Design of a GA-based fuzzy PID controller for non-minimum phase systems

In this paper, a fuzzy PID controller, is investigated on the basis of gene tic algorithms (GAs) to eliminate the undershoot of a nonminimum-phase (NMP ) system and to improve the transient response at the same time. The propos ed controller employs a two-stage control structure, where the fuzzy PI con troller is reasonably used to cancel out the effect of unstable zeros and t he fuzzy PD controller is introduced for the reason of reducing the oversho ot. The fuzzy control rules for both controllers are evolved and determined by the GAs. It is demonstrated by computer simulations in which satisfacto ry performance can be achieved even if the system is under perturbed condit ions. (C) 2000 Published by Elsevier Science B.V. All rights reserved.