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针对火星进入段制导存在的“进入状态偏差”问题进行脱敏轨迹设计研究,以增强制导鲁棒特性,提升末端状态精度。首先分析倾侧角反转逻辑对弱机动能力航天器制导精度的影响,结果表明,存在倾侧角调整性能约束时,反转逻辑会引起末端状态偏差并使系统对进入状态偏差敏感度上升,当制导采用现有纵向脱敏方法时其影响尤为突出,会导致严重失效问题;然后在解决敏感度传播奇异问题的基础上提出三自由度脱敏设计。其主要思路是轨迹优化中采用三自由度动力学方程,而敏感度罚项仍由纵向敏感度传播方程得出。蒙特卡洛仿真结果表明本文方法对进入状态偏差具有显著增强的鲁棒性能。
In order to improve the guidance robustness and improve the accuracy of the end state, a desensitization trajectory design study on the “entry state deviation” existing in the segment guidance of Mars has been carried out. Firstly, the influence of tilt angle reversal logic on the guidance precision of weak maneuvering spacecraft is analyzed. The results show that when the tilt angle adjustment performance constraint exists, the reversal logic will cause the end state deviation and make the sensitivity of the system to the entering state deviation increase. When using the existing method of vertical desensitization, the influence is particularly prominent, leading to serious failure problems. Then, a three-degree-of-freedom desensitization design is proposed on the basis of solving the singularity problem of sensitivity propagation. The main idea is to use three-degree-of-freedom kinetic equation in trajectory optimization, while the sensitivity penalty is still derived from the longitudinal sensitivity propagation equation. The Monte Carlo simulation results show that the proposed method has significantly enhanced robustness to entry state deviations.