic of an accelerometer)
The principle of working of an accelerometer can be explained by a simple mass (m) attached to a
spring of stiffness (k) that in turn is attached to a casing as illustrated in figure3 The mass used in
accelerometers is often called the seismic-mass or proof-mass In most cases the system also
includes a dashpot to provide a desirable damping effect
The dashpot with damping coefficient (c) is normally attached to the mass in parallel with the
spring When the spring mass system is subjected to linear acceleration a force equal to mass times
acceleration acts on the proof-mass causing it to deflect This deflection is sensed by a suitable
means and converted into an equivalent electrical signal Some form of damping is required
otherwise the system would not stabilize quickly under applied acceleration
To derive the motion equation of the system Newton‟s second law is used where all real forces
acting on the proof-mass are equal to the inertia force on the proof-mass Accordingly a dynamic
problem can be treated as a problem of static equilibrium and the equation of motion can be
obtained by direct formulation of the equations of equilibrium This damped mass-spring system
with applied force constitutes a classical second order mechanical system
312Accelerometer as Gesture Control Sensor
The accelerometer can be used in gesture controlled application As seen the accelerometer sensor measures the physical acceleration experienced by an object due to inertial forces or due to
mechanical excitationSo this means it will give different values for different gestures when
mounted on human handThis can be used as an advantage ieit can be interfaced with any of the
microcontroller or other device and can be used to control any robot or any oher device
313 Key factors while selecting an accelerometer
Some of the Key factors while selecting an accelerometer are
1Analog vs digital Depending on the interface to which you will be connecting the accelerometer
you need to select analog or digital output accelerometer
2Output Accelerometer comes with different outputs-Charge output IEPE output Voltage
output current output
17
3Number of axis Depending on your requirement you need to select single double or tri axis
accelerometer The 3 axis accelerometer will measure acceleration in all directions
4Acceleration range Acceleration Range is measured in units of g 1g is equal to the earths
gravity at sea level
5Sensitivity is the ratio of change in acceleration (input) to change in the output signal Sensitivity
is specified at a particular supply voltage and is typically expressed in units of mVg
314 Applications of Accelerometers
Used in cars to study shock and vibrations
Camcorders use accelerometers for image stabilization
Still cameras use accelerometers for anti-blur capturing
Used in mobile phones for multiple functions including tilt detection motion detectionetc
32 IR SENSOR
The InfraRed receiver transmitter pair is to use be worn around the fingers and controls the opening
and closing of the end effector
321 Introduction
An infrared sensor is an electronic instrument that is used to sense certain characteristics of its
surroundings by either emitting andor detecting infrared radiation It is also capable of measuring
heat of an object and detecting motion Infrared waves are not visible to the human eye
In the electromagnetic spectrum infrared radiation is the region having wavelengths longer than
visible light wavelengths but shorter than microwaves The infrared region is approximately
demarcated from 075 to 1000microm The wavelength region from 075 to 3microm is termed as near
infrared the region from 3 to 6microm is termed mid-infrared and the region higher than 6microm is termed
as far infrared
18
Infrared technology is found in many of our everyday products For example TV has an IR detector
for interpreting the signal from the remote control Key benefits of infrared sensors include low
power requirements simple circuitry and their portable feature
322 Working Principle
A typical system for detecting infrared radiation using infrared sensors includes the infrared source
such as blackbody radiators tungsten lamps and silicon carbide In case of active IR sensors the
sources are infrared lasers and LEDs of specific IR wavelengths Next is the transmission medium
used for infrared transmission which includes vacuum the atmosphere and optical fibers
Thirdly optical components such as optical lenses made from quartz CaF2 Ge and Si polyethylene
Fresnel lenses and Al or Au mirrors are used to converge or focus infrared radiation Likewise to
limit spectral response band-pass filters are ideal
Finally the infrared detector completes the system for detecting infrared radiation The output from
the detector is usually very small and hence pre-amplifiers coupled with circuitry are added to
further process the received signals
Figure 8 Circuit Diagram Of An IR Sensor
19
323 Applications
The following are the key application areas of infrared sensors
Tracking and art history
Climatology meteorology and astronomy
Thermography communications and alcohol testing
Heating hyperspectral imaging and night vision
Biological systems photobiomodulation and plant health
Gas detectorsgas leak detection
Water and steel analysis flame detection
Anesthesiology testing and spectroscopy
Petroleum exploration and underground solution
Rail safety
33 SERVO MOTORS
A servomotor is a rotary actuator that allows for precise control of angular position velocity and
acceleration It consists of a suitable motor coupled to a sensor for position feedback It also requires
a relatively sophisticated controller often a dedicated module designed specifically for use with
servomotors
331 Controlling Of A Servo Motor
Servos are controlled by sending an electrical pulse of variable width or pulse width
modulation (PWM) through the control wire There is a minimum pulse a maximum pulse and a
repetition rate A servo motor can usually only turn 90 degrees in either direction for a total of 180
degree movement The motors neutral position is defined as the position where the servo has the
same amount of potential rotation in the both the clockwise or counter-clockwise direction The
PWM sent to the motor determines position of the shaft and based on the duration of the pulse sent
via the control wire the rotor will turn to the desired position The servo motor expects to see a
pulse every 20 milliseconds (ms) and the length of the pulse will determine how far the motor turns
For example a 15ms pulse will make the motor turn to the 90-degree position Shorter than 15ms
moves it to 0 degrees and any longer than 15ms will turn the servo to 180 degrees as diagramed
below
20
Figure 9 Controlling an servo
332 Types of Servo Motors
There are two types of servo motors - AC and DC AC servo can handle higher current surges and
tend to be used in industrial machinery DC servos are not designed for high current surges and are
usually better suited for smaller applications Generally speaking DC motors are less expensive
than their AC counterparts These are also servo motors that have been built specifically
for continuous rotation making it an easy way to get your robot moving They feature two ball
bearings on the output shaft for reduced friction and easy access to the rest-point
adjustment potentiometer
333Servo Motor Applications
Servos are used in radio-controlled airplanes to position control surfaces like elevators rudders
walking a robot or operating grippers Servo motors are small have built-in control circuitry and
have good power for their size
In food services and pharmaceuticals the tools are designed to be used in harsher environments
where the potential for corrosion is high due to being washed at high pressures and temperatures
repeatedly to maintain strict hygiene standards Servos are also used in in-line manufacturing
where high repetition yet precise work is necessary
21
Of course you dont have to know how a servo works to use one but as with most electronics the
more you understand the more doors open for expanded projects and projects capabilities Whether
youre a hobbyist building robots an engineer designing industrial systems or just constantly
curious where will servo motors take you
334 Specifications
It is highly desirable to control or to maintain a certain location of motor rotor in a robotic arm not
only to determine its precise motion and position but also to control it in desired fashion most of the
industrial robotic arm contains pneumatic hydraulic and stepper motor to actuates they have very
high payload capacity but GuRoo is a low powered high degree of freedom robotic arm we uses
servo motor due their easy availability and high weight to torque ratio
HS-645mg standard deluxe high torque servo
Figure 10HS-475-SERVO
Detailed Specifications of above shown servo
Motor Type 3 Pole
Bearing Type Top Ball Bearing
22
Speed 023 018 sec 60 deg
Torque 44 55 kgcm
Size 3880 x 1980 x 3600mm
Weight 4000g
34 ATMega32
A microcontroller is the brain of the robot The main features of this controller are
Advanced RISC Architecture
Up to 16 MIPS Throughput at 16 MHz
16K Bytes of In-System Self-Programmable Flash
512 Bytes EEPROM
1K Byte Internal SRAM
32 Programmable IO Lines
In-System Programming by On-chip Boot Program
8-channel 10-bit ADC
Two 8-bit TimerCounters with Separate Prescalers and Compare Modes
One 16-bit TimerCounter with Separate Prescaler Compare Mode and Capture
Four PWM Channels
Programmable Serial USART
MasterSlave SPI Serial Interface
Byte-oriented Two-wire Serial Interface
Programmable Watchdog Timer with Separate On-chip Oscillator
External and Internal Interrupt Sources
23
Figure 11 - Pin configuration
CHAPTER 4 METHODOLOGY
The setup consists of a robotic arm having 5 degrees of freedom and 6 servo motors
The movements of the joints are controlled using servo motors that can move a fixed angle ranging from 0 to
180 degrees
Accelerometer 1
ADC of Microcontroller
Servo for wrist movement
24
IR sensor
Microcontroller
Servomotor for gripping
mechanism
Figure121 Flowchart for First Accelerometer
Figure122 Flowchart for second Accelerometer
Figure123 Flowchart for IR sensor
Accelerometer 2
ADC of Microcontroller
Servomotor for elbow
movement
25
Figure124 Flowchart for POTENTIOMETER
Potentiometer
ADC of microcontroller
servomotor for base movement
26
Figure 125 Complete Flow Chart
Complete flow chart depicting each sensor interfaced with microcontroller and the
movement of each and every servos (ie robotic arm)
27
41 SETUP USED amp SCHEMATIC
A setup consisting of
1 IR sensors
2 Two accelerometers and
3 A potentiometer is to be worn around the human hand for sensing the gesture
movements
The InfraRed receiver transmitter pair is to be worn around the fingers and controls the
opening and closing of the end effector
2 accelerometers are used for sensing the movement of the forearm and the wrist movement
A potentiometer is used to track the elbow movement
Figure13 Schematic of the components used
28
Figure 14 Setup Used
29
Figure 151 Linear prediction for wrist movement 1
CHAPTER 5 ALGORITHIM USED
(PREDICTION AND CORRECTION ALGORITHM)
An algorithm has been devised to make the robotic arm replicate the motions of the human arm
The robotic arm does not exactly have an idea of the exact movement of the human arm and takes
input from noisy sensors
The algorithm consists of the following parts
1 LINEAR PREDICTION
The values of the sensors and motors for every joint have been stored for certain predefined
positions for each joint movement The position of the robotic arm is predicted linearly using the
given formulae
119823119851119838119837119842119836119853119838119837 119852119838119851119855119848 119855119834119845119854119838 = (119846120784 minus 119846120783) lowast119842119847119849119854119853 119852119838119847119852119848119851 119855119834119845119854119838 minus 119852120783
(119852120784 minus 119852120783)
-
30
Figure 152 Linear prediction for wrist movement 2
Figure 153 Linear prediction for elbow movement 1
31
Figure 154 Linear prediction for elbow movement 2
m2- predefined value of the servo motor for the next known position
m1- predefined value of the servo motor for the previous known position
s1- predefined sensor value for the last known position
s2- predefined sensor value for the next known position
2) CORRECTION
The predicted value is then compared to the present value and the difference between the two
120782 119838119851119851119848119851 ge 119853119841119851119838119852119841119848119845119837
33
CHAPTER 6 APPLICATIONS
1) Industrial Applications
Such arms may prove handy in such sectors where the precision has to be adjusted from
time to time
Such arms make the job of the controller easier and have the capability of being operated at
faster speed than the traditional robotic arms used in the industries
A combination of the traditional and gesture controlled robotic arm may prove to be very
handy providing the arm both flexibility as well as accuracy
Disposing off radioactive wastes or any other hazardous chemical that may be dangerous
for human beings
Can be used in mines and space where human intervention is not possible
2) Defense
It Can be used for bomb disposal offering as much accuracy as a human arm and also
saving a human life
3) Medical Uses
Can be used by doctors to perform surgical operations at distant places
Such a technology can prove to be helping hand to physically disabled people or extremely
old people
34
CHAPTER 7 CONCLUSION AND FUTURE PROSPRCTS
71 CONCLUSION
As the error can be both positive and negative hence the robotic arm becomes less susceptible to
vibrations as when the human arm vibrates the error would eventually cancel itself or become small
in magnitude than the threshold value and at the same time it can detect small changes made in the
human arm because the error adds up to cross the threshold
In the paper an algorithm is proposed to control a gesture based robotic arm The position of each
motor is predicted based on the sensory input later the position is corrected while comparing it to
the actual position of the motor This algorithm is helpful in reducing the effects of vibrations that
may take place in a human arm and hence it can find great use in the area of medical surgery
72 FUTURE PROSPECTS
Modern robot systems provide graphical simulation and virtual environment for programming of
robots Our system can be enhanced to include these facilities Vision is one of the most important
features of the industrial robot systems present today For this purpose a pair of cameras can be
attached to the robotic arm which will allow robot to automatically identify and grasp the objects
Imitation based learning capability can be added to the robotic arm which will allow path tracking
by a different technique The instruction set for the language and the teach pendant can be enhanced
to include vision forces torques imitation etc The communication from the host can be made
wireless this will allow programming and teaching from a remote location and would create a lot of
other applications for this robotic arm A robotic arm with remotely located control A wearable
robotic arm (exoskeleton) with high force reflection capability
35
CHAPTER 8 REFRENCES
[1] Cyber Technology in Automation Control and Intelligent Systems (CYBER) 2012 IEEE
International Conference on Mechatronics(ICOM)
[2] Matthias Rehm Nikolaus Bee Elisabeth Andreacute Wave Like an Egyptian - Accelerometer
Based Gesture Recognition for Culture Specific InteractionsBritish Computer Society
2007
[3] Pavlovic V Sharma R amp Huang T (1997) Visual interpretation of hand gestures for
human- computer Interaction A review (IEEE Trans Pattern Analysis and Machine
Intelligence July 1997 Vol 19(7) pp 677 -695
[4] Micro Electro Mechanical Systems (MEMS) START Selected Topics in Assurance
Related Technologies) volume 8 number 1
[5] Wong Guan Hao Yap Yee Leck and Lim Chot Hunldquo6-DOFPC-Based robotic arm (PC-
robo arm) with efficient trajectory lanning and speed controlrdquo 2011 4th International
Conference on Mechatronics (ICOM) 17-19 May 2011 Kuala Lumpur Malaysia
13
1 Gesture control using any particular sensor
2 Gesture control using image processing
1 Gesture control using any particular sensor
This includes interpreting the human gestures by the use of any particular sensors The most widely
used sensor are accelerometer and gyroscope
We just need to wear a small transmitting device in your hand which included an acceleration
meter(either accelerometer or gyroscope) This will transmit an appropriate command to the robot
so that it can do whatever we want
2 Gesture control using any image processing
This includes following processes or steps
14
Figure 5-(steps for gesture control by image processing)
In our project we our deploying the first method ie gesture control using an
accelerometer sensor
CHAPTER 3 HARDWARE IMPLEMENTATION
31 Accelerometer
An accelerometer is a sensor that measures the physical acceleration experienced by an object due
to inertial forces or due to mechanical excitation In aerospace applications accelerometers are used
along with gyroscopes for navigation guidance and flight control Conceptually an accelerometer
behaves as a damped mass on a spring When the accelerometer experiences acceleration the mass
is displaced and the displacement is then measured to give the acceleration
In these devices piezoelectric piezoresistive and capacitive techniques are commonly used to
convert the mechanical motion into an electrical signal Piezoelectric accelerometers rely on
piezoceramics (eg lead zirconate titanate) or single crystals (eg quartz tourmaline) They are
unmatched in terms of their upper frequency range low packaged weight and high temperature
range Piezoresistive accelerometers are preferred in high shock applications Capacitive
accelerometers performance is superior in low frequency range and they can be operated in servo
mode to achieve high stability and linearity
15
Figure 6 An accelerometer
311 Working principle of accelerometer
16
Figure 7(schematic of an accelerometer)
The principle of working of an accelerometer can be explained by a simple mass (m) attached to a
spring of stiffness (k) that in turn is attached to a casing as illustrated in figure3 The mass used in
accelerometers is often called the seismic-mass or proof-mass In most cases the system also
includes a dashpot to provide a desirable damping effect
The dashpot with damping coefficient (c) is normally attached to the mass in parallel with the
spring When the spring mass system is subjected to linear acceleration a force equal to mass times
acceleration acts on the proof-mass causing it to deflect This deflection is sensed by a suitable
means and converted into an equivalent electrical signal Some form of damping is required
otherwise the system would not stabilize quickly under applied acceleration
To derive the motion equation of the system Newton‟s second law is used where all real forces
acting on the proof-mass are equal to the inertia force on the proof-mass Accordingly a dynamic
problem can be treated as a problem of static equilibrium and the equation of motion can be
obtained by direct formulation of the equations of equilibrium This damped mass-spring system
with applied force constitutes a classical second order mechanical system
312Accelerometer as Gesture Control Sensor
The accelerometer can be used in gesture controlled application As seen the accelerometer sensor measures the physical acceleration experienced by an object due to inertial forces or due to
mechanical excitationSo this means it will give different values for different gestures when
mounted on human handThis can be used as an advantage ieit can be interfaced with any of the
microcontroller or other device and can be used to control any robot or any oher device
313 Key factors while selecting an accelerometer
Some of the Key factors while selecting an accelerometer are
1Analog vs digital Depending on the interface to which you will be connecting the accelerometer
you need to select analog or digital output accelerometer
2Output Accelerometer comes with different outputs-Charge output IEPE output Voltage
output current output
17
3Number of axis Depending on your requirement you need to select single double or tri axis
accelerometer The 3 axis accelerometer will measure acceleration in all directions
4Acceleration range Acceleration Range is measured in units of g 1g is equal to the earths
gravity at sea level
5Sensitivity is the ratio of change in acceleration (input) to change in the output signal Sensitivity
is specified at a particular supply voltage and is typically expressed in units of mVg
314 Applications of Accelerometers
Used in cars to study shock and vibrations
Camcorders use accelerometers for image stabilization
Still cameras use accelerometers for anti-blur capturing
Used in mobile phones for multiple functions including tilt detection motion detectionetc
32 IR SENSOR
The InfraRed receiver transmitter pair is to use be worn around the fingers and controls the opening
and closing of the end effector
321 Introduction
An infrared sensor is an electronic instrument that is used to sense certain characteristics of its
surroundings by either emitting andor detecting infrared radiation It is also capable of measuring
heat of an object and detecting motion Infrared waves are not visible to the human eye
In the electromagnetic spectrum infrared radiation is the region having wavelengths longer than
visible light wavelengths but shorter than microwaves The infrared region is approximately
demarcated from 075 to 1000microm The wavelength region from 075 to 3microm is termed as near
infrared the region from 3 to 6microm is termed mid-infrared and the region higher than 6microm is termed
as far infrared
18
Infrared technology is found in many of our everyday products For example TV has an IR detector
for interpreting the signal from the remote control Key benefits of infrared sensors include low
power requirements simple circuitry and their portable feature
322 Working Principle
A typical system for detecting infrared radiation using infrared sensors includes the infrared source
such as blackbody radiators tungsten lamps and silicon carbide In case of active IR sensors the
sources are infrared lasers and LEDs of specific IR wavelengths Next is the transmission medium
used for infrared transmission which includes vacuum the atmosphere and optical fibers
Thirdly optical components such as optical lenses made from quartz CaF2 Ge and Si polyethylene
Fresnel lenses and Al or Au mirrors are used to converge or focus infrared radiation Likewise to
limit spectral response band-pass filters are ideal
Finally the infrared detector completes the system for detecting infrared radiation The output from
the detector is usually very small and hence pre-amplifiers coupled with circuitry are added to
further process the received signals
Figure 8 Circuit Diagram Of An IR Sensor
19
323 Applications
The following are the key application areas of infrared sensors
Tracking and art history
Climatology meteorology and astronomy
Thermography communications and alcohol testing
Heating hyperspectral imaging and night vision
Biological systems photobiomodulation and plant health
Gas detectorsgas leak detection
Water and steel analysis flame detection
Anesthesiology testing and spectroscopy
Petroleum exploration and underground solution
Rail safety
33 SERVO MOTORS
A servomotor is a rotary actuator that allows for precise control of angular position velocity and
acceleration It consists of a suitable motor coupled to a sensor for position feedback It also requires
a relatively sophisticated controller often a dedicated module designed specifically for use with
servomotors
331 Controlling Of A Servo Motor
Servos are controlled by sending an electrical pulse of variable width or pulse width
modulation (PWM) through the control wire There is a minimum pulse a maximum pulse and a
repetition rate A servo motor can usually only turn 90 degrees in either direction for a total of 180
degree movement The motors neutral position is defined as the position where the servo has the
same amount of potential rotation in the both the clockwise or counter-clockwise direction The
PWM sent to the motor determines position of the shaft and based on the duration of the pulse sent
via the control wire the rotor will turn to the desired position The servo motor expects to see a
pulse every 20 milliseconds (ms) and the length of the pulse will determine how far the motor turns
For example a 15ms pulse will make the motor turn to the 90-degree position Shorter than 15ms
moves it to 0 degrees and any longer than 15ms will turn the servo to 180 degrees as diagramed
below
20
Figure 9 Controlling an servo
332 Types of Servo Motors
There are two types of servo motors - AC and DC AC servo can handle higher current surges and
tend to be used in industrial machinery DC servos are not designed for high current surges and are
usually better suited for smaller applications Generally speaking DC motors are less expensive
than their AC counterparts These are also servo motors that have been built specifically
for continuous rotation making it an easy way to get your robot moving They feature two ball
bearings on the output shaft for reduced friction and easy access to the rest-point
adjustment potentiometer
333Servo Motor Applications
Servos are used in radio-controlled airplanes to position control surfaces like elevators rudders
walking a robot or operating grippers Servo motors are small have built-in control circuitry and
have good power for their size
In food services and pharmaceuticals the tools are designed to be used in harsher environments
where the potential for corrosion is high due to being washed at high pressures and temperatures
repeatedly to maintain strict hygiene standards Servos are also used in in-line manufacturing
where high repetition yet precise work is necessary
21
Of course you dont have to know how a servo works to use one but as with most electronics the
more you understand the more doors open for expanded projects and projects capabilities Whether
youre a hobbyist building robots an engineer designing industrial systems or just constantly
curious where will servo motors take you
334 Specifications
It is highly desirable to control or to maintain a certain location of motor rotor in a robotic arm not
only to determine its precise motion and position but also to control it in desired fashion most of the
industrial robotic arm contains pneumatic hydraulic and stepper motor to actuates they have very
high payload capacity but GuRoo is a low powered high degree of freedom robotic arm we uses
servo motor due their easy availability and high weight to torque ratio
HS-645mg standard deluxe high torque servo
Figure 10HS-475-SERVO
Detailed Specifications of above shown servo
Motor Type 3 Pole
Bearing Type Top Ball Bearing
22
Speed 023 018 sec 60 deg
Torque 44 55 kgcm
Size 3880 x 1980 x 3600mm
Weight 4000g
34 ATMega32
A microcontroller is the brain of the robot The main features of this controller are
Advanced RISC Architecture
Up to 16 MIPS Throughput at 16 MHz
16K Bytes of In-System Self-Programmable Flash
512 Bytes EEPROM
1K Byte Internal SRAM
32 Programmable IO Lines
In-System Programming by On-chip Boot Program
8-channel 10-bit ADC
Two 8-bit TimerCounters with Separate Prescalers and Compare Modes
One 16-bit TimerCounter with Separate Prescaler Compare Mode and Capture
Four PWM Channels
Programmable Serial USART
MasterSlave SPI Serial Interface
Byte-oriented Two-wire Serial Interface
Programmable Watchdog Timer with Separate On-chip Oscillator
External and Internal Interrupt Sources
23
Figure 11 - Pin configuration
CHAPTER 4 METHODOLOGY
The setup consists of a robotic arm having 5 degrees of freedom and 6 servo motors
The movements of the joints are controlled using servo motors that can move a fixed angle ranging from 0 to
180 degrees
Accelerometer 1
ADC of Microcontroller
Servo for wrist movement
24
IR sensor
Microcontroller
Servomotor for gripping
mechanism
Figure121 Flowchart for First Accelerometer
Figure122 Flowchart for second Accelerometer
Figure123 Flowchart for IR sensor
Accelerometer 2
ADC of Microcontroller
Servomotor for elbow
movement
25
Figure124 Flowchart for POTENTIOMETER
Potentiometer
ADC of microcontroller
servomotor for base movement
26
Figure 125 Complete Flow Chart
Complete flow chart depicting each sensor interfaced with microcontroller and the
movement of each and every servos (ie robotic arm)
27
41 SETUP USED amp SCHEMATIC
A setup consisting of
1 IR sensors
2 Two accelerometers and
3 A potentiometer is to be worn around the human hand for sensing the gesture
movements
The InfraRed receiver transmitter pair is to be worn around the fingers and controls the
opening and closing of the end effector
2 accelerometers are used for sensing the movement of the forearm and the wrist movement
A potentiometer is used to track the elbow movement
Figure13 Schematic of the components used
28
Figure 14 Setup Used
29
Figure 151 Linear prediction for wrist movement 1
CHAPTER 5 ALGORITHIM USED
(PREDICTION AND CORRECTION ALGORITHM)
An algorithm has been devised to make the robotic arm replicate the motions of the human arm
The robotic arm does not exactly have an idea of the exact movement of the human arm and takes
input from noisy sensors
The algorithm consists of the following parts
1 LINEAR PREDICTION
The values of the sensors and motors for every joint have been stored for certain predefined
positions for each joint movement The position of the robotic arm is predicted linearly using the
given formulae
119823119851119838119837119842119836119853119838119837 119852119838119851119855119848 119855119834119845119854119838 = (119846120784 minus 119846120783) lowast119842119847119849119854119853 119852119838119847119852119848119851 119855119834119845119854119838 minus 119852120783
(119852120784 minus 119852120783)
-
30
Figure 152 Linear prediction for wrist movement 2
Figure 153 Linear prediction for elbow movement 1
31
Figure 154 Linear prediction for elbow movement 2
m2- predefined value of the servo motor for the next known position
m1- predefined value of the servo motor for the previous known position
s1- predefined sensor value for the last known position
s2- predefined sensor value for the next known position
2) CORRECTION
The predicted value is then compared to the present value and the difference between the two
120782 119838119851119851119848119851 ge 119853119841119851119838119852119841119848119845119837
33
CHAPTER 6 APPLICATIONS
1) Industrial Applications
Such arms may prove handy in such sectors where the precision has to be adjusted from
time to time
Such arms make the job of the controller easier and have the capability of being operated at
faster speed than the traditional robotic arms used in the industries
A combination of the traditional and gesture controlled robotic arm may prove to be very
handy providing the arm both flexibility as well as accuracy
Disposing off radioactive wastes or any other hazardous chemical that may be dangerous
for human beings
Can be used in mines and space where human intervention is not possible
2) Defense
It Can be used for bomb disposal offering as much accuracy as a human arm and also
saving a human life
3) Medical Uses
Can be used by doctors to perform surgical operations at distant places
Such a technology can prove to be helping hand to physically disabled people or extremely
old people
34
CHAPTER 7 CONCLUSION AND FUTURE PROSPRCTS
71 CONCLUSION
As the error can be both positive and negative hence the robotic arm becomes less susceptible to
vibrations as when the human arm vibrates the error would eventually cancel itself or become small
in magnitude than the threshold value and at the same time it can detect small changes made in the
human arm because the error adds up to cross the threshold
In the paper an algorithm is proposed to control a gesture based robotic arm The position of each
motor is predicted based on the sensory input later the position is corrected while comparing it to
the actual position of the motor This algorithm is helpful in reducing the effects of vibrations that
may take place in a human arm and hence it can find great use in the area of medical surgery
72 FUTURE PROSPECTS
Modern robot systems provide graphical simulation and virtual environment for programming of
robots Our system can be enhanced to include these facilities Vision is one of the most important
features of the industrial robot systems present today For this purpose a pair of cameras can be
attached to the robotic arm which will allow robot to automatically identify and grasp the objects
Imitation based learning capability can be added to the robotic arm which will allow path tracking
by a different technique The instruction set for the language and the teach pendant can be enhanced
to include vision forces torques imitation etc The communication from the host can be made
wireless this will allow programming and teaching from a remote location and would create a lot of
other applications for this robotic arm A robotic arm with remotely located control A wearable
robotic arm (exoskeleton) with high force reflection capability
35
CHAPTER 8 REFRENCES
[1] Cyber Technology in Automation Control and Intelligent Systems (CYBER) 2012 IEEE
International Conference on Mechatronics(ICOM)
[2] Matthias Rehm Nikolaus Bee Elisabeth Andreacute Wave Like an Egyptian - Accelerometer
Based Gesture Recognition for Culture Specific InteractionsBritish Computer Society
2007
[3] Pavlovic V Sharma R amp Huang T (1997) Visual interpretation of hand gestures for
human- computer Interaction A review (IEEE Trans Pattern Analysis and Machine
Intelligence July 1997 Vol 19(7) pp 677 -695
[4] Micro Electro Mechanical Systems (MEMS) START Selected Topics in Assurance
Related Technologies) volume 8 number 1
[5] Wong Guan Hao Yap Yee Leck and Lim Chot Hunldquo6-DOFPC-Based robotic arm (PC-
robo arm) with efficient trajectory lanning and speed controlrdquo 2011 4th International
Conference on Mechatronics (ICOM) 17-19 May 2011 Kuala Lumpur Malaysia
14
Figure 5-(steps for gesture control by image processing)
In our project we our deploying the first method ie gesture control using an
accelerometer sensor
CHAPTER 3 HARDWARE IMPLEMENTATION
31 Accelerometer
An accelerometer is a sensor that measures the physical acceleration experienced by an object due
to inertial forces or due to mechanical excitation In aerospace applications accelerometers are used
along with gyroscopes for navigation guidance and flight control Conceptually an accelerometer
behaves as a damped mass on a spring When the accelerometer experiences acceleration the mass
is displaced and the displacement is then measured to give the acceleration
In these devices piezoelectric piezoresistive and capacitive techniques are commonly used to
convert the mechanical motion into an electrical signal Piezoelectric accelerometers rely on
piezoceramics (eg lead zirconate titanate) or single crystals (eg quartz tourmaline) They are
unmatched in terms of their upper frequency range low packaged weight and high temperature
range Piezoresistive accelerometers are preferred in high shock applications Capacitive
accelerometers performance is superior in low frequency range and they can be operated in servo
mode to achieve high stability and linearity
15
Figure 6 An accelerometer
311 Working principle of accelerometer
16
Figure 7(schematic of an accelerometer)
The principle of working of an accelerometer can be explained by a simple mass (m) attached to a
spring of stiffness (k) that in turn is attached to a casing as illustrated in figure3 The mass used in
accelerometers is often called the seismic-mass or proof-mass In most cases the system also
includes a dashpot to provide a desirable damping effect
The dashpot with damping coefficient (c) is normally attached to the mass in parallel with the
spring When the spring mass system is subjected to linear acceleration a force equal to mass times
acceleration acts on the proof-mass causing it to deflect This deflection is sensed by a suitable
means and converted into an equivalent electrical signal Some form of damping is required
otherwise the system would not stabilize quickly under applied acceleration
To derive the motion equation of the system Newton‟s second law is used where all real forces
acting on the proof-mass are equal to the inertia force on the proof-mass Accordingly a dynamic
problem can be treated as a problem of static equilibrium and the equation of motion can be
obtained by direct formulation of the equations of equilibrium This damped mass-spring system
with applied force constitutes a classical second order mechanical system
312Accelerometer as Gesture Control Sensor
The accelerometer can be used in gesture controlled application As seen the accelerometer sensor measures the physical acceleration experienced by an object due to inertial forces or due to
mechanical excitationSo this means it will give different values for different gestures when
mounted on human handThis can be used as an advantage ieit can be interfaced with any of the
microcontroller or other device and can be used to control any robot or any oher device
313 Key factors while selecting an accelerometer
Some of the Key factors while selecting an accelerometer are
1Analog vs digital Depending on the interface to which you will be connecting the accelerometer
you need to select analog or digital output accelerometer
2Output Accelerometer comes with different outputs-Charge output IEPE output Voltage
output current output
17
3Number of axis Depending on your requirement you need to select single double or tri axis
accelerometer The 3 axis accelerometer will measure acceleration in all directions
4Acceleration range Acceleration Range is measured in units of g 1g is equal to the earths
gravity at sea level
5Sensitivity is the ratio of change in acceleration (input) to change in the output signal Sensitivity
is specified at a particular supply voltage and is typically expressed in units of mVg
314 Applications of Accelerometers
Used in cars to study shock and vibrations
Camcorders use accelerometers for image stabilization
Still cameras use accelerometers for anti-blur capturing
Used in mobile phones for multiple functions including tilt detection motion detectionetc
32 IR SENSOR
The InfraRed receiver transmitter pair is to use be worn around the fingers and controls the opening
and closing of the end effector
321 Introduction
An infrared sensor is an electronic instrument that is used to sense certain characteristics of its
surroundings by either emitting andor detecting infrared radiation It is also capable of measuring
heat of an object and detecting motion Infrared waves are not visible to the human eye
In the electromagnetic spectrum infrared radiation is the region having wavelengths longer than
visible light wavelengths but shorter than microwaves The infrared region is approximately
demarcated from 075 to 1000microm The wavelength region from 075 to 3microm is termed as near
infrared the region from 3 to 6microm is termed mid-infrared and the region higher than 6microm is termed
as far infrared
18
Infrared technology is found in many of our everyday products For example TV has an IR detector
for interpreting the signal from the remote control Key benefits of infrared sensors include low
power requirements simple circuitry and their portable feature
322 Working Principle
A typical system for detecting infrared radiation using infrared sensors includes the infrared source
such as blackbody radiators tungsten lamps and silicon carbide In case of active IR sensors the
sources are infrared lasers and LEDs of specific IR wavelengths Next is the transmission medium
used for infrared transmission which includes vacuum the atmosphere and optical fibers
Thirdly optical components such as optical lenses made from quartz CaF2 Ge and Si polyethylene
Fresnel lenses and Al or Au mirrors are used to converge or focus infrared radiation Likewise to
limit spectral response band-pass filters are ideal
Finally the infrared detector completes the system for detecting infrared radiation The output from
the detector is usually very small and hence pre-amplifiers coupled with circuitry are added to
further process the received signals
Figure 8 Circuit Diagram Of An IR Sensor
19
323 Applications
The following are the key application areas of infrared sensors
Tracking and art history
Climatology meteorology and astronomy
Thermography communications and alcohol testing
Heating hyperspectral imaging and night vision
Biological systems photobiomodulation and plant health
Gas detectorsgas leak detection
Water and steel analysis flame detection
Anesthesiology testing and spectroscopy
Petroleum exploration and underground solution
Rail safety
33 SERVO MOTORS
A servomotor is a rotary actuator that allows for precise control of angular position velocity and
acceleration It consists of a suitable motor coupled to a sensor for position feedback It also requires
a relatively sophisticated controller often a dedicated module designed specifically for use with
servomotors
331 Controlling Of A Servo Motor
Servos are controlled by sending an electrical pulse of variable width or pulse width
modulation (PWM) through the control wire There is a minimum pulse a maximum pulse and a
repetition rate A servo motor can usually only turn 90 degrees in either direction for a total of 180
degree movement The motors neutral position is defined as the position where the servo has the
same amount of potential rotation in the both the clockwise or counter-clockwise direction The
PWM sent to the motor determines position of the shaft and based on the duration of the pulse sent
via the control wire the rotor will turn to the desired position The servo motor expects to see a
pulse every 20 milliseconds (ms) and the length of the pulse will determine how far the motor turns
For example a 15ms pulse will make the motor turn to the 90-degree position Shorter than 15ms
moves it to 0 degrees and any longer than 15ms will turn the servo to 180 degrees as diagramed
below
20
Figure 9 Controlling an servo
332 Types of Servo Motors
There are two types of servo motors - AC and DC AC servo can handle higher current surges and
tend to be used in industrial machinery DC servos are not designed for high current surges and are
usually better suited for smaller applications Generally speaking DC motors are less expensive
than their AC counterparts These are also servo motors that have been built specifically
for continuous rotation making it an easy way to get your robot moving They feature two ball
bearings on the output shaft for reduced friction and easy access to the rest-point
adjustment potentiometer
333Servo Motor Applications
Servos are used in radio-controlled airplanes to position control surfaces like elevators rudders
walking a robot or operating grippers Servo motors are small have built-in control circuitry and
have good power for their size
In food services and pharmaceuticals the tools are designed to be used in harsher environments
where the potential for corrosion is high due to being washed at high pressures and temperatures
repeatedly to maintain strict hygiene standards Servos are also used in in-line manufacturing
where high repetition yet precise work is necessary
21
Of course you dont have to know how a servo works to use one but as with most electronics the
more you understand the more doors open for expanded projects and projects capabilities Whether
youre a hobbyist building robots an engineer designing industrial systems or just constantly
curious where will servo motors take you
334 Specifications
It is highly desirable to control or to maintain a certain location of motor rotor in a robotic arm not
only to determine its precise motion and position but also to control it in desired fashion most of the
industrial robotic arm contains pneumatic hydraulic and stepper motor to actuates they have very
high payload capacity but GuRoo is a low powered high degree of freedom robotic arm we uses
servo motor due their easy availability and high weight to torque ratio
HS-645mg standard deluxe high torque servo
Figure 10HS-475-SERVO
Detailed Specifications of above shown servo
Motor Type 3 Pole
Bearing Type Top Ball Bearing
22
Speed 023 018 sec 60 deg
Torque 44 55 kgcm
Size 3880 x 1980 x 3600mm
Weight 4000g
34 ATMega32
A microcontroller is the brain of the robot The main features of this controller are
Advanced RISC Architecture
Up to 16 MIPS Throughput at 16 MHz
16K Bytes of In-System Self-Programmable Flash
512 Bytes EEPROM
1K Byte Internal SRAM
32 Programmable IO Lines
In-System Programming by On-chip Boot Program
8-channel 10-bit ADC
Two 8-bit TimerCounters with Separate Prescalers and Compare Modes
One 16-bit TimerCounter with Separate Prescaler Compare Mode and Capture
Four PWM Channels
Programmable Serial USART
MasterSlave SPI Serial Interface
Byte-oriented Two-wire Serial Interface
Programmable Watchdog Timer with Separate On-chip Oscillator
External and Internal Interrupt Sources
23
Figure 11 - Pin configuration
CHAPTER 4 METHODOLOGY
The setup consists of a robotic arm having 5 degrees of freedom and 6 servo motors
The movements of the joints are controlled using servo motors that can move a fixed angle ranging from 0 to
180 degrees
Accelerometer 1
ADC of Microcontroller
Servo for wrist movement
24
IR sensor
Microcontroller
Servomotor for gripping
mechanism
Figure121 Flowchart for First Accelerometer
Figure122 Flowchart for second Accelerometer
Figure123 Flowchart for IR sensor
Accelerometer 2
ADC of Microcontroller
Servomotor for elbow
movement
25
Figure124 Flowchart for POTENTIOMETER
Potentiometer
ADC of microcontroller
servomotor for base movement
26
Figure 125 Complete Flow Chart
Complete flow chart depicting each sensor interfaced with microcontroller and the
movement of each and every servos (ie robotic arm)
27
41 SETUP USED amp SCHEMATIC
A setup consisting of
1 IR sensors
2 Two accelerometers and
3 A potentiometer is to be worn around the human hand for sensing the gesture
movements
The InfraRed receiver transmitter pair is to be worn around the fingers and controls the
opening and closing of the end effector
2 accelerometers are used for sensing the movement of the forearm and the wrist movement
A potentiometer is used to track the elbow movement
Figure13 Schematic of the components used
28
Figure 14 Setup Used
29
Figure 151 Linear prediction for wrist movement 1
CHAPTER 5 ALGORITHIM USED
(PREDICTION AND CORRECTION ALGORITHM)
An algorithm has been devised to make the robotic arm replicate the motions of the human arm
The robotic arm does not exactly have an idea of the exact movement of the human arm and takes
input from noisy sensors
The algorithm consists of the following parts
1 LINEAR PREDICTION
The values of the sensors and motors for every joint have been stored for certain predefined
positions for each joint movement The position of the robotic arm is predicted linearly using the
given formulae
119823119851119838119837119842119836119853119838119837 119852119838119851119855119848 119855119834119845119854119838 = (119846120784 minus 119846120783) lowast119842119847119849119854119853 119852119838119847119852119848119851 119855119834119845119854119838 minus 119852120783
(119852120784 minus 119852120783)
-
30
Figure 152 Linear prediction for wrist movement 2
Figure 153 Linear prediction for elbow movement 1
31
Figure 154 Linear prediction for elbow movement 2
m2- predefined value of the servo motor for the next known position
m1- predefined value of the servo motor for the previous known position
s1- predefined sensor value for the last known position
s2- predefined sensor value for the next known position
2) CORRECTION
The predicted value is then compared to the present value and the difference between the two
120782 119838119851119851119848119851 ge 119853119841119851119838119852119841119848119845119837
33
CHAPTER 6 APPLICATIONS
1) Industrial Applications
Such arms may prove handy in such sectors where the precision has to be adjusted from
time to time
Such arms make the job of the controller easier and have the capability of being operated at
faster speed than the traditional robotic arms used in the industries
A combination of the traditional and gesture controlled robotic arm may prove to be very
handy providing the arm both flexibility as well as accuracy
Disposing off radioactive wastes or any other hazardous chemical that may be dangerous
for human beings
Can be used in mines and space where human intervention is not possible
2) Defense
It Can be used for bomb disposal offering as much accuracy as a human arm and also
saving a human life
3) Medical Uses
Can be used by doctors to perform surgical operations at distant places
Such a technology can prove to be helping hand to physically disabled people or extremely
old people
34
CHAPTER 7 CONCLUSION AND FUTURE PROSPRCTS
71 CONCLUSION
As the error can be both positive and negative hence the robotic arm becomes less susceptible to
vibrations as when the human arm vibrates the error would eventually cancel itself or become small
in magnitude than the threshold value and at the same time it can detect small changes made in the
human arm because the error adds up to cross the threshold
In the paper an algorithm is proposed to control a gesture based robotic arm The position of each
motor is predicted based on the sensory input later the position is corrected while comparing it to
the actual position of the motor This algorithm is helpful in reducing the effects of vibrations that
may take place in a human arm and hence it can find great use in the area of medical surgery
72 FUTURE PROSPECTS
Modern robot systems provide graphical simulation and virtual environment for programming of
robots Our system can be enhanced to include these facilities Vision is one of the most important
features of the industrial robot systems present today For this purpose a pair of cameras can be
attached to the robotic arm which will allow robot to automatically identify and grasp the objects
Imitation based learning capability can be added to the robotic arm which will allow path tracking
by a different technique The instruction set for the language and the teach pendant can be enhanced
to include vision forces torques imitation etc The communication from the host can be made
wireless this will allow programming and teaching from a remote location and would create a lot of
other applications for this robotic arm A robotic arm with remotely located control A wearable
robotic arm (exoskeleton) with high force reflection capability
35
CHAPTER 8 REFRENCES
[1] Cyber Technology in Automation Control and Intelligent Systems (CYBER) 2012 IEEE
International Conference on Mechatronics(ICOM)
[2] Matthias Rehm Nikolaus Bee Elisabeth Andreacute Wave Like an Egyptian - Accelerometer
Based Gesture Recognition for Culture Specific InteractionsBritish Computer Society
2007
[3] Pavlovic V Sharma R amp Huang T (1997) Visual interpretation of hand gestures for
human- computer Interaction A review (IEEE Trans Pattern Analysis and Machine
Intelligence July 1997 Vol 19(7) pp 677 -695
[4] Micro Electro Mechanical Systems (MEMS) START Selected Topics in Assurance
Related Technologies) volume 8 number 1
[5] Wong Guan Hao Yap Yee Leck and Lim Chot Hunldquo6-DOFPC-Based robotic arm (PC-
robo arm) with efficient trajectory lanning and speed controlrdquo 2011 4th International
Conference on Mechatronics (ICOM) 17-19 May 2011 Kuala Lumpur Malaysia
15
Figure 6 An accelerometer
311 Working principle of accelerometer
16
Figure 7(schematic of an accelerometer)
The principle of working of an accelerometer can be explained by a simple mass (m) attached to a
spring of stiffness (k) that in turn is attached to a casing as illustrated in figure3 The mass used in
accelerometers is often called the seismic-mass or proof-mass In most cases the system also
includes a dashpot to provide a desirable damping effect
The dashpot with damping coefficient (c) is normally attached to the mass in parallel with the
spring When the spring mass system is subjected to linear acceleration a force equal to mass times
acceleration acts on the proof-mass causing it to deflect This deflection is sensed by a suitable
means and converted into an equivalent electrical signal Some form of damping is required
otherwise the system would not stabilize quickly under applied acceleration
To derive the motion equation of the system Newton‟s second law is used where all real forces
acting on the proof-mass are equal to the inertia force on the proof-mass Accordingly a dynamic
problem can be treated as a problem of static equilibrium and the equation of motion can be
obtained by direct formulation of the equations of equilibrium This damped mass-spring system
with applied force constitutes a classical second order mechanical system
312Accelerometer as Gesture Control Sensor
The accelerometer can be used in gesture controlled application As seen the accelerometer sensor measures the physical acceleration experienced by an object due to inertial forces or due to
mechanical excitationSo this means it will give different values for different gestures when
mounted on human handThis can be used as an advantage ieit can be interfaced with any of the
microcontroller or other device and can be used to control any robot or any oher device
313 Key factors while selecting an accelerometer
Some of the Key factors while selecting an accelerometer are
1Analog vs digital Depending on the interface to which you will be connecting the accelerometer
you need to select analog or digital output accelerometer
2Output Accelerometer comes with different outputs-Charge output IEPE output Voltage
output current output
17
3Number of axis Depending on your requirement you need to select single double or tri axis
accelerometer The 3 axis accelerometer will measure acceleration in all directions
4Acceleration range Acceleration Range is measured in units of g 1g is equal to the earths
gravity at sea level
5Sensitivity is the ratio of change in acceleration (input) to change in the output signal Sensitivity
is specified at a particular supply voltage and is typically expressed in units of mVg
314 Applications of Accelerometers
Used in cars to study shock and vibrations
Camcorders use accelerometers for image stabilization
Still cameras use accelerometers for anti-blur capturing
Used in mobile phones for multiple functions including tilt detection motion detectionetc
32 IR SENSOR
The InfraRed receiver transmitter pair is to use be worn around the fingers and controls the opening
and closing of the end effector
321 Introduction
An infrared sensor is an electronic instrument that is used to sense certain characteristics of its
surroundings by either emitting andor detecting infrared radiation It is also capable of measuring
heat of an object and detecting motion Infrared waves are not visible to the human eye
In the electromagnetic spectrum infrared radiation is the region having wavelengths longer than
visible light wavelengths but shorter than microwaves The infrared region is approximately
demarcated from 075 to 1000microm The wavelength region from 075 to 3microm is termed as near
infrared the region from 3 to 6microm is termed mid-infrared and the region higher than 6microm is termed
as far infrared
18
Infrared technology is found in many of our everyday products For example TV has an IR detector
for interpreting the signal from the remote control Key benefits of infrared sensors include low
power requirements simple circuitry and their portable feature
322 Working Principle
A typical system for detecting infrared radiation using infrared sensors includes the infrared source
such as blackbody radiators tungsten lamps and silicon carbide In case of active IR sensors the
sources are infrared lasers and LEDs of specific IR wavelengths Next is the transmission medium
used for infrared transmission which includes vacuum the atmosphere and optical fibers
Thirdly optical components such as optical lenses made from quartz CaF2 Ge and Si polyethylene
Fresnel lenses and Al or Au mirrors are used to converge or focus infrared radiation Likewise to
limit spectral response band-pass filters are ideal
Finally the infrared detector completes the system for detecting infrared radiation The output from
the detector is usually very small and hence pre-amplifiers coupled with circuitry are added to
further process the received signals
Figure 8 Circuit Diagram Of An IR Sensor
19
323 Applications
The following are the key application areas of infrared sensors
Tracking and art history
Climatology meteorology and astronomy
Thermography communications and alcohol testing
Heating hyperspectral imaging and night vision
Biological systems photobiomodulation and plant health
Gas detectorsgas leak detection
Water and steel analysis flame detection
Anesthesiology testing and spectroscopy
Petroleum exploration and underground solution
Rail safety
33 SERVO MOTORS
A servomotor is a rotary actuator that allows for precise control of angular position velocity and
acceleration It consists of a suitable motor coupled to a sensor for position feedback It also requires
a relatively sophisticated controller often a dedicated module designed specifically for use with
servomotors
331 Controlling Of A Servo Motor
Servos are controlled by sending an electrical pulse of variable width or pulse width
modulation (PWM) through the control wire There is a minimum pulse a maximum pulse and a
repetition rate A servo motor can usually only turn 90 degrees in either direction for a total of 180
degree movement The motors neutral position is defined as the position where the servo has the
same amount of potential rotation in the both the clockwise or counter-clockwise direction The
PWM sent to the motor determines position of the shaft and based on the duration of the pulse sent
via the control wire the rotor will turn to the desired position The servo motor expects to see a
pulse every 20 milliseconds (ms) and the length of the pulse will determine how far the motor turns
For example a 15ms pulse will make the motor turn to the 90-degree position Shorter than 15ms
moves it to 0 degrees and any longer than 15ms will turn the servo to 180 degrees as diagramed
below
20
Figure 9 Controlling an servo
332 Types of Servo Motors
There are two types of servo motors - AC and DC AC servo can handle higher current surges and
tend to be used in industrial machinery DC servos are not designed for high current surges and are
usually better suited for smaller applications Generally speaking DC motors are less expensive
than their AC counterparts These are also servo motors that have been built specifically
for continuous rotation making it an easy way to get your robot moving They feature two ball
bearings on the output shaft for reduced friction and easy access to the rest-point
adjustment potentiometer
333Servo Motor Applications
Servos are used in radio-controlled airplanes to position control surfaces like elevators rudders
walking a robot or operating grippers Servo motors are small have built-in control circuitry and
have good power for their size
In food services and pharmaceuticals the tools are designed to be used in harsher environments
where the potential for corrosion is high due to being washed at high pressures and temperatures
repeatedly to maintain strict hygiene standards Servos are also used in in-line manufacturing
where high repetition yet precise work is necessary
21
Of course you dont have to know how a servo works to use one but as with most electronics the
more you understand the more doors open for expanded projects and projects capabilities Whether
youre a hobbyist building robots an engineer designing industrial systems or just constantly
curious where will servo motors take you
334 Specifications
It is highly desirable to control or to maintain a certain location of motor rotor in a robotic arm not
only to determine its precise motion and position but also to control it in desired fashion most of the
industrial robotic arm contains pneumatic hydraulic and stepper motor to actuates they have very
high payload capacity but GuRoo is a low powered high degree of freedom robotic arm we uses
servo motor due their easy availability and high weight to torque ratio
HS-645mg standard deluxe high torque servo
Figure 10HS-475-SERVO
Detailed Specifications of above shown servo
Motor Type 3 Pole
Bearing Type Top Ball Bearing
22
Speed 023 018 sec 60 deg
Torque 44 55 kgcm
Size 3880 x 1980 x 3600mm
Weight 4000g
34 ATMega32
A microcontroller is the brain of the robot The main features of this controller are
Advanced RISC Architecture
Up to 16 MIPS Throughput at 16 MHz
16K Bytes of In-System Self-Programmable Flash
512 Bytes EEPROM
1K Byte Internal SRAM
32 Programmable IO Lines
In-System Programming by On-chip Boot Program
8-channel 10-bit ADC
Two 8-bit TimerCounters with Separate Prescalers and Compare Modes
One 16-bit TimerCounter with Separate Prescaler Compare Mode and Capture
Four PWM Channels
Programmable Serial USART
MasterSlave SPI Serial Interface
Byte-oriented Two-wire Serial Interface
Programmable Watchdog Timer with Separate On-chip Oscillator
External and Internal Interrupt Sources
23
Figure 11 - Pin configuration
CHAPTER 4 METHODOLOGY
The setup consists of a robotic arm having 5 degrees of freedom and 6 servo motors
The movements of the joints are controlled using servo motors that can move a fixed angle ranging from 0 to
180 degrees
Accelerometer 1
ADC of Microcontroller
Servo for wrist movement
24
IR sensor
Microcontroller
Servomotor for gripping
mechanism
Figure121 Flowchart for First Accelerometer
Figure122 Flowchart for second Accelerometer
Figure123 Flowchart for IR sensor
Accelerometer 2
ADC of Microcontroller
Servomotor for elbow
movement
25
Figure124 Flowchart for POTENTIOMETER
Potentiometer
ADC of microcontroller
servomotor for base movement
26
Figure 125 Complete Flow Chart
Complete flow chart depicting each sensor interfaced with microcontroller and the
movement of each and every servos (ie robotic arm)
27
41 SETUP USED amp SCHEMATIC
A setup consisting of
1 IR sensors
2 Two accelerometers and
3 A potentiometer is to be worn around the human hand for sensing the gesture
movements
The InfraRed receiver transmitter pair is to be worn around the fingers and controls the
opening and closing of the end effector
2 accelerometers are used for sensing the movement of the forearm and the wrist movement
A potentiometer is used to track the elbow movement
Figure13 Schematic of the components used
28
Figure 14 Setup Used
29
Figure 151 Linear prediction for wrist movement 1
CHAPTER 5 ALGORITHIM USED
(PREDICTION AND CORRECTION ALGORITHM)
An algorithm has been devised to make the robotic arm replicate the motions of the human arm
The robotic arm does not exactly have an idea of the exact movement of the human arm and takes
input from noisy sensors
The algorithm consists of the following parts
1 LINEAR PREDICTION
The values of the sensors and motors for every joint have been stored for certain predefined
positions for each joint movement The position of the robotic arm is predicted linearly using the
given formulae
119823119851119838119837119842119836119853119838119837 119852119838119851119855119848 119855119834119845119854119838 = (119846120784 minus 119846120783) lowast119842119847119849119854119853 119852119838119847119852119848119851 119855119834119845119854119838 minus 119852120783
(119852120784 minus 119852120783)
-
30
Figure 152 Linear prediction for wrist movement 2
Figure 153 Linear prediction for elbow movement 1
31
Figure 154 Linear prediction for elbow movement 2
m2- predefined value of the servo motor for the next known position
m1- predefined value of the servo motor for the previous known position
s1- predefined sensor value for the last known position
s2- predefined sensor value for the next known position
2) CORRECTION
The predicted value is then compared to the present value and the difference between the two
120782 119838119851119851119848119851 ge 119853119841119851119838119852119841119848119845119837
33
CHAPTER 6 APPLICATIONS
1) Industrial Applications
Such arms may prove handy in such sectors where the precision has to be adjusted from
time to time
Such arms make the job of the controller easier and have the capability of being operated at
faster speed than the traditional robotic arms used in the industries
A combination of the traditional and gesture controlled robotic arm may prove to be very
handy providing the arm both flexibility as well as accuracy
Disposing off radioactive wastes or any other hazardous chemical that may be dangerous
for human beings
Can be used in mines and space where human intervention is not possible
2) Defense
It Can be used for bomb disposal offering as much accuracy as a human arm and also
saving a human life
3) Medical Uses
Can be used by doctors to perform surgical operations at distant places
Such a technology can prove to be helping hand to physically disabled people or extremely
old people
34
CHAPTER 7 CONCLUSION AND FUTURE PROSPRCTS
71 CONCLUSION
As the error can be both positive and negative hence the robotic arm becomes less susceptible to
vibrations as when the human arm vibrates the error would eventually cancel itself or become small
in magnitude than the threshold value and at the same time it can detect small changes made in the
human arm because the error adds up to cross the threshold
In the paper an algorithm is proposed to control a gesture based robotic arm The position of each
motor is predicted based on the sensory input later the position is corrected while comparing it to
the actual position of the motor This algorithm is helpful in reducing the effects of vibrations that
may take place in a human arm and hence it can find great use in the area of medical surgery
72 FUTURE PROSPECTS
Modern robot systems provide graphical simulation and virtual environment for programming of
robots Our system can be enhanced to include these facilities Vision is one of the most important
features of the industrial robot systems present today For this purpose a pair of cameras can be
attached to the robotic arm which will allow robot to automatically identify and grasp the objects
Imitation based learning capability can be added to the robotic arm which will allow path tracking
by a different technique The instruction set for the language and the teach pendant can be enhanced
to include vision forces torques imitation etc The communication from the host can be made
wireless this will allow programming and teaching from a remote location and would create a lot of
other applications for this robotic arm A robotic arm with remotely located control A wearable
robotic arm (exoskeleton) with high force reflection capability
35
CHAPTER 8 REFRENCES
[1] Cyber Technology in Automation Control and Intelligent Systems (CYBER) 2012 IEEE
International Conference on Mechatronics(ICOM)
[2] Matthias Rehm Nikolaus Bee Elisabeth Andreacute Wave Like an Egyptian - Accelerometer
Based Gesture Recognition for Culture Specific InteractionsBritish Computer Society
2007
[3] Pavlovic V Sharma R amp Huang T (1997) Visual interpretation of hand gestures for
human- computer Interaction A review (IEEE Trans Pattern Analysis and Machine
Intelligence July 1997 Vol 19(7) pp 677 -695
[4] Micro Electro Mechanical Systems (MEMS) START Selected Topics in Assurance
Related Technologies) volume 8 number 1
[5] Wong Guan Hao Yap Yee Leck and Lim Chot Hunldquo6-DOFPC-Based robotic arm (PC-
robo arm) with efficient trajectory lanning and speed controlrdquo 2011 4th International
Conference on Mechatronics (ICOM) 17-19 May 2011 Kuala Lumpur Malaysia
16
Figure 7(schematic of an accelerometer)
The principle of working of an accelerometer can be explained by a simple mass (m) attached to a
spring of stiffness (k) that in turn is attached to a casing as illustrated in figure3 The mass used in
accelerometers is often called the seismic-mass or proof-mass In most cases the system also
includes a dashpot to provide a desirable damping effect
The dashpot with damping coefficient (c) is normally attached to the mass in parallel with the
spring When the spring mass system is subjected to linear acceleration a force equal to mass times
acceleration acts on the proof-mass causing it to deflect This deflection is sensed by a suitable
means and converted into an equivalent electrical signal Some form of damping is required
otherwise the system would not stabilize quickly under applied acceleration
To derive the motion equation of the system Newton‟s second law is used where all real forces
acting on the proof-mass are equal to the inertia force on the proof-mass Accordingly a dynamic
problem can be treated as a problem of static equilibrium and the equation of motion can be
obtained by direct formulation of the equations of equilibrium This damped mass-spring system
with applied force constitutes a classical second order mechanical system
312Accelerometer as Gesture Control Sensor
The accelerometer can be used in gesture controlled application As seen the accelerometer sensor measures the physical acceleration experienced by an object due to inertial forces or due to
mechanical excitationSo this means it will give different values for different gestures when
mounted on human handThis can be used as an advantage ieit can be interfaced with any of the
microcontroller or other device and can be used to control any robot or any oher device
313 Key factors while selecting an accelerometer
Some of the Key factors while selecting an accelerometer are
1Analog vs digital Depending on the interface to which you will be connecting the accelerometer
you need to select analog or digital output accelerometer
2Output Accelerometer comes with different outputs-Charge output IEPE output Voltage
output current output
17
3Number of axis Depending on your requirement you need to select single double or tri axis
accelerometer The 3 axis accelerometer will measure acceleration in all directions
4Acceleration range Acceleration Range is measured in units of g 1g is equal to the earths
gravity at sea level
5Sensitivity is the ratio of change in acceleration (input) to change in the output signal Sensitivity
is specified at a particular supply voltage and is typically expressed in units of mVg
314 Applications of Accelerometers
Used in cars to study shock and vibrations
Camcorders use accelerometers for image stabilization
Still cameras use accelerometers for anti-blur capturing
Used in mobile phones for multiple functions including tilt detection motion detectionetc
32 IR SENSOR
The InfraRed receiver transmitter pair is to use be worn around the fingers and controls the opening
and closing of the end effector
321 Introduction
An infrared sensor is an electronic instrument that is used to sense certain characteristics of its
surroundings by either emitting andor detecting infrared radiation It is also capable of measuring
heat of an object and detecting motion Infrared waves are not visible to the human eye
In the electromagnetic spectrum infrared radiation is the region having wavelengths longer than
visible light wavelengths but shorter than microwaves The infrared region is approximately
demarcated from 075 to 1000microm The wavelength region from 075 to 3microm is termed as near
infrared the region from 3 to 6microm is termed mid-infrared and the region higher than 6microm is termed
as far infrared
18
Infrared technology is found in many of our everyday products For example TV has an IR detector
for interpreting the signal from the remote control Key benefits of infrared sensors include low
power requirements simple circuitry and their portable feature
322 Working Principle
A typical system for detecting infrared radiation using infrared sensors includes the infrared source
such as blackbody radiators tungsten lamps and silicon carbide In case of active IR sensors the
sources are infrared lasers and LEDs of specific IR wavelengths Next is the transmission medium
used for infrared transmission which includes vacuum the atmosphere and optical fibers
Thirdly optical components such as optical lenses made from quartz CaF2 Ge and Si polyethylene
Fresnel lenses and Al or Au mirrors are used to converge or focus infrared radiation Likewise to
limit spectral response band-pass filters are ideal
Finally the infrared detector completes the system for detecting infrared radiation The output from
the detector is usually very small and hence pre-amplifiers coupled with circuitry are added to
further process the received signals
Figure 8 Circuit Diagram Of An IR Sensor
19
323 Applications
The following are the key application areas of infrared sensors
Tracking and art history
Climatology meteorology and astronomy
Thermography communications and alcohol testing
Heating hyperspectral imaging and night vision
Biological systems photobiomodulation and plant health
Gas detectorsgas leak detection
Water and steel analysis flame detection
Anesthesiology testing and spectroscopy
Petroleum exploration and underground solution
Rail safety
33 SERVO MOTORS
A servomotor is a rotary actuator that allows for precise control of angular position velocity and
acceleration It consists of a suitable motor coupled to a sensor for position feedback It also requires
a relatively sophisticated controller often a dedicated module designed specifically for use with
servomotors
331 Controlling Of A Servo Motor
Servos are controlled by sending an electrical pulse of variable width or pulse width
modulation (PWM) through the control wire There is a minimum pulse a maximum pulse and a
repetition rate A servo motor can usually only turn 90 degrees in either direction for a total of 180
degree movement The motors neutral position is defined as the position where the servo has the
same amount of potential rotation in the both the clockwise or counter-clockwise direction The
PWM sent to the motor determines position of the shaft and based on the duration of the pulse sent
via the control wire the rotor will turn to the desired position The servo motor expects to see a
pulse every 20 milliseconds (ms) and the length of the pulse will determine how far the motor turns
For example a 15ms pulse will make the motor turn to the 90-degree position Shorter than 15ms
moves it to 0 degrees and any longer than 15ms will turn the servo to 180 degrees as diagramed
below
20
Figure 9 Controlling an servo
332 Types of Servo Motors
There are two types of servo motors - AC and DC AC servo can handle higher current surges and
tend to be used in industrial machinery DC servos are not designed for high current surges and are
usually better suited for smaller applications Generally speaking DC motors are less expensive
than their AC counterparts These are also servo motors that have been built specifically
for continuous rotation making it an easy way to get your robot moving They feature two ball
bearings on the output shaft for reduced friction and easy access to the rest-point
adjustment potentiometer
333Servo Motor Applications
Servos are used in radio-controlled airplanes to position control surfaces like elevators rudders
walking a robot or operating grippers Servo motors are small have built-in control circuitry and
have good power for their size
In food services and pharmaceuticals the tools are designed to be used in harsher environments
where the potential for corrosion is high due to being washed at high pressures and temperatures
repeatedly to maintain strict hygiene standards Servos are also used in in-line manufacturing
where high repetition yet precise work is necessary
21
Of course you dont have to know how a servo works to use one but as with most electronics the
more you understand the more doors open for expanded projects and projects capabilities Whether
youre a hobbyist building robots an engineer designing industrial systems or just constantly
curious where will servo motors take you
334 Specifications
It is highly desirable to control or to maintain a certain location of motor rotor in a robotic arm not
only to determine its precise motion and position but also to control it in desired fashion most of the
industrial robotic arm contains pneumatic hydraulic and stepper motor to actuates they have very
high payload capacity but GuRoo is a low powered high degree of freedom robotic arm we uses
servo motor due their easy availability and high weight to torque ratio
HS-645mg standard deluxe high torque servo
Figure 10HS-475-SERVO
Detailed Specifications of above shown servo
Motor Type 3 Pole
Bearing Type Top Ball Bearing
22
Speed 023 018 sec 60 deg
Torque 44 55 kgcm
Size 3880 x 1980 x 3600mm
Weight 4000g
34 ATMega32
A microcontroller is the brain of the robot The main features of this controller are
Advanced RISC Architecture
Up to 16 MIPS Throughput at 16 MHz
16K Bytes of In-System Self-Programmable Flash
512 Bytes EEPROM
1K Byte Internal SRAM
32 Programmable IO Lines
In-System Programming by On-chip Boot Program
8-channel 10-bit ADC
Two 8-bit TimerCounters with Separate Prescalers and Compare Modes
One 16-bit TimerCounter with Separate Prescaler Compare Mode and Capture
Four PWM Channels
Programmable Serial USART
MasterSlave SPI Serial Interface
Byte-oriented Two-wire Serial Interface
Programmable Watchdog Timer with Separate On-chip Oscillator
External and Internal Interrupt Sources
23
Figure 11 - Pin configuration
CHAPTER 4 METHODOLOGY
The setup consists of a robotic arm having 5 degrees of freedom and 6 servo motors
The movements of the joints are controlled using servo motors that can move a fixed angle ranging from 0 to
180 degrees
Accelerometer 1
ADC of Microcontroller
Servo for wrist movement
24
IR sensor
Microcontroller
Servomotor for gripping
mechanism
Figure121 Flowchart for First Accelerometer
Figure122 Flowchart for second Accelerometer
Figure123 Flowchart for IR sensor
Accelerometer 2
ADC of Microcontroller
Servomotor for elbow
movement
25
Figure124 Flowchart for POTENTIOMETER
Potentiometer
ADC of microcontroller
servomotor for base movement
26
Figure 125 Complete Flow Chart
Complete flow chart depicting each sensor interfaced with microcontroller and the
movement of each and every servos (ie robotic arm)
27
41 SETUP USED amp SCHEMATIC
A setup consisting of
1 IR sensors
2 Two accelerometers and
3 A potentiometer is to be worn around the human hand for sensing the gesture
movements
The InfraRed receiver transmitter pair is to be worn around the fingers and controls the
opening and closing of the end effector
2 accelerometers are used for sensing the movement of the forearm and the wrist movement
A potentiometer is used to track the elbow movement
Figure13 Schematic of the components used
28
Figure 14 Setup Used
29
Figure 151 Linear prediction for wrist movement 1
CHAPTER 5 ALGORITHIM USED
(PREDICTION AND CORRECTION ALGORITHM)
An algorithm has been devised to make the robotic arm replicate the motions of the human arm
The robotic arm does not exactly have an idea of the exact movement of the human arm and takes
input from noisy sensors
The algorithm consists of the following parts
1 LINEAR PREDICTION
The values of the sensors and motors for every joint have been stored for certain predefined
positions for each joint movement The position of the robotic arm is predicted linearly using the
given formulae
119823119851119838119837119842119836119853119838119837 119852119838119851119855119848 119855119834119845119854119838 = (119846120784 minus 119846120783) lowast119842119847119849119854119853 119852119838119847119852119848119851 119855119834119845119854119838 minus 119852120783
(119852120784 minus 119852120783)
-
30
Figure 152 Linear prediction for wrist movement 2
Figure 153 Linear prediction for elbow movement 1
31
Figure 154 Linear prediction for elbow movement 2
m2- predefined value of the servo motor for the next known position
m1- predefined value of the servo motor for the previous known position
s1- predefined sensor value for the last known position
s2- predefined sensor value for the next known position
2) CORRECTION
The predicted value is then compared to the present value and the difference between the two
