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中文核心期刊

空间机械臂柔性捕获机构建模与实验研究

DYNAMICS MODELING AND EXPERIMENT OF A FLEXIBLE CAPTURING MECHANISM IN A SPACE MANIPULATOR

  • 摘要: 柔性捕获机构是空间机械臂的关键性部件, 对空间在轨服务过程中的抓捕操作起着至关重要的作用. 捕获机构的原理分析与仿真建模工作对在轨捕获工况预测分析和任务规划有着重要的应用价值. 本文以空间机械臂的末端柔性捕获机构为研究对象, 建立了柔性捕获机构软捕获过程的动力学仿真模型. 考虑了软捕获过程中柔性绳索的空间构型和大变形特性, 采用绝对节点坐标方法建立了三维空间柔性绳索单元, 并通过引入一圆柱参考坐标系来建立柔性绳索与目标适配器端刚性捕获杆的接触碰撞模型. 为满足三维运动工况验证, 搭建了纯被动边界条件的悬吊实验, 通过对比软捕获过程中被捕获目标的运动信息和受力信息, 验证了模型的准确性. 实验结果表明该模型能够有效地模拟在轨捕获任务中柔性机构软捕获阶段的动力学行为, 可以用于后续与空间机械臂联合仿真任务预测以及作为地面气浮台二维试验的必要补充. 此外, 针对在轨任务中的舱外状态巡检和漂浮目标捕获两种典型工况, 进行了机械臂捕获动力学联合仿真分析, 在给定条件下成功完成软捕获阶段的操作.

     

    Abstract: An end-effector with flexible capturing mechanisms, which can accomplish on-orbit capturing operations with large tolerance, is a vital component of a large-scale space manipulator. Dynamics modeling and theoretical analysis of the flexible capturing mechanisms are very important for on-orbit servicing task simulation and prediction. In this paper, a dynamics model of a flexible capturing mechanism with three cables in a space end-effector is developed firstly. The three-dimensional absolute nodal coordinate formulation (ANCF) is used to create nonlinear finite elements of flexible cables. Both bending and longitudinal deformation of the cables are considered, furthermore, contact between the flexible cables and the rigid target is analyzed by introducing an intermediate cylinder reference coordinate system. Then, an experiment with passive spring suspension is built to validate the proposed model and signals of both motions and forces of the target are collected and compared with the simulation results. The comparison shows that the values of the simulation match well with the experimental measuring ones. The presented model could be used as supplements for the two-dimension planar air-bearing experiment and could be used for capturing task simulations of large-scale space manipulators. At last, capturing simulations of two representative on-orbit operations are conducted by co-simulation with the proposed model and a dynamics model of a large-scale space manipulator. One of the operations is the soft capturing process of an inspection task on the spacecraft surface, the other is the soft capturing of a floating target. The main difference between the two simulations is that the target in the first simulation is fixed on the base of the manipulator. Results of these simulations show that the soft capturing process can be accomplished on the prescribed condition.

     

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