Fuzzy boundary layer adaptive sliding mode controller design for a hypersonic vehicle based on tangent reaching law
Due to the problem of serious nonlinear, strong coupling, uncertain parameters existed in the process of hypersonic vehicle's flight, this paper designs a fuzzy boundary layer adaptive sliding mode controller based on tangent reaching law. Firstly, the longitudinal model is linearized exactly, and then by introducing a parameters adjusted by online fuzzy logic system as sliding boundary layer, quasi-sliding mode control based on tangent reaching law is applied to the outside of the boundary layer, so the system states can reach the sliding boundary layer quickly. When the system states reach the boundary layer, inputs transform smoothly to the improved boundary control law designed with a saturation function. The system states are ensured to reach the sliding surface in a finite time, and the high frequency chattering is lowered. Simulation results illustrate the effectiveness of the control algorithm.