基于温度积分方法的大型数控机床光栅定位热误差建模及实时补偿

Modeling of Thermally Induced Grating Positioning Error of Large Machine Tools Based on Temperature Integral Method and Real-time Compensation

为了提高大型数控机床的光栅定位精度,提出了基于热特性分析的光栅定位热误差建模理论及补偿方法.阐述了光栅受热膨胀产生热伸长从而导致定位偏差的机理,并对光栅定位误差产生的影响及表现形式进行了说明.建立了光栅热伸长量和温升量的线性关系表达式.在光栅尺上均匀布置多个温度传感器,实时采集光栅尺多点温度,通过插值运算,拟合出光栅尺各点的温度值.由于在机床运动过程中,光栅尺各点的温升量不尽相同,采用对光栅尺各点温升量积分的方法,求出光栅各点热伸长量,建立了光栅定位热误差模型.利用自主研发的数控机床误差补偿系统,应用光栅定位热误差模型,对落地镗床TK6920进行光栅尺定位热误差补偿.结果显示:光栅定位热误差模型对运动过程中的光栅定位误差进行准确的预测,补偿后残差控制在15μm以内,定位精度提升90%以上,显著提高了光栅的定位精度.

To decrease the grating positioning error of large machine tools,a novel modeling theory based on thermal characteristic analysis with its compensation method were proposed.The case of the error was analyzed to be the thermal deformation of the grating scale,whose manifestations were discussed.By analyzing the thermal characteristic,the mathematical expression between the elongation of grating scale and the variation of temperature was established.Several temperature sensors were installed on the grating scale,with which the temperature of grating scale were recorded.The temperature of each point on the grating scale were calculated by interpolating between adjacent sensors.The thermally induced positioning error of the grating scale model was established by conducting the integral for the variations of position and temperature.By using the developed compensation system,the compensation for floor type borer TK6920 was implemented by applying the established model.The results show that the thermally induced positioning error of the grating scale has been decreased by 90% and the residual error is less than 1.5μm/m.The positioning accuracy of the grating scale is significant improved.