Ascent Adaptive Guidance For Power System Fault Of Launch Vehicle

Modern launch vehicle need a more powerful power system to meet the need of carrying capacity, but the impact of power system fault on the launch mission is particularly serious. Especially when the engine is in fault, the traditional perturbation guidance method based on the standard trajectory is difficult to correct the large trajectory bias.In order to ensure that the launch vehicle can autonomously complete the reconstruction and ensure the completion of the transport task when power system is in fault, the guidance method which could adapt to the power system fault is proposed. In this paper, the two stage launch vehicle was selected as the study object., the orbit injection point adaptive updated iterative guidance method and the online trajectory optimization closed-loop guidance method based on the indirect method were used respectively for the exo-atmospheric and indo-atmospheric fault of power system, to complete the study of adaptive guidance for the fault of power system during the launch vehicle ascent phase.Firstly, the cases and its influence about power system faults in launch vehicle ascent phase were investigated. And the research status of the exo-atmospheric adaptive guidance and the trajectory online optimization closed-loop guidance with the indirect method were investigated and analyzed.Secondly, the dynamic model of launch vehicle ascent trajectory was researched including the definition of coordinate systems and transformation relations between them and the derivation of 3-DOF dynamic and kinematic equations of launch vehicle in the Launch Inertial Coordinate System. And the faults mode of the power system were analyzed, as the foundation of later research.Then, the orbit injection point adaptive updated iterative guidance method was formulated where the simplified thrust direction command iterative guidance method was introduced. The estimation of time-to-go, gravity integration, the thrust integration and the update of injection point argument of latitude were given. The simulation of exo-atmospheric power system faults of launch vehicle proved the efficiency and rationality of the proposed method.Eventually, the online trajectory optimization and closed-loop guidance method were studied. Based on the indirect method, the expression of the endo-atmosphere launch vehicle ascent trajectory optimal body axis direction, co-state variable differential equations and terminal boundary conditions were derived. The Hamiltonian two-point boundary value problems considering the path constraint were conducted, and this problem was solved by finite difference method. Then, the nonlinear algebraic equations were solved with improved Newton iteration algorithm. And the rapid vacuum analytic initial value, parameter homotopy were combined to solve the problems of initial value conjecture. By analysing the simulation of endo-atmospheric power system fault conditions, the efficiency and rationality of the online trajectory optimization based on the indirect method and the trajectory following closed-loop guidance method with LQR was verified.