Research On End-Tools Exchange De Vice Of Space Robot

With the pace of the advance of human space exploration, space robots and robot astronauts have become the focus of the space competition. Space and ex-travehicular missions are becoming more and more complicated and diverse. Different space missions often require different end-tools. To achieve the diver-sification of the functions of space robots by developing a device for exchanging the end-tools also becomes one of the key technologies. An end-tool exchanging device with large range of capture tolerance is developed in this paper.Through comprehensive analysis of similar research abroad, a scheduling mechanism evolved from the intermittent mechanism is presented in this paper, so that three functions of the end-tool exchanging device could be done in suc-cession within one drive, including capture & lock, shaft connection and electri-cal connection. Surface of cone and cylinder with perpendicular axes is used as the docking surface, so as the orientation of pose & position of the tool in 6 DOF is achieved. Design, virtual assembly, weight analysis and interference detection of all parts and components of the device using 3D modeling software is accom-plished. Intensities are checked of important components of complex structures and typical structural parts using finite-element analysis software and calculation methods. As a mechatronic product, a hierarchical embedded control system is used, the motor-driver board and sensor-acquisition module are designed. Poten-tiometers, position limitative Hall sensor, conditioning circuit of the force sensor and A/D converter circuit are included in the sensor-acquisition module.According to design requirements, the range of capture tolerance is one of the important indicators of the end-tool exchanging device in dock & capture. Friction and geometry conditions of successful docking using the cone surface as orienting surface are derived by establishing the reference frames fixed on the two end for docking, and the homogeneous transformation matrix between them. The overall capturing strategy of end-tool exchange of space robots is studied, on this occasion, simulations of the capture process and the range of tolerance of the exchanger using virtual prototyping software. It's shown by the simulation re-sults that the design of the end-tool exchanging device has reached the design requirement of the tolerance of pose & position, and well matches the theoretical analysis.Finally, a cubic-polynomial planning is done with the boundary conditions of start & end positions of a single motor, and a PD controller is designed in this case. In the realization of system functions, experiments have been done for testing the capability of the end-tool exchanging device in capturing targets. It's shown by the results of the experiments that: using PD control in this system, the motor could track the optimal trajectory preferable in different loads; the track-ing error is small; the capability of the end-tool exchanging device in capturing targets has reached the design requirements.