Performance Indicator for Benchmarking Force-Controlled Robots

Robot-based sensitive assembly is a recent and growing trend in robotics. Force-controlled robots are expected to interact with an unknown environment using solely force feedback information. In general, the exact contact is difficult to predict due to various impact factors, such as the dynamics of the interaction, work-piece stiffness and geometry, the robot's configuration, and the efficiency of the control algorithm. Currently, there is no general indicator for evaluating the performance of a force-controlled robot. This work presents a concept of such a performance indicator. In order to test the proposed concept for comparison, an experimental setup is presented that simulates a contour-following task under force control. This setup is used to test two robots with different force-controllers and control principles, namely direct force and impedance control. The results indicate good applicability of the proposed performance indicator to benchmark force-controlled robots, and this is extensively discussed.