Research On Online Trajectory Optimization And Adaptive Guidance For Power System Fault Of Launch Vehicle

As the foundation of aerospace technology development and space exploration,the development of a new generation of large-carrying-capable launch vehicles is urgently needed.To achieve the improvement of carrying capacity,it is necessary to study new,high-thrust rocket engines.However,the development of new power systems requires the application of new theories,new materials,and new technologies,which inevitably reduce the reliability of the power system.Once the power system fails during the launch process,it will cause incalculable losses.With the development of computing equipment technology and optimization theory,online trajectory planning has become an effective way for future aircraft to face emergencies and realize emergency trajectory and mission reconstruction.In this context,this paper uses the convex optimization algorithm as the main tool to achieve rapid trajectory optimization,focusing on the research of online trajectory planning,mission reconstruction and adaptive guidance technology for the failure of the launch vehicle's power system in the ascent phase.The main work of the thesis includes the convex method of non-convex trajectory planning problem,the improved solution technology of convex optimization problem,and the high-precision guidance strategy.The main research content of the paper is as follows:Carry out detailed analysis of the dynamic model and typical ballistic characteristics of the launch vehicle ascending section,and give the definition and conversion method of the relevant coordinate system;carry out detailed analysis and classification of the common conditions of the launch vehicle power failure,and establish the power system failure model for online planning The model is established to lay the foundation;the mathematical theory of convex optimization problems and the pseudo-spectral discrete method are analyzed.In different flight stages of the launch vehicle,different degrees of power system failures occur,and different online trajectory planning and adaptive guidance algorithms need to be considered.Aiming at the mid-degree power system failure of the launch vehicle during the non-orbiting flight section,this paper studies the on-line planning method of the launch vehicle energy optimal trajectory.First,the optimal trajectory planning model for fixed-time terminal energy is given based on the assumption of exhausted shutdown;then,the non-convex thrust amplitude constraint is converted into convex constraint by the lossless convexity method,and the convexity process is given based on the optimal control theory The non-destructive proof of;secondly,the application of pseudo-spectral discrete method and non-convex item iterative update strategy has completed the processing of non-convex items in the dynamic model.The paper carried out numerical simulation experiments on the above methods,analyzed the characteristics and applicability of the algorithm,and laid the foundation for the subsequent online trajectory planning of the orbital section.For the launch vehicle's orbiting flight segment,not only the trajectory reconstruction under the condition of large deviations need to be considered,but also the accuracy of the orbiting into orbit must be ensured to meet the mission requirements.For this reason,this paper proposes a multi-terminal constrained trajectory online planning algorithm.First of all,in order to facilitate the expression of the target trajectory element,this paper establishes a trajectory planning problem model in the near focus coordinate system,and studies a two-step correction iterative strategy to solve the trajectory planning problem after the sequence convexity,and realizes the rapid and accurate solution of the multi-terminal constraint problem.In order to ensure the accuracy of orbiting,the calculation strategy of taxiing time is studied,and the requirement of orbiting timeposition accuracy is ensured.Aiming at the problem of long calculation period of online trajectory planning algorithm and insufficient accuracy of orbiting guidance,the switching strategy of guidance algorithm is studied.The simulation experiment verifies the accuracy,rapidity and robustness of the algorithm,and has the potential for online application.When the launch vehicle has a serious failure and cannot enter the target orbit,or even cannot enter the space,online trajectory reconstruction is also required to reduce mission loss.Aiming at the situation that the launch vehicle cannot enter the predetermined target trajectory,this paper studies the optimal rescue trajectory design method,and proposes the fault homotopy technology to ensure the convergence of the algorithm in the case of severe faults.In view of the serious failure of the launch vehicle and the failure of the load to enter orbit,a safe reentry strategy was studied to achieve reentry at a predetermined location and speed,ensure the accuracy of the fall location,and avoid greater losses and international disputes.In order to further improve the efficiency of solving convex optimization problems in online trajectory planning,this paper first conducts an in-depth study on the principle of the primal dual interior point algorithm commonly used to solve convex optimization problems,and derives its solution ideas and steps in detail.At the same time,in view of the strong enthusiasm of the inequality constraints of the launch vehicle trajectory planning problem and the better sparse characteristics of the equality constraint matrix,an improved primal dual interior point algorithm for solving the convex optimization problem of the launch vehicle trajectory planning problem is given,and the typical fault conditions are passed.The simulation experiment below verifies the effectiveness of the improved strategy.In summary,this article has conducted an in-depth study on trajectory online planning and adaptive guidance technology in the case of a launch vehicle power system failure.The convex optimization technology is applied to the online trajectory planning of the launch vehicle,and the traditional method is improved to ensure that the loss caused by the failure is reduced or even eliminated under the conditions of different flight stages and different failure levels.The related results have good theoretical and application innovation,and provide a good reference for the future generation of launch vehicle trajectory online planning and adaptive guidance technology applications.