基于EFAST的三轴立式加工中心几何误差敏感性分析

EFAST Based Geometric Error Sensitivity Analysis for Three-axis Vertical Machining Center

为了正确识别和判定机床关键几何误差元素对机床精度设计的影响,提出一种基于指数积(Product of exponential,POE)旋量理论和拓展傅里叶幅度检验(Extended Fourier amplitude sensitivity test,EFAST)的机床关键几何误差元素识别方法。首先,基于POE旋量理论建立机床几何误差模型,得到机床几何误差元素与机床空间误差之间的关联函数;其次,采用EFAST全局敏感性分析方法分析和量化误差敏感性,识别关键几何误差元素和强耦合几何误差元素;最后,在具有开放式数控系统Carver800T型三轴立式加工中心上进行基于全局敏感性分析的误差补偿试验,在制定补偿策略时,利用建立的方差和敏感度系数之间的定量关系来补偿机床几何误差的随机特性。结果表明,误差补偿后机床精度得到明显提高,沿X轴、Y轴和Z轴方向的平均补偿率分别达到60%、66%和74%,验证了本文方法的可行性、准确性和有效性。

In order to correctly identify and determine the influence of geometric error elements on the accuracy design of machine tool,taking Beijing Jingdiao Carver800T three-axis vertical machining center as the research object,a method for identifying key geometric error elements of machine tool based on product of exponential(POE)screw theory and extended Fourier amplitude sensitivity test(EFAST)method was proposed.For the three-axis vertical machining center,firstly,the geometric error model of machine tool was built on the basis of POE screw theory,and the correlation function between the geometric error elements of machine tool and the volumetric error of machine tool was obtained.Secondly,EFAST global sensitivity analysis method was used to analyze and quantify error sensitivity,and the key geometric error elements and strong coupling geometric error elements were identified.Finally,the error compensation experiment based on global sensitivity analysis was carried out on the Beijing Jingdiao Carver800T three-axis vertical machining center with open CNC system.The stochastic characteristics of the geometric errors of machine tools were compensated by using established quantitative relationship between stand variances and sensitivity coefficients when formulating the compensation strategy.The results showed that the precision of machine tool with compensation was improved significantly,and the average compensation rates along the X-axis,Y-axis and Z-axis directions were 60%,66%and 74%,respectively,which validated the feasibility,accuracy,and effectiveness of the proposed method.The research had practical guiding significance for further improving the effect and efficiency of error compensation of CNC machine tool,and can be further applied to the design and manufacturing stage of CNC machine tool.