chapter 1 - introduction to robotics

8/2/2019 Chapter 1 - Introduction to Robotics

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Introduction ToRobotics

Lecture 1

Instructor: Monica Nicolescu


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CS 491/691(X) - Lecture 1 2

The term robot

Karel Capeks 1921 play RUR (Rossums UniversalRobots)

It is (most likely) a combination of rabota (obligatory

work) and robotnik (serf)

Most real-world robots today do perform such

obligatory work in highly controlled environments

Factory automation (car assembly)

But that is not what robotics research about; the

trends and the future look much more interesting


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CS 491/691(X) - Lecture 1 3

What is a Robot?

In the past A clever mechanical device automaton

Robotics Industry Association, 1985

A re -programmable, multi-functional manipulator designed

to move material, parts, tools, or specialized devices []

for the performance of various tasks

What does this definition missing?

Notions of thought, reasoning, problem solving, emotion,consciousness


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CS 491/691(X) - Lecture 1 4

A Robot is

a machine able to extract information from itsenvironment and use knowledge about its world to

act safely in a meaningful and purposeful manner

(Ron Arkin, 1998)

an autonomoussystem which exists in the

physical world, can senseits environment and can

acton it to achieve some goals


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CS 491/691(X) - Lecture 1 5

What is Robotics?

Robotics is the study of robots, autonomous

embodied systems interacting with the physical

world

Robotics addresses perception, interaction and

action, in the physical world


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CS 491/691(X) - Lecture 1 6

Robots: Alternative Terms

UAV unmanned aerial vehicle

UGV (rover)

unmanned ground vehicle

UUV

unmanned undersea vehicle


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CS 491/691(X) - Lecture 1 7

An assortment of robots


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CS 491/691(X) - Lecture 1 8

Anthropomorphic Robots


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CS 491/691(X) - Lecture 1 9

Animal-like Robots


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CS 491/691(X) - Lecture 1 10

Humanoid Robots

Robonaut (NASA) Sony Dream Robot

Asimo (Honda)

DB (ATR)

QRIO


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CS 491/691(X) - Lecture 1 11

What is in a Robot?

Sensors

Effectors and actuators

Used for locomotion and manipulation

Controllers for the above systems

Coordinating information from sensors with commands for

the robots actuators


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CS 491/691(X) - Lecture 1 12

Sensors

Sensor = physical device that provides informationabout the world

Process is called sensing or perception

What does a robot need to sense?

Depends on the task it has to do

Sensor (perceptual) space

All possible values of sensor readings

One needs to see the world through the robots eyes

Grows quickly as you add more sensors


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CS 491/691(X) - Lecture 1 13

State

State: A description of the robot (of a system in general)

For a robot state can be:

Observable: the robot knows its state entirely

Partially observable: the robot only knows a part of its state

Hidden (unobservable): the robot does not have any access

to its state

Discrete: up, down, blue, red

Continuous: 2.34 mph


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CS 491/691(X) - Lecture 1 14

Types of State

External The state of the world as perceived by the robot

Perceived through sensors

E.g.: sunny, cold

Internal The state of the robot as it can perceive it

Perceived through internal sensors, monitoring (stored,

remembered state)

E.g.: Low battery, velocity

The robots state is the combination of its internal

and external state


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CS 491/691(X) - Lecture 1 15

State Space

All possible states a robot could be in E.g.: light switch has two states, ON, OFF; light switch with

dimmer has continuous state (possibly infinitely many

states)

Different than the sensor/perceptual space!!

Internal state may be used to store information about the

world (maps, location of food, etc.)

How intelligent a robot appears is stronglydependent on how much and how fast it can sense

its environment and about itself


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CS 491/691(X) - Lecture 1 16

Representation

Internal state that stores information about the worldis called a representation or internal model

Self: stored proprioception, goals, intentions, plans

Environment: maps

Objects, people, other robots

Task: what needs to be done, when, in what order

Representations and models influence determine

the complexity of a robots brain


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CS 491/691(X) - Lecture 1 17

Action

Effectors: devices of the robot that have impact onthe environment (legs, wings robotic legs,

propeller)

Actuators: mechanisms that allow the effectors to

do their work (muscles motors)

Robotic actuators are used for

locomotion (moving around, going places)

manipulation (handling objects) This divides robotics into two basic areas

Mobile robotics

Manipulator robotics


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CS 491/691(X) - Lecture 1 18

Autonomy

Autonomy is the ability to make ones own decisionsand act on them.

For robots: take the appropriate action on a given situation

Autonomy can be complete (R2D2) or partial

(teleoperated robots)

Controllers enable robots to be autonomous

Play the role of the brain and nervous system in animals

Typically more than one controller, each process

information from sensors and decide what actions to take

Challenge in robotics: how do all these controllers

coordinate with each other?


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CS 491/691(X) - Lecture 1 19

Control Architectures

Robot control is the means by which the sensing andaction of a robot are coordinated

Control architecture

Guiding principles and constraints for organizing a robots

control system

Robot control may be implemented:

In hardware: programmable logic arrays

In software

Controllers need not (should not) be a single program

Should control modules be centralized?


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CS 491/691(X) - Lecture 1 20

Languages for Programming Robots

What is the best robot programming language? There is no best language

In general, use the language that

Is best suited for the task

Comes with the hardware

You are used to

General purpose:

JAVA, C

Specially designed:

the Behavior Language, the Subsumption Language


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CS 491/691(X) - Lecture 1 21

Spectrum of robot control

From Behavior-Based Robotics by R. Arkin, MIT Press, 1998


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CS 491/691(X) - Lecture 1 22

Robot control approaches

Reactive Control

Dont think, (re)act.

Deliberative (Planner-based) Control

Think hard, act later.

Hybrid Control

Think and act separately & concurrently.

Behavior-Based Control (BBC)

Think the way you act.


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CS 491/691(X) - Lecture 1 23

Thinking vs. Acting

Thinking/Deliberating slow, speed decreases with complexity

involves planning (looking into the future) to avoid bad

solutions

thinking too long may be dangerous requires (a lot of) accurate information

flexible for increasing complexity

Acting/Reaction

fast, regardless of complexity

innate/built-in or learned (from looking into the past)

limited flexibility for increasing complexity

H t Ch C t l


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CS 491/691(X) - Lecture 1 24

How to Choose a ControlArchitecture?

For any robot, task, or environment consider: Is there a lot of sensor noise?

Does the environment change or is static?

Can the robot sense all that it needs?

How quickly should the robot sense or act?

Should the robot remember the past to get the job done?

Should the robot look ahead to get the job done?

Does the robot need to improve its behavior and be able tolearn new things?

R C l


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CS 491/691(X) - Lecture 1 25

Reactive Control:Dont think, react!

Technique for tightly coupling perception and action to provide

fast responses to changing, unstructured environments

Collection of stimulus-response rules

Limitations

No/minimal state

No memory

No internal representations

of the world

Unable to plan ahead

Unable to learn

Advantages

Very fast and reactive

Powerful method: animals

are largely reactive

D lib i C l


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CS 491/691(X) - Lecture 1 26

Deliberative Control:Think hard, then act!

In DC the robot uses all the available sensory information andstored internal knowledge to create a plan of action: sense

plan act (SPA) paradigm

Limitations

Planning requires search through potentially all possible plans these take a long time

Requires a world model, which may become outdated

Too slow for real-time response

Advantages

Capable of learning and prediction

Finds strategic solutions


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CS 491/691(X) - Lecture 1 27

Textbooks

Lectures The Robotics Primer, 2001. Author: Maja

Mataric'

Available in draft form at the bookstore

chapter 1 - introduction to robotics

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