Achieving or exceeding maximum available feedback

Mitchell, R.J. (2006) Achieving or exceeding maximum available feedback. Control and Intelligent Systems, 34 (2). 166 - 172. ISSN 1480-1752 doi: 10.2316/Journal.201.2006.2.201-1638

Abstract/Summary

A feedback system for control or electronics should have high loop gain, so that its output is close to its desired state, and the effects of changes in the system and of disturbances are minimised. Bode proposed a method for single loop feedback systems to obtain the maximum available feedback, defined as the largest possible loop gain over a bandwidth pertinent to the system, with appropriate gain and phase margins. The method uses asymptotic approximations, and this paper describes some novel adjustments to the asymptotes, so that the final system often exceeds the maximum available feedback. The implementation of the method requires the cascading of a series of lead-lag element. This paper describes a new way to determine how many elements should be used.