基于神经模糊控制理论的数控机床热误差建模

将基于神经模糊控制理论的建模方法--模糊神经网络建模法应用到数控机床热误差建模当中,讨论了热误差模糊神经网络的结构及建模原理;对大型数控龙门导轨磨床主轴箱系统进行建模试验,采用非接触式红外温度测量仪和千分表分别测量主轴箱系统温度值与主轴热误差,得到两组独立的试验数据,一组用来建立主轴箱系统热误差模糊神经网络预报模型,另一组用来对模型进行验证。试验结果表明,模糊神经网络模型预测精度高,泛化能力强;将模糊神经网络建模方法与径向基函数神经网络建模方法进行综合对比,分析结果表明,模糊神经网络建模方法具有更好的建模效率、建模鲁棒性及预测性能。     

An identification method for spindle rotation error of a diamond turning machine based on the wavelet transform

This paper presents an identification method for the spindle rotation error from the flatness error in the workpiece surface. The spindle rotation error is identified by the wavelet transform, Weierstrass function, and power spectral density (PSD). The flatness error comprises various errors of the machine tool, such as spindle rotation error, guideway error, motor error, and ball screw error, therefore, wavelet transform is used to process the measured result of the workpiece and the signal is decomposed into high-frequency and low-frequency signal. Weierstrass function is used to fit the spindle rotation error. According to the PSD analysis of the processed signal in the frequency domain, the spindle rotation error is identified from the measured flatness error, this method provides a basis for the identification of machine tool errors.     

大螺纹在线测试系统

一种大型螺纹自动检测的方法采用了新型螺纹测头,其中包括TESA电感传感器和测针,测针按螺纹牙型选择。测量方法基于螺纹综合测量原理,采用接触式测量方式。通过试验分析完成了螺纹作用中径数值的检测。通过频谱分析,对螺纹作用中径数值测试的动态误差进行了剔除并且得到了相关信息。检测方式的测量力远小于用常规的螺纹量规检测的测量力从而解决了接触应力引起薄壁管件测量误差的问题,试验表明这种新型螺纹测头能够提高测量精度,经过数据处理测头测量精度达到1 µm。     

车床主轴回转精度测量系统的研制

车床作为制造业的基础设备,零件加工精度受到诸多因素制约,其中主轴回转误差是主要的影响因素之一.该车床主轴回转精度计算机测量系统由光电编码器、电涡流传感器、微机、变送器、数据采集卡及辅助工具构成.在测量车床主轴回转精度的同时,可获得与主轴角位置对应的径向跳动、端面跳动和角度摆动误差,使用数理统计法误差分离技术编制LabV...     

机床主轴径向误差运动在线检测与信号处理

在机床加工工件时,实时测量机床主轴的径向运动误差。测量对象是在该机床上加工的圆柱形工件,而不是通常所使用的标准棒。采用误差分离技术将工件的形状误差从所测信号中分离出来,实现在线测量主轴的径向误差运动。并采用基于自适应阈值的小波包算法去除加工时存在的噪声。同时,从谐波抑制特性和总体频域特性两个方面分析了测量系统频域特征。     

NON-CONTACT MEASUREMENT OF SCULPTURED SURFACE OF ROTATION

A method for measuring the sculptured surface of rotation by using coordinate measuring machine (CMM) and rotary table is proposed. The measurement is realized during the continuous rotation of the workpiece mounted on the rotary table while the probe moves along the generatrix of the surface step by step. This method possesses lots of advantages such as simplicity of probe motion, high reliability and efficiency. Some key techniques including calibration of the effective radius of the probing system, determination of the position of axis of rotation, auto-centering of the workpiece, data processing algorithm, are discussed. Approaches for determining the coordinates on measured surface, establishing workpiece coordinate system and surface fitting are presented in detail. The method can be used with contact or non-contact probes. Some fragile ceramic and plaster parts are measured by using the system consisting of a CMM, rotary table, motorized head and non-contact laser triangulation probe. The measurin     

Self-calibration and compensation of setting errors for surface profile measurement of a microstructured roll workpiece

Microstructured roll workpieces have been widely used as functional components in the precision industries. Current researches on quality control have focused on surface profile measurement of microstructured roll workpieces, and types of measurement systems and measurement methods have been developed. However, low measurement efficiency and low measurement accuracy caused by setting errors are the common disadvantages for surface profile measurement of microstructured roll workpieces. In order to shorten the measurement time and enhance the measurement accuracy, a method for self-calibration and compensation of setting errors is proposed for surface profile measurement of microstructured roll workpieces. A measurement system is constructed for the measurement, in which a precision spindle is employed to rotate the roll workpiece and an air-bearing displacement sensor with a micro-stylus probe is employed to scan the microstructured surface of the roll workpiece. The resolution of the displacement sensor is 0.14 nm and that of the rotary encoder of the spindle was 0.15r~. Geometrical and mathematical models are established for analyzing the influences of the setting errors of the roll workpiece and the displacement sensor with respect to the axis of the spindle, including the eccentric error of the roll workpiece, the offset error of the sensor axis and the zero point error of the sensor output. Measurement experiments are carded out on a roll workpiece on which periodic microstructures are a period of 133 i~m along the circumferential direction. Experimental results demonstrate the feasibility of the self-compensation method. The proposed method can be used to detect and compensate the setting errors without using any additional accurate artifact.     

Radial deviation gauge

Preferred commercial methods of measuring the out-of-roundness of a workpiece are based upon radial methods. These incorporate a very accurate spindle either to carry the transducer or via a table to the workpiece. Consequently they are best operated in a controlled environment such as in an inspection room. However, there is a requirement for measuring the workpiece near to the machine. This paper describes one possibility both in theory and practice.     

Spindle with built-in acoustic emission sensor to realize contact detection

Recently, the demand for realizing micromachining through small-diameter tools has increased. When performing microfabrication using a numerically controlled machine tool, a machining error may be introduced if the relative position of the tool tip and workpiece surface deviates during tool change. Therefore, it is critical to determine this relative position in an actual machining condition at a specific spindle speed. We are currently developing an air bearing turbine spindle with a built-in acoustic emission sensor that can detect the contact of the tool tip with the workpiece surface in real time. The acoustic emission (AE) signal generated at the tool tip can be accurately detected by placing the AE sensor in direct contact with the tool end surface inside the main shaft floated by air. In this study, we investigated the possibility of contact detection between the tool tip and the workpiece surface at the submicrometer level through the proposed spindle. The results of the performed evaluation experiments indicated that by using the spindle with a built-in acoustic emission sensor, the contact of the small-diameter tool tip with the workpiece surface could be detected with damage to the workpiece at the submicrometer level on average.     

金刚石刀具刀尖圆弧波纹度的测量及评价

为实现金刚石刀具刀尖圆弧波纹度超精密测量,构建了基于原子力显微镜(AFM)和精密回转轴系的刀尖圆弧轮廓测量系统,研究了刀尖圆弧波纹度评价方法和控制测量系统引入误差的策略。提出了评价刀尖圆弧波纹度时截止波长的确定原则和方法,并介绍了刀尖圆弧波纹度测量原理及评价流程。讨论了精密回转轴系径向回转误差的测量和评定、刀具安装偏心和偏角误差的控制和原子力扫描系统Z向非线性误差的校准方法。最后,在构建的测量系统上测量了了金刚石刀具刀尖圆弧波纹度并对测量不确定度进行了分析。实验测量显示:所评价金刚石刀具的刀尖圆弧波纹度为0.106μm,测量不确定度为23.8nm,表明所构建的测量系统基本满足金刚石刀具刀尖圆弧波纹度纳米级测量及评价的需求,测量结果稳定可靠、精度高。     

基于磁悬浮轴承高速电主轴的法向磨削力检测方法

利用磁悬浮轴承高速电主轴作为检测器件解决高速磨削法向磨削力实时在线测量困难的问题。通过对磁悬浮轴承高速电主轴转子的动力学分析,得到法向磨削力与电主轴转子位移的两阶导数和转子受到的电磁力的关系。转子的位移数据可由磁悬浮轴承电主轴中的位移传感器的输出得到。为了精确求取电磁力,气隙磁通密度采用图解法求出,消除线性化引入的系统误差;气隙宽度由遍历搜索法标定,消除系统加工装配误差对电磁力测量带来的影响;引入修正系数对由漏磁、磁滞和边缘效应带来的测量误差进行补偿,修正系数由三层神经网络动态实时求出。通过静态和动态试验对电磁力和动态磨削力的检测结果进行验证,试验结果证明基于磁悬浮轴承高速电主轴的法向磨削力检测方法的有效性和准确性。     

A new method for characterizing axis of rotation radial error motion: Part 1. Two-dimensional radial error motion theory

In the current standards of spindle metrology, the fundamental component of radial probe measurement is considered radial throw (eccentricity) of the installed test artifact and the fundamental radial error motion is treated as non-existent. The goals of this paper are: (1) to make evident the fact that fundamental radial error motion can actually exist; (2) to present a new two-dimensional (2D) method to analyze spindle radial error motion measurement; (3) to discuss the limitations of current spindle motion analysis methods. In the 2D framework, the radial error motion is an application-independent geometric property and thus separate from the consequence of radial error motion in spindle applications. The 2D method can not only determine the axis of rotation radial error motion, but also the consequence of error motion in all classes of spindle applications, including a new class of spindle applications with two radial sensitive directions. In comparison, the radial error motion values specified in current standards give the consequence of radial error motion in two classes of spindle applications, but do not represent radial error motion itself. The new method is presented in two parts. Part 1 focuses on the theory and illustration of the 2D method. Part 2 presents the experimental results of a ball bearing spindle and an aerostatic bearing spindle.     

基于光电技术的圆度测量

圆度误差的测量是长度计量中一个重要项目,它的测量常转化成对位移的测量。本文采用光电技术对其进行测量,提出了一种基于理想光组轴向放大率理论来实现微位移的放大,并通过采用位置敏感探测器(PSD)将光斑像点的位移转化为电信号的输出,从而实现位移与电信号的转化;在测量圆度的同时,采用圆光栅来测量工件转角,实现整周的圆轮廓实时记录;对于圆度误差的评定采用最小二乘法。     

A new method for characterizing axis of rotation radial error motion: Part 2. Experimental results

In the current standards of spindle metrology, the fundamental component of radial probe measurement is considered radial throw (eccentricity) of the installed test artifact and the fundamental radial error motion is treated. The goals of this paper are: (1) to make evident the fact that fundamental radial error motion can actually exist; (2) to present a new two-dimensional (2D) method to analyze spindle radial error motion measurement; (3) to discuss the limitations of current spindle motion analysis methods. In the 2D framework, the radial error motion is an application-independent geometric property and thus separate from the consequence of radial error motion in spindle applications. The 2D method can not only determine the axis of rotation radial error motion, but also the consequence of error motion in all classes of spindle applications, including a new class of spindle applications with two radial sensitive directions. In comparison, the radial error motion values specified in current standards give the consequence of radial error motion in two classes of spindle applications, but do not represent radial error motion itself. The new method is presented in two parts. Part 1 focuses on the theory and illustration of the 2D method. Part 2 presents the experimental results of a ball bearing spindle and an aerostatic bearing spindle.     

主轴回转误差补偿机理和动力学模型研究

从补偿作用机理角度分析了主轴回转误差与加工系统之间的动态相互作用。在此基础上,着重从拉普拉斯频域和时间域分析了镗床主轴回转误差补偿切削系统的动力学特性。通过理论分析和仿真试验,得出有效补偿位移不仅受工件-主轴系统刚度和刀具刚度的影响,而且还受到切削参数,如切削重叠系数的影响。仿真和试验结果表明,SREC(主轴回转误差补偿)技术能有效地提高加工精度,在实际工程应用中是可行的。     

Measurement and analysis of typical motion error traces from a circular test

The circular test provides a rapid and efficient way of measuring the contouring accuracy of a machine tool. To get the actual point coordinate in the work plane, an improved measurement instrument - a new ball bar test system - is presented in this paper to identify both the radial error and the rotation angle error when the machine is manipulated to move in circular traces. Based on the measured circular error, a combination of Fourier components is chosen to represent the systematic form error that fluctuates in the radial direction. The typical motion errors represented by the corresponding Fourier components can thus be identified. The values for machine compensation can be calculated and adjusted until the desired results are achieved.     

Measurement and analysis of typical motion error traces from a circular test

The circular test provides a rapid and efficient way of measuring the contouring accuracy of a machine tool. To get the actual point coordinate in the work plane, an improved measurement instrument - a new ball bar test system - is presented in this paper to identify both the radial error and the rotation angle error when the machine is manipulated to move in circular traces. Based on the measured circular error, a combination of Fourier components is chosen to represent the systematic form error that fluctuates in the radial direction. The typical motion errors represented by the corresponding Fourier components can thus be identified. The values for machine compensation can be calculated and adjusted until the desired results are achieved.     

动态测量中测量力的确定

在动态测量中应使测量头与工件保持接触,因此,必须合理地确定测量力的大小.本文讨论了动态测量中影响测量力大小的因素,导出了动态测量力的计算公式.     

龙门数控机床主轴热误差及其改善措施

依据ISO和ASME标准建立龙门数控(Numerical control,NC)机床热误差测试条件,通过主轴恒转速和变转速热误差试验分析主轴箱温度场分布及其对主轴热误差的影响趋势。建立龙门机床误差元素模型,分析影响机床各坐标轴加工精度的主轴热误差分量。研究发现,主轴热误差和主轴箱温度存在单调对应关系,温度对主轴轴向的热伸长误差的影响要远大于主轴径向的热漂移误差,但温度变化相对各坐标变形存在热延迟和热惯性等特性。对主轴径向精度影响最大的热误差分量是由机床生热产生的同方向的偏移误差和与之垂直的偏转误差;对轴向精度影响最大的则是轴向的偏移误差。针对热误差特点和分布规律,提出结构优化、热平衡、误差补偿建模等3种减小热误差的措施,并对其各自优点进行了分析。     

Monitoring force in precision cylindrical grinding

Aerostatic spindles are used in precision grinding applications requiring high stiffness and very low error motions (5–25 nm). Forces generated during precision grinding are small and present challenges for accurate and reliable process monitoring. These challenges are met by incorporating non-contact displacement sensors into an aerostatic spindle that are calibrated to measure grinding forces from changes in the gap between the rotor and stator. Four experiments demonstrate the results of the force-sensing approach in detecting workpiece contact, process monitoring with small depths of cut, detecting workpiece defects, and evaluating abrasive wheel wear/loading. Results indicate that force measurements are capable of providing useful feedback in precision grinding with excellent contact sensitivity, resolution, and detection of events occurring within a single revolution of the grinding wheel.