Kinematic Design of a 2DoFs Remote Center of Motion Mechanism for Minimally Invasive Surgical Robot

Robot-assisted technology for minimally invasive surgery (MIS) can improve the quality of surgery and help surgeons carry out surgery more easily. The remote center of motion (RCM) mechanism with multiple degrees of freedom (DoFs) is one of the key parts of the MIS robot. A linear motion unit is usually used to realize the translation of the surgical tool along its axis in existing RCM mechanisms, which occupies a large space above the patient’s body and is prone to interference. Based on the double parallelogram mechanism, an RCM mechanism is proposed, which can realize pitch and translation motion of the surgical tool. The geometrical modeling is introduced first to prove that there is a remote center of the mechanism during its movement. Then, the inverse kinematics is analyzed on the basis of geometrical modeling of the mechanism. Furthermore, the singularity, Jacobian matrix and the kinematic performance of the mechanism are analyzed, and the workspace is verified with the kinematics equation. Finally, a prototype based on the proposed RCM mechanism was built to test its function. The results indicate that the remote center motion can be realized by this mechanism, and it can be used to develop an MIS manipulator.