Robust Adaptive Approach For Near Space Vehicles Based On Trajectory Linearization Control

Near Space Vehicle (NSV) as a novel aerospace technology is arousing more attention in global range than ever. NSV which have great martial values is different from traditional aircrafts and orbital space vehicles. NSV's special characteristics such as special flight airspace, large flight envelop, high maneuverability, multi-mission profiles and complicated flight conditions make the design of flight control system face more challenge and innovation. In this dissertation, the large envelope modeling and characteristics analysis on NSV are demonstrated. Time-varying nonlinear system robust adaptive is introduced. The main results of the subject are exhibited as follows:First of all, based on the research contributions of abroad institution and our lab, the simulation model of high dynamic NSV is presented via flight environment analysis, parameter adjustment and aerodynamic coefficients treatment. Then the control characteristics such as channels coupling, uncertainty influence demonstrate that the proposed dynamic model is according with current data and researching and simulating advanced guidance and control methods.Secondly, this dissertation introduces Trajectory Linearization Control (TLC) method and how to design a flight control system for the NSV based on TLC. The TLC method may be disabling based on Theoretical analysis when uncertainties exist and turn large, though it has been proven to be inherently robust to regular and singular perturbations. So we bring forward a FTRBFNN based robust adaptive TLC, which adopts FTRBFNN to realize online approximation of the compound disturbance consisting of uncertainties and disturbance. We worked out the adaptive control law of the control strategy according to Lyapunov stability principle, and proved its feasibility. It has been proved that FTRBFNN has excellent approximation capability, and it can effectively eliminate the the tracing error and lift the control precision level if robust item is added to the control law. We conducted some attitude simulations of NSV under the condition of hypersonic, and we concluded that, the compound control strategy performs better control ability and robust even some big disturbance is encountered.Then, following the universal approximation property we bring forward a wavelet neural network (WNN), the Trajectory Linearization Control based on WNN is investigated. Single-Scaling Wavelet Frame function is chosen to be neural network radical function for it's suitable for MIMO system. Configuration is introduced, and we worked out the adaptive control law of the Single-Scaling wavelet neural network according to Lyapunov stability principle, and proved its feasibility. It can effectively eliminate the the tracing error and lift the control precision level if robust item is added to the control law. Simulation results demonstrate the control strategy works well.Subsequently, we investigate wavelet neural networks disturbance observers (WDO). as the intelligent disturbance. The WDO can make use of more useful information of the NSV and can get excellent approximation online. At the same time the adaptive law of WDO adjusts both the error of system and the error of the disturbance itself. Simulation results demonstrate the proposed scheme can provide better performance and strong robust for the NSV during the hypersonic.At Last, for the WNN, combining with the technology of fuzzy, it comes to fuzzy wavelet neural network (FWNN). The study capability of the WNN can optimize fuzzy rules and their corresponding membership function. Based on the TLC, we worked out the adaptive control law of the FWNN according to Lyapunov stability principle, and proved its feasibility. Simulation results demonstrate the proposed scheme can provide better performance and strong robust for the NSV during the hypersonic.