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.