Teleoperation of a Truss Structure by Force Command in ETS-VII Robotics Mission

Abstract

In space teleoperation under time delay, performance differs significantly for the various control techniques, for example, 1) compliance control by a position/orientation command and 2) force control by a force/torque command. With the latter control technique, the robot arm moves toward the point where the external force/torque applied to the end effector becomes equal to the commanded value. This technique is effective for tracking a restricted trajectory or in peg-in-hole insertion, even though the teleoperation is performed under time delay. The effectiveness of force control is discussed. Experimental results for verification based on an on-orbit experiment for deploying and assembling a truss structure on the Engineering Test Satellite VII (ETS-VII) are presented. To perform the deployable truss operation task within the strongly limited experimental time on ETS-VII, it is necessary to choose the timing of sending commands and the direction of forces in correspondence to the current truss configuration. It is also shown that force control is effective for truss insertion during a truss assembly task, regardless of the time delay.