His book is unique. It is somewhat of a guided tour across the entire field of feedback control system design. It is also a personal statement, deeply felt and strongly held, based on over a quarter of a century of experience in the automatic control profession. It is not easy for a reviewer to separate out these two aspects. To do justice, the review ought to start with a full reprint of the four-page preface. A few extracts may give the flavour.
This book is addressed...to engineers who deal with feedback control in their everyday routine and wish to... expand their proficiency in the application of theoretical methods to solving practical problems... The book may also prove of interest to students and researchers seeking a pragmatic approach to feedback control theory .... The book departs.., from recent usage, harking back to the traditional approach to the subject .... The problems are given an inductive treatment .... Only certain portions of the book are deductive .... Two basic methods are predominantly used .... the phase-plane method .. . and frequency response analysis. If...we look back at the evolution of feedback control theory over the past years, we... see how it has been isolating itself more and more from genuine technological problems. The only time when the theoretical developments.., did match closely the needs of technology was during and just after the Second World War .... The first ominous step marking the separation of theory from applications was.., the excessive ground gained by the.., root locus method in the U.S.A. and by the trapezoidal method developed.., in the U.S.S.R. Watching keenly for years the fortunes and ill-fortunes of the control theory and carrying on my own studies at the same time, I waited in vain for someone to write a book vindicating the traditional apparatus .... But as I became aware that I would soon see this useful tool pass into oblivion, I decided to write such a book myself. I did not feel it necessary to include references in the book. It contains no... quotations, nor does it enter into any personal polemics... The material is organized into five chapters. Chapter 1 employs a large number of examples drawn for the most part from electromechanics to illustrate fundamental concepts. The error self-nulling principle is discussed in the first section. Next come definitions of input, output, state, order and energy stores, and an accuracy vs stability discussion. The idea of "strong feedback" is introduced, but without quantification by loop gain or sensitivity functions. Two classes of basic constraints are then defined: the "energy barrier", such as power limiting, which comes into play far from equilibrium, and the "information barrier", typically measurement noise, hysteresis, or transportation lag, which occurs near equilibrium. The third section deals with classifications and examines the applicability Feedback Control: Theory and Design by K. J. Kurman.