Collision Detection of Robots Based on a Force/Torque Sensor at the Bedplate

For a collaborative robot that shares the workspaces with humans, physical human-robot interactions are unavoidable. Therefore, it must be capable to detect collisions. Usual collision detection algorithms are based on the robot's dynamic model that frequently suffers from complex joint frictions. The uncertainty of commonly modeled frictions could lead to low sensitivity of the collision detection algorithm. This article presents a novel collision detection scheme based on the robot's dynamic model that calculates the reaction force/torque (F/T) at the bedplate. This dynamic model could avoid modeling joint frictions. To identify the dynamic model, a systematic procedure by measuring the force and torque at the robot's bedplate with an F/T sensor is introduced. Moreover, a compensation method for the F/T sensor signal coupling is developed. The proposed identification procedure has been demonstrated on a six-degree-of-freedom collaborative robot. Finally, collision detection experiments are conducted on a test-bed and humans. The results show that the proposed scheme is reliable and can effectively reduce the impact force with simple reaction strategies.