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Contents

Introduction History Of Robot Motion of Robot Types of Robot BehaviorBasedRobotics History of Behavior Based Robotics Needof Behavior Based Robotics Technology & workingof Behavior Based RoboticsApplicationof Behavior Based Robotics Merits of Behavior Based Robotics Demeritsof Behavior Based Robotics Robotics for today & tomorrow Conclusion Reference


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IntroductionA robot is an electro-mechanicaldevice that can perform autonomous or preprogrammed tasks. A robot may

act under the direct control of a human (eg. the robotic arm of the space

shuttle) or autonomously under the control of a programmed computer.

Robots may be used to perform tasks that are too dangerous or difficult for

humans to implement directly (e.g. nuclear waste clean up) or may be used

to automate repetitive tasks that can be performed more cheaply by a robot

than by the employment of a human (e.g. automobile production.)

Specifically, robot can be used to describe an

intelligent mechanical device in the form of a human. This form of robot iscommon in science fiction stories. However, such robots are yet to become

common-place in reality.

Robotics is the science and technology of robots,

their design, manufacture, and application. Robotics requires a working

knowledge of electronics, mechanics, and software and a person working in

the field has become known as a roboticist. The word robotics was first used

in print by Isaac Asimov, in his science fiction short story "Runaround"

(1941).

Although the appearance and capabilities of robots

vary vastly, all robots share the features of a mechanical, movable structure

under some form of control. The structure of a robot is usually mostly

mechanical and can be called a kinematic chain (its functionality being akin

to the skeleton of a body). The chain is formed of links (its bones), actuators

(its muscles) and joints which can allow one or more degrees of freedom.

Most contemporary robots use open serial chains in which each link

connects the one before to the one after it. These robots are called serial

robots and often resemble the human arm. Some robots, such as the Stewartplatform, use closed parallel kinematic chains. Other structures, such as

those that mimic the mechanical structure of humans, various animals and

insects, are comparatively rare.

The mechanical structure of a robot must be

controlled to perform tasks. The control of a robot involves three distinct


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phases - perception, processing and action (robotic paradigms). Sensors

give information about the environment or the robot itself (e.g. the position

of its joints or its end effector). Using strategies from the field of control

theory, this information is processed to calculate the appropriate signals to

the actuators (motors) which move the mechanical structure. The control of

a robot involves various aspects such as path planning, pattern recognition,

obstacle avoidance, etc. More complex and adaptable control strategies can

be referred to as artificial intelligence.

HistoryThe word robot comes from the Czech

word "robota", meaning "forced labor." The stuff of science fiction robotics

in the 21st century is different than your parents or your grandparentsideas of robotics. What used to be thought of as futuristic improbability is

now becoming a reality.

Isaac Asimovs Laws of Robotics

0. A robot may not injure humanity or, through inaction, allow humanity to

come to harm.

1. A robot may not injure a human being, or through inaction allow a humanbeing to come to harm, except where that would conflict with the 0th Law.

2. A robot must obey the orders given it by human beings, except where such

orders would conflict with the first law.

3. A robot must protect its own existence as long as such protection does not

conflict with the first or second law.

MotionOf

RobotAny task involves the motion ofthe robot. The study of motion can be divided intokinematics and dynamics.


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Direct kinematics refers to the calculation of end effector position,

orientation, velocity and acceleration when the corresponding joint values

are known.

Inverse kinematics refers to the opposite case in which required joint

values are calculated for given end effector values, as done in path

planning. Some special aspects of kinematics include handling of

redundancy (different possibilities of performing the same movement),

collision avoidance and singularity avoidance. Once all relevant positions,

velocities and accelerations have been calculated using kinematics, methods

from the field of dynamics are used to study the effect of forces upon these

movements.

Direct dynamics refers to the calculation of accelerations in the robot once

the applied forces are known. Direct dynamics is used in computersimulations of the robot.

Inverse dynamics refers to the calculation of the actuator forces necessary

to create a prescribed end effector acceleration. This information can be

used to improve the control algorithms of a robot.

Types of

Robot

"The way robots function now, if

something goes wrong, humans modify their programming code and reload

everything, then hope it eventually works," said JPL robotics engineer Barry

Werger. "What we hope to do eventually is get robots to be more

independent and learn to adjust their own programming."

Scientists and engineers take several

approaches to control robots. The two extreme ends of the spectrum are

called "deliberative control" and "reactive control." The former is thetraditional, dominant way in which robots function, by painstakingly

constructing maps and other types of models that they use to plan sequences

of action with mathematical precision. The robot performs these sequences

like a blindfolded pirate looking for buried treasure; from point A, move 36

paces north, then 12 paces east, then 4 paces northeast to point X; thar be

the gold.


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The downside to this is that if anything

interrupts the robot's progress (for example, if the map is wrong or lacks

detail), the robot must stop, make a new map and a new plan of actions. This

re-planning process can become costly if repeated over time. Also, to ensure

the robot's safety, back-up programs must be in place to abort the plan if the

robot encounters an unforeseen rock or hole that may hinder its journey.

"Reactive" approaches, on the other hand,

get rid of maps and planning altogether and focus on live observation of the

environment. Slow down if there's a rock ahead. Dig if you see a big X on

the ground.

The JPL Telerobotics Research and

Applications Group, led by technical group supervisor Dr. Homayoun

Seraji, focuses on "behavior-based control," which lies toward the"reactive" end of the spectrum. Behavior-based control allows robots to

follow a plan while staying aware of the unexpected, changing features of

their environment. Turn right when you see a red rock, go all the way down

the hill and dig right next to the palm tree; thar be the gold.

There are two main theories regarding the techniques and approaches that

are required to control robots. These are "deliberative" and "reactive".

**The Deliberative (classical AI/traditional) approach involves the robot

knowing its environment, developing an internal world model, a map andmaking decisions based on this information. This robot will move about and

perform tasks in a deliberate manner.

**The Reactive (behavior based/new AI) approach involves the robot

reacting to its environment with tight sensing - acting connections. These

robots do not have a plan nor do they have a map. These robots explore

their world and react to the environments as they encounter it - they are

reactive.

BehaviorBasedRoboticsReactive robots became popular at a

later date. This approach involves programming the robot to react

quickly to its environment. The robot must react to the obstacles and


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objects it encounters. The robots do not build a model of their world they

simply act in response to the things they encounter whilst existing there.

Achieving this paradigm requires developing behaviors for the robot to

execute or exhibit. These behaviors enable the robot to explore its

environment. The behaviors are built up until the robot can function in

its world e.g. "avoid objects", "move forward", "move backwards". This

form of robotics has proved to be successful in environments that are

unknown to the robot, environments that are busy or noisy such as a

place with moving objects or people (the busy corridor or football

pitch).

An important part of the behavior

based theory is "embodiment" This means that a robot must be embodied,

have a presence (it is an entity in itself). In order to react the robot must

be surrounded by the real world. If the robot is not embodied anysimulation of the robot would simply be an hallucination having no

bearing on what would happen in the real world.

History ofBehaviorBasedRoboticsWhile behavior-based robotics is a

relatively new field as academic fields go, it is possible to find historical

predecessors. Ronald Arkin looks all the way back to 1947, whencybernetics used control theory, information science and biology to seek

principles common to biological life and machine intelligence. It is generally

agreed that W. Grey Walters Tortoise, a small robot made from vacuum

tubes, was the first behavior-based robot. It had no high-level knowledge

and could not translate its actions into symbolic meaning. However, it could

effectively exhibit certain behaviors such as backing away from strong light

and heading toward weak light. It did not model human intelligence or

cognition of any kind; rather, it provided reactive response without

reliance on representation. The complexity of the action produced lay not in

the design but in the behavior that arose through interaction with a chaoticworld. (Arkin 1998)

Massachusetts Institute of Technology

by Professor Rodney Brooks, who with students and colleagues built a series

of wheeled and legged robots utilising the subsumption architecture. Brooks'

papers, often written with lighthearted titles such as "Planning is just a way


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of avoiding figuring out what to do next", the anthropomorphic qualities of

his robots, and the relatively low cost of developing such robots,

popularised the behavior-based approach.

Brooks' work builds - whether by

accident or not - on two prior milestones in the behavior-based approach. In

the 1950s, W. Grey Walter, an English scientist with a background in

neurological research, built a pair of vacuum tube-based robots that were

exhibited at the 1951 Festival of Britain, and which have simple but effective

behavior-based control systems.

The second milestone is Valentino

Braitenberg's 1984 book, "Vehicles - Experiments in Synthetic Psychology"

(MIT Press). He describes a series of thought experiments demonstrating

how simply wired sensor/motor connections can result in some complex-appearing behaviors such as fear and love.

NeedofBehaviorBasedRoboticsPerception takes too long.Perception is not a solvedproblem, nor will it be solved in the near

future.Modeling/planning component assumes complete models are

available.

Overall system cannot respond in real-time.Most robots built this way have failed (or run very slowly).

Technology & workingofBehaviorBasedRoboticsWe focus on two of the many approaches to

implementing behavior-based control: fuzzy logic and neural networks. The

main difference between the two systems is that robots using fuzzy logic

perform with a set knowledge that doesn't improve; whereas, robots with

neural networks start out with no knowledge and learn over time.

Fuzzy Logic


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"Fuzzy logic rules are a way of expressing

actions as a human would, with linguistic instead of mathematical

commands; for example, when one personsays to another person, It's hot inhere,' the other person knows to either open the window or turn up the air

conditioning. That person wasn't told to open the window, but he or she

knew a rule such as when it is hot, do something to stay cool,'" said Seraji,

a leading expert in robotic control systems who was recently recognized as

the most published author in the Journal of Robotic Systems' 20-year

history.

By incorporating fuzzy logic into their engineering technology, robots can

function in a humanistic way and respond to visual or audible signals, or in

the case of the above example, turn on the air conditioning when it thinks the

room is hot.

Neural NetworksNeural networks are tools that allow robots to

learn from their experiences, associate perceptions with actions and adapt

to unforeseen situations or environments.

"The concepts of 'interesting' and 'rocky' are

ambiguous in nature, but can be learned using neural networks," said JPL

robotics research engineer Dr. Ayanna Howard, who specializes in artificial

intelligence and creates intelligent technology for space applications. "We

can train a robot to know that if it encounters rocky surfaces, then the

terrain is hazardous. Or if the rocky surface has interesting features, then it

may have great scientific value."

Neural networks mimic the human brain in that

they simulate a large network of simple elements, similar to brain cells, that

learn through being presented with examples. A robot functioning with such

a system learns somewhat like a baby or a child does, only at a slower rate.

"We can easily tell a robot that a square is an

equilateral object with four sides, but how do we describe a cat?" Werger

said. "With neural networks, we can show the robot many examples of cats,and it will later be able to recognize cats in general."

Similarly, a neural network can 'learn' to

classify terrain if a geologist shows it images of many types of terrain and

associates a label with each one. When the network later sees an image of a

terrain it hasn't seen before, it can determine whether the terrain is

hazardous or safe based on its lessons.


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WorkingThere are basically four steps in working of Behavior Based robotics:

Basic Navigation ( Exploring )Landmark Detection

Mapping Landmarks

Path Planning

BasicNavigation(Exploring):

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NNooddeess ccoommmmuunniiccaattee wwiitthh nneeiigghhbboorrss..Landmark node has a set < T, C, L, P > where

T is { LW, RW, C, I }; qualitative landmark type.

C is [ 0 15 ]; averaged compass bearing.

L is [ 1 127 ]; rough estimate of landmarks length.P = ( x, y ) -128


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ApplicationofBehaviorBasedRobotics

Merits of Behavior Based RoboticsFor one thing, behavior is simple to

implement. It does not involve modeling the environment. The robot can

directly react to real world stimulus. The gap between perception and

action is reduced. If the task is highly predictive and structured (e.g.

assembly line automation or virtual predictive environments) then

deliberative approaches are preferred. But if information is uncertain or

unknown (e.g. navigation in an unknown room with moving obstacles) then

behavior can help importance. Again, a combination gives the right result.

For example, the behaviors at the following levels may be integrated for

group performance.

the 3Ds

entertainment,

healthcare, ...

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1. SELF - behaviors to do with self- preservation, like recharging a low

battery.

2. SPECIES - behaviors concerned with interaction between robots

3. ENVIRONMENT - behaviors such as obstacle avoidance, concerned

with moving around the environment

4. UNIVERSE- behavior such as navigating towards a particular beacon

concerned with overall task achievement.

Demeritsof Behavior Based Robotics

No easy way to incorporate global knowledge (symbolic maps, rulesetc.)Hardwired behaviors -- robot cannot adapt to new unforeseen

situations

Lacks a planning/reasoning component -- cannot predictconsequences of actions

Extensions:o New behaviors can be learned using neural networks and

reinforcement learning

o Global knowledge and planning achieved using a higher level

deliberative system on top of behavior-based system.

Robotics for today & tomorrow

With continuous advances in robotic

methods like behavior-based control, future space missions might be able to

function without relying heavily on human commands. On the home front,

similar technology is already used in many practical applications such asdigital cameras, computer programs, dishwashers, washing machines and

some car engines. The post office even uses neural networks to read

handwriting and sort mail.

"Does this mean robots in the near future will think like humans? No,"

Werger said. "But by mimicking human techniques, they could become


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easier to communicate with, more independent, and ultimately more

efficient."

.

ConclusionAlthough the implemented robot behaviors are

simple as a robot that works in a real environment, the experimental results

has convinced us of the possibility of the proposed architecture. We believe

it is possible to develop robot systems in a progressive manner based on the

proposed architecture.

Referencewww.ieeexplore.ieee.org {Robotics & Automation Magazine, March2006,

Vol 13,Issue 1}

www.wikipedia.com

http://EzineArticles.com

www.mec.ua.pt/robotics


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