The SEA-Scope: Torque-limited endoscopic joint control for telemanipulation or visual servoing through tendon force control with series elastic actuation

When performing minimally invasive surgeries, surgeons are currently restricted by the rigidity and limited maneuverability of their tools. The tools could be extended by joints to provide additional degrees of freedom. However, manually controlling the movement of distal joints is challenging since the effective interaction forces at the tip are difficult to feel. Therefore, manipulation of distal joints to increase the maneuverability can lead to additional risks for harming the patient. To overcome limited maneuverability while providing inherent safety, we propose a novel concept for minimally invasive tool actuation based on the principle of series elastic actuation. In previous work, we showed successful torque control of an articulated robotic endoscope. In this paper, we extended torque control by high-level position control. We evaluated the position control experimentally for the case of a telemanipulated joint as well as for automatic target following. Automatic target following was achieved with visual servoing, i.e., an image stream from a miniature camera was processed to compute the joint position setpoint. The results showed that accurate and stable position control is feasible with an actuation based on series elastic actuation. Compared to traditional robotic endoscope actuation, which is designed to be as stiff as possible, our approach reduced impact forces and allowed to set the torque limit in the joint as desired. Therefore, torques exerted by the endoscope joint to adjacent structures can be kept within desired limits.