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Contents 1 Definitions and Problem Formulations 1 1.1 Introduction 1 1.2 Definitions 1 1.2.1 Systems and Signals 1 1.2.2 SISO/MIMO Systems 3 1.2.3 Linear/Nonlinear Systems 4 1.3 System Classification 5 1.4 Models 6 1.5 Control Systems 8 1.6 Control System Design Problems 11 1.6.1 General Remarks 11 1.6.2 Systems Analysis 11 1.6.3 Reference Tracking 12 1.6.4 Disturbance Rejection 12 1.6.5 TradeofF Robustness versus Performance 12 1.6.6 Stabilization 13 1.6.7 Noise Attenuation 13 2 Modeling of Dynamic Systems 15 2.1 Introduction 15 2.2 General Modeling Guidelines 16 2.3 Some Examples 17 2.3.1 Example Water Tank 17 2.3.2 Example Stirred Reactor 18 2.3.3 Example Cruise Control 20 2.3.4 Example Loudspeaker 22 2.3.5 Example Conveyor Belt 23 2.4 Model Uncertainty 24
VIII Contents 3 System Representation and Transformation 27 3.1 Introduction 27 3.1.1 Loudspeaker, First-Order Equations 28 3.1.2 Objectives 28 3.2 Normalization 29 3.2.1 Example Water Tank, Normalization 30 3.2.2 Example Cruise Control, Normalization 30 3.3 Linearization 31 3.3.1 Example Water Tank, Linearization 33 3.3.2 Example Cruise Control, Linearization 34 3.4 Parametric Uncertainty 35 3.4.1 General Remarks 35 3.4.2 Example Cruise Control, Parametric Uncertainty 35 3.5 Linear State Space Forms 37 3.5.1 Example Loudspeaker System, State Space Form 37 3.5.2 State Space and System Coordinates 38 3.5.3 Plant and Control System Interface 39 4 Analysis of Linear Systems Part I 41 4.1 Introduction 41 4.2 Time Domain Behavior of Linear Systems 42 4.2.1 Matrix Exponentials 42 4.2.2 General Solution 43 4.3 First-Order Systems 45 4.3.1 Impulse Response 46 4.3.2 Step Response 47 4.3.3 Ramp Response 48 4.3.4 Harmonie Response 49 4.4 Stability 50 4.4.1 Definitions 50 4.4.2 Spectral Methods 51 4.4.3 Stability of the Inverted Pendulum 53 4.4.4 Non-Exponential Asymptotic Stability* 54 5 Analysis of Linear Systems Part II 55 5.1 Introduction 55 5.2 Reachability, Controllability and Stabilizability 56 5.2.1 Introduction 56 5.2.2 Reachability Conditions 56 5.2.3 An Explicit Feedforward Control Signal* 58 5.2.4 Example Controllability of a Geostationary Satellite... 59 5.2.5 Nonlinear Systems* 60 5.3 Observability Conditions 62 5.3.1 Observability of the Inverted Pendulum 63 5.4 State Space Decomposition 64
Contents IX 5.5 Spectral Decompositions* 65 5.6 I/O Descriptions and Canonical Realizations 67 5.6.1 I/O Description State-Space Description 67 5.6.2 State-Space -+ I/O Description* 71 5.6.3 Coordinate Transformations* 73 5.7 Concluding Remarks 74 Laplace Transformation Part I 75 6.1 Introduction 75 6.2 Properties of the Laplace Transformation 76 6.3 Transfer Functions 78 6.3.1 Introduction and Definitions 78 6.3.2 Properties of Transfer Functions 79 6.3.3 Transfer Functions and System Realizations 81 6.3.4 Transfer Functions as Conformal Mappings* 84 6.3.5 Overview System Representations and Transformations 86 Laplace Transformation Part II 87 7.1 Introduction 87 7.2 Solution of Low-Order ODE 87 7.2.1 Example of a Inverse Laplace Transformation 89 7.3 Poles and Zeros of Transfer Functions 89 7.3.1 Poles and BIBO Stability 89 7.3.2 Definition and Interpretation of System Zeros 91 7.3.3 Influence of Poles and Zeros on System Dynamics 93 7.4 Algebraic Stability Criteria* 100 7.4.1 Introduction 100 7.4.2 The Hurwitz Criterion 101 7.4.3 The Kharitonov Theorem 104 Frequency Responses 107 8.1 Introduction 107 8.2 Frequency Responses 107 8.2.1 Definition of Frequency Responses 107 8.2.2 Representation of Frequency Responses 110 8.2.3 Bode's Amplitude/Phase Law* 113 8.3 Asymptotic System Properties 115 8.4 System Identification Using Frequency Responses 116 8.4.1 General Remarks 116 8.4.2 Example System Identification 117 8.5 Nonparametric Uncertainty 120 8.5.1 Introduction 120 8.5.2 Uncertainty Representations 120 8.5.3 Uncertainty Estimation 122
X Contents 9 Analysis of Feedback Systems 131 9.1 Introduction 131 9.2 Definitions 131 9.3 Closed-Loop System Stability 133 9.4 Nyquist Theorem 135 9.4.1 Nominal Closed-Loop System Stability 135 9.4.2 Robust Closed-Loop System Stability 138 9.5 Constraints on Closed-Loop Systems 138 9.5.1 Spectral Properties of Noise and Disturbance 138 9.5.2 Sensitivity Constraints 140 9.5.3 Limitations on Crossover Frequencies 142 9.5.4 Example Pendulum on a Cart* 151 9.6 Summary 153 10 Specifications for Feedback Systems 155 10.1 Introduction 155 10.2 Static Errors 155 10.3 Specifications Based on Second-Order Systems 156 10.4 Frequency-Domain Specifications 159 10.4.1 Introduction 159 10.4.2 Peaking Limitations 161 10.4.3 Multiplicative Specifications of the Sensitivity* 161 10.5 Summary 168 11 Feedback Control Design 1 169 11.1 Introduction 169 11.2 PID Controllers 170 11.2.1 Introduction 170 11.2.2 PID Tuning Rules 172 11.2.3 Loop Shaping by Parameter Tuning 176 11.3 Classical Iterative Loop Shaping 179 11.3.1 First-Order Lead/Lag Elements 180 11.3.2 Second-Order Lead/Lag Elements 181 11.4 Closed-Form Cross-Over Specification* 184 11.5 Aström and Hägglund Rules* 187 11.6 Predictive PI Control Systems* 189 11.6.1 Predictive PI Control of Simple Plants 190 11.6.2 Smith Predictors 191 11.6.3 Numerical Optimization 193 12 Feedback Control Design II 199 12.1 Introduction 199 12.2 Loop Shaping and Robustness 199 12.2.1 Introduction 199 12.2.2 Plant Inversion Methods 200
Contents XI 12.3 Loop Shaping and Non-Minimum Phase Zeros 204 12.3.1 Introduction 204 12.3.2 Example Loop Shaping for NMP Plants 204 12.4 Loop Shaping for Unstable Systems 207 12.4.1 Introduction 207 12.4.2 Example Control of Inverted Pendulum I 207 13 Feedback Control Design III 211 13.1 Introduction 211 13.2 Cascaded Control Loops 211 13.2.1 General Remarks 211 13.2.2 An Example 213 13.3 Root-Locus Methods 216 13.3.1 Introduction 216 13.3.2 General Rules of Root Locus Designs 217 13.3.3 Compensation in Root Locus Designs 218 14 Control Systems Implementation* 225 14.1 Introduction 225 14.2 PID Controllers in Practical Applications 226 14.2.1 Enhanced PID Structures 226 14.2.2 Dealing with Actuator Saturation 227 14.2.3 Bumpless Transfer and Gain Scheduling 229 14.3 Realization with Analog Components 231 14.4 Realization with Digital Computers 233 15 Case Study* 237 15.1 Introduction 237 15.2 Modeling 237 15.2.1 General Remarks 237 15.2.2 Model Development 238 15.2.3 Linearization and Controller development 240 15.2.4 Estimation of the model uncertainties 241 15.3 Specifications 242 15.4 Controller Design 245 A Library of Standard Elements 251 A.l Integrator Element 252 A.2 Differentiator Element 253 A.3 First-Order Element 254 A.4 Realizable Derivative Element ("Dirty D") 255 A.5 Second-Order Element 256 A.6 Lag Element 257 A.7 Lead Element 258 A.8 PID Element 259
XII Contents A.9 First-Order All-Pass Element 260 A.10 Delay Element 261 B Some Mathematical Results 263 B.l Linear Algebra 263 B.l.l Notation 263 B.1.2 Geometry 264 B.l.3 Determinants and Traces 267 B.l.4 Linear Equations 269 B.l.5 Characteristic Polynomials 270 B.1.6 Eigenproblems 272 B.l.7 Structured Matrices 274 B.2 Complex Analysis 276 B.2.1 Signal Power Spectra 277 B.2.2 Some Theorems 278 B.3 Proof of the Nyquist Theorem 279 B.4 Proof of the Cross-Over Frequency Specification Method 281 B.5 Proof of the Apollonius Circle Condition 284 C Solutions to Quick Checks 285 C.l Definitions and Problem Formulations 285 C.l.l Introduction 285 C.1.2 Definitions 285 C.l.3 System Classification 287 C.1.4 Models 287 C.1.5 Control Systems 288 C.l.6 Control System Design Problems 289 C.2 Modeling of Dynamic Systems 290 C.2.1 Introduction 290 C.2.2 General Modeling Guidelines 290 C.2.3 Some Examples 290 C.3 System Representation and Transformation 291 C.3.1 Introduction 291 C.3.2 Normalization 291 C.3.3 Linearization 292 C.3.4 Linear State Space Forms 293 C.4 Analysis of Linear Systems Part I 293 C.4.1 Introduction 293 C.4.2 Time-Domain Behavior of Linear Systems 293 C.4.3 First-Order Systems 295 C.4.4 Stability 297 C.5 Analysis of Linear Systems Part II 299 C.5.1 Introduction 299 C.5.2 Reachability, Controllability and Stabilizability 299 C.5.3 Observability Conditions 301
Contents XIII C.5.4 State Space Decomposition 302 C.5.5 Spectral Decompositions 302 C.5.6 I/O Descriptions and Canonical Realizations 303 C.6 Laplace Transformation Part 1 306 C.6.1 Introduction 306 C.6.2 Properties of the Laplace Transformation 306 C.6.3 Transfer Functions 307 C.7 Laplace Transformation Part II 310 C.7.1 Introduction 310 C.7.2 Solution of Low-Order ODE 310 C.7.3 Poles and Zeros of Transfer Functions 311 C.7.4 Algebraic Stability Criteria 313 C.8 Frequency Responses 315 C.8.1 Introduction 315 C.8.2 Frequency Responses 315 C.8.3 Asymptotic System Properties 318 C.8.4 System Identification Using Frequency Responses 319 C.8.5 Nonparametric Uncertainty 321 C.9 Analysis of Feedback Systems 322 C.9.1 Introduction 322 C.9.2 Definitions 322 C.9.3 Closed-Loop System Stability 323 C.9.4 Nyquist Theorem 323 C.9.5 Constraints on Closed-Loop Systems 327 C.10 Specifications for Feedback Systems 329 C.10.1 Introduction 329 C.10.2 Specs Based on Second-Order System Approximations. 330 C.10.3 Frequency Domain Specifications 330 C.ll Feedback Control Design I 333 C.ll.l Introduction 333 C.11.2 PID Controllers 333 C.ll.3 Classical Iterative Loop Shaping 336 C.ll.4 Closed-Form Cross Over Specification 336 C.ll.5 Predictive PI Control Systems 336 C.12 Feedback Control Design II 337 C.12.1 Introduction 337 C.12.2 Loop Shaping and Robustness 337 C.12.3 Loop Shaping and Non-Minimum Phase Zeros 338 C.12.4 Loop Shaping for Unstable Systems 338 C.13 Feedback Control Design III 340 C.13.1 Introduction 340 C.13.2 Root-Locus Methods 340 C.14 Control Systems Implementation 341 C.14.1 Introduction 341 C.14.2 PID Controllers in Practical Applications 341
XTV Contents C.14.3 Realization with Analog Components 342 C.14.4 Realization with Digital Computers 343 D Translation English to German 345 E List of Symbols 347 References 351