Research On Motion Error And Calibration System Based On 2-DOF Parallel Machine Tools

With the development of industrial automation and intelligent manufacturing,people have higher and higher requirements for CNC machine tools,while parallel machine tools are more and more widely used in industry due to a series of advantages such as high stiffness,high bearing capacity,high precision,etc.Baseing on traditional Stewart parallel configuration,experts in various fields have obtained low degree of freedom parallel machine tools which can adapt to a certain working condition by improving the degree of freedom arrangement scheme,making the structure of machine tools greatly simplified,the accuracy further improved and the dynamic performance more excellent.The error and accuracy of parallel machine tool is one of the important factors that perplex the development of parallel machine tool.The high rigidity and high bearing capacity of parallel machine tool have not been reflected,and the machining accuracy of parallel machine tool with the same level of machining and assembly process is still poor.The nonlinear characteristics of parallel machine tool make the related research more difficult,and the related problems have not been properly solved.In this paper,the two degree of freedom parallel grinding machine tool is used as the principle machine,and the joint error mapping modeling and analysis,flexible error analysis,calibration algorithm modeling and analysis,calibration system design and experimental research of the machine tool are carried out respectively.Also the error problem of the parallel machine tool is further analyzed and studied.The main research contents of this paper include:(1)Analysis of the research status at home and abroad.This part summarizes the development trend and research status of parallel machine tools,and summarizes the general problems encountered in the development of parallel machine tools.This part also puts forward the source,purpose,significance and main research contents of this topic.(2)Kinematic modeling and error mapping analysis.This paper establishes the kinematic model of the machine tool,analyzes the working space of the machine tool,and obtains the inverse solution model with errors.In this part,the influence of the joint error of machine tool on the end error is analyzed in detail.The error sensitivity model is established by using the error mapping matrix,and the error distribution law of any point in the workspace is analyzed.(3)Flexible error modeling and analysis.Based on the Lagrangian method,the differential dynamic equation of the parallel bar of machine tool is established.The rigid flexible coupling error simulation model of machine tool is established by using ANSYS and Adams,and the influence of the flexible bar on the end pose is analyzed.(4)Calibration algorithm analysis and modeling.This paper analyzes the error sources and avoidance methods of the machine tool,establishes the mathematical model of the external calibration method based on genetic algorithm,and analyzes the reliability of the algorithm with an example;then,according to the actual situation of the machine tool,the calibration algorithm is improved,and the calibration model of the contact measurement method of the standard gauge block is established by using the standard gauge block and measuring needle.(5)Calibration system design and experimental research.According to the basic principle and mathematical model of the standard gauge block touch measurement method,the control scheme of the calibration system of the machine tool is established,the operation interface of the calibration system of the machine tool is designed,and the calculation example of the standard gauge block touch measurement method is used to verify the reliability of the calibration system.