A novel design and tuning procedure for PID type fuzzy logic controllers

In this work a new methodology for designing and tuning PID type fuzzy logic controllers (PID-FLC) is presented. The employed PID-FLC is a modified version of a hybrid structure constructed by integrating a PI type FLC and a PD type FLC. First, a direct relationship between the scaling factors of the modified hybrid PID-FLC (MHPID-FLC) and the proportional, integral and derivative actions of its traditional counterpart are established. Thus, based on this relationship, well-known methods used for tuning traditional PID controllers, i.e. the Ziegler-Nichols method, can be used to rind the scaling factors of their fuzzy counterparts. A fine tuning procedure, if necessary, can be followed to further improve the MHPID-FLC performance. This fine-tuning can be developed in two ways: (1) modifying the scaling factors, (2) modifying the control surface of the fuzzy control system inside the MHPID-FLC structure; general guidelines for these procedures are given. The effectiveness of this approach is shown in benchmark processes taken from the literature.