Study On Performance And Synthesis Of A Single Plane Symmetrical Three Translational Parallel Mechanism

The parallel mechanism has so many advantages,such as large stiffness,strong carrying capacity,little accumulation error and high control precision,that it has been gradually applied in aerospace,industrial robots and other fields.With more and more applications,more attention has been paid to the development of less freedom parallel mechanisms.And then,the theoretical study of less freedom of parallel mechanism is also becoming popular.In this paper,five new parallel mechanisms which like planar symmetric parallel mechanism 3-CPR are proposed and the main performances of 3-CPR are studied.The main contents are as follows:Based on screw theory in the principle of comprehensive and under a given mode of mechanism motion,the relationship between the branch screw system and mechanism has been considered.This determines the branch constraint screw system and motion screw system.Through the type synthesis principle,60 parallel mechanisms are obtained.Then eighteen basic configurations which have plane symmetries are given and five configurations are first proposed.Finally,the degrees of freedom parallel mechanism of 3-CPR has been solved and the degrees of freedom has been verified in SolidWorks and ADAMS.The positive and inverse kinematics equations of the 3-CPR parallel mechanism are solved and the verification is completed using MATLAB and ADAMS by trajectory planning.Based on the boundary limit search method,the workspace has been generated in MATLAB by determining constraints of the mechanism position.The solving process of Jacobi matrix is given and the Jacobi matrix is established in one case.Then through analyzing the constraint submatrix and motion submatrix,the singular points in the working space are find out.Finally the singular points are generated using MATLAB.According to the concept of stiffness matrix of parallel mechanism coordinate transformation based on the principle of conservation,the stiffness matrix model has been established.Then the paper considers four conditions and program in MATLAB for stiffness on the map in X,Y and Z axis,finally analyses the distribution map of stiffness,summarizes the regularity and verifies the result of analysis using ANSYS.