Robust discrete-time fuzzy control of composite nonlinear systems by tuning consequent membership functions

A discrete-time fuzzy controller is proposed to achieve the robust tracking control of composite multivariable nonlinear systems. The control strategy is to decouple the subsystems and to facilitate the robust property by fine-tuning the consequent membership functions of the fuzzy controllers. An online tuning mechanism enables the discrete-time fuzzy system to effectively deal with the equivalent uncertainty resulting from function approximation error, disturbance, measurement noise or effect of interconnection among subsystems. Using Lyapunov stability theory, the tracking error residual set of the overall system with the proposed controller has been proved to be uniform ultimate bounded. Simulation results of a two-link robot control demonstrate the effectiveness and robustness of the design