数控机床切削力误差建模及三维热变形临界点分析与应用
发布时间：2018-12-07 18:17
【摘要】：建立精确的数控机床误差模型是对机床误差修正的前提和基础。数控机床在加工过程中产生的几何误差与所承受的切削力有关,而大部分已有的数控机床几何误差建模方法没有考虑切削力的影响。数控机床光栅测量系统在传统的固定方式下,机床床身的热变形会通过光栅固定螺钉传递到光栅测量系统上,对光栅测量系统零位误差和示值误差产生附加影响,很难通过误差建模补偿理论进行精确补偿。 为了提高数控机床几何误差建模精度和补偿效果,本文通过测力环等仪器模拟施加和测量机床主切削力,采用激光干涉仪同步测量机床俯仰角和偏摆角误差,应用粒子群优化算法(PSO)优化支持向量机(SVM)的相应参数,利用实际测量数据进行训练,建立了基于PSO-SVM的力-几何误差预测模型。 本文根据形体热变形理论,提出了一种基于热变形临界点的数控机床光栅测量系统新的固定方式。定义了数控机床三维热变形临界点,利用有限元仿真分析对三轴数控机床仿真模型进行分析,确定了机床不同方向床身的热变形临界点,作为该方向上的光栅测量系统的固定点,使床身热变形无法传递至光栅上。光栅两端采用浮动支撑的方式使其只能在测量方向自由变形,这样就减小甚至消除数控机床床身的热变形对光栅测量系统产生的附加影响。最后根据光栅测量系统本身热变形理论和上述光栅固定方法,建立了光栅测量系统零位误差和示值误差精确预测模型,用于后续的机床热误差综合补偿。为了提高数控机床各类误差的综合补偿效果,本文建立了数控机床综合误差数学模型,为提高数控机床的加工精度提供了很好的理论基础。 通过实际试验验证,所建立的PSO-SVM误差预测模型输出的偏摆角误差预测值与实际测量数据的最大差值仅为0.6μrad,俯仰角误差预测值与实际测量数据的最大差值仅为0.21grad,远远小于利用BP神经网络以及常规方法优化的SVM所建立的力-几何误差预测模型的建模误差,因此所建立的误差预测模型可以用于后续数控机床几何误差的高精度实时补偿。
[Abstract]:Accurate error model of NC machine tool is the premise and foundation of error correction. The geometric error produced by NC machine tool in machining process is related to the cutting force, but most of the existing modeling methods of NC machine tool geometric error do not consider the influence of cutting force. In the traditional fixed mode, the hot deformation of the machine bed will be transferred to the grating measuring system through the grating fixed screw, which has additional influence on the zero position error and the indication error of the grating measuring system. It is difficult to accurately compensate by error modeling compensation theory. In order to improve the modeling accuracy and compensation effect of NC machine tool geometric error, this paper simulates and measures the main cutting force of the machine tool by means of force measuring loop, and uses laser interferometer to measure the error of pitch angle and deflection angle of machine tool synchronously. The particle swarm optimization algorithm (PSO) is applied to optimize the parameters of support vector machine (SVM). The force-geometry error prediction model based on PSO-SVM is established by training the actual measurement data. Based on the theory of body thermal deformation, a new fixed method of grating measuring system for CNC machine tool based on critical point of thermal deformation is proposed. The critical point of 3D thermal deformation of NC machine tool is defined. The simulation model of 3-axis NC machine tool is analyzed by finite element simulation analysis, and the critical point of hot deformation of machine tool in different directions is determined. As the fixed point of the grating measuring system in this direction, the hot deformation of the bed can not be transferred to the grating. The two ends of the grating can only deform freely in the measuring direction by means of floating support, which reduces or even eliminates the additional influence of the hot deformation of the bed of the NC machine tool on the grating measurement system. Finally, according to the thermal deformation theory of the grating measurement system and the grating fixing method mentioned above, an accurate prediction model of the zero error and the indication error of the grating measurement system is established, which can be used to compensate the thermal error of the subsequent machine tool. In order to improve the comprehensive compensation effect of various kinds of errors of NC machine tools, the mathematical model of synthetic errors of NC machine tools is established in this paper, which provides a good theoretical basis for improving the machining accuracy of NC machine tools. Experimental results show that the maximum difference between the predicted value of deflection angle error of the established PSO-SVM error prediction model and the actual measurement data is only 0.6 渭 rad, pitch angle error prediction value and the maximum difference value of the actual measurement data is only 0.21grad. It is much smaller than the modeling error of the force-geometry error prediction model established by the BP neural network and the SVM optimized by the conventional method, so the established error prediction model can be used to compensate the geometric error of the NC machine tool with high precision and real time.
【学位授予单位】：安徽理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG659
[Abstract]:Accurate error model of NC machine tool is the premise and foundation of error correction. The geometric error produced by NC machine tool in machining process is related to the cutting force, but most of the existing modeling methods of NC machine tool geometric error do not consider the influence of cutting force. In the traditional fixed mode, the hot deformation of the machine bed will be transferred to the grating measuring system through the grating fixed screw, which has additional influence on the zero position error and the indication error of the grating measuring system. It is difficult to accurately compensate by error modeling compensation theory. In order to improve the modeling accuracy and compensation effect of NC machine tool geometric error, this paper simulates and measures the main cutting force of the machine tool by means of force measuring loop, and uses laser interferometer to measure the error of pitch angle and deflection angle of machine tool synchronously. The particle swarm optimization algorithm (PSO) is applied to optimize the parameters of support vector machine (SVM). The force-geometry error prediction model based on PSO-SVM is established by training the actual measurement data. Based on the theory of body thermal deformation, a new fixed method of grating measuring system for CNC machine tool based on critical point of thermal deformation is proposed. The critical point of 3D thermal deformation of NC machine tool is defined. The simulation model of 3-axis NC machine tool is analyzed by finite element simulation analysis, and the critical point of hot deformation of machine tool in different directions is determined. As the fixed point of the grating measuring system in this direction, the hot deformation of the bed can not be transferred to the grating. The two ends of the grating can only deform freely in the measuring direction by means of floating support, which reduces or even eliminates the additional influence of the hot deformation of the bed of the NC machine tool on the grating measurement system. Finally, according to the thermal deformation theory of the grating measurement system and the grating fixing method mentioned above, an accurate prediction model of the zero error and the indication error of the grating measurement system is established, which can be used to compensate the thermal error of the subsequent machine tool. In order to improve the comprehensive compensation effect of various kinds of errors of NC machine tools, the mathematical model of synthetic errors of NC machine tools is established in this paper, which provides a good theoretical basis for improving the machining accuracy of NC machine tools. Experimental results show that the maximum difference between the predicted value of deflection angle error of the established PSO-SVM error prediction model and the actual measurement data is only 0.6 渭 rad, pitch angle error prediction value and the maximum difference value of the actual measurement data is only 0.21grad. It is much smaller than the modeling error of the force-geometry error prediction model established by the BP neural network and the SVM optimized by the conventional method, so the established error prediction model can be used to compensate the geometric error of the NC machine tool with high precision and real time.
【学位授予单位】：安徽理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG659
【参考文献】
相关期刊论文 前10条
1 傅建中;姚鑫骅;贺永;沈洪W，
本文编号：2367622
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