Global Robust Fuzzy Sliding Mode Control for a Class of Non-Linear System

Abstract

It is well known that sliding mode control can give good transient performance and system robustness. However, due to the sensitivity of the sliding mode control before reaching the sliding surface, the presence of chattering may introduce problems to the tracking control of the system. In this paper, a scheme of fuzzy time-varying sliding mode controller with global robustness is proposed for a class of non-linear system with uncertainties. Since the proper fuzzy logic control is applied to the time-varying sliding surface, the state of the control system always lies on the sliding surface from the beginning of any initial state and the reaching phase is avoided. As a consequence, the system is robust with respect to external disturbances and parameter uncertainties. Furthermore, the chattering phenomenon, which is inherent to a conventional sliding mode control, is avoided by proper fuzzy tuning of the controller. The effectiveness of proposed controller is demonstrated through comparative simulations for a second-order non-linear uncertain system.