基于高斯Quadrature配置的端到端上升段任务性能Optimization
End-to-End Ascent-Entry Mission Performance Optimization Using Gaussian Quadrature Collocation
摘要：
研究了上升-进入组合飞行器在加热速率和加热负荷约束下的性能优化问题。上升飞行器被建模为三级火箭，将飞行器置于亚轨道大气层外轨道，之后飞行器经历无动力进入并下降到垂直向下的终端条件。进入飞行器被建模为能够承受高水平的热载荷和结构载荷的高升阻比飞行器。设计了一个性能指标，以提高控制裕度，同时衰减进入大气层时的长周期振荡。此外，在本研究中使用了与原型发射和目标点相对应的飞行任务。将轨迹最优化问题转化为多阶段最优控制问题，采用自适应高斯正交配置法求解最优控制问题。优化轨迹的一个关键方面是，对于进入大气层期间的最大允许加热速率和加热负荷的特定范围，在上升期间进行的相对较小的调整可能会减少进入大气层期间所需的控制努力。然而，在最大允许加热速率和加热负荷的这些范围之外，发现所需的控制力增加，并最终在初始下降时使指令迎角饱和。确定了优化轨迹和控制的关键特征，本文开发的方法为端到端上升进入轨迹优化提供了一种系统的方法。
英文摘要：
The performance optimization for a combined ascent-entry mission subject to constraints on heating rate and heating load is studied. The ascent vehicle is modeled as a three-stage rocket that places the vehicle onto a suborbital exo-atmopheric trajectory after which the vehicle undergoes an unpowered entry and descent to a vertically downward terminal condition. The entry vehicle is modeled as a high lift-to-drag ratio vehicle that is capable of withstanding high levels of thermal and structural loads. A performance index is designed to improve control margin while attenuating phugoid oscillations during atmospheric entry. Furthermore, a mission corresponding to a prototype launch and target point is used in this study. The trajectory optimization problem is formulated as a multiple-phase optimal control problem, and the optimal control problem is solved using an adaptive Gaussian quadrature collocation method. A key aspect of the optimized trajectories is that, for particular ranges of maximum allowable heating rate and heating load during entry, relatively small adjustments made during ascent can potentially decrease the control effort required during atmospheric entry. Outside of these ranges for maximum allowable heating rate and heating load, however, it is found that the required control effort increases and eventually saturates the commanded angle of attack upon initial descent. The key features of the optimized trajectories and controls are identified, and the approach developed in this paper provides a systematic method for end-to-end ascent-entry trajectory optimization.
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