Fundamentals of Process Control

Fundamentals of Process Control: Principles and Concepts offers an introduction to how engineers and technicians ensure that industrial processes, such as heating, mixing or pumping, are safe and efficient. It covers core concepts, including what a process is, how feedback control loops work and why measurements, valves and controllers matter. This book also provides practical tools, including proportional-integral-derivative (PID) tuning, cascade and ratio control and statistical methods for measuring and reducing variability. Later chapters introduce modeling and simulation, along with more advanced topics such as adaptive and fuzzy logic control, all grounded in clear examples and step-by-step explanations. Designed for learners and practitioners, this book strikes a balance between real-world applications and the key math and science necessary to understand and design control systems.

Preface xvii About the Author xxi Section 1 Principles and Concepts 1 Chapter 1 Introduction and Overview 3 1.1 History 4 1.2 What Is Process Control? 4 1.3 Process Intend 6 1.4 Why Study Process Control? 8 1.5 Control Strategies 9 1.6 Process Design 10 1.7 Conservation of Mass and Energy 10 1.8 Concepts of Calculus 11 1.9 Process Documentation 15 1.10 Units 17 1.11 Process Variables 18 1.12 Summary 31 Chapter 2 Basic Control Concepts 33 2.1 Process and Process Control 33 2.2 The Process 35 2.3 The Control Loop Concept 37 2.4 Summary 40 2.5 Exercises 40 Chapter 3 The Control Loop 43 3.1 A Typical Feedback Control Loop 43 3.2 The Three Tasks 44 3.3 Process Instruments 46 3.4 Elements of a Closed-Loop System 49 3.5 Process Control Terms 50 3.6 Combining Functions in a Single Instrument 54 3.7 Summary 54 3.8 Exercise 55 Chapter 4 Functional Structure of Feedback Control 57 4.1 The Transfer Function 57 4.2 Block Diagrams 58 4.3 The Functional Layout of a Feedback Control Loop 61 4.4 Mathematics of Block Diagrams 62 4.5 Gain and Sensitivity 63 4.6 Process Gain 72 4.7 Summary 73 4.8 Exercises 74 Chapter 5 Dynamics of Systems 75 5.1 Dynamic Components 76 5.2 First-Order Lag 77 5.3 Time Constants 79 5.4 Elements of Systems 83 5.5 Dead Time 88 5.6 First-Order plus Dead Time 91 5.7 Higher Order Systems 92 5.8 Closed-Loop versus Open-Loop Response 94 5.9 Sensor Dynamics 97 5.10 Actuator Dynamics 99 5.11 Process Gain and Time Constant 101 5.12 Summary 109 5.13 Exercises 110 Chapter 6 Process Characteristics 113 6.1 Introduction 113 6.2 The Integral or Ramp Process 116 6.3 First-Order Lag Process 123 6.4 Second-Order Lag Process 134 6.5 Summary 140 Chapter 7 Sensors, Transducers, and Transmitters 141 7.1 The Sensor, Transducer, and Transmitter 141 7.2 Selection of Measuring Devices 143 7.3 Accuracy and Precision 144 7.4 Sensitivity, Resolution, Repeatability, and Reproducibility 150 7.5 Rangeability and Turndown Ratio 152 7.6 Measurement Uncertainty Analysis 152 7.7 Transmission Systems 153 7.8 The 4 to 20 mA Current Loop 157 7.9 Smart Sensors 159 7.10 Summary 159 7.11 Exercises 160 Chapter 8 Actuators and Final Control Elements 161 8.1 Introduction 161 8.2 Control Valves and Actuators 162 8.3 Control Valve Selection and Sizing 171 8.4 Motors 173 8.5 Pumps 182 8.6 Solenoids 186 8.7 Summary 188 8.8 Exercises 188 Chapter 9 Controllers 191 9.1 The PID Controller 191 9.2 On-Off Control 194 9.3 Proportional Control 198 9.4 Integral (Reset) Control 209 9.5 Differential (Rate) Control 214 9.6 PID Control 217 9.7 Summary 220 9.8 Exercises 222 Chapter 10 Tuning Control Loops 225 10.1 Know Your Controller 226 10.2 Criteria of Good Control 228 10.3 The Tuning Concept 229 10.4 Closed-Loop Tuning Methods 231 10.5 The Process Reaction Curve 234 10.6 A Simple Open-Loop Method (Ziegler-Nichols) 236 10.7 The Need to Retune and Adaptive Tuning 239 10.8 Summary 240 10.9 Exercises 240 Section 2 Control Strategies 241 Chapter 11 Cascade Control 243 11.1 The Concept of Cascade Control 243 11.2 Applications 246 11.3 Implementing Cascade Control 250 11.4 Selection of Cascade Controller Modes and Tuning 251 11.5 Summary 252 11.6 Exercises 253 Chapter 12 Feedforward Control 255 12.1 Feedforward Control 255 12.2 Steady-State Feedforward Control 258 12.3 Steady-State or Dynamic Feedforward Control 262 12.4 General Feedforward Control 264 12.5 Combined Feedforward and Feedback Control 265 12.6 Summary 267 12.7 Exercises 267 Chapter 13 Multivariable Control 269 13.1 The Multivariable Control Concept 269 13.2 Implementing Multivariable Control 271 13.3 Summary 273 13.4 Exercises 273 Chapter 14 Ratio Control 275 14.1 The Ratio Control Concept 275 14.2 Applying Ratio Control 277 14.3 Summary 279 14.4 Exercises 279 Chapter 15 Special Control Strategies 281 15.1 Introduction 281 15.2 Three-Element Boiler Control 283 15.3 Selective, Override, and Split-Range Control 285 15.4 Summary 294 15.5 Exercises 294 Chapter 16 Statistical Process Control 295 16.1 Introduction 296 16.2 Statistics (Mean and Standard Deviation) 296 16.3 The Tools of SPC 303 16.4 Statistical Process Optimization 306 16.5 Summary 306 16.6 Exercises 307 Chapter 17 Fuzzy Logic Control 309 17.1 Origin of Fuzzy Logic 309 17.2 What Is Fuzzy Logic? 310 17.3 Operating Rules 310 17.4 Linguistic Variables 312 17.5 Defuzzification 314 17.6 Single-Input Control Example 314 17.7 Two-Input Control System Example 320 17.8 Summary 325 Section 3 Advanced Topics 327 Chapter 18 Process Modeling and Simulation 329 18.1 Introduction 329 18.2 How to Build a Model 331 18.3 Differential Equations of Physical Systems 332 18.4 Case Study: Direct Current Motor 333 18.5 Case Study: Two-Tank Level Control (Revisited) 340 18.6 Simulating Control Objective 343 18.7 Summary 344 Chapter 19 Model-Based Control 345 19.1 Introduction 345 19.2 Dead Time 346 19.3 The Smith Predictor Algorithm 349 19.4 Lambda Tuning 353 19.5 Summary 355 19.6 Exercise 355 Chapter 20 Nonlinear and Adaptive Control 357 20.1 Nonlinearity 358 20.2 Valve Characteristics 359 20.3 Process Characteristics 360 20.4 Adaptive Control 363 20.5 Adaptive Gain Control 365 20.6 Three-Mode Adaptive Tuning 367 20.7 Summary 367 20.8 Exercises 368 Chapter 21 Control System Architecture 369 21.1 Basic Components 370 21.2 System Components 372 21.3 Historical Perspective 374 21.4 Distributed Control Systems 381 21.5 Supervisory Control and Data Acquisition 386 21.6 Sequential or Batch Control 388 21.7 Summary 388 Chapter 22 Digital Systems 389 22.1 Hardware Elements 390 22.2 What Is Digital Signal Processing? 392 22.3 Digital Signals 394 22.4 Mathematical Operations on Discrete Signals 399 22.5 Design of Digital Control Systems 404 22.6 Design and Implementation of a PID Controller 408 22.7 Computer Implementation 412 22.8 The Z-Transform 413 22.9 Bilinear Transform 420 22.10 Summary 422 Appendix A: System of Units 423 Appendix B: Graphic Symbols for Process Measurement and Control 433 Appendix C: The Laplace Transform 447 Appendix D: Exercise Solutions 455 Bibliography 477 Index 481