Module 2 - Robot Configurations

Outline
 What is a Robot Configuration?
 Why is it important?
 Several types of Configurations
 Roomba Configuration

What is a Robot
Configuration?
 Describes how a robot can move and where it can go
 Includes


Physical shape of the Robot
Model of how the Robot can move in the
Environment

What is a Robot
Configuration?
 Holonomic vs. Non-holonomic


Holonomic Robots can move in any direction
Non-holonomic Robot is contrained to certain types of movement
 Example: A Car is non-holonomic

What is a Robot
Configuration?
 For ground robots, the Configuration often describes how it


Rotates (How the robot turns)
Translates (How the robot moves forward or backward)

Why is it important?


With the Configuration you can tell how a
Robot will operate prior to controlling it
Important to understand a Robot’s limitations while designing it

Several Types of Configurations

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
Wheeled Robots
 Differential Drive

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Ackerman Steer
Tricycle Drive
Synchro Drive
Skid Steer
Roller Wheeled
Legged Robots
Flying Robots
 Fixed-wing
 Rotorcraft
QuickTime™ and a
TIFF (LZW) decompressor are needed to see this picture.

Differential Drive
 2 Wheels


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Independently powered in-line with each other
Usually in the center of the robot
 Often has 1 or 2 casters
 Non-powered


Swivel in any direction
Add stability

Differential Drive
 Advantage


Simple Design
Can go anywhere the robot can fit
 Disadvantage


Has difficulty with uneven terrain (both wheels need to touch the ground to work)
Has to rotate before traveling in a new direction

Differential Drive
 Shape matters
 In this example, the Circle robot can turn freely while the
Square robot cannot

Ackerman Steer
 Like a Car
 4 Wheels


2 Rear wheel are powered, fixed-rotation
2 Front wheels are non-powered that turn
 Turn at different Angles

Ackerman Steer
 Advantage


Drive and Rotation functionality are separated
Typically more stable
 Disadvantage


Mechanically complicated
Often complicated maneuvers (non-holonomic)

Tricycle Drive
 Similar to Ackerman Steer
 Only 1 front wheel that turns

Tricycle Drive
 Advantage
 Mechanically Simpler
 Disadvantage


Similar motion limitations as Ackerman Steer
Less Stable

Synchro Drive
 At least 3 wheels


All rotate together
All are powered together

Synchro Drive
 Advantage


Can travel in any direction without turning the top base
Separate motors for turning and driving
 Disadvantage


Very Mechanically Complicated
Top base cannot face another direction

Skid Steer
 Like a tank
 Several wheels on each side or tank treads
 Turning Requires skidding

Skid Steer
 Advantage
 Can handle uneven terrain well
 Disadvantage
 Poor odometry due to skidding

Roller Wheeled
 3 Wheels
 Arranged around the circumference of the robot


Wheels are Roller
Wheels (Next Slide)
Non-Steering
 Independently
Powered

Roller Wheeled
 Roller Wheels
 Includes Rollers
 Perpendicular to the
Wheel
 Around the wheel
 Non-powered

Roller Wheeled
 Advantage


Can go in any direction without first rotating
Can go anywhere the robot can physically fit
 Disadvantage
 Tracking position through odometry is difficult

Legged Robots
 Uses legs instead of wheels
 Any number of legs

Legged Robots
 Advantage
 Can travel over rugged terrain
 Disadvantage
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Mechanically complicated
Hard to control

Fixed Wing Aerial
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Like a Plane
Not Restricted to the ground

Rotorcraft Aerial
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Like a Helicopter
Not Restricted to the ground
Can take-off vertically

Other Configurations
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Many other Configurations
Robots are not restricted to Ground (or even Air)
Can be manipulated in many different ways

Roomba Configuration

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Wheels

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2 Wheels
Independently Powered


Non-Steered
Arranged at approximately the center of the robot on opposite sides of each other
Shape
 Circular
 Few inches tall

Roomba Configuration
 Round Differential-Drive
Configuration


Can travel anywhere the
Roomba can fit and get to
Can move in any direction, but first need to turn to that direction

Questions?