Nonlinear Control For A Hypersonic Flight Vehicle

Hypersonic vehicle technology is a new research subject in near space exploration area. Compared with common airplane or flight vehicles, there is a larger flight envelope and more complex flight condition for hypersonic vehicles. Therefore, it is more essential for hypersonic vehicles to keep stable and highly maneuverable in flight.Based on the generic hypersonic vehicle longitudinal model for the study, this paper mainly research the relevant nonlinear inversion control for improving flight performance. The prominent properties of the paper are to present the modified adaptive backstepping method and to adopt the switching mechanism, and then the dynamic inversion control for hypersonic vehicle is studied. The main work is as follows:Firstly, the differential equations and complex dynamic characteristics of the hypersonic vehicle longitudinal model are introduced. The theory of feedback linearization introduced can convert accurately the nonlinear model of the hypersonic vehicle into equivalent linear model for control design.Secondly, based on the modified backstepping method, the nonlinear dynamic inversion controllers is designed. Compared with the backstepping controller, the modified controller can more quickly track the set targets. In addition, the paper proposes the modified adaptive backstepping controller which is evaluated for robustness with respect to parameter uncertainties. Simulation results demonstrate that the controller meets the control system requirements despite parameter uncertainties.Thirdly, switched theory is applied to the control of hypersonic flight vehicle. By analyzing the characteristics of the given controllers, the thesis proposes switched control law between the stabilizing controllers. The switched law is determined from the minimization of target function built by output error variables. Besides, compound transition controller based on the convex combination of weight function is designed for increasing the transient response. Simulation results show that these switched approaches are superior to the method of simple controller in improving the flight performance.Concluding remarks are presented at the end of this dissertation. Some open problems are also pointed out, which deserve further study.