Design of a flexure-based compliant grasper for the master arm of a surgical robot

A master arm of a tele-operated surgical robot serves as an input device to the system. A master arm typically has 6 Degrees of Freedom (DoF) input apart from grasping input used to control the grasping motion of the surgical tool located at the slave arm. The typical design of a master arm grasper makes use of either a gear driven or a crank-slider linkage to capture the grasping input from the surgeon. Such a mechanism has several moving components and needs joints with minimal clearance for reliable operation. A compliant mechanism that features a joint-less design offers superior performance and would serve as an ideal replacement for such a mechanism. This paper presents the design and analysis of a master arm grasper based on a partially compliant mechanism. An inherent advantage of the proposed mechanism for this application is the reduced number of components. Design details and the pseudo-rigid body analysis of the grasper are presented. A prototype of the grasper has been fabricated, and experimental verifications were carried out. The grasper was integrated into a custom-built master arm manipulator to demonstrate its utility in a surgical robot. Results show that the compliant grasper performs well for its intended purpose.