Fuzzy sliding mode fault tolerant control for a class of perturbed nonlinear systems

This paper proposes an adaptive FTC approach which combines a sliding mode controller (SMC) and a proportional integral (PI) controller for nonlinear MIMO systems. The main contribution of the proposed method is that the structure of the controller system is partially unknown and does not require the knowledge of the bounds of uncertainties and disturbances. This method uses adaptive fuzzy systems to approximate the unknown nonlinear functions. Then, in order to reduce the chattering phenomenon without degrading the tracking performances, the discontinuous term in the conventional sliding mode technique is replaced by an adaptive PI term. According to Lyapunov approach, the dynamic tracking performance of the closed-loop system is optimised despite the presence of faults. Finally, the proposed method is applied to an inverted pendulum as a nonlinear SISO system and to a robot manipulator as a nonlinear MIMO system. It achieves satisfactory simulation results in both cases.