A Self-Tuning Fuzzy PD Controller

Abstract

In this article we present a self-tuning PD-type fuzzy logic controller (FLC). The output scaling factor (SF) of the proposed controller is modified on-line by an updating factor (α) according to the process trend. The value of a is determined from a rule-base defined on error (e) and change of error (Δe) of the controlled variable. The proposed self-tuning FLC is designed using a very simple control rule-base and the most natural and unbiased membership functions (MFs) (symmetric triangles with equal base and 50% overlap with neighbouring MFs). The effectiveness of the scheme is established through simulation experiments on various types of second order processes such as (i) marginally stable, (ii) non-linear and (iii) non-minimum phase-pole (unstable) systems with different values of dead time. Performance of the proposed self-tuning FLC is compared with that of its conventional counterpart with respect to both step set-point change and load disturbance using several performance indices. In each case the proposed controller shows remarkably improved performance over the conventional one.