Tuning of PID controllers with fuzzy logic

The paper presents a comparison between different methods, based on fuzzy l ogic, for the tuning of PID controllers. Specifically considered are differ ent control structures in which a fuzzy mechanism is adopted to improve the performances given by Ziegler-Nichols parameters. To verify the full capab ilities of each controller, genetic algorithms are used to tune the paramet ers of the fuzzy inference systems (scaling coefficients, shape of the memb ership functions, etc.). Furthermore, a discussion about the practical impl ementation issue of the controllers is provided, and comparisons made with a typical PID-like fuzzy controller and a standard and a nonlinear PID cont roller. The results show the superiority of the fuzzy set-point weighting m ethodology over the other methods.