This paper presents a novel kinematic control scheme based on the Virtual Incision Ports (VIPs) for redundancy resolution of redundant robotic arms for single-port access (SPA) surgery. In general, manipulators have 6 DoFs except grippers to be able to reach the desired pose in 3D space. If a surgical robot for SPA surgery has only 6 DoFs, then its workspace could be restricted severely. Therefore most robots including our developed robot consist of more than 6 DoFs with an elbow to maintain triangulation. This means they have a redundancy resolution problem. One of the most popular methods for a redundancy resolution is a pseudo-inverse Jacobian method [1]. In case of robotic SPA surgery, however, this method intrinsically has a high possibility for hurting abdominal organs and muscles or conflicting with other instruments because of the unexpected elbow movements. Our control scheme can decrease the possibility of a collision with them and provide a more flexible working area for surgical tasks by reallocating the VIP. Results presented from simulation and experiment will demonstrate them.

In this paper, we introduce a remote center-of-motion (RCM) mechanism with a conical shape for laparoscopic surgeries that involve a single incision. The mechanism, which has two revolute joints and one prismatic joint, is designed to maintain a stationary point at the apex of the conical shape. By aligning the stationary point with the incision area, the mechanism allows a surgical instrument to explore the abdominal area through a small incision point. We have previously analyzed the reachable workspace of this mechanism. Here, we arrange two RCM mechanisms on a single conical structure but separated in space to avoid mutual interference, so as to enable the entire system to manipulate two surgical instruments through a single incision point without colliding. We describe the operational principle of this system, in addition to comparisons of various RCM mechanisms and the kinematics for parameter design and motion control. Finally, we describe preliminary experiments on peg transfer and suture motion by using the proposed RCM mechanism.