Adaptive fuzzy system-based variable-structure controller for uncertain MIMO nonlinear systems subject to actuator nonlinearities

An adaptive fuzzy variable structure control approach is developed for a class of uncertain multi-input and multi-output (MIMO) nonlinear systems. The MIMO system under study is a strict-feedback uncertain nonlinear system with non-symmetric input nonlinearities. Variable structure control (VSC) technique in combination with backstepping is proposed to tackle the input saturation and dead-zone. The adaptive fuzzy systems are used to appropriately approximate the unknown nonlinear functions. The so-called SDU decomposition of the control gain matrix is exploited in the controller design and the stability analysis. It is proved that the proposed adaptive fuzzy control scheme can guarantee that all involved signals in the closed-loop system are semi-globally uniformly ultimately bounded (SGUUB), and the tracking error converges to a small neighbourhood of the origin. Finally, simulation results are presented to illustrate the effectiveness of the proposed controller.