Control-oriented modeling and characteristic analysis of an airbreathing hypersonic vehicle

Abstract

This paper describes a physics-based model (PBM) of the longitudinal dynamics for airbreathing hypersonic vehicle (AHV), and then by linearizing the PBM, it is concluded that the flight control system of the vehicle is a typical open-loop unstable system. The short period mode includes of a stable and an unstable pole, which is coupled with the first three modes of vibration. Although the PBM captures the coupling effects among the aerodynamic, propulsive system and flexible airframe in the longitudinal motion of AHV, it is not tractable for control design. Thus, by replacing the complicated computation of the forces, thrust and moment with curve-fitted approximations, and employing the same equations of motion as the PBM, this paper develops a control-oriented model of AHV. The coefficients of the fit are determined with the least squares (LS) method. Finally, it is verified that the control-oriented model provides a useful approximations of the PBM dynamics.