Research On Anti-interference Robust Flight Control For Near Space Vehicle

The development of near space vehicle (NSV) is related to national security and peaceful use ofspace, and it is a new vehicle which attracts increasing attention of many military powers. The flightprocess of NSV shows characteristics such as large flight envelope, multi-flight status andmulti-tasking mode. Moreover, due to its special flight environment, NSV also possesses objectsfeatures of serious nonlinearity, fast time variation, strong uncertainty and intense coupling. Therefore,the flight control system design of the NSV has become an innovative and challenging issue. Aroundthis problem, the dissertation carries out an intensive study in NSV modeling and analysis, and thenonlinear adaptive control of attitude and trajectory system in uncertain environments. The mainresults are as follows:Firstly, based on the contributions of NSV modeling in our lab and the available literatures, thedynamic equations and the corresponding simulation platform of NSV are presented. Via thesimulation analysis of open-loop dynamics, it is demonstrated that once there was no control input,the complex uncertain system is unstable.Secondly, the T-S fuzzy model of NSV kinematic model is established based on fuzzyapproximation theory and a new fuzzy robust tracking control law is designed using the feedforwardcontrol of linear system for reference. In the case that no augmented matrix is introduced, the controllaw is designed as the compound form of feedback and feedforward, and the gains of feedback andfeedforward are solved by LMI. The strategy is applied into the anti-interference control of NSVattitudes. The convergence of tracking errors is analyzed by Lyapunov method.Thirdly, considering the slow loop control system of NSV with disturbances, the variable domainfuzzy control method is presented. The control accuracy and anti-interference velocity are improvedand the calculated quantity is decreased by the change of fuzzy domain. To overcome the chatteringphenomenon, the dynamic adaptive terminal sliding-mode control strategy is raised. The control lawis designed by intermediate auxiliary system step by step. Also, Lyapunov method is used to provethat the tracking errors are converged in limited time.Fourthly, a fast adaptive disturbance observer is presented for NSV in interference environment.The approximating rate of disturbance observer is improved by adding nonlinear exponential item intoadaptive laws of parameters and approximating errors to make the tracking errors are converged tozero in limited time. Moreover, the control characters are systematically analyzed and the superiorities in rapidity and convergence are demonstrated by simulation analysis of the control of NSV athypersonic speed.Lastly, longitudinal control of NSV under uncertainty is studied. An approach of backsteppingcontrol based on adaptive dynamic surface is proposed. RBFNN is used to approximate the unknowncompound disturbance and the robust item is introduced into the virtual controller to cancel theinfluence of compound disturbance and improve the robustness and adaptation of the system.Simulation results show that the proposed strategy possesses good robustness and briefness.