PRESENTATION ON

SENSORS

PRESENTED BY:

SHASHANK SONI

13MT07IND016

M.Tech (Industrial Engg), Sem II

What is a Sensor?

A device that measures a physical variable (e.g. force, pressure, temperature, velocity, flow rate, etc.)

And converts the physical quantity into another form

Which can be read by an observer or by an instrument.

The most common conversion is to electrical form as the converted signal is more convenient to use and evaluate.

General Electronic Sensor• Primary Transducer: changes “real world” parameter into electrical signal

• Secondary Transducer: converts electrical signal into analog or digital values

Typical Electronic Sensor System

usable

valuesreal

worldanalog

signal

primary

transducer

secondary

transducer

sensor

microcontrollersignal processing

communication

sensor

input

signal

(measurand)sensor data

analog/digital

network

display

Desirable features of sensors

Accuracy

Precision

Operating range

Speed of response

Calibration

Reliability

Cost and ease of operation

Resolution

Accuracy vs. Precision

Precision without accuracy

Accuracy without precision

Precision and accuracy

internal information

What is the angle of my arm?

Why Sensors are Required?

Where am I?

localization

?

Why Sensors are Required?

Will I hit anything?

obstacle detection

Why Sensors are Required?

Autonomous material handling

Where are the forkholes?

Why Sensors are Required?

Where is the face?

Face detection & tracking

Why Sensors are Required?

Sensors used in Robotics

The sensors used in robotics include a wide range of devices which can be divided into following categories:

Tactile Sensors

Proximity and Range sensors

Miscellaneous sensors and sensor based systems

Machine vision systems

Tactile Sensors Tactile sensors are devices which indicate contact

between themselves and some other solid object.

Tactile sensing devices can be divided into two classes: Touch sensors and Force sensors.

Touch Sensors

force voltagemeasurement

electrical flow

a simpleswitch

• Touch sensors provide a binary output signal which indicates whether or not contact has been made with the object without regard to the magnitude of the contacting force.

Force Sensing

• Force sensor (also known as stress sensor) indicate not only that contact has been made with the object but also the magnitude of the contact force between the two objects.

Metal foil strain-gauge based (load cell) Good in low frequency response

High load rating

Resolution lower than piezoelectricity-based

Rugged, typically big size, heavy weight

Force Sensing

Piezoelectricity based (force sensor)

lower cutoff frequency at 0.01 Hz

can NOT be used for static load measurement

Good in high frequency

High resolution

Limited operating temperature (can not be used for high temperature applications)

Compact size, light

Proximity and Range Sensors

Proximity sensors are devices that indicate when one object is close to another object.

Some of these sensors can also be used to measure the distance between the object and the sensor, and these devices are called Range sensors.

Range sensors would be useful for determining the location of an object(e.g., the work part) in relation to robot.

Types of Proximity and Range Sensors

Eddy Current Detectordevice that emits an alternating magnetic field at the tip of a probe, which induces eddy currents in any conductive object in the range of the device.

Photometric sensor

used to sense light. category includes photocells , photoelectric transducers ,photo tubes, phototransistor and photoconductors. Can be used to indicate presence or absence of an object.

Optical Pyrometer

device used to measure high temperatures by sensing the brightness of an object’s surface. Can be used to indicate presence or absence of an object.

Vacuum Switches

device used to indicate negative air pressures. Can be used with a vacuum gripper to indicate presence or absence of an object.

Miscellaneous Sensors and Sensor Based Systems

The miscellaneous category covers the remaining types of sensors that might be used for interlocks and other purposes in manufacturing work cells.

This category includes devices with the capability to sense variables such as temp., pressure, fluid flow, and electrical properties.

Types of Miscellaneous Sensor

• Ammeter: Electrical meter used to measure electrical current.

• Linear variable differential transformer: Electromechanical transducer used to measure linear or angular displacement.

• Ohmmeter: used to measure electrical resistance.

• Potentiometer: Electrical meter used to measure voltage.

Types of Miscellaneous Sensor

• Piezoelectric accelerometer: sensor used to indicate or measure vibration.

• Pressure transducer: Various transducers used to indicate air pressure and other fluid pressures.

• Thermistor : device based on electrical resistance used to measure temperatures.

• Thermocouple: used to measure temperatures. Based on the principle that a junction of two dissimilar metals will emit an emf which can be related to temperatures.

Machine Vision System

Vision sensors: Advanced sensor system used together with pattern recognition and other techniques to view and interpret events occuring in the robot workplace.

Magnetic Field Sensor

Magnetic Field sensors are used for power steering, security, and current measurements on transmission lines

Hall voltage is proportional to magnetic field

x x x x x x

x x x x x x

x x x x x x

+ + + + + + + + + + + + + + +

- - - - - - - - - - - - - - -

I (protons) +

VH

-B

tqn

BIVH

Ultrasonic Sensor

Ultrasonic sensors are used for position measurements

Sound waves emitted are in the range of 2-13 MHz

Sound Navigation And Ranging (SONAR)

Radio Detection And Ranging (RADAR) –ELECTROMAGNETIC WAVES

15° - 20°

Applications of Sensors in Manufacturing

Distance sensing

Contour Tracking

Machine Vision / Pattern recognition

Machine diagnosis

Process Parameter sensing

Safety monitoring

Parts inspection for quality control

Distance Sensing

• Sensors for such application are of two types,either contact type or non contact type.

•Contact type sensors are like dial gauge, gaugeblocks, pins, etc. However these sensors have alimitation of wear and tear, and are not verycommonly used.

•Non contact types may be inductive, acoustic,capacitive or optical sensors.

Contour tracking:

This is a kind of scanning process and is performed by using electrical sensors such as inductive and capacitive ones and optical sensors mostly laser based scanners.

Machine Vision:Here also tactile arrays and ultrasonic scanning serve some useful purpose. Besides optical systems with binary vision, grey level sensing and stereovision are widely used.

Machine Diagnosis:

Well known sensors are used to measure forces, torque, strain, frequency and a lot of other indirect diagnostic data.

Process Parameters Monitoring:

Parameters such as pressure, force, speed, temperature, fluid levels, chemical composition and pH value data are measured in different environmental conditions.

END OF PRESENTATION