Type Synthesis of Parallel 2R1T Remote Center of Motion Mechanisms Based on Screw Theory

Abstract

Abstract. The remote center of motion (RCM) mechanism is an important part of a minimally invasive surgery (MIS) robot. As a practical type of RCM mechanisms, 2R1T RCM mechanisms are synthesized in this paper using a modified screw theory method. Differing from the conventional screw theory method, the modified method brings forward the assessment of different wrench systems, and proposes several general subchains to satisfy each geometrical condition of the wrench system, which can ensure the motion continuity to a great degree. First, the motion pattern and the twist system of 2R1T RCM mechanisms are presented. According to the reciprocal rules of screw theory, three corresponding wrench systems, along with the geometrical conditions for them, are enumerated. After assessing these wrench systems by the comparison of their geometrical conditions, the optimum wrench system is selected for synthesis, and then it is decomposed into sub-wrench-systems. To satisfy each condition of the subwrench-systems, several general subchains are proposed, and consequently some preferred general chains are constructed by the serial assembly of the corresponding subchains. These general chains are applied to the leg synthesis. Finally, practical examples of 2R1T RCM mechanisms are constructed by assembling the legs.

Structural Synthesis of 2R1T Type Mechanisms for Minimally Invasive Surgery Applications

“…The results are comparable with Li and Hervé's [5] results for classifying non-parasitic 1T2R manipulators, which are the kinematic inversion of the 2R1T case. Recently Huang et al [1] also worked on RCM mechanisms with 2R1T motion, where they have similar results for synthesizing the legs, but the manipulators they obtained are few in number. After the classification, proper mechanical structures are compared according to design criteria for MIS applications with RCM.…”

Kinematic analysis and optimum design of a novel 2PUR-2RPU parallel robot

“…In response to the applications, many type-synthesis methods of 2R1T PKMs were introduced, such as screw theory [11,12], Lie-groups [13,14], and conformal geometric algebra [15]. With the methods at hand, a variety of mechanisms were designed and investigated, such as 3-PRS [16], 3-CUP [17], 3-CRS/PU [18], 3-PUU [19], Tex3 [20], 2PRU-UPR [21], and 3-CRC [22], where P, R, S, C, U stand for prismatic, revolute, spherical, cylindrical, and universal joint, respectively.…”