Sliding-mode-based direct adaptive fuzzy controller design for a class of uncertain multivariable nonlinear systems

A practical design of fuzzy logic controller is presented in which the sliding mode control method and the adaptive control scheme are properly incorporated to enhance robustness and sliding performance in a class of uncertain MIMO nonlinear systems. The proposed fuzzy controller requires no knowledge of an MIMO nonlinear system and facilitates robust properties by fine-tuning the consequent membership functions. By employing the fuzzy descriptions to overcome the interaction among the subsystem, a fuzzy sliding mode controller is used to approximate the equivalent control in the neighborhood of the switching hyperplane. The hitting control is appended to assure that the fuzzy sliding mode control can achieve a stable closed-loop system through Lyapunov stability theory for the trajectories tracking control of a plant with unknown nonlinear dynamics. Finally, the simulation results of a two-link robotic manipulator confirm that the effect of both the fuzzy approximation error and external disturbance on the tracking error can be attenuated efficiently by the proposed method.