Compliant Grasp Strategy for Three-fingered Space Robot End-effector

When space robot is capturing an object,the disturbance force produced by interactive collisions may induce the robot arm dithering and distortion;moreover,it may also pop-up the target object away from the capture zone,which will lead to the failure of capturing operation.To solve this problem,the design of three-fingered space robot end-effector of Harbin Institute of Technology(HIT) is introduced firstly,and then the disturbance force produced by interactive collisions during the progress of grasping a target object is analyzed.A compliant grasp strategy is proposed to weaken the interactive collisions disturbance force,and a new structure of controller based on the combination of feed-forward compensation and fuzzy-sliding mode control is proposed.The deterministic disturbance,the linear part of the friction,and the part associated with end-effector's structure itself can be gained by modeling and off-line testing,which can be controlled effectively by feed-forward compensation,and the fuzzy mode control rules can compensate the external uncertain disturbance,nonlinear part of friction,grasp force and so on.Using satellite on-orbit self-servicing manipulator and three-fingered space robot end-effector designed by Harbin Institute of Technology,some grasp experiments are performed on micro-gravity platform. Experimental results show that the proposed strategy and the designed controller can effectively eliminate the disturbance force during grasping.