Analysis of tendon tension and hysteresis by tendon twisting and development of anti-twist tendon mechanism of robotic surgical instruments.

BACKGROUND: Control of the joints of robotic surgical instruments is difficult owing to hysteresis, and tendon twisting due to axial rotation of surgical tools also causes hysteresis. Therefore, a new mechanism is needed to prevent tendon twisting. METHODS: Tendon tension and hysteresis change were analysed by observing the movement of the joint depending on whether the tendons twisted for the same input signal. An anti-twist tendon mechanism to prevent twisting was developed. A 3-mm needle driver applied with the proposed mechanism was manufactured. RESULTS: The anti-twist mechanism makes no tension change because of twisting or friction between the tendon and the system, that is, the operating performance was the same regardless of rotation. CONCLUSION: The proposed mechanism has been verified and can be applied to small surgical instruments 3 mm in size. These findings can be applied in the development of instruments for precise surgeries such as microsurgery.

A novel encountered-type master device with precise manipulation for robot-assisted microsurgery.

BACKGROUND: The unconstrained master devices have emerged as attractive alternatives to the existing linkage-based counterparts. However, the conventional unconstrained master device's manipulation methods have several disadvantages in efficiency and precision. METHODS: We propose an encountered-type master device based on an electromagnetic tracking solution with a prismatic joint at the tip, capable of continuous spatial manipulation with the tip supported on the surface. We performed path-following task and pointing tasks to analyze the performance of the master device. RESULTS: The most convenient, efficient, accurate positioning and precise pointing were possible with a closed loop support condition. Moreover, the tasks under this condition were also completed with higher accuracy, and precision when applying lower motion scale factors. CONCLUSIONS: The proposed master device allowed precise and accurate manipulation for microsurgical tasks. Compared with the conventional unconstrained master devices, the proposed master device provides the ability to perform precise work with a clutching-free motion.

A novel microsurgery robot mechanism with mechanical motion scalability for intraocular and reconstructive surgery.

BACKGROUND: Intraocular surgery and reconstructive surgery are challenging microsurgery procedures that require two types of motion: precise motion and larger motion. To effectively perform the requisite motion using a robot, it is necessary to develop a manipulator that can adjust the scale of motion between precise motion and less precise, yet larger motion. AIMS: In this paper, we propose a novel microsurgery robot using the dual delta structure (DDS) to mechanically scale the motion to seamlessly adjust between precise and larger motion. MATERIALS & METHODS: The DDS forms a lever mechanism that enables the motion scaling at the end-effector using two delta platforms. Seamless scale adjustment enables the robot to effectively perform various surgical moves. RESULTS: A prototype robot system was developed to validate the effectiveness of the DDS. The experiment results in various scale settings validated the scaling mechanism of the DDS. CONCLUSION: Through a graphical simulation and measurement experiment, the robot's precision level and attainable workspace has been confirmed adequate for intraocular and reconstructive surgery.

A single port surgical robot system with novel elbow joint mechanism for high force transmission.

BACKGROUND: Despite its evident clinical benefits, single-incision laparoscopic surgery (SILS) imposes inherent limitations of collision between external arms and inadequate triangulation because multiple instruments are inserted through a single port at the same time. METHODS: A robot platform appropriate for SILS was developed wherein an elbowed instrument can be equipped to easily create surgical triangulation without the interference of robot arms. A novel joint mechanism for a surgical instrument actuated by a rigid link was designed for high torque transmission capability. RESULTS: The feasibility and effectiveness of the robot was checked through three kinds of preliminary tests: payload, block transfer, and ex vivo test. Measurements showed that the proposed robot has a payload capability >15 N with 7 mm diameter. CONCLUSIONS: The proposed robot is effective and appropriate for SILS, overcoming inadequate triangulation and improving workspace and traction force capability.