Study On Error Analysis And Accuracy Synthesis Of Three Parallel Universal Head CNC Machine Tool

Accuracy is on of the most important indicators to measure the working performance of the parallel mechanism.With the development of parallel mechanism in the direction of high speed and lightweight,more and more rigid materials are replaced by lightweight materials,which has the advantages of light weight,high speed and high load-carrying capacity.However,the existence of elastic deformation in the mechanism rods,which results elastic vibration errors,and the errors influence the movement accuracy in the mechanism itself that are caused by other factors.Therefore,it is of great theoretical and practical value to analyze,compensate and accuracy synthesis study for the mechanism errors.In this paper,the pose,structural and elastic vibration error existing in the three parallel universal head structures are analyzed and compensated,and the mechanism is further studied from the aspect of precision synthesis.The specific research work are as follows:Firstly,the position and workspace of three parallel mechanism are analyzed.Based on the establishment of the mechanism coordinate system,the mathematical models of forward and inverse position solution are established through the geometric relationship among the components that solved by Matlab software.For the workspace of the mechanism,the working range of the end actuator of the mechanism is obtained by simulation analysis,which provides a reference for the error analysis and compensation of the mechanism.Then,the mathematical model of the three parallel mechanism is established.On the basis of the position analysis,the rigid system model of the mechanism is established,and the elastic system model of the mechanism is established by the theory of elastic dynamics.Finally,the hybrid position error model of the mechanism is obtained by synthesizing the two mathematical models.Secondly,the error of three parallel mechanism is analyzed and compensated.The error of posture parameters,structure parameters,input angle of active arm and elastic vibration are analyzed simulating by Matlab,ANSYS and ADAMS software.For the error compensation,the active arm input angle error and the elastic vibration error are compensated by the trajectory planning method,and the error compensation of the input angle of the active arm is verified by experiments.Finally,the accuracy synthesis of three parallel mechanisms is studied.By combining the orthogonal design method with the impact factor weighting method,and based on the principle of the original error equivalent action,the accuracy synthesis model of the mechanism is obtained,and the tolerance values corresponding to the structural parameters of the mechanism are calculated.It provides the theory basis for the prototypes's manufacture and installation.