Autonomous Robots Tutorial 1

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Autonomous RobotsTutorial 1

• Kinematics of a Differential Drive Robot

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Degree of Mobility

• Degree of freedom of the robot motion

No ICR Degree of mobility 0
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Degree of Mobility

• Degree of freedom of the robot motion

One ICR Degree of mobility 1
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Degree of Mobility

• Degree of freedom of the robot motion

Line of ICRs Degree of mobility 2
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Degree of Mobility

• Degree of freedom of the robot motion

ICR anywhere Degree of mobility 3
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Degree of Steerability

• Number of steerable standard wheels that can be
  steered independently

No steerable standard wheel Degree of
steerability 0
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Degree of Steerability

• Number of steerable standard wheels that can be
  steered independently

No steerable standard wheel Degree of
steerability 0
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Degree of Steerability

• Number of steerable standard wheels that can be
  steered independently

1 steerable standard wheel Degree of
steerability 1
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Degree of Steerability

• Number of steerable standard wheels that can be
  steered independently

2 mutually dependent steerable standard wheels
Degree of steerability 1
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Degree of Steerability

• Number of steerable standard wheels that can be
  steered independently

2 mutually independent steerable standard wheels
Degree of steerability 2
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Robot Simulator

• Created by the journal ct
• Simulator is written in Java
• Robot code is written in C

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Development Tools

• Eclipse with C plugin

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Getting Started

• Download the source code from the course website
• http//www-ds.e-technik.uni-dortmund.de/new/CEI/en
  /teaching/ar.shtml
• Unpack code to your home directory
• In eclipse import
• General ? Existing Projects into Workspace
• ct-bot
• ct-Sim
• Code should automatically be compiled now

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Starting the Simulator

• Right klick on ctSim.controller
• Run As..
• Java Application
• Open a world
• Open robot code (Simulate Bot)
• Start simulation with play button
• Choose an appropriate time scaling (TR)
• Time runs slower than in real world

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Using the Simulator
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Structure of the Robot Code
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The Programming Task

• How to control the wheel speeds w for a given
  velocity vector (X,Y,R) and robot dimensions?
• Differential Drive with
• Wheel diameter r57mm
• Wheel distance l97 mm
• Inverse Kinematics
• wf(X,Y,R,l,r)

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The Programming Task

• Do your implementation in
• ct-bot ? bot-logic ? behaviour_ar.c
• void control_wheels(int16 vX, int16 vR)
• Input
• vX in mm/s
• vR in degrees/s
• Output
• speedWishLeft
• speedWishRight
• More hints in the code

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Hints for your calculations

• Calculate the contribution for the overall
  velocity separately for the wheels
• Find a way to combine them
• Book Chapter 3.2.2

x
y