Kinematic Analysis And Optimization Design Of A 2-PURR-PUR Surgical Robot

Minimally invasive surgery(MIS)is a rapidly developing robotic technology.With the assistance of MIS robots,it dramatically enhances safety and reduces the patient's pain.The structure of the MIS robot will directly affect the flexibility,universality and accuracy of the manipulator.In this paper,a novel 2-PURR-PUR parallel manipulator(PM)is presented.The main contents cover the following aspects:A simple model of the 2-PURR-PUR PM is established.A fixed coordinate system,a moving coordinate system and relevant parameters are determined.Based on the screw theory,the degrees-of-freedom(DOF)of the 2-PURR-PUR PM is calculated,which shows that the mechanism have two rotational and one translational DOFs.The inverse kinematic analysis of the 2-PURR-PUR PM is carried out by using the closed-loop vector method.Differentiating the inverse kinematics equation yields the velocity equations and Jacobian matrix.Based on the method of calculating the determinant of Jacobi matrix,it is revealed that this PM only has inverse singularities but no forward or combined singularities.Considering the limitation of the length of the rod,the maximun rotation angle,mutual interference and the singularity limitations,the reachable workspace is obtained by numerical search method using MATLAB.Based on the screw theory,the motion/force transmission index LTI and the constraint index TCI are discussed.A Global Transmission Workspace(GTW)is defined as the optimization objectives.The proposed LTI,TCI and GTW are coordinate-free and have clear physical interpretation.Finally,the optimization results provide the foundation in the design of prototype.The research of this paper provides the theoretical basis for medical surgery robot.