Instrumentation and Control Systems - William Bolton [2021, PDF]

Contents

Preface ix
Acknowledgement xiii
1. Measurement Systems 1
1.1 Introduction 1
1.1.1 Systems 1
1.2 Instrumentation Systems 2
1.2.1 The Constituent Elements of an Instrumentation System 2
1.3 Performance Terms 4
1.3.1 Resolution, Accuracy, and Error 4
1.3.2 Range 6
1.3.3 Precision, Repeatability, and Reproducibility 7
1.3.4 Sensitivity 7
1.3.5 Stability 8
1.3.6 Dynamic Characteristics 9
1.4 Dependability 9
1.4.1 Reliability 10
1.5 Requirements 11
1.5.1 Calibration 12
1.5.2 Safety Systems 13
Problems 14
2. Instrumentation System Elements 17
2.1 Introduction 18
2.2 Displacement Sensors 18
2.2.1 Potentiometer 18
2.2.2 Strain-Gauged Element 19
2.2.3 Capacitive Element 20
2.2.4 Linear Variable Differential Transformer 21
2.2.5 Optical Encoders 21
2.2.6 Moiré Fringes 22
2.2.7 Optical Proximity Sensors 23
2.2.8 Mechanical Switches 24
2.2.9 Capacitive Proximity Sensor 25
2.2.10 Inductivity Proximity Sensor 26
2.3 Speed Sensors 26
2.3.1 Optical Methods 26
2.3.2 Incremental Encoder 26
2.3.3 Tachogenerator 26
2.4 Fluid Pressure Sensors 26
2.4.1 Diaphragm Sensor 27
2.4.2 Piezoelectric Sensor 28
2.4.3 Bourdon Tube 28
2.5 Fluid Flow 29
2.5.1 Differential Pressure Methods 29
2.5.2 Turbine Meter 31
2.5.3 Ultrasonic Time of Flight Flow Meter 32
2.5.4 Vortex Flow Rate Method 32
2.5.5 Coriolis Flow Meter 33
2.6 Liquid Level 33
2.6.1 Floats 34
2.6.2 Displacer Gauge 34
2.6.3 Differential Pressure 34
2.6.4 Load Cell 34
2.6.5 Electrical Conductivity Level Indicator 35
2.6.6 Capacitive Level Indicator 35
2.6.7 Ultrasonic Level Gauge 35
2.6.8 Nucleonic Level Indicators 36
2.7 Temperature Sensors 36
2.7.1 Bimetallic Strips 36
2.7.2 Liquid in Glass Thermometers 36
2.7.3 Resistance Temperature Detectors (RTDs) 36
2.7.4 Thermistors 37
2.7.5 Thermocouples 37
2.7.6 Thermodiodes and Transistors 40
2.7.7 Pyrometers 40
2.8 Sensor Selection 41
2.9 Signal Processing 42
2.9.1 Resistance to Voltage Converter 42
2.9.2 Temperature Compensation 45
2.9.3 Thermocouple Compensation 45
2.9.4 Protection 47
2.9.5 Analogue-to-Digital Conversions 47
2.9.6 Digital-to-Analogue Conversions 50
2.9.7 Microcontroller Systems 51
2.9.8 Op-Amps 52
2.9.9 Pressure-to-Current Converter 56
2.10 Signal Transmission 56
2.10.1 Noise 59
2.11 Smart Systems 60
2.11.1 MEMS 61
2.12 Data Presentation Element 62
2.12.1 Indicator 62
2.12.2 Illuminative Displays 62
2.12.3 Graphical User Interface (GUI) 64
2.12.4 Data Loggers 64
2.12.5 Printers 65
Problems 66
3. Measurement Case Studies 71
3.1 Introduction 71
3.2 Case Studies 72
3.2.1 A Temperature Measurement 72
3.2.2 An Absolute Pressure Measurement 73
3.2.3 Detection of the Angular Position of a Shaft 74
3.2.4 Air Flow Rate Determination 74
3.2.5 Fluid Level Monitoring 75
3.2.6 Measurement of Relative Humidity 75
3.2.7 Dimension Checking 76
3.2.8 Temperature of a Furnace 77
3.2.9 Automobile Tyre Pressure Monitoring 77
3.2.10 Control System Sensors with Automobiles 77
3.3 Data Acquisition Systems 78
3.3.1 Data Acquisition Software 80
3.3.2 Data Loggers 80
3.4 Testing 80
3.4.1 Maintenance 80
3.4.2 Common Faults 81
Problems 82
4. Control Systems 85
4.1 Introduction 85
4.2 Control Systems 86
4.2.1 Open- and Closed-Loop Control 87
4.3 Basic Elements 89
4.3.1 Basic Elements of a Closed-Loop System 89
4.4 Case Studies 91
4.4.1 Control of the Speed of Rotation of a Motor Shaft 91
4.4.2 Control of the Position of a Tool 92
4.4.3 Power Steering 92
4.4.4 Control of Fuel Pressure 93
4.4.5 Antilock Brakes 93
4.4.6 Thickness Control 94
4.4.7 Control of Liquid Level 95
4.4.8 Robot Gripper 95
4.4.9 Machine Tool Control 97
4.4.10 Fluid Flow Control 97
4.5 Discrete-Time Control Systems 98
4.6 Digital Control Systems 99
4.7 Hierarchical Control 100
Problems 101
5. Process Controllers 103
5.1 Introduction 103
5.1.1 Direct and Reverse Actions 104
5.1.2 Dead Time 104
5.1.3 Capacitance 104
5.2 On-Off Control 104
5.2.1 Relays 106
5.3 Proportional Control 107
5.3.1 Proportional Band 107
5.3.2 Limitations of Proportional Control 109
5.4 Derivative Control 110
5.4.1 PD Control 110
5.5 Integral Control 112
5.5.1 PI Control 112
5.6 PID Control 114
5.6.1 PID Process Controller 116
5.7 Tuning 117
5.7.1 Process Reaction Tuning Method 118
5.7.2 Ultimate Cycle Tuning Method 120
5.7.3 Quarter Amplitude Decay 121
5.7.4 Lambda Tuning 121
5.7.5 Software Tools 121
5.7.6 Adaptive Controllers 122
5.8 Digital Systems 122
5.8.1 Embedded Systems 123
5.9 Fuzzy Logic Control 124
5.9.1 Fuzzy Logic 124
5.9.2 Fuzzy Logic Control Systems 126
5.9.3 Fuzzy Logic Controller 127
5.9.4 Fuzzy Logic Tuning of PID Controllers 130
5.10 Neural Networks 130
5.10.1 Neural Networks for Control 132
Problems 133
6. Correction Elements 137
6.1 Introduction 137
6.1.1 The Range of Actuators 138
6.2 Pneumatic and Hydraulic Systems 138
6.2.1 Current to Pressure Converter 138
6.2.2 Pressure Sources 138
6.2.3 Control Valves 139
6.2.4 Actuators 140
6.3 Directional Control Valves 141
6.3.1 Sequencing 143
6.3.2 Shuttle Valve 145
6.4 Flow Control Valves 146
6.4.1 Forms of Plug 147
6.4.2 Rangeability and Turndown 149
6.4.3 Control Valve Sizing 149
6.4.4 Valve Positioners 151
6.4.5 Other Forms of Flow Control Valves 151
6.4.6 Fail-Safe Design 152
6.5 Motors 152
6.5.1 D.C. Motors 152
6.5.2 Brushless Permanent Magnet D.C. Motor 154
6.5.3 Stepper Motor 154
6.6 Case Studies 159
6.6.1 A Liquid Level Process Control System 159
6.6.2 Milling Machine Control System 159
6.6.3 A Robot Control System 159
Problems 160
7. PLC Systems 165
7.1 Introduction 165
7.2 Logic Gates 166
7.2.1 Field-Programmable Gate Arrays 169
7.3 PLC System 170
7.4 PLC Programming 171
7.4.1 Logic Gates 173
7.4.2 Latching 174
7.4.3 Internal Relays 174
7.4.4 Timers 175
7.4.5 Counters 176
7.5 Testing and Debugging 178
7.6 Case Studies 179
7.6.1 Signal Lamp to Monitor Operations 179
7.6.2 Cyclic Movement of a Piston 179
7.6.3 Sequential Movement of Pistons 179
7.6.4 Central Heating System 181
Problems 182
8. System Models 189
8.1 Introduction 189
8.1.1 Static Response 189
8.1.2 Dynamic Response 189
8.2 Gain 190
8.2.1 Gain of Systems in Series 191
8.2.2 Feedback Loops 191
8.3 Dynamic Systems 193
8.3.1 Mechanical Systems 193
8.3.2 Rotational Systems 194
8.3.3 Electrical Systems 196
8.3.4 Thermal Systems 198
8.3.5 Hydraulic Systems 200
8.4 Differential Equations 202
8.4.1 First-Order Differential Equations 202
8.4.2 Second-Order Differential Equations 204
8.4.3 System Identification 205
Problems 206
9. Transfer Function 209
9.1 Introduction 209
9.2 Transfer Function 210
9.2.1 Transfer Function 211
9.2.2 Transfer Functions of Common System Elements 212
9.2.3 Transfer Functions and Systems 213
9.3 System Transfer Functions 214
9.3.1 Systems in Series 214
9.3.2 Systems with Feedback 215
9.4 Block Manipulation 216
9.4.1 Blocks in Series 217
9.4.2 Moving Takeoff Points 217
9.4.3 Moving a Summing Point 217
9.4.4 Changing Feedback and Forward Paths 217
9.5 Multiple Inputs 220
9.6 Sensitivity 221
9.6.1 Sensitivity to Changes in Parameters 221
9.6.2 Sensitivity to Disturbances 223
Problems 223
10. System Response 227
10.1 Introduction 227
10.2 Inputs 227
10.3 Determining Outputs 228
10.3.1 Partial Fractions 230
10.4 First-Order Systems 233
10.4.1 First-Order System Parameters 235
10.5 Second-Order Systems 237
10.5.1 Second-Order System Parameters 240
10.6 Stability 245
10.6.1 The s Plane 246
10.7 Steady-State Error 250
Problems 252
11. Frequency Response 257
11.1 Introduction 257
11.1.1 Sinusoidal Signals 258
11.1.2 Complex Numbers 258
11.2 Sinusoidal Inputs 260
11.2.1 Frequency Response Function 260
11.2.2 Frequency Response for First-Order Systems 262
11.2.3 Frequency Response for Second-Order Systems 264
11.3 Bode Plots 265
11.3.1 Transfer Function a Constant K 266
11.3.2 Transfer Function 1/sⁿ 266
11.3.3 Transfer Function sᵐ 267
11.3.4 Transfer Function 1/(1+τs) 267
11.3.5 Transfer Function (1+τs) 269
11.3.6 Transfer Function ωₙ²/(s² + 2ζωₙs + ωₙ²) 270
11.3.7 Transfer Function (s² + 2ζωₙs + ωₙ²)/ωₙ² 272
11.4 System Identification 274
11.5 Stability 276
11.5.1 Stability Measures 277
11.6 Compensation 278
11.6.1 Changing the Gain 278
11.6.2 Phase-Lead Compensation 280
11.6.3 Phase-Lag Compensation 281
Problems 283
12. Nyquist Diagrams 287
12.1 Introduction 287
12.2 The Polar Plot 287
12.2.1 Nyquist Diagrams 289
12.3 Stability 290
12.4 Relative Stability 292
Problems 293
13. Control Systems 297
13.1 Introduction 297
13.2 Controllers 298
13.2.1 Proportional Steady-State Offset 300
13.2.2 Disturbance Rejection 301
13.2.3 Integral Wind-Up 301
13.2.4 Bumpless Transfer 302
13.3 Frequency Response 302
13.4 Systems with Dead Time 303
13.5 Cascade Control 305
13.6 Feedforward Control 306
13.7 Digital Control Systems 307
13.7.1 The z-Transform 309
13.7.2 The Digital Transfer Function G(z) 311
13.7.3 PID Controller 314
13.7.4 Software Implementation of PID Control 317
13.8 Control Networks 317
13.8.1 Data Transmission 318
13.8.2 Networks 319
13.8.3 Control Area Network (CAN) 320
13.8.4 Automated Assembly Lines 321
13.8.5 Automated Process Plant Networks 321
13.8.6 PLC Networks 323
13.8.7 Supervisory Control and Data Acquisition (SCADA) 325
13.8.8 The Common Industrial Protocol (CIP) 326
13.8.9 Security Issues 326
Problems 327
Answers 329
Appendix A: Errors 341
Appendix B: Differential Equations 347
Appendix C: Laplace Transform 353
Appendix D: The z-Transform 361
Index 367