CHARACTERIZATION OF A MINIMAL-ORDER ROBUST SERVOCOMPENSATOR

In recent papers (Davison 1972, 1975, 1976, Davison and Goldenberg 1975), Davison and co-workers have given the characterization of a minimal-order robust feedback controller containing an error-driven compensator which achieves asymptotic tracking and disturbance rejection using state space methods. More recently, Desoer and Wang (1977, 1978) rederived the minimal order of a similar controller (Ferreira 1976) using frequency domain methods. It is the purpose of this paper to give a detailed demonstration that the latter controller must contain a Davison servocompensator (Davison and Goldenberg 1975) using frequency domain methods. This adds perspective and information to Desoer and Wang (1978, 1977: Proof of the Corollary of Theorem IV.1). © 1979 Taylor & Francis Ltd.