Lead-Screw-Driven Revolute Joint for Use in the Remote Center of Motion Mechanism

The revolute joint of the remote center of motion (RCM) mechanism should be operated within a limited rotation range to ensure patient safety. To achieve this with the conventional revolute joint, the rotation range was limited with the use of software-based methods. However, to eliminate electrical malfunction risks, the rotation range should be limited by the mechanism itself. In this study, we design, analyze, and test a new type of revolute joint for the RCM mechanism. In the proposed mechanism, a lead-screw-driven linear actuator was applied to implement the rotational motion. The stroke range of the linear actuator was physically limited. In turn, this limited the rotation range. In addition, the lead-screw-based mechanism can improve the angular resolution and torque efficiency compared with the conventional mechanism. We conducted comparative analyses and experiments between the proposed and conventional revolute joints. Based on these comparisons, it was confirmed that the resolution could be improved by at least 75 times, and the required motor torque was reduced by approximately 158 times compared with the conventional mechanism. The proposed revolute joint is the first successful trial based on a lead-screw driven linear actuator that ensures operation safety and high-torque efficiency compared with previous revolute joints.