Self-tuning mechanism for sliding surface slope adjustment in fuzzy sliding mode controllers

There is an important relationship between fuzzy logic control and sliding mode control and integrating them to exploit the superior sides of these two techniques is an active area in control theory. The dynamic behaviour of the hybrid fuzzy sliding mode depends quite heavily on the sliding surface on which the control structure is switched. The main objective of this paper is to improve the system performance by continuously updating the slope of the sliding surface by a new timevarying coefficient. General and system independent meta-rules are generated in order to update this coefficient. Then, an algorithm that satisfies these meta-rules is first obtained using a fuzzy inference mechanism. Later, the fuzzy inference mechanism is replaced by an empirical formula that also satisfies the related meta-rules. The effectiveness of the proposed methods over the conventional fuzzy sliding mode controller is illustrated through the simulations performed on a second-order system with uncertain parameters.