An algorithm for the adaptation of a robust controller to reduced plant uncertainty

A robust fixed parameter controller, with prefilter F and feedback compensator G designed according to the Horowitz method, for a minimum phase uncertain plant P, is considered. The uncertainty is defined as a compact set p{cyrillic}₀ in the parameter space. Assume that it becomes known that the actual plant parameter uncertainty is p{cyrillic}₁ ⊂ p{cyrillic}₀. This paper presents an algorithm that changes the parameters of F and G in such a way that the closed loop behaviour stays within the original specifications while lowering the "cost of feedback". The algorithm is simple to use, and few calculations are needed to apply it.