A dynamic input membership scheme for a fuzzy logic DC motor controller

Conventional fuzzy logic controller uses input membership functions that consist of identical triangular input membership functions (MF) for all the subsets that are not located at the two ends of the universal set (center width constant or CWC). Some researchers in the field of motor controllers have started using narrower base triangular membership functions for the input subsets that are located at the center of the universal set and wider base triangles towards the two ends of the universal set (center width narrow or CWN). This new approach has proved to enhance the performance of the controller. This paper proposed a dynamic input membership function scheme which combines the center width narrow and the center width constant scheme together with a new scheme where the center triangular input membership functions has a wider width than those that are located more towards the two ends of the input universal set (center width wide or CWW). The dynamic input membership scheme (DIMS) applies CWN, CWC and CWW at different stages of the transient states of the controller step response to achieve a superior step response for a DC motor controller as compared to applications of only one type of input membership functions throughout the controller operation. Matlab simulation studies have been done to confirm the improved performance of the dynamic input membership functions as compared to the other schemes commonly employed.