基于特征模型的失效航天器消旋控制

失效航天器一般有复杂的运动和较大的角速度,采用机械臂直接抓捕目标容易导致非预期碰撞,如果先采用接触式消旋操作降低目标角速度,会大大降低服务卫星抓捕目标的难度。针对空间翻滚非合作目标的接触式消旋控制存在接触动力学模型不确定性的问题,提出了一种基于特征模型的自适应控制方法。首先通过接触式消旋的物理机理分析,建立消旋系统动力学模型;进一步在动力学特性分析基础上构建描述接触碰撞后目标角速度的特征模型,并确定模型参数范围;然后基于该模型设计黄金分割自适应控制律。仿真结果表明,该方法有效克服了消旋过程中接触碰撞模型存在的不确定性,并且消旋速度快且消旋后的残余角速度小。     

自由翻滚故障卫星外包络抓捕及抓捕路径优化

自由翻滚故障卫星抓捕是航天器在轨服务及空间碎片清理的基础。由于难以确定固定抓捕点及目标运动参数不确定,传统机械臂抓捕方法无法适用类似自由翻滚故障卫星的空间非合作目标。提出一种具有鲁棒性的外包络抓捕方法及抓捕路径优化方案。外包络抓捕方式能够适用于自由翻滚故障卫星抓捕问题,其特点在于,第一,由抓捕末端执行器构成的抓捕包络可以包络空间目标,约束其运动并最终实现抓捕,因此不需要固定抓捕点;第二,末端执行器构成的抓捕包络,能够约束故障卫星运动,而两者之间的摩擦可以有效消除两者之间的相对运动最终成功抓捕翻滚目标。进一步,针对外包络抓捕方法,提出了一种最小燃料消耗及最小抓捕扰动的机械臂抓捕路径。为验证外包络抓捕方法的有效性,构建旋转立方星抓捕地面实验,并利用数值仿真验证外包络抓捕机械臂最优路径规划,仿真结果验证了所提出方法的有效性。     

空间多功能在轨维护机器人系统及其末端执行器设计

空间机器人是空间在轨服务的一种重要工具。以合作目标与非合作目标的在轨维护为目的,通过对现有空间机器人研究现状的调研和分析,提出了基于末端工具可快换的多功能在轨维护机器人系统,并提出多种末端执行器设计方案。其中三指-三瓣式末端执行器作为末端工具快换装置,不仅具有机械接口捕获对接的功能,还具有电力/信号传输功能,以及机械臂动力传输功能;钢丝绳缠绕式末端执行器具有优越的容差和软捕获性能,适合用于实现对安装有捕获接口的合作目标以及非合作目标卫星发动机喷管的捕获;而欠驱动三指末端执行器具有良好的待捕获目标物体形状自适应功能以及软捕获功能,因此可用于对空间形状不规则的太空垃圾等目标进行非合作目标捕获。通过对多功能在轨维护机器人系统及其末端工具快换过程以及末端执行器对目标捕获操作的研究,所提出的基于末端工具快换的多功能在轨维护机器人系统有较好的应用前景。     

漂浮基空间机器人捕获卫星过程动力学模拟及捕获后混合体运动的RBF神经网络控制

 讨论了漂浮基空间机器人在轨捕获目标卫星过程的碰撞动力学建模,以及捕获操作结束后空间机器人与卫星混合体的稳定控制问题。首先采用多刚体动力学建模方法并结合空间机器人捕获目标卫星过程中的碰撞动力学特性,建立了漂浮基空间机器人在轨捕获漂浮卫星过程的动力学模型,并在此基础上计算出完成捕获操作后空间机器人与目标卫星混合体关节的运动速度。然后针对卫星及空间机器人系统惯性参数均是未知的复杂情况,应用上述模型、神经网络控制理论和Lyapunov稳定性理论,设计了空间机器人与卫星混合体在捕获过程碰撞冲击影响下稳定运动的高斯径向基函数神经网络控制方案,以达到对捕获卫星的有效控制。此外,高斯径向基函数神经网络控制方案具有不需要测量和反馈载体位置、移动速度与加速度的显著优点。系统数值仿真证实了上述控制方案的有效性。     

微型航天器与空间非合作目标交会制导方法

星载设备能力有限的微型航天器在与空间非合作目标交会任务开始前,存放在空间轨道平台内,为了使其完成此项任务,需要设计制导方法。本文首先根据希尔（C-W）方程,设计了初制导律,然后在视线坐标系内建立了微型航天器与非合作目标间的相对运动方程,并设计了空间交会自寻的末制导律。交会任务开始时,为节省微型航天器的燃料,轨道平台根据初制导律以一定速度及释放角度释放微型航天器,微型航天器进入交会轨道,在初制导的作用下,经过若干个过渡轨道周期后接近空间非合作目标,并为末制导提供良好的交班条件,当末制导导引设备捕获并跟踪目标后可通过自寻的末制导最终完成与空间非合作目标交会任务。     

非合作慢旋目标即时状态位姿确定

对失效卫星等非合作慢旋目标进行在轨服务，需要精确测量追踪航天器与目标之间的姿态信息。因此，如何在复杂的光照条件下快速、准确地对非合作慢旋目标进行即时状态位姿确定具有一定的挑战性。应用ORB-SLAM技术，首先定位关键帧，并估计姿态。然后用当前帧的特征点与地图点对应的特征点进行匹配。最后，将完成匹配的特征点通过重投影确定其在地图中的位置，如果出现跟踪丢失，则根据已有的地图点估计姿态。实验结果表明：在复杂的光照条件下，分别对以10(°)/s角速度运动和以3(°)/s角速度运动的非合作目标进行测量，当测量稳定后，平均角速度误差约为0.1(°)/s和0.02(°)/s，可以满足工程上空间非合作目标相对姿态测量的精度要求。     

基于机器学习的空间翻滚目标实时运动预测

借助监督式机器学习（ML）方法,对空间翻滚目标的运动状态预测问题进行研究,为空间机器人抓捕空间翻滚目标提供可靠的数据依据。基于物理模型的运动预测方法依赖理想的建模假设,需要连续的视觉反馈信息,解决目标预测问题的能力有限。因此,本文采用机器学习中纯数据驱动方式的稀疏伪输入高斯过程（SPGP）回归方法进行空间翻滚目标的运动预测。给定空间翻滚目标运动状态的历史观测数据,通过连续优化真实观测数据,得到稀疏的伪训练数据集,进而在线快速预测目标的运动状态,预测的计算效率达到毫秒级。此外,利用马尔科夫链蒙特卡洛（MCMC）法处理连续优化过程,克服由于随机初始值造成的优化过程陷入局部极小值问题。利用Snelson数据验证了所提稀疏伪输入高斯过程回归方法的正确性,并通过4组仿真算例验证了所提方法对于空间翻滚目标运动预测的有效性和鲁棒性。     

翻滚非合作目标逼近与跟踪的轨道和姿态控制

面向近距离逼近与捕获翻滚非合作目标的在轨服务空间清理任务需求,研究了航天器非合作式交会对接的轨道和姿态控制问题。在控制输入受限约束下,考虑存在参数不确定性和外部扰动的情况,结合滑模控制和自适应控制技术,分别进行鲁棒自适应位置和姿态控制器设计。利用自适应控制估计参数不确定性、未知干扰上界以及滑模控制反馈系数矩阵,提高了系统的鲁棒性。通过李雅普诺夫理论证明了系统在控制器作用下全局一致最终有界稳定。仿真结果验证了控制器的有效性,能够有效解决与高速旋转非合作目标的稳定相对位姿关系建立的难题。     

基于机器人柔性毛刷的空间翻滚目标消旋

设计了一种柔性减速刷消旋机构，将其安装于七自由度机械臂的末端，通过与翻滚目标帆板之间的接触碰撞进行消旋。利用绝对节点坐标法推导了柔性减速刷的动力学模型，并对其接触碰撞进行分析。针对自由漂浮空间机器人动力学建模和基座姿态的控制进行了研究，采用基于计算力矩法的滑模控制策略，对末端参数不确定的七自由度机械臂进行控制。滑模控制具有快速响应、对参数变化及扰动不灵敏等特点，确保了系统的全局鲁棒性和稳定性。有利于节省消旋时间，提高消旋效率。通过PD控制和滑模控制消旋仿真验证，该消旋策略能够成功消除初始旋转速度，消旋程度达90%以上，具有可行性与有效性。     

卫星在空间碎片撞击下的易损性分析方法研究

针对厘米/毫米级空间碎片对卫星的撞击风险评估,在对卫星部件的失效模式及影响分析（FMEA）的基础上,结合射线跟踪法和失效树分析法建立一种卫星目标的易损性分析方法,计算卫星在空间碎片撞击下导致不同损伤等级的系统失效概率PK/H。详细介绍了该易损性分析方法的总体思路和各项关键技术,并给出了应用实例。该方法可推广应用于载人航天器上,对于航天器的撞击风险评估和防护结构优化设计有重要意义。     

Capture and detumbling control for active debris removal by a dual-arm space robot

Active debris removal (ADR) technology is an effective approach to remediate the proliferation of space debris, which seriously threatens the operational safety of orbital spacecraft. This study aims to design a controller for a dual-arm space robot to capture tumbling debris, including capture control and detumbling control. Typical space debris is considered as a non-cooperative target, which has no specific capture points and unknown dynamic parameters. Compliant clamping control and the adaptive backstepping-based prescribed trajectory tracking control (PTTC) method are proposed in this paper. First, the differential geometry theory is utilized to establish the constraint equations, the dynamic model of the chaser-target system is obtained by applying the Hamilton variational principle, and the compliance clamping controller is further designed to capture the non-cooperative target without contact force feedback. Next, in the post-capture phase, an adaptive backstepping-based PTTC is proposed to detumble the combined spacecraft in the presence of model uncertainties. Finally, numerical simulations are carried out to validate the feasibility of the proposed capture and detumbling control method. Simulation results indicate that the target detumbling achieved by the PTTC method can reduce propellant consumption by up to 24.11%.     

Detumbling strategy based on friction control of dual-arm space robot for capturing tumbling target

The rotational motion of a tumbling target brings great challenges to space robot on successfully capturing the tumbling target. Therefore, it is necessary to reduce the target’s rotation to a rate at which capture can be accomplished by the space robot. In this paper, a detumbling strategy based on friction control of dual-arm space robot for capturing tumbling target is proposed. This strategy can reduce the target’s rotational velocity while maintaining base attitude stability through the establishment of the rotation attenuation controller and base attitude adjustment controller. The rotation attenuation controller adopts the multi-space hybrid impedance control method to control the friction precisely. The base attitude adjustment controller applies the dual-arm extended Jacobian matrix to stabilize the base attitude. The main contributions of this paper are as follows: (1) The compliant control method is adopted to achieve a precise friction control, which can reduce the target angular velocity steadily; (2) The dual-arm extended Jacobian matrix is applied to stabilize the base attitude without affecting the target capture task; (3) The detumbling strategy of dual-arm space robot is designed considering base attitude stabilization, realizing coordinated planning of the base attitude and the arms. The strategy is verified by a dual-arm space robot with two 7-DOF (degrees of freedom) arms. Simulation results show that, target with a rotation velocity of 20 (°)/s can be effectively controlled to stop within 30 s, and the final deflection of the base attitude is less than 0.15° without affecting the target capture task, verifying the correctness and effectiveness of the strategy. Except to the tumbling target capture task, the control strategy can also be applied to other typical on-orbit operation tasks such as space debris removal and spacecraft maintenance.     

Area-oriented coordinated trajectory planning of dual-arm space robot for capturing a tumbling target

The growing amount of space debris poses a threat to operational spacecraft and the long-term sustainability of activities in outer space. According to the orbital mechanics, an uncontrolled space object will be tumbling, bringing great challenge to capture and remove it. In this paper, a dual-arm coordinated ‘‘Area-Oriented Capture"(AOC) method is proposed to capture a non-cooperative tumbling target. Firstly, the motion equation of the tumbling target is established, based on which, the dynamic properties are analyzed. Then, the ‘‘Area-Oriented Capture"concept is presented to deal with the problem of large pose(position and attitude) deviation and tumbling motion. An area rather than fixed points/devices is taken as the object to be tracked and captured. As long as the manipulators' end-effectors move to a specified range of the objective areas(not fixed points on the target, but areas), the target satellite will be hugged by the two arms.At last, the proposed method and the traditional method(i.e. fixed-point oriented capture method)are compared and analyzed through simulation. The results show that the proposed method has larger pose tolerance and takes shorter time for capturing a tumbling target.     

电动力缆绳离轨系统中绳索建模研究

 空间碎片对在轨运行航天器的安全构成重大威胁,使废弃卫星脱离原轨道进入大气层烧毁是减少空间碎片的有效途径。利用导电缆绳与地磁场相互作用产生的洛仑兹力使卫星特别是低地球轨道卫星的轨道高度快速衰减是一种很有应用前景的离轨方式。在研究电动力缆绳离轨的刚性杆模型基础上,建立了更符合电动力缆绳特性的柔索模型,并对刚性杆模型和柔索模型进行仿真。结果表明柔索模型能更精确地体现电动力缆绳的性质。     

Solid rocket propulsion technology for de-orbiting spacecraft

This paper presents the topic of using solid rocket propulsion for de-orbiting spacecraft,in order to fulfil space debris mitigation requirements. The benefits and disadvantages of using such means are discussed. A dedicated system can be implemented in the satellite design phase and shall be a key subsystem of platforms inserted into orbit. Uncontrolled, semi-controlled and controlled de-orbit can be completed using solid rocket motors. Their impact on the space debris environment is discussed....     

Tangling and instability effect analysis of initial in-plane/out-of-plane angles on electrodynamic tether deployment under gravity gradient

The space debris occupies the orbit resources greatly, which seriously threats the safety of spacecraft for its high risks of collisions. Many theories about space debris removal have been put forward in recent years. The Electro Dynamic Tether (EDT), which can be deployed under gravity gradient, is considered to be an effective method to remove debris in low orbit for its low power consumption. However, in order to generate sufficient Lorentz force, the EDT needs to be deployed to several kilometers, which increases the risks of tangling and the instability of the EDT system. In the deployment process, different initial in-plane/out-of-plane angles, caused by direction error at initial release or the initial selection of ejection, affect the motion of EDT system seriously. In order to solve these problems, firstly, this paper establishes the dynamic model of the EDT system. Then, based on the model, safety metrics of avoiding tangling and assessing system stability during EDT deployment stage are designed to quantitatively evaluate the EDT system security. Finally, several numerical simulations are established to determine the safety ranges of the initial in-plane/out-of-plane angles on the EDT deployment.     

交会对接任务碰撞规避策略制定研究简

针对交会对接任务目标飞行器与追踪器轨道运行特性,综合考虑规避策略计算方法与工程实际相结合的问题,提出高度规避、时间规避以及与正常轨控相结合的碰撞规避策略计算方法等三种空间目标碰撞规避策略计算方法.高度规避计算方法采用了Lambert飞行原理,用简化二体开普勒模型取代高精度轨道预报方法,迭代求解规避机动速度增量,实现了通过约束过交点与目标径向距离差得到速度增量的最优解;时间规避计算方法通过轨道周期与速度增量的关系,实现了通过约束过交点与目标的时间差得到速度增量的最优解;与正常轨控相结合的碰撞规避策略计算方法,在正常控制考虑冗余控制量的基础上,对控制策略的控制开始时间或沿迹方向的速度增量进行较小的修正,使两者通过碰撞点的时刻或径向距离错开,达到碰撞规避的目的,该方法不仅可以节省燃料、而且对任务的影响较小.通过对三种空间目标碰撞规避策略计算方法仿真分析结果表明,完全适用于交会对接任务,可为我国载人航天任务飞行安全提供技术保障.