Tuning of PID controllers with fuzzy logic

The paper presents a comparison between different methods, based on fuzzy logic, for the tuning of PID controllers. Specifically considered are different control structures in which a fuzzy mechanism is adopted to improve the performances given by Ziegler-Nichols parameters. To verify the full capabilities of each controller, genetic algorithms are used to tune the parameters of the fuzzy inference systems (scaling coefficients, shape of the membership functions, etc.). Furthermore, a discussion about the practical implementation issue of the controllers is provided, and comparisons made with a typical PID-like fuzzy controller and a standard and a nonlinear PID controller. The results show the superiority of the fuzzy set-point weighting methodology over the other methods.