Key technologies of TianGong-2 robotic hand and its on-orbit experiments

Abstract

With the development of robotics in recent years, space robotic manipulators have become a research focus on space technologies. In the TianGong-2 (TG-2) spacelab mission, a human-robot collaborative on-orbit servicing experiment was planned as one of the three key tasks. The central component of this task is the TG-2 robotic manipulator, which is a multisensory in-vehicle space robot with multiple control modes, including a 6-DOF robotic arm, a five-fingered humanoid hand, hand-eye and global cameras, and on-orbit human-machine interfaces(space mouse and cyber glove). The design purpose of TG-2 robotic task is to complete various prototypical experiments under micro-g environment to validate key technologies of space robots and on-orbit human-robot collaboration and gain experience and experimental data about robotic on-orbit servicing by assisting or cooperating with human astronauts. A variable time-scale motion plan method, which could adjusts the trajectories of the robot to reduce or eliminate the collision force between the robot collide with the environment, is developed for safe human-robot collaboration. The five-fingered hand grasp control is based on an approach coined as “coordinated grasp control based object Cartesian stiffness” for the adaptation of external forces and robust grasp. To solve the kinematic mapping from cyber glove commands to five-fingered robotic hand, a fingertip-position-based method is proposed to acquire precise solutions. The TG-2 robotic manipulator was launched to space in Sep. 15, 2016. From Oct. 27 to Nov. 13, 2016, all the planned experiments, including dynamic parameter identification, grasping floating objects and prototypical on-orbit servicing, were carried out successfully under the supervision and assistance of the two astronauts, laying foundations for the future applications of space robots.