FINE TUNING OF MULTILOOP PI CONTROLLERS USING FUZZY SET THEORY

Abstract

This paper proposes an intelligent way of fine-tuning multiloop PI controllers for distillation processes using linguistic fuzzy sets and fuzzy inference logic. This approach first requires reference dynamic curves which reflect the setpoint tracking and interaction rejection performance requirement by control engineer or operator. Linguistic fuzzy sets which describe the deviation degree from the reference dynamic curve patterns are then defined for each controlled output, and by minimizing the summation of corrected membership values of controlled outputs we can get the proper values of PI parameters which improve the overall performance of the transient and steady state behavior of closed-loop control systems. Initial tuning parameters are set by the conventional multiloop PI controller tuning methods such as the BLT method which guarantees the stability of control system.