数控磨床几何误差辨识方法的研究与应用

给出机床关键几何误差和影响因子的定义,基于多体系统理论建立机床综合误差与几何误差的映射关系模型,通过计算和比较影响因子实现对关键几何误差项的识别,提出了机床关键几何误差的辨识方法。以磨齿机床为例,运用上述方法进行研究,最终识别出15项影响机床精度的关键几何误差。该方法可以有效地辨识出对机床综合空间误差有较大影响的几何误差因素。     

基于多体理论的极坐标数控铣齿机床几何误差建模

基于多体系统理论,以极坐标数控铣齿机床为研究对象,建立了机床整机空间几何误差模型.根据建立的几何误差模型,并利用辨识得到的误差数据,可以准确计算出机床的几何误差,为误差补偿提供了理论依据.     

机床关键几何误差辨识方法研究

在给出机床关键几何误差和影响因子定义的基础上,提出了识别机床关键几何误差的新方法。以一台精密卧式加工中心为例,利用多体系统理论建立了机床几何误差与综合误差的映射关系模型,通过计算和比较影响因子,最终识别出16项影响机床精度的关键几何误差。示例表明：该方法可以有效地识别出对机床综合空间误差影响较大的几何误差因素,从而为合理经济地进行精度设计和控制提供重要的理论依据。     

基于敏感度分析的机床关键性几何误差源识别方法

零部件几何误差耦合而成的机床空间误差是影响其加工精度的主要原因,如何确定各零部件几何误差对加工精度的影响程度从而经济合理地分配机床零部件的几何精度是目前机床设计所面临的一个难题。基于多体系统理论,在敏感度分析的基础上提出一种识别关键性几何误差源参数的新方法。以一台四轴精密卧式加工中心为例,基于多体系统理论构建加工中心的精度模型,并利用矩阵微分法建立四轴数控机床误差敏感度分析的数学模型,通过计算与分析误差敏感度系数,最终识别出影响机床加工精度的关键性几何误差。计算和试验分析表明,该方法可以有效地识别出对机床综合空间误差影响较大的主要零部件几何误差因素,从而为合理经济地提高机床的精度提供重要的理论依据。     

复合数控机床几何误差建模及灵敏度分析北大核心

为了提高复合数控机床的加工精度,研究了机床的几何误差建模及灵敏度分析。以CHD-25型9轴5联动车铣复合数控机床为对象,介绍基于多体系统运动学理论的机床几何误差建模方法,模型涉及37项几何,分别对37项几何误差进行了误差灵敏度分析。通过计算与分析误差灵敏度系数,最终识别出影响机床加工精度的关键性几何误差,为复合数控机床的设计提供有效的理论依据。     

数控蜗杆砂轮磨齿机几何误差检测与分析

分析数控蜗杆砂轮磨齿机结构,得出机床全部45项几何误差元素;使用球杆仪对机床平移轴及旋转轴进行误差检测,得到四组机床运动圆轨迹,对机床整体几何精度进行评估,分析得出平移轴为机床几何误差的主要来源,进一步得出影响平移轴精度的主要几何误差元素;最后基于机床几何误差特性,提出机床几何误差简化补偿策略,对快速提升机床几何精度有一定的参考意义。     

基于几何误差灵敏度的卧式数控镗床运动精度分析

提出了一种基于几何误差灵敏度的卧式数控镗床运动精度分析方法。针对典型卧式镗床进行几何误差溯源分析,确定影响机床X,Y,Z轴运动精度的21项几何误差,基于多体系统运动学理论,考虑机床各典型体间误差耦合作用机制,建立机床的空间误差模型。借助激光干涉仪对某大型卧式数控镗床进行几何误差检测试验,将检测结果输入九线法几何误差辨识模型,分离该机床的21项几何误差,并对各几何误差进行多项式拟合,据此分析该机床的空间误差场的分布特征,并针对各几何误差项进行灵敏度分析。结果表明:X,Y轴关键误差因素为位移误差,Z轴关键误差因素为直线度误差。通过对各关键因素进行精度补偿,实现该机床空间误差场分布的优化分析。对比分析表明,补偿后的空间误差场在各线性轴分布趋于均匀,最大误差从0.056 4 mm减小为0.027 8 mm,机床的空间运动精度得到明显提高。该分析方法可为此类型机床运动精度分析及空间误差补偿提供理论依据。     

复合数控机床几何误差建模及灵敏度分析

为了提高复合数控机床的加工精度,研究了机床的几何误差建模及灵敏度分析。以CHD-25型9轴5联动车铣复合数控机床为对象,介绍基于多体系统运动学理论的机床几何误差建模方法,模型涉及37项几何,分别对37项几何误差进行了误差灵敏度分析。通过计算与分析误差灵敏度系数,最终识别出影响机床加工精度的关键性几何误差,为复合数控机床的设计提供有效的理论依据。     

QMB125球笼沟道磨床几何误差建模与敏感度分析

机床的加工精度受诸多方面的误差因素的影响，而组成机床的误差主要包括热、力、几何、运动误差等，其中机床部件的几何误差对球笼沟道床的加工精度有着举足轻重的作用。以QMB125数控磨床为研究对象，基于多体系统理论，通过低序体阵列来描述磨床的拓扑结构，对磨床的27项几何误差源进行误差取样检测，建立起机床的运动学模型，进而计算出各个误差源的敏感度系数来找出影响程度较高的几何误差项，为合理经济的提高机床精度提供有效依据。     

基于模糊控制的数控机床几何误差补偿控制研究

旨在填补机床几何误差补偿控制方面的不足。考虑机床为多体系统,建立了相邻低序体不同运动形式下的几何误差数学模型,基于模糊控制理论提出了数控机床几何误差的模糊控制补偿方法,通过MATLAB12.0对其进行了仿真分析,并进行了实验验证。验证结果表明,有效减小了机床因运动位姿的改变导致的机床几何误差,实验值和仿真值有着极高的一致性。     

机械制造业数控机床几何误差自动控制

为了降低数控机床几何误差,提升加工精度,提出机械制造业数控机床几何误差自动控制方法。通过激光跟踪仪辨识机械制造业数控机床的几何误差,采用快速定位补偿算法与圆弧插补补偿算法相结合的方法补偿数控机床几何误差。利用计算机辅助制造软件生成刀位文件,依据刀位文件生成数控机床加工程序,通过补偿控制器生成数控机床各轴运动的控制指令,数控机床伺服系统接收控制指令后,自动控制数控机床各轴运动,以达到数控机床几何误差自动控制的目的。实验结果表明,采用该方法自动控制数控机床几何误差后,方向与角度的几何误差分别低于0.03 mm与0.1°,实际应用效果较好。     

任意拓扑结构机床运动轴误差传递链建模方法

在对任意结构机床进行空间几何误差建模时,必须要获得该机床运动轴误差传递链,从而基于微分变换实现任意结构机床误差建模。通过运用多体系统理论,构建任意结构机床拓扑结构与低序体阵列,利用机床拓扑结构与低序体序列提出了机床运动轴连接支承件相对运动矩阵与机床支承件连接矩阵概念,建立了获取运动轴误差传递链的数学模型。该数学模型将描述机床拓扑结构的低序体序列与机床支承件相对运动关系结合起来,给出了获取任意机床运动轴误差传递链的建模方法。并且将利用此建模方法获得的运动轴误差传递链运用于基于微分变换的机床空间几何误差建模中,实现了对任意结构机床空间几何误差建模。最后以五轴立式加工中心为算例,验证了该运动轴误差传递链建模方法的有效性。     

Position error reduction of tool center point in multi-tasking machine tools through compensating influence of geometric deviations identified by ball bar measurements

A method to compensate the influence of geometric deviations on tool center point (TCP) for a multi-tasking machine tool is proposed in this paper. Some methods to compensate geometric deviations of a rotary axis in five-axis machining centers have been proposed. However, due to the special topological structure of multi-tasking machine tools, the identification and compensation methods for geometric deviations are different from those of the five-axis machining centers, which have been seldom researched until now. In this paper, the main attention is paid to analyze the eccentricities of the trajectories measured by a ball bar under simultaneous three-axis motions and to reduce the influence of the identified geometric deviations on the position error of TCP by the compensation method. It is divided into two sequential subtasks. At first, the geometric deviations are identified by using the eccentricities of measured trajectories. A simple and practical measuring procedure is proposed to identify geometric deviations of rotary axes existing in a multi-tasking machine tool. For the second step, a method is proposed by modifying the original NC code according to the kinematic chain model of the targeted machine tool to compensate the influence of the existing geometric deviations on TCP. An experiment is conducted on a multi-tasking machine tool with a swivel tool spindle head in the horizontal position. The repeatability of the measured eccentricities based on three experimental results is also investigated to reduce the influence of measuring error on the identified results. As a result, the corresponding values of geometric deviations after the compensation are less than 2.2 arcseconds or 2.4 μm. It is concluded that the influence of geometric deviations on TCP is compensated effectively, and the position error of TCP is reduced significantly.     

Simultaneous geometric error identification of rotary axis and tool setting in an ultra-precision 5-axis machine tool using on-machine measurement

This paper presents a method to identify the position independent geometric errors of rotary axis and tool setting simultaneously using on-machine measurement. Reducing geometric errors of an ultra-precision five-axis machine tool is a key to improve machining accuracy. Five-axis machines are more complicated and less rigid than three axis machine tools, which leads to inevitable geometric errors of the rotary axis. Position deviation in the process of installing a tool on the rotary axis magnifies the machining error. Moreover, an ultra-precision machine tool, which is capable of machining part within sub-micrometer accuracy, is relatively more sensitive to the errors than a conventional machine tool. To improve machining performance, the error components must be identified and compensated. While previous approaches have only measured and identified the geometric errors on the rotary axis without considering errors induced in tool setting, this study identifies the geometric errors of the rotary axis and tool setting. The error components are calculated from a geometric error model. The model presents the error components in a function of tool position and angle of the rotary axis. An approach using on-machine measurement is proposed to measure the tool position in the range of 10 s nm. Simulation is conducted to check the sensitivity of the method to noise. The model is validated through experiments. Uncertainty analysis is also presented to validate the confidence of the error identification.     

Mapping and compensation of geometric errors of a machine tool at different constant ambient temperatures

Thermo-mechanical effects due to changes in the ambient temperature on the shop floor and internal heat sources caused by the manufacturing process significantly contribute to the geometric deviations of a machine tool and therefore, the geometric deviations of the manufactured workpiece. Minimizing these thermally induced geometric deviations is worthwhile since the requested tolerances of machined workpieces become continually smaller nowadays. To investigate the overall deformations of a machine tool structure due to variations in ambient temperature the geometric errors of a five-axis machine tool at different ambient temperatures by means of a portable climate simulation chamber are systematically mapped. While positioning and squareness errors of the linear axes are significantly influenced by the ambient temperature, straightness as well as rotational errors were less sensitive to temperature effects. For the investigated machine tool errors of the two rotational axes are negligible due to an active cooling of these axes. Through numerical error compensation of the linear axes, the geometric errors of the investigated machine tool can be reduced up to 80%. Finally, an outlook how a temperature-dependent compensation could be derived from previously measured compensation fields at discrete temperatures and afterwards applied on-the-fly during manufacturing is given.     

一种新的机床位置误差灵敏度分析方法

本文提出一种新的机床位置误差灵敏度分析方法。首先基于多体理论和齐次变换矩阵建立了五轴龙门机床位置误差模型。其次通过截断傅里叶技术来表征与位置有关的几何误差参数,每个误差参数对位置误差的灵敏度值可表示为其傅里叶幅值平方。然后归一化处理,关键的几何误差参数为第2,3,8,15和26项误差。通过与传统的Sobol法对比,仿真结果表明两种灵敏度分析方法辨识的关键几何误差相同且灵敏度值相近。此外,本文提出的灵敏度分析计算效率优于传统Sobol法。最后为了验证关键几何误差的有效性,提出了一个关于机床关键几何误差的补偿实验。实验结果表明,补偿关键几何误差后机床的加工精度提升了48%。因此,本文提出的机床位置误差灵敏度分析方法是可行的和有效的。     

Error analysis and compensation for the volumetric errors of a vertical machining centre using a hemispherical helix ball bar test

Machining accuracy is directly influenced by the quasi-static errors of a machine tool. Since machine errors have a direct effect upon both the surface finish and geometric shape of the finished workpiece, it is imperative to measure the machine errors and to compensate for them. A laser measurement system to identify geometric errors of a machine tool has disadvantages, such as a high cost, a long calibration time and the usage of a volumetric error synthesis model. In this study, we proposed a novel analysis of the geometric errors of a machine tool using a ball bar test without using a complicated error synthesis model. Also, a statistical analysis method was employed to derive geometric errors using a hemispherical helix ball bar test. According to the experimental result, we observed that geometric errors of the vertical machining centre were compensated by 88%.     

[误差建模及精度保证方法]几何误差贡献值影响下五轴数控机床运动轴误差灵敏度分析方法

针对现有误差元素灵敏度分析与后续误差补偿关联性不强的问题,建立运动轴几何误差贡献值模型并提出运动轴几何误差灵敏度分析方法,以获得本身几何误差对机床精度有很大影响的关键运动轴。结合指数积理论和坐标系微分运动理论建立基于误差敏感矩阵的运动轴几何误差贡献值模型,各运动轴几何误差贡献值相加得到机床综合误差模型;计算各运动轴误差权重分量和误差综合权重实现运动轴误差灵敏度分析,选择误差综合权重平均值最大的运动轴为机床关键运动轴,并对关键运动轴的误差补偿方法进行分析讨论。最后,在北京精雕集团的五轴加工中心上进行仿真实验验证。研究结果表明：所建立模型和所提出分析方法是有效的,且只补偿关键运动轴的几何误差贡献值能有效地提高五轴机床加工精度。     

基于激光干涉仪的数控机床几何误差检测与辨识

数控机床误差补偿技术通过设计和制造途径消除或减少数控机床可能的误差源,是提高数控机床加工精度的有效途径。其内容包括误差检测、误差建模和误差补偿。数控机床误差补偿效果好坏在很大程度上取决于误差综合数学模型建立的准确性。而误差元素模型是误差综合数学模型的基础。所以,误差补偿的首要任务是对数控机床误差元素进行准确检测。文中介绍了利用激光干涉仪检测和辨识数控机床几何误差的方法,建立了基于激光干涉仪的数控机床几何误差元素模型。     

Identification and measurement of geometric errors for a five-axis machine tool with a tilting head using a double ball-bar

Geometric errors are one of the primary potential sources of error in a five-axis machine tool. There are two types of geometric errors: position-dependent geometric errors and position-independent geometric errors. A method is proposed to identify and measure the position-independent geometric errors of a five-axis machine tool with a tilting head by means of simultaneous multi-axis controlled movements using a double-ball bar (DBB). Techniques for identifying position-independent geometric errors have been proposed by other researchers. However, most of these are based on the assumption that position-dependent geometric errors (such as linear displacement, straightness, and angular errors) are eliminated by compensation, once the position-independent geometric errors have been identified. The approach suggested in this paper takes into account the effect of position-dependent geometric errors. The position-dependent geometric errors are first defined. Path generation for circle tests with two or three simultaneous control movements is then carried out to measure the position-independent geometric errors. Finally, simulations and experiments are conducted to confirm the validity of the proposed method. The simulation results show that the proposed method is sufficient to accurately identify position-independent geometric errors. The experimental results indicate that the technique can be used to identify the position-independent errors of a five-axis machine tool with a tilting head.