Trajectory tracking control of flexible hypersonic vehicle based on sliding mode observer

The robust trajectory tracking control of flexible near space hypersonic vehicle(HSV) during cruising flight phase was investigated. Firstly, the sliding-mode controller based on the inversion model of HSV was provided to deal with the control performance deterioration due to the model uncertainty. Secondly, considering the difficulty to measuring the angle of attack(AOA) and the flight-path angle when the HSV flew at hypersonic velocity and a small AOA, the tracking error sliding surface was designed using the observed states. With the switching of the control law of the nonlinear sliding mode observer, the AOA and the flight-path angle can be obtained at a good reconstructing effect. Thirdly, in order to eliminate the elastic vibration on system stability, the notch filter was designed to filtering the one-order vibration in the angle rate control loop. The simulation results show that the designed controller provides robust trajectory tracking for the flexible hypersonic vehicle.