High-efficiency Modeling And Sensitivity Research On Geometric Errors Of Reconfigurable CNC Machine Tools

Accuracy is an important performance index of machine tools,and geometric errors is one of the main error sources that affect the machining accuracy of machine tools.With the increasing requirements of the machinery manufacturing industry for processing efficiency and economic benefits,reconfigurable machine tools emerge as the times require.After the structure of the reconfigurable machine tool is reorganized,the geometric error model and the sensitive geometric errors of the machine tool will also change,which needs to be calculated and analyzed again.In addition,the traditional machine tool geometric error modeling results contain a large number of high order error terms,and the explicit derivation of error compensation and the analysis of sensitive errors require a huge amount of calculation.The complex process is not conducive to the efficient establishment of the geometric error model of the reconfigurable machine tool and the rapid identification of the sensitive error terms.Therefore,this paper studies the efficient modeling of geometric errors and the rapid identification of sensitive errors for reconfigurable machine tools,including the following contents:1.Based on the theory of multi-body system,an efficient modeling method of geometric errors of CNC machine tools is proposed without high order error terms.First,establish a comprehensive motion transformation matrix module of the CNC machine tool including the position and attitude transformation matrix,position and attitude error transformation matrix,motion transformation matrix and motion error transformation matrix of each moving part.The comprehensive motion transformation matrix of the error-free high order terms is established,and finally the geometric error model of the CNC machine tool without the high order error terms is established.The method can realize the rapid establishment of the geometric error model of the machine tool,greatly reduce the modeling workload,and improve the calculation efficiency.The proposed method can quickly respond to the geometric error model after the machine tool structure is restructured.2.The partial differential method and the Morris global sensitivity analysis method are used to analyze the sensitive geometric errors of the three-axis and five-axis reconfigurable CNC machine tools respectively.Through systematic analysis and calculation,the variation law of sensitive geometric errors of reconfigurable machine tool with machine tool structure is studied,and the structural correlation law of sensitive geometric errors is summarized.The sensitive geometric error terms in the x,y,and z coordinate directions can be directly identified according to the structural configuration information.The proposed method avoids the repeated error modeling and analysis process for identifying sensitive geometric errors of machine tools with different structures,and can improve the identification efficiency of sensitive geometric errors.3.The actual inverse kinematics of the machine tool based on the high-efficiency modeling method of error-free high order terms is studied,the error compensation code is deduced explicitly,and the compensation method is verified by simulation cutting and experiments.Based on the structural correlation law of sensitive geometric errors,the sensitive errors identification results are verified by numerical simulation.The analysis shows the accuracy of the proposed error-free high order geometric error modeling and the structural correlation law of sensitive geometric errors for reconfigurable machine tools are accurate.