Sliding mode control for hypersonic flight vehicle with sliding mode disturbance observer

Firstly, aimed at the longitudinal dynamics model of generic hypersonic flight vehicle in the presence of external disturbances and input saturation, an anti-windup sliding mode controller based on sliding mode disturbance observer is proposed. The sliding mode controller employs nonlinear reaching law, which makes the system track reference command fast and steadily; at the same time it eliminates the chattering phenomenon existing in the traditional sliding mode control, adds saturation compensator according to the problem of actuator saturation to improve the stability for the system. Secondly, a sliding mode disturbance observer is proposed to overcome the disturbances and uncertainties of the system, which can exactly estimate the equivalent disturbances added in the system. The estimated value evaluated by the observer is applied to the sliding mode controller as compensation to achieve the goal of eliminating disturbance. Thirdly, the stability of the proposed anti-windup sliding mode controller based on sliding mode disturbance observer is analyzed by means of Lyapunov theory. Finally, the simulation is conducted for cruise flight condition of hypersonic flight vehicle. Simulation results show that the suggested method can improve the stability and disturbance rejection performance for the system effectively, which has certain actual application value.