Quasi-perfect tracking control of non-minimal phase systems

Abstract

The authors describe a new digital algorithm for quasi-perfect tracking control (QPTC) of non-minimal phase systems. The algorithm computes a feedforward signal in two steps: (1) a feedforward signal based on the zero phase error tracking control (ZPETC) algorithm of M. Tomizuka (1987); and (2) a compensation of the remaining tracking error with an additional feedforward. First, a closed-form expression is derived for the relation between the z-transform of the desired output signal and the z-transform of the tracking error resulting from the ZPETC algorithm. From this expression, the time and frequency domain properties are derived. These properties give insight into the parameters that influence the tracking error. Second, the QPTC algorithm is discussed and verified by simulation results. It shows a drastic improvement of tracking over the ZPETC algorithm. >