Sliding Mode Control with Fuzzy Boundary Layer for a Class of Uncertain Nonlinear Systems

The saturation function control method is effective for reducing the sliding mode chattering.The boundary layer should be adjusted adaptively so as to achieve a trade-off between tracking precision and robustness to unmodeled dynamics.A fuzzy controller was designed to regulate the thickness of boundary layer.The fuzzy controller adopted the distance to sliding surface s and the angle θ between the sliding surface and the state vector.The method was applied to the control of a second order uncertain nonlinear system.Simulation results show system chattering is eliminated, the thickness of boundary layer is optimized, system tracking error is reduced, and the tracking performance of the controlled system is better than that of two methods:the method of boundary layer adaptive regulation and the method of boundary layer approach angle regulation.