Linear Parameter Varying Model And Robust Control For Hypersonic Vehicles

Hypersonic vehicles, considered as new generation of aircraft, become a research hotspot in the vehicle design field due to the unique advantages. Because hypersonic vehicles use the body-frame integration design technology, the flight dynamics is a strong coupling among aero-dynamic properties, propulsion system and the structure. During the flight, not only altitude and Mach number expand a wide range, but also flight environment is complex. This will result in aero-thermal coupling relations which make the dynamic characteristics change violently. As a result, it is necessary to ensure flight stability throughout the whole envelope. Therefore, it is essential to establish the integrated model associated with the large flight envelope mission.The linear parameter varying(LPV) system is a very important kind of time-varying system. In this study, the implementation of the LPV system modeling method can be divided into two categories. One is based on system dynamic nonlinear equations, called the analysis method. the other one is experimental method. For the analysis method, there are three main kinds. The first kind is Jacobian linearization method, and the second is the State Transformation method, and the third is the Function Substitution method. This thesis will establish the control oriented longitudinal LPV model for the hypersonic vehicle. First, based on the physical principle, the advanced longitudinal dynamics model of the hypersonic aircraft is built in terms of the aerodynamic parameter values obtained from the data in open foreign literatures. Then the nonlinear model is simplified accordingly. Using Jacobian linearization method, the longitudinal LPV model is established. Next, the LPV model is applied to design of the flight control system of the hypersonic aircraft. Based on the classical control synthesis technical, linear quadratic regulator and h-infinity controller were designed hypersonic vehicle longitudinal LTI model.Because aerodynamic characteristics of hypersonic vehicles changes dramatically and there are large amounts of uncertainty and external disturbance during the flight, Jacobian linearization method is used to establish the longitudinal LPV model of the vehicle, and the gain scheduled h-infinity state feedback controller is designed based on this LPV model. The simulation result shows that the designed h-infinity robust controller can make the hypersonic vehicle have good dynamic characteristics throughout the large flight envelope. Meantime, the designed LPV controller can guarantee overall stability and system robustness.