Study On Design And Performance Of A Novel 3-PRS-XY Series-parallel Machine Tool

The parallel mechanism is more and more widely used in the fields of industrial production,medical equipment,aviation,flight simulation and so on.Compared with the series mechanism,the parallel mechanism has many advantages,such as high stiffness,high response speed and small accumulated error,but it also has the disadvantage of small working space.Therefore,the series-parallel mechanism combined with the series mechanism can make up the defect of the parallel mechanism,so its research and application is more valuable.In the dissertation,the 3-PRS-XY series-parallel machine tool with adjustable workspace is designed based on the analysis of the traditional 3-RPS parallel mechanism.The mechanism model is established,and the prototype of the machine tool is built.The kinematics,dynamics,workspace,error and kinematics calibration,performance index are analyzed.The main research contents are as follows:(1)The forward and reverse kinematics mathematical models of the 3-PRS-XY series-parallel machine tool are established.In order to solve the problem of the forward kinematics of parallel mechanism,the kinematics of the mechanism is solved and visually analyzed based on the geometric analysis method.The moving platform end pose obtained by forward solution is in agreement with the initial attitude,and the kinematical mathematical model of the 3-PRS-XY series-parallel machine tool is accordingly verified.(2)The dynamic mathematical model of the 3-PRS-XY series-parallel machine tool is established using Lagrange method,and the dynamic equation of 3-PRS-XY series-parallel machine tool is derived.The kinematics and dynamics of 3-PRS-XY parallel machine tool are analyzed theoretically and simulated.The variation of driving force of the drive block is obtained,and the variation of displacement,attitude,velocity and acceleration of the drive slider and end effector on the moving platform is obtained.The influence of structural parameters on kinematics and dynamics of 3-PRS-XY series-parallel machine tool is discussed,and the variation of kinematics and dynamics of 3-PRS-XY parallel machine tool with the change of mechanism parameters is obtained.The correctness of the kinematics and dynamics model is verified by comparing the results obtained through theoretical analysis and simulation.(3)Based on inverse kinematics analysis,the workspace of the 3-PRS-XY seriesparallel machine tool is determined using searching algorithm.The influence of the structure parameters such as the fixed platform radius,the moving platform radius and the connecting rod length on the workspace of the 3-PRS-XY series-parallel machine tool is discussed.The workspace nephogram of 3-PRS-XY series-parallel machine tool with different parameters and the projection on XOY plane,YOZ plane and XOZ plane are obtained.The corresponding workspace volume of machine tool is solved,and the relation between structural parameters and the workspace of machine tool is obtained.(4)The error model of the 3-PRS-XY series-parallel machine tool is established based on the kinematics analysis,and the error of the 3-PRS-XY series-parallel machine tool is solved using Monte Carlo method.The error numerical characteristics,error distribution and limit error of 3-PRS-XY series-parallel machine tools are obtained.The influence on the error of the mechanism and the limit error in the workspace is discussed under different error sources and mechanism configurations.The error distribution of the 3-PRS-XY series-parallel machine tool and the variation of the error limits in the workspace are obtained under different error sources and mechanism configurations.(5)According to the spatial model and kinematical analysis of mechanism,the velocity Jacobian matrix,Hessian matrix,force Jacobian matrix and stiffness matrix are deduced.The kinematics dexterity indices,statics dexterity indices,kinematics global performance indices and statics global performance indices and stiffness global performance indices are presented,and the performance index is obtained.The relation between the performance index and structural parameters of the 3-PRS-XY seriesparallel machine tool is obtained.(6)This dissertation presents the design of the key components and the hardware of the 3-PRS-XY series-parallel machine tool,and builds the prototype platform of the 3-PRS-XY series-parallel machine tool.The synthetic motion test and path planning experiment are carried out,and it verifies the correctness of the theoretical analysis.