DERIVATIVE ACTION IN PID-FUZZY CONTROLLERS

Fuzzy control has made possible the establishment of intelligent contr ol. However, fuzzy logic controllers (FLCs) are used only in simply co nfigurations and analytic knowledge about them is poor. In this paper, a quantita tive study of fuzzy controllers is done for the most compl ete case of a fuzzy-PID. Although the derivative action increases the complexity, it makes it possible to complete a study of FLCs in a simi lar way to the study of conventional controllers. The derivative term can improve the stability and gives more flexibility. The analytic per formance of a fuzzy-PID is summarized in terms of its three input vari ables. These equations yield initial values for the PID-FLC scale fact ors in terms of the classical PID parameters. The initial parameters h ave been tested for several system (initial tuning); a finer adjustmen t based in the influence of each gain has also been established (quali tative tuning).