小行星探测近轨操作的轨道动力学与控制

Dynamics and control of proximity operations for asteroid exploration mission

探测器接近小行星后开展的逼近、伴飞/绕飞和悬停等一系列近轨操作是实现小行星采样返回等任务活动的前提和关键.本文结合我国未来小行星探测任务构想,以弱引力快自旋小行星2016HO3为背景,针对其近轨操作过程中的轨道动力学与控制问题开展研究.首先,针对逼近段,考虑路径约束和视线角约束,采用滑移制导律设计了小行星多脉冲逼近轨道,并提出了一种抗扰动的重构迭代逼近策略;其次,为了实现小行星物理特征的初步测量,分别设计了探测器相对小行星的伴飞轨道和慢飞越轨道,建立了伴飞距离与伴飞速度间的联系,发现了飞越速度随飞越高度和飞越时间的变化规律,并给出利用慢飞越实现小行星全球观测的轨道设计方法;最后,研究了考虑太阳光压等摄动力作用和模型不确定情况下的小行星定点与区域悬停控制,设计了自适应鲁棒控制律并证明了其稳定性,为小行星的局部区域精细探测提供条件.以上研究可为我国未来的小行星探测任务提供参考和借鉴.

In asteroid exploration mission, the spacecraft needs to execute a series of proximity operations such as approaching, accompany flying, orbiting and hovering, which are the premise and key points to achieve asteroid sample return. Based on the concept of Chinese future asteroid exploration missions, this paper studies the dynamics and control of the proximity operation. First, considering the path and line-of-sight angle constraint, the sliding guidance law is used to design the multi-impulse approaching trajectory. A reconstruction iterative strategy is proposed for the perturbation effect including the irregular shaped gravity, solar radiation pressure, and three-body perturbations. Second, in order to obtain the preliminary physical characteristics of the asteroid, the accompany orbit and slow hyperbolic flybys are designed. The equation of the relative distance and velocity of the accompany orbit is established and the families of accompany orbits with different offsets and sizes are discussed. The spin rate and preliminary shape model of the asteroid can be established during the accompany phase. Then, by slow-flybys, the mass and coefficients of the gravity field of the asteroid can be obtained. The relation between flyby velocity, flyby distance, and flyby duration are found to achieve the global mapping of the asteroid. Several kinds of slow?flyby trajectory are presented. Finally, a self-adaptive control law is designed and proved to achieve the stable hovering at any point or region near the asteroid against varies perturbations and model uncertainty. Based on the control law, the fixed-point hovering and local region hovering are investigated respectively, which can be utilized to precise local exploration and imaging. The simulation results of asteroid 2016 HO3 verify the feasibility of the proposed method. The study can provide a reference for Chinese future asteroid exploration missions.