Space Robotics for Capture and Service to Non-Cooperative Satellites

我们研究了用于轨道服务的空间机器人的控制技术和基本系统设计，这些机器人能够使用其机械臂捕获和修复故障的非合作卫星。本课题取得了以下成果：1.接触动力学建模对自由飞行物体的接触动力学进行了理论和实验建模与分析。建立了一种识别目标物体机械阻抗的方法。我们开发了一个微重力实验装置，使用一个航天器模型，通过加压空气在水平花岗岩台上轻微浮动。我们的模型和理论的有效性已在整个实验2中得到证实。自由飞行的空间机器人捕获目标卫星时，目标物体很容易被接触力弹开。阻抗控制对减小接触力是有效的。基于“阻抗匹配”理论，研究了自由飞行机械臂与目标保持接触的动力学条件。通过实验证明，由阻抗控制得到的手臂末端等效质量是防止推靶的合理判据.空间冗余度宏-微机械臂的先进控制宏-微机械臂是一种很有前途的轨道服务系统，它由一个长（宏）臂和一个小的细（微）臂组成，宏臂提供远距离操作能力，微臂执行灵巧操作。然而，宏部件可能由于结构柔性而产生振动。小臂的运动在宏部件上引起振动，因此，导致其定位精度降低。在这项研究中，一个准确和快速的操作，防止这种振动的控制方法已经建立。

We have studied control technologies and basic system design of space robots for orbital servicing, which are able to capture and repair malfunctioning non-cooperative satellites using their manipulator arm(s). In this project, the following results have been obtained :1. Modeling of Contact DynamicsModeling and analysis of the contact dynamics for free-flying objects have been carried out both theoretically and experimentally. A method for identifying the mechanical impedance of the target object has been established. We developed a micro-gravity experimental setup using a spacecraft model that floats slightly on a horizontal granite table by pressurized air. The validity of our model and theory have been confirmed throughout the experiments2. Manipulator Control to Prevent Pushing the Target Away in the CaptureWhen a free-flying space robot captures a target satellite, the target object can be easily bounced away by the contact force. Impedance control is effective to reduce the contact force. We have investigated the dynamic conditions to maintain the contact between the free-flying manipulator arm and the target based on the "Impedance Matching" theory. It is proved throughout experiments that the equivalent mass of the end tip of the arm coming from the impedance control is a reasonable criterion for preventing pushing the target away.3. Advanced Control for Space Redundant Macro-Micro ManipulatorsThe macro-micro manipulator is a promising system for orbital servicing, which consists of a long (macro) arm and a small fine (micro) arm. The macro arm provides a long-reach capability and the micro arm performs the dexterous manipulation. However, the macro part can generate vibrations due to structural flexibility. The motion of the small arm induces vibrations onto the macro part, hence, resulting in the reduction of its positioning accuracy. In this study, a control method for an accurate and quick manipulation preventing such vibrations has been established.