A Novel Vitreoretinal Surgical Robot System to Maximize the Internal Reachable Workspace and Minimize the External Link Motion*

This paper presents a novel robotic system designed for efficient minimally invasive eye surgery. The proposed prototype integrates a concentric tube mechanism(CTM) and a belt-driven remote center of motion(RCM) mechanism, aiming to maximize the internal reachable workspace while minimizing external robot movements. The integrated system provides several advantages, including preventing collisions between surgical tools and the lens, minimizing sclera stress, and having efficient robot motion inside and outside the eyeball. It provides sufficient link motions with roll and pitch angles of ±32° and ±85° respectively at the RCM point, allowing access to 89% of the retina. The experiment evaluates the system's performance, with the RCM point accuracy at 0.718mm, CTM position accuracy at 207 μm, and a repeatability error of 246 μm. To reduce hysteresis errors at the RCM point caused by the belt, a lever-based belt tensioner is used for initial calibration while an optical tracking system tracks each joint’s movement. Targeting experiments highlight that the wider workspace was achieved by the CTM+RCM system compared to the traditional RCM mechanism with a straight tool. The results showed the system's compactness, efficiency, and dexterity, confirming its feasibility and potential for the proposed eye surgery robot.