Optimal precision tracking control of discrete time nonminimum phase systems

Abstract

The aim in command feedforward tracking control is to obtain a low pass filter of desired tracking bandwidth between the input and the output in order to reduce tracking error. The feedforward controller is designed to approximately invert the feedback controlled system for this purpose. This is achieved in the zero phase error tracking control (ZPETC) method by designing the feedforward compensator for zero phase error. The remaining gain errors are compensated for by adding gain compensating zeros to the feedforward compensator in the precision and extended precision tracking control (PTC and EPTC) methods. These methods suffer from no explicit control over the tracking bandwidth in the ZPETC case and problems with achieving the desired bandwidth in certain cases in the PTC and EPTC cases. An optimal method of feedforward controller design named optimal precision tracking control (OPTC) is, thus, introduced in this paper and its usefulness is demonstrated by applying it to the model of a hydraulic position control system available in the literature.