Compliant Task-Space Control with Back-Drivable Servo Actuators

In this paper, we propose a new approach to compliant taskspace control for high degree-of-freedom manipulators driven by positioncontrolled actuators. The actuators in our approach are back-drivable and allow to limit the torque used for position control. Traditional approaches frequently achieve compliance through redundancy resolution. Our approach not only allows to adjust compliance in the null-space of the motion but also in the individual dimensions in task-space. From differential inverse kinematics we derive torque limits for each joint by examining the contribution of the joints to the task-space motion. We evaluate our approach in experiments with specific motions. We also report on the application of our approach at RoboCup 2010, where we successfully opened and closed the fridge in the RoboCup@Home finals.