Development of a Laparoscopic Surgical Assistant Robot With an Optimal Degree-of-freedom for Compensation for the Roll of the Endoscopic Image

This paper proposes a novel surgical assistant robot composed of three active joints, two passive joints, and an additional active actuator. As a key feature of the proposed robot, image roll compensation is achieved by utilizing the additional active actuator. Some existing surgical assistant robots suffer from image roll issues due to insufficient degrees-of-freedom (DOFs). In contrast, others with redundant DOFs tend to have bulky distal active joints that interfere with the surgeon around the operating table. The proposed robot is designed with DOFs optimized for the remote center of motion, enabling a compact structure while still providing image roll compensation. The robot kinematics are derived using encoders mounted on the three active joints and the two passive joints. By rotating the additional actuator as needed, image roll is compensated, ensuring a constant roll angle in the endoscopic view during surgical assistance. A simulation environment is constructed to reproduce scenarios where image roll occurs, and the results verify that, with the compensation function, the endoscopic image maintains a constant inclination without roll motion while the endoscope is moving.