Output Tracking Control for Nonminimum Phase Flexible Air-Breathing Hypersonic Vehicle Models

Abstract

Based on the nonlinear stable inversion approach, an exact output tracking control law is designed for flexible air-breathing hypersonic vehicles (FAHVs). This problem is challenging because of the inherent couplings between the propulsion system, the airframe dynamics, and the presence of strong flexibility effects. Because of the complex nonlinear dynamics of the vehicles, a control-oriented model, which can retain the dominant features of the higher-fidelity model, is adopted for the control design. With respect to velocity and altitude as the regulated outputs, a partially linearized model of FAHVs is obtained through input/output linearization. Then the internal dynamics of FAHVs model are constructed and the stability of the zero dynamics are discussed. Based on the noncausal stable inversion approach, the ideal internal dynamics of FAHVs are computed. A state tracking model is derived from the output tracking problem, and an optimal controller is designed. The stability of the closed-loop system, including the unstable internal dynamics, is guaranteed by the designed control law. Finally, simulations are given to show the effectiveness of the proposed control method.