Research On Flight Control System Designing Theories And Simulation For A Hypersonic Vehicle

The hypersonic vehicles have become a very important direction in the fields of aeronautics and astronautics around the world. And the flight control technology of the hypersonic vehicles is a main and difficult point, besides it is a hotspot in the research of all the countries. Compared with general vehicles, the hypersonic vehicles adopt the engine-airframe integration technology, which results in strong coupling between propulsion system and structural dynamics, and brings highly nonlinear characteristics to the hypersonic vehicle models, in which there are also many uncertain aerodynamic parameters. Furthermore, the hypersonic vehicles are flying in the conditions of high altitudes and Mach numbers, the perturbations from the environment and uncertainties are obvious, so the flight stability of the hypersonic vehicles is influenced. All the factors mentioned have brought great challenges to the model confirming and control system designing of the hypersonic vehicles. In this paper, the related control research is carried out based on the generic hypersonic vehicle longitudinal model published overseas.In order to grasp the hypersonic vehicles'complex aerodynamic characteristics, firstly, the full-state, nonlinear and 6-freedom motion differential equations of the hypersonic vehicle model are established. And the engine model is analyzed.Secondly, the numerical method is adopted to estimate aerodynamic coefficients of the hypersonic vehicles in different flight conditions. By analyzing the results, the aerodynamic characteristics are understood. And the longitudinal dynamics equations are obtained by decoupling analysis. Eigenvalue and dynamic response of the longitudinal dynamics equations are studied to deeply know the particularities of the hypersonic vehicles. And it is possible to provide an appropriate control object to flight control system designing for the hypersonic vehicle.For the strong coupled and highly nonlinear hypersonic vehicle longitudinal model, feedback linearization method is utilized to make the longitudinal model output/input exact linearization. And based on it, the dynamic inversion control system is designed combining with the linear quadratic controller. The control system designed not only can decouple the output and input of the longitudinal model, but also can ensure the veracity of commands tracking and flight stability. Numerical simulation is done via MATLAB/SIMULINK to verify the good performance of control system designed. For the hypersonic vehicle uncertainties, sliding model control technology is used to design flight control system of the hypersonic vehicle. And it solves the control problems brought by the imprecise mathematical model, enhances the robust performance of the control system. Numerical simulation is done to verify the robust and control performance of the sliding mode control system designed. Also a sliding mode observer is designed to estimate difficultly measured states, which can satisfy the full-state feedback requested by sliding mode control system. Numerical simulation is done to verify the robust performance of the hypersonic vehicle sliding mode observer designed.For the hypersonic vehicle uncertainties, which are not counteracted by control effects, the dynamic surface control method is adopted. It can restrain the uncertain perturbations brought by the changes of parameters and structure. It enlarges the applied range of control system, and it can satisfy control request when the flight condition is more complex. Numerical simulation is done to verify the availability of the control system designed.Above all, the flight control methods of the hypersonic vehicles are deeply studied in this paper. For unstable, highly nonlinear and strong coupled mathematic model and structural and parameters uncertainties, the control methods are detailed discussed. Numerical simulations show the validity of every control method, and useful results are found.