Abstract: For the problem of tracking control of the Hypersonic Flight Vehicle (HFV) with uncertain model parameters and external disturbances, a Backstepping-based anti-saturation nonlinear controller is proposed. The longitudinal dynamical model of the vehicle is divided into the velocity subsystem and the flight path angle subsystem, and then the controller is designed individually for each subsystem. A tracking differentiator is designed to obtain the first derivative of a signal, which is used to estimate the uncertainties existing in systems and avoid the problem of "explosion of complexity". Occurrence of saturation of control inputs is considered in the design of the controller. The stability of closed-loop system signals is proved based on the Lyapunov theory. In comparison with the conventional Backstepping method applied to HFVs, the proposed method adopts the actual error between the state to be tracked and the desired control command as the feedback variable, relaxes the restriction on system disturbances and improves the adaptability of controller to variation of control gains, which enhances the tracking control performance of the closed-loop system. The comparative simulation results verify the effectiveness of the proposed method.

Key words: hypersonic flight vehicle, tracking control, Backstepping, tracking differentiator, disturbance observer, input saturation