A new approach for adjusting scale factor in fuzzy PD+I controllers with anti-windup

Abstract

In fuzzy controllers, the adjusting of scale factors, both input and output, is critical to the performance of the plant being controlled. The adjustment of scale factors in Fuzzy PD+I controllers (FPD+I) is well documented; however, in systems that have control signal saturation, FPD+I requires anti-windup systems (AW) that limit the controller's integral action. The adjustment procedure for FPD+I controllers cannot be used in Fuzzy PD+I controllers with anti-windup system (FPD+I AW), as it increases the overall gain system, which causes oscillatory behaviour and even critical stability in the controlled variable. The main motivation of this research was to have an approach for adjusting Fuzzy PD+I controllers with anti-windup system (FPD+I AW) without having oscillatory behaviour. In order to verify the proposed approach, both the input and output scale factors of a FPD+I AW controller were adjusted and used to control speed in a direct current motor with control signal saturation and were compared with the responses of conventional PID, Adaptive Neuro Fuzzy Inference System (ANFIS) and Fuzzy sliding controllers, all with AWs based on tracking back calculation, thereby demonstrating the effectiveness of the proposed approach.