基于平面光栅的机床几何误差测量与辨识

Geometric error measurement and identification of machine tool based on gross grid encoder

几何误差是影响数控机床准静态精度的重要因素,针对几何误差测量、辨识问题,提出基于平面光栅的面—线机床空间几何误差辨识方法。依据多体系统理论和齐次坐标变换方法建立了三轴数控机床21项几何误差元素与3项误差向量之间的映射关系;规划了3个相互垂直的平面内的测量路径和辨识方案,通过单轴运动和两轴联动的形式可连续测量每个平面内的5条直线,进而依次确定垂直度、俯仰和偏摆误差、定位及直线度误差、滚转误差,减少了多次安装过程中安装误差累积对测量结果的影响;通过基于面—线法的21项几何误差测量和辨识实验,并与基于激光干涉仪测量辨识结果对比显示,平面光栅测量结果与激光干涉测量结果的空间误差向量最大偏差为2.4μm,平均偏差为0.77μm,验证了该方法对辨识机床精度是准确、有效的。

Geometric error plays an important role that affecting the quasi-static accuracy of CNC machine tools.Aiming at the geometric error measurement and identification,plane-line based on Gross Grid Encoder(GGE)identification method was proposed.Based on multi-body system theory and homogeneous coordinate transformation method,the functional relationship between 21 geometric error and 3 error vectors of three-axis CNC machine tools was established.Three measurement paths and identification schemes in mutually perpendicular planes were planned.Through the single-axis motion and the two-axis synchronous motion,five straight lines in each plane were continuously measured to determine each geometric error in sequence.The impact of the accumulation of installation errors could be effectively reduced on the results during multiple installations.With the experiment of 21 geometric errors measurement and identification,the result showed that the maximum deviation of spatial error vector between the measurement result of plane-line and the laser interferometer result was 2.4μm,and the average deviation was 0.77μm,thus the effectiveness of the proposed method for identifying geometric error of machine tools was verified.