Investigation of Torque Controlled Robots with Flexible Links Using a Flexible Multibody Simulation

Abstract

The past two decades have brought forward a new class of robotic arms designed for close human-robot cooperation. Their lighter design has greater structural flexibilities compared to classical industrial robots, which leads to undesired vibrations at the tool center point. Joint torque feedback controllers have been designed to counteract effects of robot joint flexibility. The goal of this project is to study the impact of link flexibilities on the accuracy of robots with such torque controllers. The study is performed using a flexible multibody simulation that is experimentally validated with the torque controlled robot Franka Panda. It is shown that, for both a single link and a 6-axis robot model, the torque controllers can dampen structural vibrations within the joint space if the torque feedback loop has high enough bandwidth. However, modes orthogonal to the joint space cannot be dampened.