00_200256_FM/Bergren 4/10/03 11:54 AM Page i ANATOMY OF A ROBOT CHARLES M. BERGREN McGraw-Hill New York Chicago San Francisco Lisbon London Madrid Mexico City Milan New Delhi San Juan Seoul Singapore Sydney Toronto Copyright © 2003 by The McGraw-Hill Companies, Inc. All rights reserved. Manufactured in the United States of America. Except as permitted under the United States Copyright Act of 1976, no part of this publication may be reproduced or distributed in any form or by any means, or stored in a data- base or retrieval system, without the prior written permission of the publisher. 0-07-142930-1 The material in this eBook also appears in the print version of this title: 0-07-141657-9 All trademarks are trademarks of their respective owners. Rather than put a trademark symbol after every occurrence of a trademarked name, we use names in an editorial fashion only, and to the benefit of the trademark owner, with no intention of infringement of the trademark. 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McGraw-Hill has no responsibility for the content of any information accessed through the work. Under no circumstances shall McGraw-Hill and/or its licensors be liable for any indirect, incidental, special, punitive, consequential or similar damages that result from the use of or inability to use the work, even if any of them has been advised of the possibility of such damages. This limitation of lia- bility shall apply to any claim or cause whatsoever whether such claim or cause arises in contract, tort or otherwise. DOI: 10.1036/0071429301 00_200256_FM/Bergren 4/10/03 11:54 AM Page iii To my son and my wonderful family This page intentionally left blank. 00_200256_FM/Bergren 4/10/03 11:54 AM Page v For more information about this title, click here. CONTENTS Preface xv Introduction xvii Chapter 1 Project Management 1 Project Management 2 Project Process Flowchart 3 How This Works When It’s Implemented Right 5 The User’s Manual for the “Boss” 5 The User’s Manual for PMs 6 Conclusion 17 Chapter 2 Control Systems 19 Distributed Control Systems 22 Central Control Systems 24 Open-Loop Control 24 Closed-Loop Control 26 Designing the Control System 39 Notes on Robot Design 50 Multivariable Control Systems 58 Time 67 Space 69 Chapter 3 Computer Hardware 73 Leverage Existing Technology 75 Speeding Up Engineering 77 Computer Architecture 77 Process for Choosing a Robot’s Computer Hardware 113 V Copyright 2003 by The McGraw-Hill Companies, Inc. Click Here for Terms of Use. 00_200256_FM/Bergren 4/10/03 11:54 AM Page vi VI CONTENTS Chapter 4 Reliability, Safety, and Compliance 123 Reliability 123 Safety 128 Environmental Considerations 132 Common Sense 135 Emissions 138 Quality Issues 143 Testing 144 Chapter 5 Design Steps: HLD 147 Power 147 Locomotion 148 Automation 148 Chapter 6 Energy and Power Systems 153 Energy 154 Energy Sources 157 Chapter 7 Energy Control and Software 159 Considerations 159 Energy Conservation 162 Hardware Considerations 164 Spy-hopping 176 Software Considerations for Energy Control 178 Mechanical Considerations: Software for Energy Control 183 Chapter 8 Digital Signal Processing (DSP) 191 The Nyquist-Shannon Sampling Theorem 192 A/D Conversion 198 A/D Dithering 200 Sample and Hold (S/H) 201 Antialias Filters 201 D/A Effects: Sinc Compensation 207 DSP Filter Design 208 00_200256_FM/Bergren 4/10/03 11:54 AM Page vii CONTENTS VII Physical Implementation of DSP Filters 215 Multirate DSP 220 Chapter 9 Communications 221 OSI Seven-Layer Model 224 Physical Layer 226 Baseband Transmission 228 Modulated Communications 232 Error Control 238 Shared Access 258 Compression 265 Encryption and Security 266 Popular Communication Channels 269 Chapter 10 Motors and Actuators 275 AC Motors 275 DC Motors 276 Exotic Motors 279 Chapter 11 Mechanics 281 Materials 282 Some Cautions 285 Static Mechanics 287 Dynamic Mechanics 288 Index 293 This page intentionally left blank. 00_200256_FM/Bergren 4/10/03 11:54 AM Page ix PREFACE Two years ago, I took my six-year-old son to a “robot race” up in the Rockies near Boulder. It was held in the community center of a small mountain town. Nevertheless, it was packed with about 100 enthusiastic people and many interesting exhibits. The central event was to be a timed race along a prescribed course. Several school-aged kids had entered plastic robots clearly built from parts from the same toy manufacturer. The racecourse was a plastic mat approximately 15 feet on each side. The robots had to fol- low a one-inch-wide, serpentine black line on the mat from beginning to end. The win- ner would be the robot finishing with the fastest time. I watched the kids tuning up their robots on the racecourse before the race. Each robot had a sensor on each side that could detect the black line. If the robot moved forward and started to cross the line, the electronics would correct the steering and move the robot back on course. It was clear the kids were all having trouble. None of the robots could follow the course from beginning to end. They would invariably lurch too far over the black race- course line and get lost, spinning in useless circles. Legions of adult advisors huddled with the kids, making all sorts of changes, yet nobody was making progress. To me, the answer was obvious and I wanted to help. IX Copyright 2003 by The McGraw-Hill Companies, Inc. Click Here for Terms of Use. 00_200256_FM/Bergren 4/10/03 11:54 AM Page x X PREFACE Off in the corner, a bit cowed and unsure of himself, was the youngest competitor. Let’s call him Sam. He may have been 13 and was there with his mom. They, too, were making changes without good results. I approached Sam’s mom, discretely asked per- mission to help, and joined their team. Without going into the theory, I explained that the robots were all too fast and powerful for their own control systems. I recommended slowing down Sam’s robot by adding more weight at the back end. We finally decided to build a sled for the robot to drag and set about finding the materials. With the race deadline approaching, Sam himself came up with the solution. With a quick glance to ask permission, he grabbed his mom’s handheld camera and slipped the wrist strap over a post on the rear of the robot. We confirmed the robot could still move slowly down the racecourse line towing the camera. Sam took the batteries out of the camera until it was near the right weight. All too soon, race time came and we had to halt our experiment. One after another, the older competitors’ robots raced down the course only to stray off the black line and be disqualified. A couple of the robots did finish after wandering around lost and wasting a good deal of time. Eventually, the time came for Sam to race his robot. He placed his robot on the starting line, plopped his mom’s camera down behind it, confidently put the wrist strap on the rear bumper, and pushed the start but- ton with a bit of ceremony. As Sam’s robot left the starting line, it lurched forward, tug- ging the camera behind it. The crowd started to buzz and I watched the highly amused advisors talking among themselves. It was clear some of them understood what was going on. To make a long story short, Sam’s robot reliably chugged around the racecourse and he won. The look on his face alone was worth the effort. Sam’s nominal reward was a kit for a bigger robot, but I think he walked away with much more than that.