火星进入段纵向脱敏局限性分析与三自由度脱敏设计

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。

Limitation Analysis of Longitudinal Desensitize Method for Mars Entry Phase and Three Degree of Freedom Desensitize Design

With focus on the “entry state deviation” problem of the mars entry phase guidance a desensitized trajectory design method is used to enhance guidance robustness and improve terminal state accuracy. Firstly, the influence of bank angle inverse logic on the guidance accuracy of a spacecraft with weak maneuver capability is analyzed. Analysis result shows that the inverse logic will cause terminal state error and make system more sensitive to entry state error if bank angle adjust performance is limited, and even worse when guidance principle is chosen to be longitudinal desensitization method, and serious failure will arise. Secondly, on the basis of solution to the sensitivity propagation singular problem, a three degree of freedom desensitization design is proposed. Its main idea is to adopt three degree of freedom dynamics equations in trajectory optimization while the longitudinal sensitivity propagation equation is still used to obtain the sensitivity penalty term. Monte-Carlo simulation results have shown its remarkable robustness improvement in dealing with entry state deviation.