Exploiting potential energy storage for cyclic manipulation: An analysis for elastic dribbling with an anthropomorphic robot

For achieving dynamic manipulation capabilities that are comparable to human performance in terms of speed, energetic properties, and robustness, intrinsic elasticity is widely proposed as a necessary robot design element. In this paper we show how passive compliance can be exploited for a 6-degree-of-freedom (DoF) cyclic ball dribbling task with a 7-DoF articulated Cartesian impedance controlled DLR Lightweight Robot III. For this, the robot is equipped with an elastic hand, which extends the contact time and therefore, also enlarges both, observability and controllability of the ball. We show via simulation and experiment that it is possible to achieve a stable dynamic cycle based on a 1 DoF analysis from [1] for the main axis together with control strategies for the secondary translations and rotations of the task. The scheme allows also the continuous tracking of a desired dribbling height and horizontal position. As a human is able to dribble blindly, we decided to solve the task by force sensing only, i.e. no vision is used for our approach, however, it could be easily incorporated.