月球软着陆接近段最优开关制导律设计分析

Optimal Switching Guidance for the Approach Phase of Lunar Soft Landing

对月球软着陆接近段的最优开关制导律进行了研究,并对飞行轨迹进行了分析。在接近段近乎垂直下降的基础上,利用最大值原理获得了最优开关制导律,并根据实际飞行情况采用质量不变假设,从而得到了开关切换量的解析形式,利于星上计算和控制。最后,对不同制动力、下降速度和下降角等因素影响下的飞行轨迹进行了仿真分析,得到了一些有意义的结论,同时证明了该制导律的有效性。

The optimal switching guidance law for the approach phase of a lunar soft landing module is studied and the descending trajectory is analyzed. Based on the nearly perpendicular descent in the approach phase, the optimal switching guidance law is obtained by the maximum principle. Moreover, according to the practical fights, the constant-mass hypothesis is adopted and the analytical form of the switching variable is got, which is convenient for on-board calculation and control. Finally, numerical simulations and analysis of the flying trajectory under different thrusts, initial velocities and descending angles are conducted to draw some conclusions and to demonstrate the validity of the guidance law.