KUKA LWR Robot Cartesian Stiffness Control Based on Kinematic Redundancy

Abstract

This paper is dealing with one important topic for physical human-robot interaction, and that is achieving and/or optimizing of an arbitrary Cartesian stiffness of robot’s end-effector (EE). The focus is given on redundant compliant robots with serial elastic actuators with fixed joint stiffness, but can reconfigure without changing the EE position. The work presented in this paper is an approach where the robot redundancy is exploited to achieve the desired or at least some optimal Cartesian stiffness of robots EE. Robot tasks can be divided into primary and secondary tasks. In our case, the primary task is to track the Cartesian position reference and the secondary task is to optimize EE Cartesian stiffness behavior while keeping the desired EE position. This means that the EE position is a constraint in the robot Cartesian stiffness optimization. The algorithm for the Cartesian stiffness optimization has been initially tested using the simulation, and then evaluated on the 7-DOFs KUKA light weight robot.