The Kinematic Analysis And The Dexterity Research Of A Novel Parallel Mechanism With Sub Closed-chains

The parallel mechanism and the traditional series mechanism are complementary relationship in the structure and performance characteristics,which has the strong carrying capacity,high stiffness,high precision and other advantages.Since its publication,it has been widely used in manufacturing equipment,aerospace and medical fields.In recent years,with the diversified demand increasingly urgent of production and living,it has become more and more important to give full play to the advantages of parallel mechanisms and to expand their application fields.This puts higher requirements on the configuration design and performance analysis of parallel mechanisms.So,a novel 3-5RUU parallel mechanism with sub-closed chains is proposed in this paper.Its kinematics analysis,workspace analysis and dexterity research are also completed.Firstly,a five-revolve joints plane chain is used as the sub-closed structure in the mechanism.A novel 3-5RUU parallel mechanism with sub-closed chains is proposed.Its structure composition,working principle and motion process are described.And through the method of equivalent transformation and Kutzbach-Grübler formula,the freedom of the mechanism is analyzed.Secondly,the position inverse equation of the mechanism is established by using the D-H method,and the correctness of the equation is verified by ADAMS software simulation.Further,the velocity inverse equation of the mechanism is obtained by seeking a first-order guide on the position inverse equation about time,and the Jacobian matrix is directly obtained from the velocity inverse equation.Thirdly,based on the position inverse equation,the workspace of the mechanism is sloved by the extreme position search method,and its shape characteristics are analyzed.The number of points that make up the workspace represents the volume of the workspace.Through the change curve of the points,the influence of the change of the moving platform radius,the static platform radius and the upper connecting link length on workspace volume is analyzed.Finally,the linear velocity Globe Condition Index and angle velocity Globe Condition Index are chosen as the dexterity evaluation index of the mechanism.They are used to evaluate the line velocity dexterity and angle velocity dexterity of the mechanism respectively.Based on the Jacobian matrix and workspace of the mechanism,the values of the above two indexes of the 3-5RUU parallel mechanism are got.And through the change curve of the two indexs,the influence of the change of the moving platform radius,the static platform radius and the upper connecting link length on dexterity is analyzed.The Stewart platform is chosen as the object of comparison,the dexterity evaluation indexes value of the two mechanisms are compared,the result shows that the 3-5RUU parallel mechanism has better line velocity dexterity and angle velocity dexterity than the Stewart platform.