Human-robot interaction with redundant robots using force-field-dependent variable impedance control

This paper introduces an improvement of the assisting force field (AFF) concept for hand-guiding of robotic arms. The AFF guides the user to several reference paths previously learned from experienced users. The AFF concept is extended to anthropomorphic redundant robots, which are used to obtain more flexibility. The redundancy of the robot is used for collision avoidance with the robot's elbow. The motion for collision avoidance should have a low influence on position and orientation of the end effector. A corresponding algorithm is proposed. Using AFF, a force-field-dependent variable impedance controller (FF-VIC) is developed for reducing the settling time and improving the user comfort. For investigating these proposed developments a simulation study was performed in which user comfort and control performance were evaluated. Analyzing the simulation results, a suitable parametrization for the FF-VIC can be found which improves user comfort and settling time. Finally, the results were experimentally validated and the functionality of the collision avoidance is shown.