数控车床切削力谱的编制及其在功能部件可靠性试验中的应用

发布时间：2018-03-03 22:15

本文选题：数控车床载荷谱　切入点：多小波降噪　出处：《吉林大学》2017年博士论文　论文类型：学位论文

【摘要】：产品的固有可靠性首先是由设计决定的,对数控机床整机及关键功能部件进行可靠性设计是提高机床可靠性水平的主要途径之一,而数控机床载荷谱是可靠性设计的客观依据;数控机床关键功能部件可靠性试验是获取产品故障数据、进行故障分析和建立可靠性模型的主要技术手段,数控机床载荷谱是开展模拟实际工况的功能部件可靠性台架试验的前提条件。因此,研究科学、合理的数控机床载荷谱的编制方法,并编制载荷谱,具有重要的理论意义和工程应用价值。近十多年来,随着直驱技术、伺服技术和数字控制技术的发展和广泛应用,现代数控机床在结构、功能、性能指标、加工范围等方面发生了巨大变化,依据经验公式编制的静态切削力载荷谱不能准确反映真实工况,已经不再适用于数控机床可靠性设计与功能部件可靠性试验的发展需求;另外,编制反映动态切削载荷特征的数控机床载荷谱需要获取大量的机床工艺载荷数据,在此基础上,确定典型工况并进行长时间的实际切削试验测取动态载荷,该项研究工作耗时、费力,使很多研究者望而却步。本文依托吉林大学机械工业数控装备可靠性技术重点实验室,结合国家科技重大专项课题,系统的研究了数控车床载荷谱的编制方法和流程,主要包括:典型测试工况的选择、载荷数据的测取、载荷信号的处理、样本长度的确定、载荷谱的外推、切削力谱的编制等内容,并利用编制的载荷谱对机床的数控刀架进行了可靠性台架试验。论文主要研究内容如下:(1)为确保载荷谱数据来源的真实性和有效性,本文在确定机床典型用户的基础上,研究制定了机床用户现场工艺数据采集记录表和机床运行记录表,并对抽样的数控车床进行了现场切削工艺数据和机床运行数据的采集;根据数控车床加工工况及工艺的特点,制定了车床切削力实测典型测试工况及工艺的选择原则,提出了基于切削参数区间的典型测试工艺参数的确定方法;搭建了数控车床切削力测试系统,并完成了典型测试工艺的切削力载荷实测试验。(2)分析了切削力测试过程中的噪声来源,针对低信噪比的切削力载荷信号,提出了改进的多小波相邻系数降噪法,采用统计方差平滑法去除载荷信号的奇异点,通过引入关联维数和BDS统计值等指标识别载荷信号中的噪声,从而选出合理的多小波分解层数、小波函数和相邻系数块的长度;利用对不同信噪比的四种模拟信号的降噪处理,验证了多小波相邻系数法优于经典的小波阈值降噪法,并对实测载荷信号的降噪从时域波形、频域能量和雨流域损伤三方面进行对比分析;为了保证采集的载荷数据样本能够代替总体的信息,提出了基于切削载荷特性的载荷样本长度的确定方法。(3)根据数控车床恒速切削工况的载荷特性,提出了基于改进的时域载荷扩展的POT外推方法。由于传统时域载荷扩展未考虑极值载荷间的时间间隔,利用改进的MCMC时域载荷扩展法,将每组载荷数据扩展到指定的载荷作用时间;然后根据MEF图法确定载荷极值阈值的范围,针对每个阈值对应的超越量进行GPD拟合,利用灰关联分析法选择最优的阈值和载荷极值分布;合并恒速切削工况下的33组载荷的均幅值与频次的矩阵,编制了数控车床恒速切削工况下的切削力谱。(4)根据数控车床变速切削工况的载荷特性,提出了基于混合威布尔分布的参数外推方法。利用改进的MCMC时域载荷扩展法将30组载荷数据扩展到指定的载荷作用时间;根据30组载荷数据合并后的均幅值分布特性,建立了载荷均幅值的混合威布尔分布模型;利用灰关联分析法确定了混合威布尔分布的基本函数个数,并利用改进的EM算法进行了参数估计;通过载荷的均幅值相关性分析,确定备选Copula函数,采用平方欧式距离选择最优的Copula函数,建立了载荷均幅值的联合分布函数,并编制了数控车床变速切削工况下的切削力谱。(5)以数控刀架可靠性台架为例,编制了“切-转-切”的八级切削力程序加载谱,确定了可靠性试验过程中每步程序加载谱对应的动态切削力的加载角度、加载频率以及刀架的换刀频率;制定了基于载荷谱的数控刀架可靠性试验方案,在实验室开展了数控刀架可靠性台架试验,并针对试验中出现的小样本数据的情况,提出了基于融合多源先验信息的贝叶斯可靠性建模与评估方法,依据数控刀架实验室可靠性试验数据,建立了受试数控刀架的可靠性评估模型。通过本文的研究,提出了一套适用于数控车床切削力谱的测取、编制和应用的方法,为后续开展数控车床及关键功能部件的可靠性试验、加速试验、寿命预测和可靠性设计等提供理论依据。
[Abstract]:The inherent reliability of the product is the first by design, the machine and key part of NC machine reliability design is one of the main ways to improve the reliability level of machine tools, CNC machine tools and the load spectrum is the objective basis of the reliability design; key functional parts of NC machine tools reliability test is to obtain product failure data, and to establish the reliability model of the main technology of NC machine tool fault analysis, load spectrum is the precondition of simulation components reliability bench test of actual operating conditions. Therefore, the scientific research, the reasonable numerical control preparation method of machine load spectrum, and the preparation of load spectrum, which has important theoretical significance and engineering application value. In the past more than 10 years, with direct drive technology development and wide application of servo technology and digital control technology, modern CNC machine tools in the structure, function, performance index, processing range Great changes have taken place in other aspects, on the basis of experience formulas, the static cutting force spectrum can not accurately reflect the real conditions, development demand is no longer applicable to the reliability of CNC machine tool design and functional components of the reliability test; in addition, preparation of NC machine tool dynamic cutting load reflects the load spectrum of the need to get the machine sign treeing process load data, this on the basis of determining the typical working conditions and cutting tests of long time measurement of dynamic load, the work is time-consuming, laborious, so many researchers from. This paper rely on Jilin University Machinery Industry Key Laboratory of CNC equipment reliability technology, combined with the national science and technology major project, systematic study of the preparation method and process of NC lathe load the spectrum mainly includes: the typical test conditions, measured load data, the load signal processing, sample length The degree of determination, extrapolation of the load spectrum, such as the preparation of the contents of the cutting force spectrum, and the reliability test bench of machine tool CNC turret spectrum using the load. The main contents are as follows: (1) to ensure the authenticity and validity of the load spectrum data sources, this paper is based on determining the typical user machine on the study and formulate the machine tool user process data in the field acquisition table and machine operation records, and conducted on-site sampling of CNC lathe cutting process data and machine operation data acquisition; according to the characteristics of CNC lathe processing conditions and process, formulated the selection principle of lathe cutting force data of typical test conditions and process. Put forward the method of determining the typical test parameters of cutting parameters based on interval; build a CNC lathe cutting force testing system, and completed the typical cutting force test process load. Test. (2) analyzed the noise sources of the cutting force in the process of testing, according to the cutting force signal with low SNR, the proposed denoising method improved wavelet coefficients of adjacent singular points, removal of load signals using statistical variance smoothing method, using correlation dimension and BDS statistical indexes such as load identification signal in the noise, to choose the more reasonable wavelet decomposition level, wavelet function and adjacent coefficient blocks using length; noise reduction of four different signal-to-noise ratio of the analog signal, verify the wavelet threshold denoising method outperforms the classical multiwavelet neighboring coefficient method, and the measured load signal denoising from time domain waveform, frequency domain energy and rain damage basin three aspects of comparative analysis; in order to ensure the load data can replace the general information, put forward the method of determining load sample size based on the characteristics of cutting load. (3) according to the load characteristics of CNC lathe with constant speed cutting conditions, put forward the POT extrapolation method in time domain based on improved extended load. Because of the traditional time domain load expansion without considering the extreme load of the time interval between the expansion by using the method of MCMC time domain load improved, each load data extended to load the specified time; and determine the scope of the extreme load value threshold according to the MEF diagram, GPD fitting for beyond the amount of each threshold corresponding to the use of grey relational analysis method to select the optimal threshold and load extreme value distribution; 33 groups with constant speed load matrix cutting under the condition of both amplitude and frequency, the cutting force under the condition of constant speed cutting CNC lathe the spectrum is compiled. (4) according to the load characteristics of variable speed cutting condition of CNC lathe, puts forward parameter extrapolation method based on mixed Weibull distribution. Using MCMC time-domain expansion method improved 30 Group load data extended to load the specified time; according to the 30 group load data after the merger are amplitude distribution characteristics, the mixed Weibull distribution model of load amplitude; analysis method to determine the number of mixed Weibull distribution is the basic function of the grey correlation, and parameter estimation using EM algorithm improved by; the correlation analysis of the load amplitude were determined, alternative Copula function, using the squared Euclidean distance Copula optimal function, to establish a joint distribution function of load amplitude, and the cutting force of CNC lathe cutting speed under the condition of the spectrum. (5) the reliability of CNC turret rig as an example, eight level cutting force program preparation of loading "cut to cut" spectrum to determine the dynamic cutting force of each program load spectrum corresponding to the reliability test in the process of loading angle, loading frequency and frequency change knife knife system; The test scheme of CNC turret reliability based on load spectrum, in the laboratory to carry out CNC turret reliability bench test, and based on small sample data in the test case, Bias proposed reliability modeling and evaluation method for multi-source information fusion based on the basis of the reliability test data of CNC turret laboratory, established reliability evaluation model try CNC turret. Through this research, put forward a set of suitable for CNC lathe cutting force spectrum measurement, method of preparation and application of the reliability test, the component for further research on the CNC lathe and the key to successful accelerated test, to provide a theoretical basis for life prediction and reliability design.

【学位授予单位】：吉林大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TG519.1

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