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Computer control of machines and processes
428
Book Reviews
control systems. It is readable and the presentation is clear. The basic drawback of the book is that it does not merge the different areas of human knowledge into one; this is left for the reader. I am afraid that this task is not so easy for an undergraduate student. In spite of this drawback the book is one of the best textbooks introducing real-time computer control that f have read.
A b o u t the reviewer
Leo Motus has Ph.D. equivalents in stochastic control and software engineering. He has been Chairman of the fFAC working group on Distributed Computer Control Systems since 1987, is a Vice-chairman of IFAC TC on Computers, and is a candidate for the post of TC Computer Chairman for the period 1990-1993.
Computer Control of Machines and Processes* John
G. Bollinger
Reviewer: C. SCHMID
Ruhr-Universit~it Bochum, Lehrstuhl fiir Elektrische Steuerung und Regelung, Postfach 102148, D-4630 Bochum 1, Federal Republic of Germany. THIS BOOK is an excellent one for undergraduate and graduate students of all engineering disciplines interested in computer control, as well as being a superb reference book for industrial people attending refresher courses on this subject. One of its striking features is that little prior knowledge is demanded from its reader/user. Its spectrum of topics, which are of special importance in computer control, is indeed exceedingly broad. The book has naturally evolved from courses presented at the University of Wisconsin (Madison) by the authors since the mid-1960s. In its more than 600 pages, the book covers all the relevant aspects of computer control. The twelve chapters essentially give a nonmathematical introduction. After the brief introductory Chapter 1, which sets the rest of the book in proper perspective by dealing with the history of computer control and the explosion in the application of electronic technology since the 1960s, it goes on to present chapters on elements of discrete-time modelling, system response generation, discrete-controller design, control computer hardware and software, computer interfacing, sensors, command generation, sequential logical control, process modelling, analysis and design. Finally, the book closes with an appendix on the state-variable approach. Chapter 2 starts with a discussion on basic process types and develops the idea of representing components of closed-loop systems using difference equations and discretetime transfer functions, without applying any transformation techniques (which will be first introduced towards the end of the book in Chapter 11). After reading this chapter, one is on the level to understand system input-output behaviour and to analyse the stability of a system. However, the discussion of stability is different from the standards of control theory! As the stability analysis is based on the roots of the characteristic equation in terms of the backward-shift operator, all discussions about stability are treated in a domain mirrored at the unit circle. This may cause the novice reader to be confused when reading other books recommended in the bibliography attached to this chapter. Two fundamental concepts are introduced in Chapter 3: The sampling of signals generating time series, and the use of the time-shift operator to generate and determine system responses. The first design of a simple controller can be found in Chapter 4, which focuses on the desired closed-loop rezponses to specific inputs. The discussion about the selection of the sample period and the design of feedforward, cascade and noninteracting control in interactive plants * Computer Control o f Machines and Processes by John G. Bollinger and Neil A. Duffei. Addison-Wesley, Reading, MA (1988). fSBN 0-201-10645-0, $53.75.
and Neil A.
Duffei
completes the first part of this book. These four chapters give an excellent introduction to discrete-time control. The second part of this book deals with the computer. Chapter 5 is dedicated to computer hardware and software. It presents important aspects of computer architecture and operation in a way that is independent of computer manufacturer or model. This includes binary logic, basic computer hardware, the concepts of instructions and data, input/output, interrupts and programming at the assembly language level. A set of high-level language procedures is defined such that the principle of closed-loop computer control can be shown at the end of the chapter. This chapter concludes with a discussion of how closed-loop control functions can be organized on a control computer. The material and examples are well elaborated and their sequence reflects the various levels of abstraction in which designers of computer-control systems must carry out their work. Linking to external devices is the main topic of Chapter 6. The range is from analogue conversion to address decoding, device selection and interrupt interfacing. The short discussion here draws on a simplified computer architecture and is sufficient for understanding. Chapter 7 describes a spectrum of sensors that are often found in computer control systems for machines and processes. Chapter 8 adds some nonessential aspects of command signal generation in control. The implementation of logic control and the solution of Boolean equations are discussed in Chapter 9. Ladder diagrams, which are the means to describe the solution of logic on a computer, are treated. In addition, a number of design methods for logic control are described--including the use of flowcharts, switching tables and state diagrams. This chapter gives only a rough sketch about the principles of sequential control and the use of programmable logic controllers. Chapters 1-9 can be covered in one semester at an introductory level. The third part of the book portrays more control techniques, the crucial point being the application of more sophisticated system techniques to computer control. Chapter 10 reviews a number of approaches to process modelling--from physical modelling to a mathematical one. Step-response and least-squares techniques of process model identification are used. Through Chapter 11, where he can find the bases of transformation into the frequency domain, the reader will be able to gather much more insight into dynamics. The concepts of ideal samplers, hold elements and the representation of a sample sequence are also introduced here. After the analysis section in Chapter 12, the design of controllers in the frequency domain is discussed both for continuous- and discrete-time systems, illustrating their similarities and differences. An appendix gives a brief review of state-variable methods for the analysis and design, including state estimators for continuous- and discrete-time systems. Throughout the textbook, technology-based information has been strictly avoided. The simplified computer hardware which is used allows fundamental concepts to be illustrated,
Book Reviews and also allows system-level issues to be discussed without describing too complex computer architectures. The authors include PASCAL programs at many locations in the text to illustrate the use of computers. The programs are greatly simplified to improve the illustration of important concepts. Various manufacturing-related examples of processes are used to illustrate the analysis, design and implementation techniques that have been introduced. Most chapters start and/or close with an example, the layout being uniform throughout the book. Also, each chapter starts with an introduction which contains a precise description of the goals. At the end, a more complex, but still illustrative, example comprises the essentials of the chapter which are additionally highlighted in a special summary section. A bibliography is attached to each chapter, and most of its entries are books which, although not referred to directly in the text, may be used to supplement the book if additional information is required. In order to become more engaged, a well-elaborated list of many further interesting examples can be found at the end of each chapter in form of exercises. The printing is of high quality, and the figures are
429
enlightening where they should explain and illustrative where they have to describe a real object. The whole work shows the great teaching experience of the authors on this subject--towards which of course, students' feedback enjoys great credit. The book is highly readable and well organized. It may be concluded that this textbook is intended where there are great differences in the academic background of students who enrol in computer control courses. About the reviewer Dr C. Schmid received the Dipl.-Ing. degree in mechanical engineering from the University of Stuttgart in 1972 and Dr-Ing. degree in electrical engineering from the Ruhr-University Bochum in 1979, where he has been a lecturer since 1980. His main teaching activities are simulation techniques and computer-aided control system analysis and design, and his research interests are in adaptive control and the practical aspects of CAD of control systems. He is the author of a well-known industrial CAD system.
Industrial Control Electronics: Applications and Design* J. Michael Jacob
Reviewer: H. RAKE Institute of Automatic Control, Technology, Aachen, Germany.
Aachen University of
As L~ many other disciplines of our world relying on science and technology, a noticeable gap has developed in control engineering between (control) theory and (electronic) practice. The present book, by J. M. Jacob, intends to bridge this gap. Written for electrical engineering technology undergraduates it seems to be well suited to introduce control engineers who are not electronics specialists to the innards of the electronic hardware which they will have to use in order to close control loops. The book's 585 pages are divided into eight chapters and three appendices. About three quarters of the pages are devoted to material suggested by the book's title, and this material is presented in professional breadth and depth. The remaining quarter of the book is far less recommendable. It seems to have been written for the benefit of the electrical engineering technologist to provide some insight into the world of control engineering. From a control engineer's point of view, this cannot be rated as a success. (By the way, did any reader encounter a "Bod6 Plot" in theory or practice? The reviewer, remembering the American H. W. Bode, did not.) If treated as a one-way bridge, namely from control engineering to electronics, the book deserves much praise. The fascinating subject of transducers is covered in a well-structured chapter giving valuable details about almost every type of some significance. The reviewer found only the coriolis-type mass-flow transducers missing, which seems to
* Industrial Control Electronics: Applications and Design by J. Michael Jacob. Prentice-Hall International, Hemel Hempstead, U.K. (1988). ISBN 13-459322-7, $31.95.
be a minor shortcoming. Signal conditioning and transmission is treated including the peculiarities of converters, isolation circuits and cabling. Design principles of analog controllers are explained in such a way that the working of these devices including derivative overrun, integral windup and bumpless transfer from manual to automatic operation become transparent. The corresponding chapter on digital control gives very detailed and valuable information about A/D- and D/A-conversion while the rest of the chapter looks rather sketchy and a few pages devoted to programmable controllers could have been omitted. Power interfaces are the last electronic devices needed for closing the control loop. Switch-mode amplifiers and thyristor devices are described in useful detail, showing how to make low-power signals effective in a world of high voltages and high currents compelled to energy efficiency. In concluding, the reviewer highly recommends the book to all those members of the control community who are not too familiar with electronics and want to know more about the how and why of electronic devices and systems. They will surely benefit from the strengths of this book and be barely irritated by its (perhaps inevitable) weaknesses.
About the reviewer Heinrich Rake graduated in mechanical engineering from Hannover Technical University. He received his Ph.D. in 1965 for a dissertation on self-adaptive controllers. Working at the Institute of Automatic Control of Aachen Technical University since 1966, he was appointed head of this institute and Professor of Control Engineering in 1977. Main areas of research are model-based adaptive switching control, control of air conditioning plants and industrial robots, modelling of discrete-event systems, identification and parameter estimation methods and application of automatic control principles to a variety of industrial processes.
Book Reviews
control systems. It is readable and the presentation is clear. The basic drawback of the book is that it does not merge the different areas of human knowledge into one; this is left for the reader. I am afraid that this task is not so easy for an undergraduate student. In spite of this drawback the book is one of the best textbooks introducing real-time computer control that f have read.
A b o u t the reviewer
Leo Motus has Ph.D. equivalents in stochastic control and software engineering. He has been Chairman of the fFAC working group on Distributed Computer Control Systems since 1987, is a Vice-chairman of IFAC TC on Computers, and is a candidate for the post of TC Computer Chairman for the period 1990-1993.
Computer Control of Machines and Processes* John
G. Bollinger
Reviewer: C. SCHMID
Ruhr-Universit~it Bochum, Lehrstuhl fiir Elektrische Steuerung und Regelung, Postfach 102148, D-4630 Bochum 1, Federal Republic of Germany. THIS BOOK is an excellent one for undergraduate and graduate students of all engineering disciplines interested in computer control, as well as being a superb reference book for industrial people attending refresher courses on this subject. One of its striking features is that little prior knowledge is demanded from its reader/user. Its spectrum of topics, which are of special importance in computer control, is indeed exceedingly broad. The book has naturally evolved from courses presented at the University of Wisconsin (Madison) by the authors since the mid-1960s. In its more than 600 pages, the book covers all the relevant aspects of computer control. The twelve chapters essentially give a nonmathematical introduction. After the brief introductory Chapter 1, which sets the rest of the book in proper perspective by dealing with the history of computer control and the explosion in the application of electronic technology since the 1960s, it goes on to present chapters on elements of discrete-time modelling, system response generation, discrete-controller design, control computer hardware and software, computer interfacing, sensors, command generation, sequential logical control, process modelling, analysis and design. Finally, the book closes with an appendix on the state-variable approach. Chapter 2 starts with a discussion on basic process types and develops the idea of representing components of closed-loop systems using difference equations and discretetime transfer functions, without applying any transformation techniques (which will be first introduced towards the end of the book in Chapter 11). After reading this chapter, one is on the level to understand system input-output behaviour and to analyse the stability of a system. However, the discussion of stability is different from the standards of control theory! As the stability analysis is based on the roots of the characteristic equation in terms of the backward-shift operator, all discussions about stability are treated in a domain mirrored at the unit circle. This may cause the novice reader to be confused when reading other books recommended in the bibliography attached to this chapter. Two fundamental concepts are introduced in Chapter 3: The sampling of signals generating time series, and the use of the time-shift operator to generate and determine system responses. The first design of a simple controller can be found in Chapter 4, which focuses on the desired closed-loop rezponses to specific inputs. The discussion about the selection of the sample period and the design of feedforward, cascade and noninteracting control in interactive plants * Computer Control o f Machines and Processes by John G. Bollinger and Neil A. Duffei. Addison-Wesley, Reading, MA (1988). fSBN 0-201-10645-0, $53.75.
and Neil A.
Duffei
completes the first part of this book. These four chapters give an excellent introduction to discrete-time control. The second part of this book deals with the computer. Chapter 5 is dedicated to computer hardware and software. It presents important aspects of computer architecture and operation in a way that is independent of computer manufacturer or model. This includes binary logic, basic computer hardware, the concepts of instructions and data, input/output, interrupts and programming at the assembly language level. A set of high-level language procedures is defined such that the principle of closed-loop computer control can be shown at the end of the chapter. This chapter concludes with a discussion of how closed-loop control functions can be organized on a control computer. The material and examples are well elaborated and their sequence reflects the various levels of abstraction in which designers of computer-control systems must carry out their work. Linking to external devices is the main topic of Chapter 6. The range is from analogue conversion to address decoding, device selection and interrupt interfacing. The short discussion here draws on a simplified computer architecture and is sufficient for understanding. Chapter 7 describes a spectrum of sensors that are often found in computer control systems for machines and processes. Chapter 8 adds some nonessential aspects of command signal generation in control. The implementation of logic control and the solution of Boolean equations are discussed in Chapter 9. Ladder diagrams, which are the means to describe the solution of logic on a computer, are treated. In addition, a number of design methods for logic control are described--including the use of flowcharts, switching tables and state diagrams. This chapter gives only a rough sketch about the principles of sequential control and the use of programmable logic controllers. Chapters 1-9 can be covered in one semester at an introductory level. The third part of the book portrays more control techniques, the crucial point being the application of more sophisticated system techniques to computer control. Chapter 10 reviews a number of approaches to process modelling--from physical modelling to a mathematical one. Step-response and least-squares techniques of process model identification are used. Through Chapter 11, where he can find the bases of transformation into the frequency domain, the reader will be able to gather much more insight into dynamics. The concepts of ideal samplers, hold elements and the representation of a sample sequence are also introduced here. After the analysis section in Chapter 12, the design of controllers in the frequency domain is discussed both for continuous- and discrete-time systems, illustrating their similarities and differences. An appendix gives a brief review of state-variable methods for the analysis and design, including state estimators for continuous- and discrete-time systems. Throughout the textbook, technology-based information has been strictly avoided. The simplified computer hardware which is used allows fundamental concepts to be illustrated,
Book Reviews and also allows system-level issues to be discussed without describing too complex computer architectures. The authors include PASCAL programs at many locations in the text to illustrate the use of computers. The programs are greatly simplified to improve the illustration of important concepts. Various manufacturing-related examples of processes are used to illustrate the analysis, design and implementation techniques that have been introduced. Most chapters start and/or close with an example, the layout being uniform throughout the book. Also, each chapter starts with an introduction which contains a precise description of the goals. At the end, a more complex, but still illustrative, example comprises the essentials of the chapter which are additionally highlighted in a special summary section. A bibliography is attached to each chapter, and most of its entries are books which, although not referred to directly in the text, may be used to supplement the book if additional information is required. In order to become more engaged, a well-elaborated list of many further interesting examples can be found at the end of each chapter in form of exercises. The printing is of high quality, and the figures are
429
enlightening where they should explain and illustrative where they have to describe a real object. The whole work shows the great teaching experience of the authors on this subject--towards which of course, students' feedback enjoys great credit. The book is highly readable and well organized. It may be concluded that this textbook is intended where there are great differences in the academic background of students who enrol in computer control courses. About the reviewer Dr C. Schmid received the Dipl.-Ing. degree in mechanical engineering from the University of Stuttgart in 1972 and Dr-Ing. degree in electrical engineering from the Ruhr-University Bochum in 1979, where he has been a lecturer since 1980. His main teaching activities are simulation techniques and computer-aided control system analysis and design, and his research interests are in adaptive control and the practical aspects of CAD of control systems. He is the author of a well-known industrial CAD system.
Industrial Control Electronics: Applications and Design* J. Michael Jacob
Reviewer: H. RAKE Institute of Automatic Control, Technology, Aachen, Germany.
Aachen University of
As L~ many other disciplines of our world relying on science and technology, a noticeable gap has developed in control engineering between (control) theory and (electronic) practice. The present book, by J. M. Jacob, intends to bridge this gap. Written for electrical engineering technology undergraduates it seems to be well suited to introduce control engineers who are not electronics specialists to the innards of the electronic hardware which they will have to use in order to close control loops. The book's 585 pages are divided into eight chapters and three appendices. About three quarters of the pages are devoted to material suggested by the book's title, and this material is presented in professional breadth and depth. The remaining quarter of the book is far less recommendable. It seems to have been written for the benefit of the electrical engineering technologist to provide some insight into the world of control engineering. From a control engineer's point of view, this cannot be rated as a success. (By the way, did any reader encounter a "Bod6 Plot" in theory or practice? The reviewer, remembering the American H. W. Bode, did not.) If treated as a one-way bridge, namely from control engineering to electronics, the book deserves much praise. The fascinating subject of transducers is covered in a well-structured chapter giving valuable details about almost every type of some significance. The reviewer found only the coriolis-type mass-flow transducers missing, which seems to
* Industrial Control Electronics: Applications and Design by J. Michael Jacob. Prentice-Hall International, Hemel Hempstead, U.K. (1988). ISBN 13-459322-7, $31.95.
be a minor shortcoming. Signal conditioning and transmission is treated including the peculiarities of converters, isolation circuits and cabling. Design principles of analog controllers are explained in such a way that the working of these devices including derivative overrun, integral windup and bumpless transfer from manual to automatic operation become transparent. The corresponding chapter on digital control gives very detailed and valuable information about A/D- and D/A-conversion while the rest of the chapter looks rather sketchy and a few pages devoted to programmable controllers could have been omitted. Power interfaces are the last electronic devices needed for closing the control loop. Switch-mode amplifiers and thyristor devices are described in useful detail, showing how to make low-power signals effective in a world of high voltages and high currents compelled to energy efficiency. In concluding, the reviewer highly recommends the book to all those members of the control community who are not too familiar with electronics and want to know more about the how and why of electronic devices and systems. They will surely benefit from the strengths of this book and be barely irritated by its (perhaps inevitable) weaknesses.
About the reviewer Heinrich Rake graduated in mechanical engineering from Hannover Technical University. He received his Ph.D. in 1965 for a dissertation on self-adaptive controllers. Working at the Institute of Automatic Control of Aachen Technical University since 1966, he was appointed head of this institute and Professor of Control Engineering in 1977. Main areas of research are model-based adaptive switching control, control of air conditioning plants and industrial robots, modelling of discrete-event systems, identification and parameter estimation methods and application of automatic control principles to a variety of industrial processes.