Adjustment of the Length Variation With Wire-driven Using the Stand Looper Tension Technique for Surgical Robot Applications

Motivation: The wire-driven method used in the field of surgical robots has the advantage of light weight. However, in the process of pull and push for the operation of forceps, the length of the wire is not match, causing malfunction. To solve this problem, the application of looper-tension technology would be suitable. This paper contributes to adjusting the length of the wire by inserting a stand between the wire-driven joints and adding a looper-tension between the stands to adjust the rotation radius of the roll. Methods: The method consisting of three rolls and loopers for connection between the stands minimizes errors by adjusting the length of the loop in a balanced state due to the rotation change of the roll during the pull and push of the robot arm. The angle and tension applied to the looper are 25 degrees and 8.6 MPa, respectively. Results: An output response can be obtained when the reference operating point fluctuates by +/- 50% of the input angle and tension, and if the reference operating point fluctuates by +/- 30% while the input angle and tension are fixed, the output response occurs oppositely. When a .15 kg object is loaded up/down with 1.5 newton using forceps, the change in length of pull and push coincides. Conclusion: The advantage is that the error of wire pull, and push operation can be reduced, and accurate operation can be expected. Since the proposed technology is applied between joints, the integration process is not complicated, and the weight is light.