In 1976 the Control Systems Society named three distinguished control systems specialists as Consulting Editors. One of the charges to these men was to submit an invited paper on a topic of their choice for publication without the usual IDC review procedures. At the same time Professor A.G.J. MacFarlane, Professor of Control Engineering at Cambridge University, was invited by the IDC to prepare an IEEE Press reprint book of important papers on frequency-domain methods in control and systems engineering. The coincidence of these two decisions has led to the following paper. "The Development of Frequency-Response Methods in Automatic Control" is one part of the IEEE Press book, Frequency-Response Methodr in Control Systems, edited by A.G.J. MacFarlane and sponsored by the Control Systems Society. The book will appear in mid-1979. The paper has been selected by Consulting Editor Nathaniel Nichols and should be of substantial interest to TRANSACTIONS readers. It also conveys some of the spirit and content of the book which may be purchased from IEEE Press when available.

The development of frequency-response methods in automatic control [Perspectives]

This survey paper presents a comprehensive review of work in the field of non-linear oscillations. A brief discussion of second-order systems is followed by a presentation of exact criteria, approximate analytical methods and computational techniques for limit cycles in single variable systems. Multivariate systems are then covered from an analogous viewpoint which allows the reader to clearly identify both how single variable methods have been extended and the possibilities for further research. Particular emphasis is placed on describing function methods since it is believed that, where exact solutions are not possible, the approach may not only give approximate solutions but provides good insight for further computational or simulation studies. The coverage is essentially restricted to continuous lumped parameter systems and includes both free and forced oscillations. Several applications of the theories in various fields of engineering and science are discussed and indicate the broad interest in non-l...

N. Ramani

Papers

Stability of Nonlinear Multivariable Systems