A Class of 2 Degree of Freedom Planar Remote Center of Motion Mechanisms Based on Virtual Parallelograms

Abstract

Robotassisted minimally invasive surgery (MIS) has shown tremendous advances over the traditional technique. The remote centerofmotion (RCM) mechanism is one of the main components of a MIS robot. However, the widely used planar RCM mechanism, with double parallelogram structure, requires an active prismatic joint to drive the surgical tool move in–out of the patient’s body cavity, which restricts the dexterity and the backdrivability of the robot to some extent. To solve this problem, a two degreeoffreedom (DOF) planar RCM mechanism type synthesis method is proposed. The basic principle is to construct virtual double parallelogram structure at any instant during the mechanism movements. Different with the existing ones, both of the actuated joints of the obtained RCM mechanism are revolute joints. Combining the proposed mechanism with a revolute joint whose axis passes through the RCM point to drive the whole mechanism out of the plane, the spatial RCM mechanisms to manipulate surgical tool in threedimension (3D) space can be obtained; and the 3D RCM mechanism can be used for manipulating multiDOF instruments in a robotassisted MIS or can be used as an external positioner in robotic singleport surgeries.