Quasi-continuous high-order sliding mode controller and observer design for flexible hypersonic vehicle

The problem of robust output feedback control and simulation for the longitudinal model of a flexible air-breathing hypersonic vehicle (FAHV) is investigated in this paper. A control-oriented uncertainty model is established for the feedback linearization design, and the multi-input and multi-output (MIMO) quasi-continuous high-order sliding mode (HOSM) controller is formulated to track the responses of the vehicle to a step change in velocity and altitude based on full state feedback. In addition, a high order sliding mode observer is designed to estimate the angle of attack and the flight path angle, which are difficult to measure in a hypersonic flight. Furthermore, the combination of the HOSM controller and observer is proposed for vehicle model with partial state measurements. The simulation results are presented to verify the effectiveness of the proposed control strategy.