A new approach to the design of digital model reference control systems

A new approach is proposed for the design of digital model reference control systems which overcomes the problem of nonminimum phase sampling zeros. The design is based on the plant-input mapping method which was proposed recently as a digital redesign method and which guarantees the internal stability of the system for almost any sampling frequency. This method is applied, in the present work, to the direct digital design of a pole placement control system and, in particular, a model reference control system. The key to eliminating the effect of sampling zeros on the performance of a model reference control system is the use of a matched-pole-zero model of the plant in combination with the invariant model, rather than the truncated step invariant model which is used conventionally. Simulation results are presented to show that the proposed design provides superior results to the conventional model reference controller design.