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多约束月面盘旋飞跃轨迹优化控制方法

Trajectory Optimization for Lunar Hover Hop with Multi Constraints

  • 摘要: 针对无平移发动机月球探测器的多约束盘旋飞跃问题,给出了燃耗最优轨迹。盘旋飞跃划分为垂直上升段、平移段、垂直下降段,垂直上升段与垂直下降段的最优控制均为Bang-Bang形式。研究平移段最优轨迹时,考虑位置、速度、角速度等约束,首次把优化问题的控制变量由推力转化为角速度,然后基于Pontryagin极小值原理得到了最优角速度的初步形式,接着通过对奇异点连续性、控制变量切换次数的研究,得到最优角速度的最终形式由最大边值与最小边值组成且发生两次切换,最后提供了一种求解切换点的数值方法。仿真结果表明,该算法精度高、复杂度低,适用于在线轨迹优化。

     

    Abstract: The multi-constrained trajectory of minimal fuel consumption was achieved in this paper for the lunar hover hop without lateral thrusters. The hover hop was divided to 3 phases: the vertical rise, the horizontal traverse and the vertical descent. The optimal control of the vertical rise and the vertical descent was bang-bang function. For the first time the control variable of the horizontal traverse was converted from thrust to angle rate, with position, velocity and angle rate considered. The preliminary form of the optimal angle rate for the horizontal traverse was developed by application of the Pontryagin’s minimum principle. With further study on the continuity of the singular point and the number of switching times of the control variable, it was confirmed that the optimal angle rate program consisted of either the maximum or the minimum and there were 2 switchings. A numerical approach to searching the switching points was presented. Simulation results show that the approach with high accuracy and low complexity can potentially be implemented onboard for trajectory optimization.

     

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