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150 BOOK REVIEWS SYSTEMS ENGINEERING,(Second Edition), 1. J . Nagrath and M. Gopal, 725 pp, PBK, Wiley Eastern, 1982 Price: E7.50 The book is a typical introductory text on control engineering, directed primarily at undergraduate students and engineers. The authors have attempted to integrate topics from conventional and modern control theory with interdisciplinary readers in mind. This has been partially achieved at the expense of depth and at times an incomplete presentation of the subject is given. In Chapter I , a brief introduction is followed by historical background and examples of typical applications. Sampled data and multivariable systems are mentioned while nothing is said about the role of computers with regards to the development of control applications. Chapter 2 deals very briefly with mathematical modelling of continuous time systems by differential equations. A brief discussion for common physical systems is followed by the introduction of the transfer function, signal flow graph and the block diagram. The role and properties of feedback are discussed in Chapter 3 where a brief account of sensitivity analysis is also given. Chapter 4 really contains complementary material to Chapter 2. Pointing out the linearization about the operating point, electrical components such as Servomotors, Tachometer, Amplidyne and Stepper motors are described. The remainder of Chapter 4 describes hydraulic and pneumatic valves and pumps followed by an insight into the operation of gyro systems. Chapter 5 deals with time response analysis in an unusual manner. Time domain specification and simple performance indices are defined and effects of 3-term control on the time response is discussed hence optimum response is defined. Concepts of BIB0 and asymptotic stability are explained in Chapter 6 by using some carefully chosen words and emphasizing the impulse response without mentioning convolution. Mathematical arguments tend to be avoided. A description of Routh-Hurwitz criterion concludes this chapter. Classical Root Locus and its properties are presented in Chapter 7. Chapters 8 and 9 deal with frequency response analysis: basic definitions are followed by the introduction of the Polar and Bode Plots. Chapter 9 discusses Nyquist stability criteria, and the concepts of gain and phase margin. M and N circles are introduced and the Nichols Chart is presented and used for gain adjustment. Chapter CONTROL 10 gives a brief account of compensator design using classical techniques such as Root Locus and Bode diagrams. Chapter 1 I discusses sampled data systems where basic principles are followed by a brief account of stability analysis. The extension of the classical design methods to sampled data systems is however, given little attention. State space analysis is introduced in Chapter 12. The design techniques via state space are not treated in any detail except for a brief account of pole placement. At the end of this chapter the difference equation model of discrete systems and its relation with z operator is presented. An introduction to optimal control is given in Chapter 13. Transfer function approach is first discussed for both continuous and discrete systems. The state variable approach is then used to deal with regulator and tracking problems via Pontryagin principles and dynamic programming techniques. This chapter is concluded by formulating the Riccati equation for finite-time regulator problems. Chapter 14 discusses the nonlinear systems, again in much the same way as other standard text books in this field. The bang-bang type system is mentioned in the context of nonlinear systems rather than the optimality context, Lyapunov and Popov stability methods are also presented in the chapter. This book is on much of the same lines as the books written by Ogata, Dorf and D’Azzo and Houpis. Apart from the typographical errors, the list of references given at the end of each chapter is not sufficiently up to date to make the book attractive to postgraduate and research students. Several interesting examples are given at the end of each chapter which are very suitable for undergraduate tutorial and laboratory exercises. Attempts have been made to stress the interdisciplinary nature of the subject and indeed the book could be adopted for a wide range of engineering courses. On the whole the book is adequate for introducing the students and practical engineers to the basic principles of control theory. It certainly deserves a place on the shelf and is well worth considering when selecting a text book for a first course in control. The low price of the book is also an added attraction. S. D. KATEBI Shiraz University Shiraz, Iran