Table Of ContentCYAN YELLOW
MAGENTA BLACK
PANTONE 123 C
Winning Design! LEGO MINDSTORMS NXT Design Patterns for Fun and Competition TECHNOLOGY IN ACTION™
In this book you will learn…
• Good chassis design Winning Design!
• Object and wall detection
• Modular attachment design
• Playing-field navigation
• Software management practices
• Techniques to reduce variability
LEGO MINDSTORMS NXT
Also available:
W
inning Design! LEGO Mindstorms NXT Design Patterns for Fun
and Competition is about design that works. It’s about building
Design Patterns for Fun and
with LEGO MINDSTORMS NXT for fun, for education, and especially for
competition. Author James Trobaugh is an experienced coach and leader
in the FIRST LEGO League. In this book, he shares his hard-won knowl-
Competition
edge about design principles and techniques that contribute to success in
robotics competitions.
Winning Design! unlocks the secrets of reliable design using LEGO
MINDSTORMS NXT. You’ll learn proven design patterns to employ for
common tasks such as turning, pushing, and pulling. You'll see how to
reduce and compensate for variation in performance from battery charge L
levels and motor calibration differences. You’ll produce designs that won’t E
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frustrate you by not and instead will delight you with their reliable perfor-
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mance in the heat of competition.
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Good design is about more than just hardware. Software counts for a
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lot, and Winning Design! has you covered. You’ll find chapters on program N
D
design and organization with tips on effective coding and documentation
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practices. You’ll learn about master programs and the needed flexibility
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they provide. There’s even a section on presenting your robot and software O
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designs to the judges.
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Winning Design! is the book you need if you're involved in competitions
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such as FIRST LEGO League events. Whether you're a parent, or student,
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you’ll find much in this book to make your design and competition experi-
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ence fun, memorable, and educational.
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US $29.99
ISBN 978-1-4302-2964-3 Trobaugh
52999 Shelve in Robotics
User level: Beginner– Advanced
James J. Trobaugh
9 781430 229643 www.apress.com
this print for content only—size & color not accurate trim size = 7.5" x 9.25" spine = 0.6875 312 page count
Winning Design!
LEGO MINDSTORMS NXT Design Patterns
for Fun and Competition
■ ■ ■
James J. Trobaugh
i
Winning Design! LEGO MINDSTORMS NXT Design Patterns for Fun and Competition
Copyright © 2010 by James J. Trobaugh
All rights reserved. No part of this work may be reproduced or transmitted in any form or by
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owner and the publisher.
ISBN-13 (pbk): 978-1-4302-2964-3
ISBN-13 (electronic): 978-1-4302-2965-0
Printed and bound in the United States of America 9 8 7 6 5 4 3 2 1
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Dedicated to Liz, Ian, and Amy for their love, patience and inspiration
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Contents at a Glance
■Contents................................................................................................................v
■About the Author................................................................................................xiv
■About the Technical Reviewer.............................................................................xv
■Introduction .......................................................................................................xvi
Part 1: Introduction..................................................................................................1
■Chapter 1: Design Considerations.........................................................................3
■Chapter 2: Chassis Design...................................................................................23
Part 2: Navigation...................................................................................................45
■Chapter 3: Going Straight....................................................................................47
■Chapter 4: Consistent Turning.............................................................................69
■Chapter 5: Line Following and Detection.............................................................83
■Chapter 6: Squaring Up.....................................................................................103
■Chapter 7: Collision Detection...........................................................................113
Part 3: Manipulation.............................................................................................123
■Chapter 8: Passive Attachments.......................................................................125
■Chapter 9: Power Attachments.........................................................................145
■Chapter 10: Pneumatics....................................................................................165
Part 4: Programming............................................................................................177
■Chapter 11: Master Programs...........................................................................179
■Chapter 12: Program Management...................................................................195
■Chapter 13: Documentation and Presentation..................................................205
■Appendix A: Building DemoBot .........................................................................215
■Appendix B: Building the Motor Matching Machine..........................................257
■Index.................................................................................................................275
iv
Contents
■Contents at a Glance............................................................................................iv
■About the Author................................................................................................xiv
■About the Technical Reviewer.............................................................................xv
■Introduction........................................................................................................xvi
Part 1: Introduction..................................................................................................1
■Chapter 1: Design Considerations.........................................................................3
Understanding the Rules.................................................................................................3
Knowing the FLL Robot Parts Rules.......................................................................................................3
Studying the Game Mission Rules.........................................................................................................5
Grouping Missions into Zones................................................................................................................6
Tasking the Missions......................................................................................................7
Mapping Out the Field.....................................................................................................8
Working with Constraints and Obstacles........................................................................9
Field Obstacles.......................................................................................................................................9
Environmental Obstacles.....................................................................................................................10
Choosing Software........................................................................................................11
Introducing ROBOLAB...........................................................................................................................13
Introducing NXT-G................................................................................................................................14
Understanding the LEGO MINDSTORMS Hardware.......................................................15
NXT Intelligent Brick............................................................................................................................16
Touch Sensor.......................................................................................................................................17
v
■ CONTENTS
Light Sensor.........................................................................................................................................17
Ultrasonic Sensor.................................................................................................................................18
Servo Motor..........................................................................................................................................19
Beginning the Design Process......................................................................................19
Brainstorming as a Team.....................................................................................................................19
Presenting Your Design........................................................................................................................20
Drawing Your Design...........................................................................................................................21
Resource Contention.....................................................................................................21
Summary.......................................................................................................................22
■Chapter 2: Chassis Design...................................................................................23
Understanding Basic Design Aspects...........................................................................23
Size......................................................................................................................................................23
Power...................................................................................................................................................24
Speed...................................................................................................................................................24
Batteries...............................................................................................................................................24
Finding the Center of Gravity........................................................................................25
Gearing Up....................................................................................................................27
Spur Gears...........................................................................................................................................28
Crown Gears.........................................................................................................................................28
Bevel Gears..........................................................................................................................................29
Double Bevel Gears..............................................................................................................................29
Worm Gears.........................................................................................................................................30
Clutch Gears.........................................................................................................................................31
Pulleys..................................................................................................................................................31
Knob Wheel..........................................................................................................................................32
Gear Ratios...........................................................................................................................................32
Getting Your Wheels......................................................................................................34
Circumference......................................................................................................................................35
Mounting..............................................................................................................................................35
Treads...........................................................................................................................37
vi
■ CONTENTS
Exploring the Most Common Chassis............................................................................37
Two-Wheeled Robots...........................................................................................................................37
Three-Wheeled Robots.........................................................................................................................38
Four-Wheeled Robots...........................................................................................................................39
Six-Wheeled Robots.............................................................................................................................40
Tracked Robots....................................................................................................................................41
Troubleshooting............................................................................................................42
Summary.......................................................................................................................43
Part 2: Navigation...................................................................................................45
■Chapter 3: Going Straight....................................................................................47
Design Influences.........................................................................................................47
Wheelbase...........................................................................................................................................47
Weight..................................................................................................................................................48
Wheel Circumference...........................................................................................................................48
Wheel Support......................................................................................................................................49
Programming to Go Straight.........................................................................................51
Move Block..........................................................................................................................................52
Motor Block..........................................................................................................................................53
Reset Motor Block................................................................................................................................54
Custom MyMove Block.........................................................................................................................54
Batteries........................................................................................................................59
Replaceable Batteries..........................................................................................................................59
Rechargeable Battery Packs................................................................................................................60
Helpers..........................................................................................................................60
Wall Following......................................................................................................................................60
Base Jigs..............................................................................................................................................64
Tips...............................................................................................................................64
Motor Matching....................................................................................................................................64
Removing Gear Slack...........................................................................................................................66
Troubleshooting...................................................................................................................................66
vii
■ CONTENTS
Summary.......................................................................................................................67
■Chapter 4: Consistent Turning.............................................................................69
Turning Designs............................................................................................................69
Differential Steering Systems..............................................................................................................69
Steering Drive Systems........................................................................................................................71
Calculating Turns..........................................................................................................72
Single-Wheel Turns..............................................................................................................................72
Dual-Wheel Pivot..................................................................................................................................74
Programming................................................................................................................76
Move Block..........................................................................................................................................76
Motor Blocks........................................................................................................................................76
Creating a Custom MyPivot Block........................................................................................................77
Creating a Custom MyTurn Block.........................................................................................................80
Summary.......................................................................................................................81
■Chapter 5: Line Following and Detection.............................................................83
NXT Light Sensor..........................................................................................................83
Ambient Light.......................................................................................................................................84
Reflective Light....................................................................................................................................84
Positioning the Light Sensor.........................................................................................84
Calibrating the Light Sensor.........................................................................................86
Making the Calibration.........................................................................................................................86
Viewing the Calibration........................................................................................................................89
Deleting Calibration Data.....................................................................................................................90
Shielding the Light Sensor............................................................................................90
Line Following...............................................................................................................92
A Dual-State Example..........................................................................................................................92
Defining More Than Two States...........................................................................................................93
Implementing a Proportional Algorithm...............................................................................................94
Using Dual Light Sensors.....................................................................................................................96
viii
