External Torque Estimation for an Industrial Robot Arm using Joint Torsion and Motor Current Measurements

Abstract

Human robot collaboration requires specific properties of modern lightweight robots that differ from conventional robots. One of these is the property of reacting to external forces acting on the robot structure, which typically requires joint torque measurements. In contrast to that, this paper presents an approach for estimating the external joint torques based on two different information sources, the motor current and the torsional deformation. To obtain an accurate estimation based on the torsional deformation, disturbing effects and inaccuracies of the angular measurements have to be taken into account. An approach for modeling, identification and cancellation of these effects is presented. Furthermore, the fusion of both estimations is discussed and the validation of the approach on a lightweight robot is presented.