Toward understanding the effects of visual- and force-feedback on robotic hand grasping performance for space teleoperation

This paper introduces a study aimed to help quantify the benefits of limited-performance force-feedback user input devices for space telemanipulation with a dexterous robotic arm. A teleoperated robotic hand has been developed for the European Space Agency by the German Aerospace Center (DLR) for a lunar rover prototype. Studies carried out on this telerobotic system investigated several criteria critical to telemanipulation in space: (1) grasping task completion time, (2) grasping task difficulty, (3) grasp quality, and (4) difficulty level for the operator to assess the grasp quality. Several test subjects were allocated to remotely grasp regular and irregular shaped objects, under different combinations of visual- and force-feedback conditions. This work categorized the benefits of visual- and force-feedback in teleoperated grasping through several performance metrics. Furthermore, it has been shown that, with local joint-level impedance control, good grasping performance with rigid hard objects can be achieved, even with limited force-feedback information and low communication bandwidth. On the other hand, a performance ceiling was also found when grasping deformable objects, where the limited force-feedback setup cannot sufficiently reflect the object boundary to the teleoperator.