Research On Trajectory Reshaping And Guidance Method Of Hypersonic Vehicles With Multi-constraints

Because the stability and security of hypersonic vehicles' guidance are very important,an appropriate fault-tolerant scheme is needed to ensure the safety and reliability of the hypersonic vehicles.This thesis addresses the guidance method and fault-tolerant guidance and control scheme for hypersonic vehicles in the presence of vehicle failures.Firstly,the background and the significance of the research are introduced,and the knowledge about hypersonic vehicles is summarized.Furthermore,an overview of the reentry phase and ascent phase guidance problem which is the core problem of this paper is provided,the current research status of reentry guidance technology and trajectory reshaping technology of hypersonic vehicles is presented,and the main problems in the existing achievements are analyzed.Secondly,an improved predictor-corrector re-entry guidance law for hypersonic vehicle is proposed to generate the re-entry nominal trajectory,and the trajectory satisfies all constraints.In order to overcome the disadvantages that the tracking control method can not guarantee that the actual commands satisfy multi-constraints and the traditional method adopts the strong constraint conversion method with sacrificing the tracking accuracy and flight performance,the overload is taken as an auxiliary variable in this paper.Using the theory of sliding mode tracking control to design guidance law on both lateral and longitudinal,and the genetic algorithm(GA)and the penalty function are adopted to optimize control parameters.The control commands satisfied multi-constraints are obtained,and the re-entry guidance task of hypersonic vehicle is completed.This method can provide the basic guarantee for the online trajectory reshaping scheme under the fault.Thirdly,for the safety re-entry guidance problem subject to multi-constraints of hypersonic vehicle under the fault,an online fault-tolerant guidance scheme is proposed based on the adaptive robust unscented kalman filter(ARUKF)and the improved model predictive static programming(MPSP)under the fault of the vehicle.The augmented state vector is designed,and the ARUKF online predictor scheme is used to estimate the change degree of the aerodynamic parameters under the fault.Since the original MPSP algorithm ignores the initial state deviation and does not consider the multi-constraints during the guidance process,in order to ensure that the aircraft can still land safely with high precision under the fault,the re-entry guidance trajectory satisfying multi-constraints generated by the guidance algorithm in the nominal case is taken as the initial trajectory generator,and the constraints conversion and penalty function are added to the predictor loop to design the improved MPSP algorithm.The reshaped re-entry guidance trajectory with high precision and satisfying multi-constraints is obtained.Finally,considering the ascent guidance model and the scramjet thrust model,an integrated fault-tolerant guidance and control scheme with minimum fuel consumption is designed for hypersonic vehicle in the presence of more strict multi-constraints.According to the working characteristics of scramjet engine on the ascent phase,the minimum fuel consumption problem is converted into the model predictive static programming problem for the control commands,and the optimal guidance trajectory design of the minimum fuel consumption under multi-constraints is completed.At the same time,considering the links between guidance loop and the attitude loop on the ascent phase,the integrated fault-tolerant method of flight guidance and attitude control is studied,and the integrated fault-tolerant guidance and control scheme based on the control distribution is designed.By designing the appropriate control torque,the vehicle can accurately track the attitude angle command in real time.