Research Of The Equipment For The Cooperative Space Object Graspping

Space robot is one of the important research direction of the robot field . Space gripper is the actuator of space robot in order to complete the tasks .For the special environment in the space, such as the zero gravity, float, high temperature range, vacuum and the radiation, it's strict with the machinery, sensor, drive, dynamics and kinematics research, vision feedback, testing system on the earth. According to the 863 Program this paper developed the HIT/DLR space gripper and its capture strategy.Modularization was introduced to design the HIT/DLR space gripper, the key parts such as the motor, the bearings, the power, the controller and the driver were same with that in the robot joints, so the whole system was more reliable and it was more easily to design. With the three-finger configuration, the gripper can capture the handle in large tolerance range of±40mm in three directions and±30o(X direction),±90o(Y direction),±45o(Z direction), which was more large than the requirement. Capture Interface tie with gripper design, gripper made with a high positioning accuracy by the V-shaped groove of the gripper and with round-ended scissors with cutting edge of the handle.In order to enhance the autonomy of the gripper, gripper designed with a wealth of sensor systems. Hand-eye robot camera system is the most important one of the sensors, This paper studies the visual measurement principle and the visual structure parameter optimization based on the measurement principle, to make full use of hand-eye camera field of view.In addition to the visual, communications and processing delay, gripper and objectives for the handle may exist between a high margin of error. By study the process of capture, the relation between close times, close velocity and error range was induced, then the method could be found to increase the success rate and improve the precision. Based the study, the fingers was optimized and some results could be helpful for the future research on gripper or robot control.At last, the dynamics and kinematics of space robot which were different from that on the ground were outlined in the paper. The path planning to help the base reference frame move to the desired position and attitude in free flight was induced from momentum conservation. Under real time vision feedback, the gripper could move, track and close the micro target independently without any collision. By a lot of experiments on the ground, how the initial position and attitude of the handle affected capture was analyzed too.