General Robotics

1
General Robotics

• Lab 4 Low Level Mobile Base Control
• Caleb Overman, Somchaya Liemhetcharat, Steven
  Nielsen
• Previous caretakers Avi Siegel, Mike Shum

2
Introduction

• The purpose of this lab is to design a feedback
  controlled robot base that will be used in
  subsequent motion planning labs.
• The base will need to be able to translate and
  rotate precisely.

3
Challenge Statement

• Upgrade or redesign your mobile base so that it
  can translate and rotate with accuracy. (Or build
  a new one!)
• Measure the accrued dead-reckoning error (do not
  use feedback).
• Implement some form of feedback to minimize
  dead-reckoning error.

4
Design

• What should this thing look like?
• Tracks/Wheels?
• Whats a castor?
• Ackerman/DiffDrive?
• Friction?

5
Tank Treads

• 2 treads, each turned by a motor.
• Good all-terrain (surface) performance.
• Sadly, not able to turn very precisely (friction
  issues).

6
Wheels

• 2 main driving wheels, each turned by a motor.
• Some sort of steering.
• Ackerman
• DiffDrive
• Castors, placement of wheels, balance (3D).

7
Castors and Stability

• What is a castor?
• How do I make one out of Lego?
• What it does
• Smooth turning
• Support robot
• Actuated steering?

8
Going Straight

• This is harder than you think.
• Seriously.

9
PID Control

• Proportional
• How fast are we drifting from the center?
• Integral
• How far are we from the centerline?
• Derivative
• Is the drift rate accelerating/decelerating?

10
Other Problems

• Charge your handyboard!
• Give the ECEs something to do (encoders)
• Stopping not as easy as you think.

11
Grading (see grading sheet)

• Your grade will be directly determined by the
  percentage accuracy of your robot.
• i.e. if you are asked to move 10 inches and your
  robot moves 9 inches, you will receive a 90.
• The same goes for turns.

12
Testing

• Translate Write a function that takes as input a
  number (in inches), waits for the start button to
  be pressed, waits five seconds, and then
  accurately drives the robot forward by the
  inputted value in inches (or reverse if the
  inputted number was negative). Try different
  values.
• Rotate Write a function that takes as input a
  number (in degrees), waits for the start button
  to be pressed , waits five seconds, and then
  accurately rotates the robot counter-clockwise by
  the inputted value in degrees (or clockwise if
  the inputted number was negative). Try different
  values.