Torque Control of a New Lightweight Actuator Module for Robotic Applications

Abstract

Recent years have witnessed a continuous development from classic industrial robots towards lightweight robots. These compliantly controlled lightweight systems are designed to enable safe human-machine collaboration. The classical design of a robot joint consists of a drive motor, a strain wave gearing and a link-side torque sensor. A new lightweight planetary gear, developed at the German Aerospace Center (DLR) in cooperation with the gear manufacturer Neugart GmbH, enables new sensor configurations to determine the torque present in the joint. This is only made possible by the low friction and high back-drivability of the new transmission unit. The modified design of the robot joint allows to explore new torque control structures. In this work, torque controllers based on a motor-side torque sensor as well as sensorless control approaches are developed. Moreover, the dynamics of the entire drive train is modelled and this knowledge is used to improve the controller. The proposed methods are experimentally verified on a test bed. The results show that these new control structures are promising alternatives to the current established torque controllers, which utilize a link-side torque sensor.