Robust adaptive fuzzy sliding mode control for a class of uncertain nonlinear systems with unknown dead-zone

In this paper, a robust adaptive fuzzy sliding mode control scheme is presented for a class of uncertain nonlinear systems preceded by an unknown dead-zone. Dead-zone characteristics are quite commonly encountered in actuators, such as hydraulic and pneumatic valves, electric servomotors, and electronic circuits, etc. Therefore, by using a description of a dead-zone and exploring the properties of this dead-zone model intuitively and mathematically, a robust adaptive fuzzy sliding control method is presented without constructing the dead-zone inverse. The unknown nonlinear functions of the plant are approximated by the fuzzy logic system according to some adaptive laws. Based on Lyapunov stability theorem and the theory of variable structure control, the proposed robust adaptive fuzzy sliding mode control scheme can guarantee the robust stability of the whole closed-loop system with an unknown dead-zone in the actuator and obtain good tracking performance as well. Finally, an example and simulation results are provided to illustrate the effectiveness of the proposed method.