A class of spatial remote center-of-motion mechanisms and its forward kinematics

摘要

Robot-assisted minimally invasive surgery (MIS) has shown tremendous advances over the traditional technique.A crucial challenge for developing a MIS robot is the kinematic design of the remote center-of-motion (RCM)mechanism. In this paper, a class of spatial RCM mechanism is analyzed. They are obtained by generating virtualparallelograms. The main process is to construct a line that passes through a fixed point under the mechanicalconstraint. The axis of the surgical tool is then constrained to parallel with that line. Hence, due to the geometricalfeature of the parallel lines, the axis of the surgical tool will always pass through a fixed point, i.e., the RCM point.Due to the specially designed structure, the fixed point does not need to be physically belonging to the mechanism.The geometrical analysis method is employed to obtain the closed-form solution of the forward kinematics of theproposed mechanisms. Due to the high load capacity of parallel mechanism, the robots based on the proposed RCMmechanisms have promising applications as an external positioner to be used in robotic single-port surgeries.