An Online Rcm Adjusting System for Robot-Assisted Retinal Surgeries

In robot-assisted retinal surgery, a Remote Center of Motion (Rcm) allows the surgical instrument to rotate around a distal fixed point without any lateral translations. The Rcm point should be perfectly aligned inside the trocar. Otherwise, unexpected tool translations at the expected remote center will enlarge the force applied to the trocar and consequently result in post-operative complications. Due to the narrow size of the trocar and the lack of real-time detection equipment, the Rcm point is hard to be perfectly located inside the trocar. Even if the Rcm is perfectly aligned, the movement of the tissue around the eyeball could make it inappropriate again. In this paper, inspired by the control strategy of surgeons, an online Rcm adjusting strategy is proposed. Instead of only using one fixed Rcm point, to restrict the force between the surgical tool and the trocar, the proposed strategy adjusts the position of the Rcm point during the motion. The results show our approach significantly reduces the force between the robot end-effector and surgical port by 64.2%. In addition, the results also demonstrate that our approach complies the Rcm trajectories without deforming or spoiling the working space, which is significantly important for obeying surgeon's instructions in practice.