An operating smooth man-machine collaboration method for cataract capsulorhexis using virtual fixture

摘要

Techniques in ophthalmic surgery require higher precision while cataract capsulorhexis calls for enough operating space. There is no specific methods focusing on improving the safety and flexibility of Capsulorhexis operation in recent study. Traditionally, Guidance Virtual Fixture based on parameter curve failed to be flexible, while Forbidden-Region Virtual Fixture using PD control failed to be steady enough. This paper proposes a teleoperation control scheme using integrated virtual fixture to assist in performing cataract capsulorhexis, improving operation performance in precision and flexibility. Specifically, based on the ring pipe model presented simulating the working path and permitted operating space, the control scheme is combined attractive error-reducing constraints with variety stiffness. It works by providing composite feedback force to the master-side via haptic device and letting the user aware if he on the right path and assist him in correcting operation mistakes. Experimental evaluation of the functionality of the control scheme was tested under four different configurations to verify the effectiveness of each algorithm and the combination. Significantly, the average error of operation reduces from 0.56 mm to 0.33 mm by 41% under the control scheme and reduces from 0.56 mm to 0.11 mm by 80% under the control scheme combined with motion scaling, demonstrating improvement in control by providing accurate assistance to the operator.