Air-breathing hypersonic vehicles (AHVs) are vital due to their promising prospects for reliable affordable access to space exploitation and global reach capabilities. With civilian and military application prospects being realized, the researches on AHVs have become much more attractive in recent years. The important fact is that, AHVs are sensitive to changes of flight condition as well as physical and aerodynamics parameters because of their design and flight conditions of high altitudes and Mach numbers. Therefore, the fight control has a high demand for the system robustness. This paper analyzes the aerodynamic characteristics of air-breathing hypersonic vehicles, and then proposes two tracking controllers. Firstly, the AHV is trimmed at a typical operating point. Then the linear longitudinal state equations are acquired by small perturbations linearization. By analyzing aerodynamic characteristics, the robust demand of controllers can be understood. Secondly, aiming to highly nonlinear longitudinal state equations of AHVs, the theory of feedback linearization is utilized to make the longitudinal model of hypersonic vehicles be completely linearized. The equivalent model for control design is obtained by the proper transformation. A dynamic inverse controller based on pole assignment is designed for the linearized longitudinal model. Good control effects are also shown through simulation. Finally, according to the demand of robustness, a new time-varying sliding mode surface is proposed. And then combining dynamic inversion technique and the time-varying sliding mode method, a dynamic inverse controller based on the time-varying sliding mode is designed. The controller consists of two parts –the dynamic inversion part and the time-varying sliding mode part. The former guarantees the velocity and height decoupled, and the latter can ensure that the system trajectory keeps on the sliding surface all the time, which means the system has the global robustness. Good control effects are also shown through simulation.
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