A robust model reference adaptive control for nonminimum phase systems

Abstract

In this paper, a new direct model reference adaptive control method for nonminimum phase systems is presented. The parameter estimation scheme combines adaptive data filtering with a recursive least-squares algorithm with parameter projection and signal normalization. The problem of minimum phase of the plant is handled by adaptive input output data filtering. This data filtering permits one to relocate the reros of the plant estimated model inside the unit circle and to define a good data model, which is a key issue for robust control. The scheme robustness with respect to unmodeled dynamics is also simultaneously improved. The performance of the control algorithm is illustrated by numerical examples.