【作者】 刘洋；

【导师】 蔡引娣； 薛林；

【作者基本信息】 大连理工大学 ， 机械工程， 2024， 硕士

【摘要】 现代制造业对数控机床的精度要求越来越高,促使数控机床朝着高精度方向发展,但机床各项误差的存在会制约数控机床精度的提升,其中热误差是影响数控机床加工精度和精度稳健性的重要因素,因此对数控机床热误差进行实时补偿对于提升机床加工精度具有重要意义。由于数控机床热误差具有形成原因复杂、随温度变化和变化非线性的特点,造成现有热误差补偿模型存在预测精度低和稳健性差的问题。本文以三轴加工中心为研究对象,开展热误差建模与补偿的相关研究并进行实验验证。本文的主要研究内容如下:基于热力学定律分析了引起三轴加工中心热误差的主要热源;根据三轴加工中心的热变形机理,提出了机床主轴和各进给轴热误差测量实验方案。对主轴和进给轴在不同工况下的温度变化和热误差进行了实验测量。通过实验分析了主轴和各进给轴热误差随温度的变化规律,根据实验结果采用模糊聚类分析方法和灰色关联度分析方法分别筛选主轴和各进给轴的温度敏感点。基于传统BP神经网络建模方法和粒子群算法优化后的神经网络(PSO-BP)建模方法分别建立了主轴和进给轴的热误差预测模型,对比建模效果后发现,基于PSO-BP建模方法的误差补偿模型具有更高的误差预测精度和稳健性。为对三轴加工中心热误差进行实时补偿,基于华中数控系统建立了三轴加工中心与上位机热误差补偿系统的通讯,实现了两者间的信息交互;在数控系统的自定义PLC模块中编写了误差值实时插补程序;最后基于Labview编程软件将所有功能整合。热误差补偿方式为:在上位机的热误差补偿系统中实时计算出热误差预测值,之后将热误差预测值通过网口通讯写入机床数控系统,最后在数控系统的自定义PLC模块中实现补偿值的实时插补。在不同工况下对机床热误差进行实时补偿并将补偿结果与机床未补偿情况做对比,结果显示:对于主轴的热伸长,变工况下的平均热误差补偿效果达到70%,对于X轴的定位热误差,变工况下平均热误差补偿效果达到84%,经过热误差实时补偿后,三轴加工中心的精度得到了较大的提升。更多还原

【Abstract】 The modern manufacturing industry has increasingly high requirements for the accuracy of CNC machine tools,which promotes the development of CNC machine tools towards high precision.However,the existence of various errors in machine tools will restrict the improvement of CNC machine tool accuracy.Among them,thermal error is an important factor affecting the machining accuracy and precision robustness of CNC machine tools.Therefore,real-time compensation for thermal error of CNC machine tools is of great significance for improving machining accuracy.Due to the complex causes of thermal errors in CNC machine tools,as well as their non-linear nature with temperature changes,existing thermal error compensation models suffer from low prediction accuracy and poor robustness.This article takes three-axis machining centers as the research object,conducts relevant research on thermal error modeling and compensation,and conducts experimental verification.The main research content of this article is as follows:Based on thermodynamic laws,the main heat sources causing thermal errors in three-axis machining centers were analyzed;Based on the thermal deformation mechanism of the threeaxis machining center,an experimental plan for measuring the thermal error of the machine tool spindle and each feed axis is proposed.Experimental measurements were conducted on the temperature changes and thermal errors of the spindle and feed shaft under different operating conditions.The variation law of thermal error of the spindle and each feed axis with temperature was analyzed through experiments.Based on the experimental results,fuzzy clustering analysis method and grey correlation analysis method were used to screen the temperature sensitive points of the spindle and each feed axis.Based on the traditional BP neural network modeling method and the particle swarm optimization optimized neural network(PSO-BP)modeling method,thermal error prediction models for the spindle and feed axis were established.After comparing the modeling effects,it was found that the error compensation model based on PSOBP modeling method has higher error prediction accuracy and robustness.To achieve real-time compensation for thermal errors in three-axis machining centers,a communication between the three-axis machining center and the upper computer thermal error compensation system was established based on the Huazhong CNC system,achieving information exchange between the two;A real-time interpolation program for error values was written in the custom PLC module of the CNC system;Finally,integrate all functions based on Labview programming software.The thermal error compensation method is to calculate the predicted value of the thermal error in real-time in the thermal error compensation system of the upper computer,then write the predicted value of the thermal error into the CNC system of the machine tool through network communication,and finally achieve real-time interpolation of the compensation value in the custom PLC module of the CNC system.Real time compensation was performed on the thermal error of the machine tool under different working conditions,and the compensation results were compared with the uncompensated situation of the machine tool.The results showed that for the thermal elongation of the spindle,the average thermal error compensation effect under variable working conditions reached 70%.For the positioning thermal error of the X-axis,the average thermal error compensation effect under variable working conditions reached 84%.After real-time compensation of thermal error,the accuracy of the three-axis machining center was greatly improved.更多还原