Torque Collision Detection with Experimental Validation for Protontherapy Positioning Robot

During a robotised protontherapy treatment, clinician, paramedical assistants and medical devices (stepladder, trolley, etc.) often enter the robots workspace. To overcome safety problems, a precise and reliable collision detection technique has been implemented on the LEONI Patient Positioning System (PPS) named Orion PT. This method provides safety not only for persons who are working within the robot workspace but also for environment and for the robot itself. In fact, this technique consists in two phases: to detect collisions when they occur, then to stop the robot immediately. Therefore, a classical and reliable approach based on pre-calculated torque collision detection, has been used. However, contrary to most of recent research works, which focus on lightweight robots, the method described in this paper is adapted to heavy and high inertia serial robot. Moreover a modelling and identification phase of gears kinematic irregularity has been studied. Finally, an experimental validation with force measurement during a real scenario has been carried out to demonstrate the performance of the porposed approach.