Electromechanical Motion Systems: Design and Simulation

An introductory reference covering the devices, simulations and limitations in the control of servo systems Linking theoretical material with real-world applications, this book provides a valuable introduction to motion system design. The book begins with an overview of classic theory, its advantages and limitations, before showing how classic limitations can be overcome with complete system simulation. The ability to efficiently vary system parameters (such as inertia, friction, dead-band, damping), and quickly determine their effect on performance, stability, efficiency, is also described. The author presents a detailed review of major component characteristics and limitations as they relate to system design and simulation. The use of computer simulation throughout the book will familiarize the reader as to how this contributes to efficient system design, how it avoids potential design flaws and saves both time and expense throughout the design process. The comprehensive coverage of topics makes the book ideal for professionals who need to apply theory to real-world situations, as well as students who wish to enhance their understanding of the topic. * Covers both theory and practical information at an introductory level, allowing readers to advance to further topics having obtained a strong grounding in the subject * Provides a connection between classic servo technology and the evolution of computer control and simulation * VisSim demonstration material available on an accompanying website enabling readers to experiment with system examples

Table of Contents:
Acknowledgements xiii 1 Introduction 1 1.1 Targeted Readership 2 1.2 Motion System History 2 1.3 Suggested Library for Motion System Design 5 Reference 6 2 Control Theory Overview 7 2.1 Classic Differential/Integral Equation Approach 7 2.2 LaPlace Transform-the S Domain 10 2.3 The Transfer Function 13 2.4 Open versus Closed Loop Control 15 2.4.1 Transient and Frequency Response 18 2.5 Stability 22 2.6 Basic Mechanical and Electrical Systems 23 2.6.1 Equations and Constants 23 2.6.2 Power Test 26 2.6.3 Retardation Test 26 2.7 Sampled Data Systems/Digital Control 28 2.7.1 Sampling 28 2.7.2 Quantization 30 2.7.3 Computational Delay 30 2.7.4 System Analysis 31 References 34 3 System Components 35 3.1 Motors and Amplifiers 35 3.1.1 Review of Motor Theory 36 3.1.2 The Brush Motor 37 3.1.3 The "H" Drive PWM Amplifier 46 3.1.4 The Brushless Motor 48 3.1.5 Speed/Torque Curves 57 3.1.6 Thermal Effects 59 3.1.7 Motor Constant 72 3.1.8 Linear Motor 74 3.1.9 Stepper Motors 78 3.1.10 Induction Motors 97 3.2 Gearheads 107 3.2.1 Spur Gearhead 107 3.2.2 Planetary Gearhead 109 3.2.3 Hybrid Gearhead 110 3.2.4 Worm Gearhead 110 3.2.5 Harmonic Gearhead 110 3.2.6 Gearhead Sizing - Continuous Operation 111 3.2.7 Gearhead Sizing - Intermittent Operation 112 3.2.8 Axial and Radial Load 114 3.2.9 Backlash and Stiffness 114 3.2.10 Temperature/Thermal Resistance 116 3.2.11 Planetary/Spur Gearhead Comparison 118 3.3 Leadscrews and Ballscrews 119 3.3.1 Leadscrew Specifications 120 3.3.2 Ball Screw Specifications 120 3.3.3 Critical Speed 121 3.3.4 Column Strength 122 3.3.5 Starts, Pitch, Lead 124 3.3.6 Encoder/Lead 125 3.3.7 Accuracy 125 3.3.8 Backdrive - Self-Locking 125 3.3.9 Assemblies 125 3.4 Belt and Pulley 126 3.4.1 Belt 128 3.4.2 Guidance/Alignment 128 3.4.3 Belt and Pulley versus Ball Screw 129 3.5 Rack and Pinion 129 3.5.1 Design Highlights 130 3.5.2 Backlash 130 3.5.3 Dynamics 131 3.6 Clutches and Brakes 132 3.6.1 Clutch/Brake Types 132 3.6.2 Velocity Rating 134 3.6.3 Torque Rating 134 3.6.4 Duty Cycle/Temperature Limits 135 3.6.5 Timing 137 3.6.6 Control 139 3.6.7 Brake/System Timing 140 3.6.8 Soft Start/Stop 140 3.7 Servo Couplings 140 3.7.1 Inertia 141 3.7.2 Velocity 141 3.7.3 Torque 141 3.7.4 Compliance 141 3.7.5 Misalignment 143 3.7.6 Coupling Types 143 3.8 Feedback Devices 146 3.8.1 Optical Encoders 146 3.8.2 Magnetic Encoders 152 3.8.3 Capacitive Encoders 153 3.8.4 Magnetostrictive/Acoustic Encoders 153 3.8.5 Resolvers 153 3.8.6 Inductosyn 157 3.8.7 Potentiometer 158 3.8.8 Tachometers 162 References 164 Additional Readings 165 4 System Design 167 4.1 Position, Velocity, Acceleration, Jerk, Resolution, Accuracy, Repeatability 167 4.1.1 Position 167 4.1.2 Velocity 169 4.1.3 Acceleration 170 4.1.4 Jerk 170 4.2 Three Basic Loops - Current/Voltage, Velocity, Position 170 4.2.1 Current/Voltage Loop 171 4.2.2 Velocity Loop 177 4.2.3 Position Loop 181 4.3 The Velocity Profile 182 4.3.1 Preface 182 4.3.2 Incremental Motion 183 4.3.3 Constant Motion 192 4.3.4 Profile Simulation 194 4.4 Feed Forward 195 4.5 Inertia 200 4.5.1 Preface 200 4.5.2 Motor Selection 202 4.5.3 Reflected Inertia - Gearhead 203 4.5.4 Torque versus Optimum Ratio - Gearhead 204 4.5.5 Power versus Optimum Ratio - Gearhead 204 4.5.6 Optimal Conditions 208 4.6 Shaft Compliance 210 4.6.1 Basic Equations 211 4.6.2 System Components 212 4.6.3 Initial Simulation - Lumped Inertia 212 4.6.4 Second Simulation - Inclusion of Shaft Dynamics 212 4.6.5 Third Simulation - Compensation 214 4.6.6 Coupling Simulation 215 4.7 Compensation 216 4.7.1 Routh-Hurwitz 216 4.7.2 Nyquist 217 4.7.3 Bode 217 4.7.4 Root Locus 218 4.7.5 Phase Plane 218 4.7.6 PID 218 4.7.7 Notch Filter 223 4.8 Nonlinear Effects 224 4.8.1 Coulomb Friction 224 4.8.2 Stiction 225 4.8.3 Limit 226 4.8.4 Deadband 226 4.8.5 Backlash 228 4.8.6 Hysteresis 229 4.9 The Eight Basic Building Blocks 230 4.9.1 Rotary Motion - Direct Drive 230 4.9.2 Rotary Motion - Gearhead Drive 234 4.9.3 Rotary Motion - Belt and Pulley Drive 237 4.9.4 Linear Motion - Leadscrew/Ballscrew Drive 239 4.9.5 Linear Motion - Belt and Pulley Drive 242 4.9.6 Linear Motion - Rack and Pinion Drive 245 4.9.7 Linear Motion - Roll Feed Drive 248 4.9.8 Linear Motion - Linear Motor Drive 251 References 253 5 System Examples - Design and Simulation 255 5.1 Linear Motor Drive 255 5.2 Print Cylinder Control 257 5.3 Conveyor System - Clutch/Brake Control 261 5.3.1 Determine Basic Parameters 261 5.3.2 Initial Component Selection 264 5.3.3 Simulate System 264 5.4 Bang-Bang Servo (Slack Loop System) 267 5.5 Wafer Spinner 272 Appendix 275 A.1 Brushless Motor Speed/Torque Curves 275 A.1.1 Thermal Resistance 275 A.1.2 Core Losses 276 A.2 Inertia Calculation - Excel Program 277 A.3 Time Constants versus Viscous Damping Constant 277 A.4 Current Drive Review 279 A.5 Conversion Factors 285 A.6 Work and Power 286 A.6.1 Work (Energy) 286 A.6.2 Power 286 A.6.3 Horsepower (HP) 286 A.6.4 Rotary Power 287 A.7 I2R Losses 287 A.7.1 Conventional DC Motor 287 A.7.2 Three Phase Brushless DC Motor with Trapezoidal BEMF and Six Step Drive 288 A.7.3 Three Phase Brushless DC Motor with Sine Wave BEMF and Drive 289 A.8 Copper Resistivity 290 Index 291

About the Author :
Frederick G. Moritz FM Systems, Ohio, USA