Introduction to Dynamics and Control in Mechanical Engineering Systems

Dr. To, obtained his Ph.D. in 1980 from the University of Southampton, is a professor in the Department of Mechanical and Materials Engineering at the University of Nebraska, Lincoln (UNL). Prior to joining UNL in 1996, he was a professor at the University of Western Ontario (UWO). Before joining UWO he was an associate professor at the University of Calgary. He was a University Research Fellow of the Natural Sciences and Engineering Research Council of Canada (NSERC) between 1982 and 1992. He is a Fellow of the American Society of Mechanical Engineers (ASME), and a member of several other professional societies. He served as chair of the ASME Finite Element Techniques and Computational Technologies Technical Committee. He serves as associate editors and member of editorial boards of several refereed journals. His research interests cover sound and vibration studies, solid and computational mechanics, system dynamics and controls, and design methodology.

Series Preface xiii

Preface xv

Acknowledgments xvii

1 Introduction 1

1.1 Important Difference between Static and Dynamic Responses 1

1.2 Classification of Dynamic Systems 2

1.3 Applications of Control Theory 3

1.4 Organization of Presentation 4

References 5

2 Review of Laplace Transforms 7

2.1 Definition 8

2.2 First and Second Shifting Theorems 10

2.3 Dirac Delta Function (Unit Impulse Function) 10

2.4 Laplace Transforms of Derivatives and Integrals 11

2.5 Convolution Theorem 11

2.6 Initial and Final Value Theorems 13

2.7 Laplace Transforms of Periodic Functions 13

2.8 Partial Fraction Method 15

2.9 Questions and Solutions 16

2.10 Applications of MATLAB 22

Exercise Questions 26

References 27

3 Dynamic Behaviors of Hydraulic and Pneumatic Systems 29

3.1 Basic Elements of Liquid and Gas Systems 29

3.1.1 Liquids 30

3.1.3 Remarks 31

3.2 Hydraulic Tank Systems 32

3.2.1 Non-interacting Hydraulic Tank Systems 32

3.2.2 Interacting Hydraulic Tank Systems 34

3.3 Nonlinear Hydraulic Tank and Linear Transfer Function 35

3.4 Pneumatically Actuated Valves 37

3.5 Questions and Solutions 39

Appendix 3A: Transfer Function of Two Interacting Hydraulic Tanks 49

Exercise Questions 52

4 Dynamic Behaviors of Oscillatory Systems 57

4.1 Elements of Oscillatory Systems 57

4.2 Free Vibration of Single Degree-of-Freedom Systems 59

4.3 Single Degree-of-Freedom Systems under Harmonic Forces 63

4.4 Single Degree-of-Freedom Systems under Non-Harmonic Forces 65

4.5 Vibration Analysis of Multi-Degrees-of-Freedom Systems 67

4.5.1 Formulation and Solution for Two-Degrees-of-Freedom Systems 67

4.5.2 Vibration Analysis of a System with a Dynamic Absorber 72

4.5.3 Normal Mode Analysis 73

4.6 Vibration of Continuous Systems 77

4.6.1 Vibrating Strings or Cables 78

4.6.2 Remarks 80

4.7 Questions and Solutions 81

Appendix 4A: Proof of Equation (4.19b) 97

Exercise Questions 99

References 104

5 Formulation and Dynamic Behavior of Thermal Systems 105

5.1 Elements of Thermal Systems 105

5.1.1 Thermal Resistance 105

5.1.2 Thermal Capacitance 106

5.1.3 Thermal Radiation 107

5.2 Thermal Systems 107

5.2.1 Process Control 107

5.2.2 Space Heating 108

5.2.3 Three-Capacitance Oven 109

5.3 Questions and Solutions 112

Exercise Questions 117

6 Formulation and Dynamic Behavior of Electrical Systems 121

6.1 Basic Electrical Elements 121

6.2 Fundamentals of Electrical Circuits 122

6.2.1 Resistors Connected in Series 122

6.2.2 Resistors Connected in Parallel 123

6.2.3 Kirchhoff’s Laws 124

6.4 Electromechanical Systems 126

6.4.1 Armature-Controlled DC Motor 127

6.4.2 Field-Controlled DC Motor 129

6.4.3 DC Generator 130

6.5 Questions and Solutions 131

Exercise Questions 134

References 135

7 Dynamic Characteristics of Transducers 137

7.1 Basic Theory of the Tachometer 137

7.2 Principles and Applications of Oscillatory Motion Transducers 138

7.2.1 Equation of Motion 139

7.2.2 Design Considerations of Two Types of Transducer 140

7.3 Principles and Applications of Microphones 141

7.3.1 Moving-Coil Microphone 141

7.3.2 Condenser Microphone 144

7.4 Principles and Applications of the Piezoelectric Hydrophone 146

7.5 Questions and Solutions 148

Appendix 7A: Proof of Approximated Current Solution 150

Exercise Questions 153

References 154

8 Fundamentals of Control Systems 155

8.1 Classification of Control Systems 156

8.2 Representation of Control Systems 156

8.3 Transfer Functions 156

8.3.1 Transfer Function of Elements in Cascade Connection 157

8.3.2 Transfer Function of Elements in Parallel Connection 157

8.3.3 Remarks 158

8.4 Closed-Loop Control Systems 158

8.4.1 Closed-Loop Transfer Functions and System Response 159

8.4.2 Summary of Steps for Determination of Closed-Loop Transfer Functions 161

8.5 Block Diagram Reduction 161

8.5.1 Moving Starting Points of Signals 161

8.5.2 Moving Summing Points 162

8.5.3 System Transfer Function by Block Diagram Reduction 162

8.6 Questions and Solutions 164

Exercise Questions 170

References 172

9 Analysis and Performance of Control Systems 173

9.1 Response in the Time Domain 173

9.2 Transient Responses as Functions of Closed-Loop Poles 175

9.3 Control System Design Based on Transient Responses 177

9.4 Control Types 180

9.4.2 Integral Control 181

9.4.3 Derivative Control 181

9.5 Steady-State Errors 182

9.5.1 Unit Step Input 182

9.5.2 Unit Ramp Input 183

9.5.3 Unit Parabolic Input 183

9.6 Performance Indices and Sensitivity Functions 184

9.6.1 Performance Indices 184

9.6.2 Sensitivity Functions 185

9.7 Questions and Solutions 185

Exercise Questions 190

10 Stability Analysis of Control Systems 195

10.1 Concept of Stability in Linear Control Systems 195

10.2 Routh–Hurwitz Stability Criterion 195

10.3 Applications of Routh–Hurwitz Stability Criterion 197

10.4 Questions and Solutions 202

Exercise Questions 208

References 210

11 Graphical Methods for Control Systems 211

11.1 Root Locus Method and Root Locus Plots 211

11.1.1 Rules for Root Locus Plots of Negative Feedback Control Systems 212

11.1.2 Construction of Root Loci 213

11.2 Polar and Bode Plots 215

11.3 Nyquist Plots and Stability Criterion 221

11.3.1 Conformal Mapping and Cauchy’s Theorem 221

11.3.2 Nyquist Method and Stability Criterion 223

11.4 Gain Margin and Phase Margin 226

11.5 Lines of Constant Magnitude: M Circles 229

11.6 Lines of Constant Phase: N Circles 233

11.7 Nichols Charts 234

11.8 Applications of MATLAB for Graphical Constructions 236

11.8.1 Root Locus Plots 236

11.8.2 Bode Plots 243

11.8.3 Nyquist Plots 249

Exercise Questions 257

References 260

12 Modern Control System Analysis 261

12.1 State Space Method 261

12.2 State Transition Matrix 262

12.3 Relationship between Laplace Transformed State Equation and Transfer Function 264

12.4 Stability Based on Eigenvalues of the Coefficient Matrix 267

12.6 Stabilizability and Detectability 277

12.7 Applications of MATLAB 277

Appendix 12A: Solution of System of First-Order Differential Equations 286

Appendix 12B: Maclaurin’s Series 291

Appendix 12C: Rank of A Matrix 294

Exercise Questions 294

References 296

Index 297