Performance evaluation of a fuzzy logic controller on a servo speed control system

Abstract

The study is a metonym for designing a Fuzzy Logic Controller (FLC) using various types of membership functions (MFs) and variable rule-base (RB) for a DC servo speed control application. FLCs are more useful in comparison to their crisp counterparts for attaining a desired speed in a closed loop process. Based on prior experience, the control methodology i.e. RB of a FLC is designed which comprises of 49 rules in if-then form. Initially the FLC was designed using Triangular type MF. The RB and scaling factors (SFs) were accordingly chosen to deal with system non-linearity. Next, the system is tested with other types of MFs i.e. Trapezoidal, Gaussian and Gaussian-Bell shaped. Moreover, the system is tested for all the aforesaid types of MF initially with 50% reduction in its RB and then further with 80% reduction in the RB i.e. now the system is designed with 25 rules and 9 rules in its RB respectively. This work presents the simulation results of various MFs implemented in a FLC and comparison of their results in terms of the following performance indices (PIs): Integral Absolute Error (IAE), Integral Time Absolute Error (ITAE), Integral Square Error (ISE), Integral Time Square Error (ITSE) And Rise Time (tr).