Development of a 4-DoF Surgical Instrument With a Universal Joint and 6-Axis Force Sensation

Robot-assisted endoscopic surgery (RES) has overcome the shortcomings of traditional laparoscopic surgery in observation, comfort, operation, and flexibility. However, existing systems still lack force feedback which limits the quality and efficiency of RES. This paper develops a surgical instrument with 6-axis force sensation, mechanism of the instrument includes a universal joint wrist, a gripper, and the instrument shaft, which provide the surgical instrument with 4 degrees of freedom (DoFs) in roll, pitch, yaw and gripping. A 6-axis miniature force/torque sensor (FTS) is integrated into the gripper mechanism before the wrist. The coupling between the gripping force and external force is eliminated through a decoupling pulley in the force sensing unit. The transmission, drive, and interface unit complete the system assembly of the surgical instrument prototype. A dedicated static calibration platform is designed to apply standard weight loading for the force sensing unit. The static calibration matrix is obtained based on the least square method, and technical indicators such as the measurement ranges and resolutions are analyzed. Motion performance of the surgical instrument is tested through the wrist trajectory tracking experiment and the simplified leader/follower teleoperation to verify the feasibility of applying this surgical instrument prototype in the RES system.