Asymmetric Rolling Contact Joint for Enhanced Payload Capabilities

It is challenging for a surgical joint to tolerate a sufficient payload when downsizing its diameter. The tradeoff between payload and diameter is even more evident when designing robots with strict size constraints, such as in flexible endoscopic surgery applications. To address this issue, we propose a novel asymmetric rolling contact (ARC) joint that has two different rolling radii with a wire hole slit that is actuated by a tendon-driven mechanism. The ARC joint is designed to tolerate a high payload in the dominant direction, such as when lifting tissue or pulling a suture thread. We analyzed the effects of various design variables on the payload capability of the ARC joint. The results of the payload experiment suggest that the designed ARC joint has a maximum payload of 2.6 N with a 3.4 mm diameter, which enhances the payload by 71.9% compared to the conventional symmetric rolling joint. We confirmed that the endoscopic surgical task may be feasibly conducted using the proposed joint for two major tasks: endoscopic submucosal dissection and surgical suturing.