Design and validation of a spatial two-limb 3R1T parallel manipulator with remote center-of-motion

Remote center-of-motion (RCM) manipulators play an important role in minimally invasive surgery (MIS), which reduces the risk of infection, with less pain and fast recovery. In this paper, a novel spatial two-limb parallel manipulator, with 3R1T motion capabilities, supplied with a RCM, is synthesized for applications in MIS. The proposed manipulator consists of two identical limbs with a URRH chain, in which fully decoupled parallel wrists are employed to actuate the universal joints. Moreover, a cable-driven mechanism is introduced to produce the translational and rotational motions of the end-effector about its central shaft. Because of this particular design, the synthesized RCM manipulator possesses a compact structure and is partially decoupled in kinematics, which eases the implementation and simplifies its control. In order to validate the feasibility of the proposed idea, a prototype of the synthesized RCM manipulator is developed and experiments are conducted. The results show that the four dof prototype exhibits acceptable 3R1T RCM characteristics and positioning accuracy, by virtue of the adopted fabrication procedures. Thus, the synthesized manipulator offers potential applications in MIS.