A force-sensorless approach to collision detection based on virtual powers

A collision detection approach for torque-controlled manipulators is proposed to detect and isolate a collision in an unknown environment without using external sensors. A set of artificial indexes physically representing instantaneous powers are introduced. A contact link can be detected and isolated by finding the smallest power index based on full knowledge of the link parameters. However, it is difficult to precisely obtain the link parameters. Therefore, we propose a robust way in which the collision detection and isolation processes are separated. A collision can be detected by comparing a power-based index with a unique threshold, and a contact link can be isolated by comparing power indexes without any additional threshold. The statistical simulation results using a 6 degree of freedom (DOF) spatial manipulator show the performance of the proposed approach in an ideal situation. Furthermore, the statistical experimental results using the 2- and 3-DOF planar manipulators validate the robustness of the proposed approach.