Composite controller design for an airbreathing hypersonic vehicle

Abstract

In this paper, a tracking control problem for the longitudinal model of an airbreathing hypersonic vehicle subject to external disturbances is investigated. Based on the characteristics of the longitudinal model, the model is divided into two subsystems, including an altitude subsystem and a velocity subsystem. A novel ideal is that, for each subsystem, some nonlinear coupling terms are considered to be parts of lumped disturbances, which are estimated by a nonlinear disturbance observer, and a corresponding feedforward design is then implemented to compensate the lumped disturbances. Meanwhile, by using a finite time control technique, a continuous finite time control law is introduced in the feedback control design. Then, a composite control scheme is obtained, which consists of a feedback control law based on the finite time control technique and a feedforward compensator based on the nonlinear disturbance observer technique. This scheme can guarantee stable tracking of the reference trajectories of velocity and altitude. Finally, simulation results are provided to demonstrate the effectiveness of the proposed method. The results show that the control performance of the proposed method in terms of both tracking and disturbance rejection are considerably better than the traditional method.