On self-tuning control of nonminimum phase discrete-time stochastic systems

This paper presents a new method for the self-tuning control of nonminimum phase discrete-time stochastic systems using approximate inverse systems obtained from the least-squares approximation. Using this approximate inverse system the gain response of the system can be made approximately unit and phase response exactly zero. This approximate inverse system can be used in the same manner for both minimum and nonminimum phase systems. Moreover, the order of the feedback controller does not depend upon the approximate inverse system. We just need an extra FIR filter in the feedforward path. There exists no unstable pole-zero cancellation in the system, but the effect of the unstable zeros can be cancelled approximately. Finally, several computer simulation results are presented to illustrate the effectiveness of the proposed method.