Description
Book SynopsisThis book compiles the essential concepts for understanding, designing, and operating process control systems. Authoritative coverage addresses feedback controllers; cascade control; ratio, override, and selective control; block diagrams and stability; feedforward control; dead-time compensation; and multivariable process control.
Trade Review"...explains the practical design and operation of process control systems..." (
SciTech Book News, Vol. 26, No. 2, June 2002)
“…a book worth adding to any process control library shelf…” (Measurement & Control, April 2003)
Table of ContentsPreface xi
1 Introduction 1
1-1 Process Control System 1
1-2 Important Terms and Objective of Automatic Process Control 3
1-3 Regulatory and Servo Control 4
1-4 Transmission Signals, Control Systems, and Other Terms 5
1-5 Control Strategies 6
1-5.1 Feedback Control 6
1-5.2 Feedforward Control 8
1-6 Summary 9
2 Process Characteristics 11
2-1 Process and Importance of Process Characteristics 11
2-2 Types of Processes 13
2-3 Self-Regulating Processes 14
2-3.1 Single-Capacitance Processes 14
2-3.2 Multicapacitance Processes 24
2-4 Transmitters and Other Accessories 28
2-5 Obtaining Process Characteristics from Process Data 29
2-6 Questions When Performing Process Testing 32
2-7 Summary 33
Reference 33
Problems 34
3 Feedback Controllers 38
3-1 Action of Controllers 38
3-2 Types of Feedback Controllers 40
3-2.1 Proportional Controller 40
3-2.2 Proportional–Integral Controller 44
3-2.3 Proportional–Integral–Derivative Controller 48
3-2.4 Proportional–Derivative Controller 50
3-3 Reset Windup 50
3-4 Tuning Feedback Controllers 53
3-4.1 Online Tuning: Ziegler–Nichols Technique 53
3-4.2 Offline Tuning 54
3-5 Summary 60
References 60
Problems 60
4 Cascade Control 61
4-1 Process Example 61
4-2 Implementation and Tuning of Controllers 65
4-2.1 Two-Level Cascade Systems 65
4-2.2 Three-Level Cascade Systems 68
4-3 Other Process Examples 69
4-4 Closing Comments 72
4-5 Summary 73
References 73
5 Ratio, Override, and Selective Control 74
5-1 Signals and Computing Algorithms 74
5-1.1 Signals 74
5-1.2 Programming 75
5-1.3 Scaling Computing Algorithms 76
5-1.4 Significance of Signals 79
5-2 Ratio Control 80
5-3 Override, or Constraint, Control 88
5-4 Selective Control 92
5-5 Designing Control Systems 95
5-6 Summary 110
References 111
Problems 112
6 Block Diagrams and Stability 127
6-1 Block Diagrams 127
6-2 Control Loop Stability 132
6-2.1 Effect of Gains 137
6-2.2 Effect of Time Constants 138
6-2.3 Effect of Dead Time 138
6-2.4 Effect of Integral Action in the Controller 139
6-2.5 Effect of Derivative Action in the Controller 140
6-3 Summary 141
Reference 141
7 Feedforward Control 142
7-1 Feedforward Concept 142
7-2 Block Diagram Design of Linear Feedforward Controllers 145
7-3 Lead/Lag Term 155
7-4 Extension of Linear Feedforward Controller Design 156
7-5 Design of Nonlinear Feedforward Controllers from Basic Process Principles 161
7-6 Closing Comments on Feedforward Controller Design 165
7-7 Additional Design Examples 167
7-8 Summary 172
References 173
Problem 173
8 Dead-time Compensation 174
8-1 Smith Predictor Dead-Time Compensation Technique 174
8-2 Dahlin Controller 176
8-3 Summary 179
References 179
9 Multivariable Process Control 180
9-1 Pairing Controlled and Manipulated Variables 181
9-1.1 Obtaining Process Gains and Relative Gains 186
9-1.2 Positive and Negative Interactions 189
9-2 Interaction and Stability 191
9-3 Tuning Feedback Controllers for Interacting Systems 192
9-4 Decoupling 194
9-4.1 Decoupler Design from Block Diagrams 194
9-4.2 Decoupler Design from Basic Principles 196
9-5 Summary 197
References 197
Problem 198
Appendix A Case Studies 199
Case 1: Ammonium Nitrate Prilling Plant Control System 199
Case 2: Natural Gas Dehydration Control System 200
Case 3: Sodium Hypochlorite Bleach Preparation Control System 201
Case 4: Control System in the Sugar Refining Process 202
Case 5: Sulfuric Acid Process 204
Case 6: Fatty Acid Process 205
Reference 207
Appendix B Processes For Design Practice 208
Installing the Programs 208
Process 1: NH 3 Scrubber 208
Process 2: Catalyst Regenerator 211
Process 3: Mixing Process 213
Index 215
