出版说明 序 PREFACE 1 BASIC CONCEPTS Introduction Control Terminology Functioning of a Control System Examples of Closed-Loop Control Systems Problems 2 BLOCK DIAGRAMS Introduction Definition of a Block Diagram Summing Point Takeoff Point Block Diagram Representation of an Equation Block Diagram Representation of Control Systems Transfer Functions General Transfer Function Transfer Function of a Closed-Loop System Comparison of Positive-Feedback and Negative-Feedback Systems Unity Feedback Systems Conversion to a Unity Feedback System Block Diagram Simplification Op—Amp Simulation of a Block Diagram Summing Point Summing Point with Adjustable SP Input Gain Block Constant-Gain(Noninverting)Block Constant-Gain(Inverting)Block Takeofr Point Summing Point with Multiple Inputs Problems 3 LAPLACE TRANSFORMS Introduction Transformations Laplace Transform Integral Transform Notation Rules of Transformation Forward Transformation Procedure Inverse Transformation Procedure Partial-Fraction Expansion Distinct Roots Repeated Roots Applications of Laplace Transforms: Difierential Equations Problems 4 MATHEMATlCAL MoDELING Introduction Mathematical Model Nonlinear Behavior Transfer Functions Electrical Networks Resistor Capacitor Inductor Series RC Circuit Series RL Circuit Series RLC Circuit Mechanical Systems Mass Spring Damper Spring Mass Damper System Analogy Between Physical Systems Fluid Systems Single-Tank Fluid-Level System Two-Tank Fluid-Level System Thermal Systems Heating Systems Problems 5 TRANSIENT RESPONSE Introduction Time Response Input Functions Step Function Pulse Function Impulse Function Delayed Impulse Function Ramp Function Sinusoidal Function Types of Transient Responses Overdamped Response Critically Damped Response Underdamped Response Constant Oscillations Increasing Oscillations Exponential Rise Transient Response Through Laplace Transformation Impulse Function Response Characteristic Equation Poles and Zeros of the Transfer Function s-Plane and Pole-Zero Map Pole Location and Transient Response Problems 6 FREQUENCY RESPONSE Introduction Methods Used for Frequency Response Representation Frequency Response Determination Problems 7 COMMON TRANSFER FUNCTIONS Introduction Common Blocks(Transfer Functions) Constant Block Time Response of a Constant TF Frequency Response of a Constant Block Integral Block Time Response of an Integral Block Frequency Response of an Integral Block Derivative Block Time Response of a Derivative Block Frequency Response of a Derivative Block The Relationship Between Integral and Derivative Blocks First-Order Lag Block Time Response to a Unit Step Input Frequency Response of a First-Order Lag Block First-Order Lead Block Time Response to a Unit Step Input Frequency Response of a First-Order Lead Block Second-Order Lag Block Time Response to a Unit Step Input Characteristics of Underdamped Response Frequency Response of a Second-Order Lag Block Second-Order Lead Block Time Response to a Unit Step Input Frequency Response of a Second-Order Lead Block Dead Time:TransportatiOn Lag Block Time Response to a Unit Step Input Frequency Response of a Dead-Time Block Problems 8 STABILlTY Introduction Concept of Stability Stability and the Open-Loop Transfer Function Open-Loop Gain and Operating Frequency Stability from a Bode Plot Gain and Phase Margias Gain and Phase Crossover Frequencies Gain Margin(GM) Phase Margin(PM) Desired Gain and Phase Margins Stability from the Characteristic Equation Routh Criterion for Stability Root LOCUS Analysis Root Locus Through MATLAB Problems 9 CONTROLLERS:THE oN-oFF CONTROLLER Introduction Role of a Controller Types Of Controllers Use of a Percent as Input and Output Measured Value as a Percentage Value Set Point as a Percentage Value Error as a Percentage Value On-Of Control Types of On-Off Control Electronic Implementation(Analog) TWO-Position Control Neutral Zone Controller Action Applications Electronic Implementation Multiposition(Floating)Control Problems 10 ANALOG CONTROLLER Introduction Proportional Controller(P) Transfer Characteristic Proportional Band Relationship Between Percent Output and Physical Controller Output Electronic Implementation Frequency Response of a Proportional Controller Proportional Control of a Closed Loop Steady-State Operation with Zero Error Proportional Controller with Offset Offset Voltage Adjustment Integral Controller(I) Electronic Implementation Limiting DC Gain Frequency Response of an Ideal Integral Controller Frequency Response of a DC Gain-Limited Integral Controller Derivative Controller(D) Electronic Implementation Frequency Response of a Derivative Controller Limiting High-Frequency Gain Problems 11 ANALOG CONTRoLLER II Introduction Composite Controller Modes Serial Implementation Parallel Implementation PI Controller Electronic Implementation of a PI controller Frequency Response of a PI Controller PD Controller Electronic Implementation of a PD controller Frequency Response of a PD Controller PID Controller Electronic Implementation Changing the Operating Mode Frequency Response of a PID Controller Problems 12 DIGITAL CONTROLLER Introduction Digital Controller Controller Sequence of Operation Considerations for Digital Control Digital Two-Position Control Sequence of Operation Microcontroller Implementation of a Two-Position Controller Digital PID Controller Analog PID Algorithm Digital PID Algorithm Zero-Order Hold(ZOH) Ideal Digital PID Algorithm Discrete PID Algorithm-BASIC Language Manual Control Mode Velocity Algorithm Improved Derivative Term Microcontroller Implementation of a PID controller DC Motor Control Control Software Description Problems 13 FUZZY CONTROLLER Introduction Continuum World Conventional Logic Fuzzy Logic and Fuzzy Logic Terminology Fuzzy Control System Problem Identification Conceptual Design Problems 14 CONTROLLER TUNING AND SYSTEM DESIGN Introduction Performance Criteria Controller Tuning Controller Tuning:Known Plant Model Plant Model from Experimental Response Testing Step Response Test Graphical Analysis Computational Method Frequency Response Test Experimental Determination of Controller Setting Continuous Cycling Method Reaction Curve Method Case Study:Machine Positional Control System Drive Mechanism Position Transducer Problems 15 ADDITIONAL CONTRoL TECHNIQUES Introduction Feedforward Control Disturbance Signal Ratio Control Cascade Control Autotuning Controller State-Space Techniques State Variables State Equations Transfer Function to State-Space ReDresentatiOn Problems BIBLIOGRAPHY APPENDlX A MATLAB GLOSSARY INDEX 教辅材料申请表
There are a number of excellent textbooks covering the subject of control engineering
at the engineering level.These books are typically written for a two-semester course
in control engineering or for an intense one-semester course in the senior year. As is
typical of engineering textbooks,these treat control theory from a mathematical point of view.
Elements of Control Systems does not do that.This book is suitable for two or four-year college programs requiring an in-depth understanding of control systems,
A one-semester university course at the freshman level, Industry personnel interested in developing a greater understanding of control principles.
It has been very difficult to decide on the precise content of such a textbook.It iS not
a handbook.So it cannot contain every single aspect of it,and it is not a“how-to”recipe
book focusing on very specific topics.An attempt has been made to cover the major topics in control system technology.It should permit the reader to develop sufficient understanding to operate,maintain,and regulate control systems.At the same time,it should permit the reader to design and develop basic control systems.
No attempt has been made to cover PLCs or their operation or programming.This topic is a field in itself,and a chapter in this text could not have done justice to it.Even though a number of PLCs have begun to offer continuous control modules,their primary application is in digital I/O and not in process control.
Sensors,transducers,and actuators form an important segment of control technology,but so do microcontrollers,data converters,and instrumentation interface circuits.These again have not been covered in lieu of more relevant subject matter.
Where possible,an attempt has been made to point out the issues with circuit components and their impact on system operations.A chapter has been dedicated to digital control, still treating it from the classical control point of view.A chapter on fuzzy logic control provides a solid introduction to the topic.An attempt has been made to avoid excessive use of some of the cryptic terms commonly used with fuzzy control.
How to Use the Book
The book consists of two major sections:the first part covers control system theory and
the second part covers controllers and their applications.
It is important that the first part be studied with some diligence.The reader should
be fully comfortable with the notions of time and frequency response before tackling
controllers and their applications.The first chapter introduces the concept of a control
system.The second chapter covers block diagrams,followed by a chapter on Laplace
transformation.Laplace transformation is covered with an application-oriented approach.It is not intended to provide a solid foundation in operational calculus but apply it to determine system transfor functions in the following chapter on mathematical modeling.Having an understanding of the origin of transfer functions,time and frequency response techniques are covered.The discussion on stability is the coverage on controllers.It is intended to develop awareness for the consequences of improper controller selection and adjustment.
The second part of the book deals with controllers,their operation,adjustment and analog and digital implementation.Some of these topics can actually be studied
independently of the first,but it is not recommended.The section on digital controllers
requires some understanding of microcontrollers and their programming.Annotated software listings have been provided in each case.
I would like to thank a number of people who have provided valuable support for this book project:Charles Stewart,publisher at Prentice Hall for his acceptance of the initial manuscript and his encouraging words;my copyeditor,Linda Thompson and project ditor, Lisa Garboski,for their skills and painstaking effort;Eric Sells and Al Lovrich of Microchip Technology;Mark Siegesmund of CCS,Inc.;and Naomi Fernandes of The MathWorks Inc.
Many thanks also should go to the reviewers:Jeff Slutsk,Rochester Institute
of Technology;Richard L.Windley,ECPI College of Technology;C.Richard G.Helps,Brigham Young University;John Glozy,DeVry Institute of Technology;and Dr.Nebojsa Jaksic,DeVry Institute of Technology.
I would also like to thank my family:my wife Nita for putting up with my spending
countless hours working on the manuscript,my son Sachin for very valuable help with computer work,and my daughter Avina for help in transforming the handwritten notes into a printed document.Above all I would like to thank them for their constant encouragement.
Feedback
This being the first edition,it is possible that mistakes may have been made,in spite of
the best efforts of the author and the publisher.It would be greatly appreciated if you can point these out.Any kind of constructive criticism is welcome.
Sudhir K.Gupta
sgupta@mcjournal.com