低速滚动轴承故障诊断方法研究

低速滚动轴承结构和工作条件特殊,故障机理复杂,诊断难度较大。本文根据低速滚动轴承的故障特性,提出了利用应力波与小波分析进行低速滚动轴承故障诊断的方法。首先以低速运转Cooper轴承系列01B65 EX滚子轴承为例,建立了完好和故障低速滚动轴承的三维整体接触计算模型,运用有限元软件对其进行了比较全面、精确的分析,计算出外圈故障模型的最大应力和应变及各元件之间的接触应力,将发生故障前后的外圈外表面应力应变分布规律以及接触应力分布规律进行比较。然后在应力波实验分析的基础上,选择db6母小波、尺度j=4对实验所采集的数据信号进行小波变换,成功提取了外圈模拟故障的应力波信号特征频率。     

基于SPWVD时频图纹理特征的滚动轴承故障诊断

针对如何提高滚动轴承故障诊断准确率的问题,提出一种基于平滑伪维格纳-威利分布(smooth and pseudo Wigner-Ville distribution,简称SPWVD)时频图纹理特征的故障诊断方法,对滚动轴承不同故障类型及故障程度进行识别。首先,采用SPWVD时频分析方法处理轴承故障振动信号,并获取时频图,从中提取选择表征能力优秀的特征参量作为故障特征;其次,将故障特征作为输入,结合支持向量机(support vectors machine,简称SVM)建立滚动轴承故障诊断模型;最后,采用轴承故障数据,比较SPWVD时频图纹理特征、维格纳-威利分布(Wigner-Ville distribution,简称WVD)时频图纹理特征和小波尺度谱图纹理特征3种故障特征的模式识别能力及准确率。分析结果表明,SPWVD时频图纹理故障特征分类效果最佳,敏感性最强,具有较高的故障诊断精度。     

连续小波变换在滚动轴承故障诊断中的应用

针对滚动轴承故障振动信号的特点，构造脉冲响应小波，采用连续小波变换的方法来提取滚动轴承故障振动信号的特征，在此基础上提出了两种滚动轴承故障诊断方法：尺度——小波能量谱比较法和时间——小波能量谱自相关分析法。通过对滚动轴承外圈和内圈故障振动信号的分析，说明两种方法不仅能检测到滚动轴承故障的存在，而且能有效识别滚动轴承的故障模式，从而为滚动轴承故障诊断提供了一种新途径。     

基于小波包去噪的循环自相关方法在轴承故障诊断中的应用

针对在轴承故障诊断中提取到的信号(包含噪声干扰)及表现出的复杂调制特性,采用小波包方法对信号进行降噪处理,以提高数据的准确度和精度,采用循环自相关的方法进行信号的解调处理,有效的提取故障特征频率。结果表明,用仿真信号将小波包降噪结合循环自相关方法应用于滚动轴承的内、外圈及滚动体的故障诊断,可以有效地提取出轴承的故障特征频率。     

小波变换能量谱在滚动轴承故障诊断中的应用

针对滚动轴承故障振动信号的特点,构造余弦调频小波,采用连续小波变换的方法来提取滚动轴承故障振动信号的特征,提出了一种滚动轴承故障诊断方法—小波能量谱比较法。通过对有缺陷的滚动轴承振动信号的分析,检测到轴承故障的存在,且能有效地识别出滚动轴承的故障模式。     

现代信号分析在滚动轴承故障诊断中的应用

滚动轴承是各种机电设备中的重要部件,其主要特点是其寿命的随机性较大,且它的好坏直接影响到设备的正常运行。因而掌握轴承运行的工作状态以及故障的形成和发展是目前机械故障诊断领域中研究的重要内容之一。利用轴承的随机振动信号对其工作状态进行诊断是目前最常用的方法。分析的方法主要有时域法和频域法。而传统的基于Fourier分析的方法其时间和频率这两个变量依Heisenberg测不准原理是互斥的,因此传统的功率谱分析是针对平稳随机信号而言的。滚动轴承的故障振动信号为典型的非平稳信号,而非平稳信号需要用现代信号分析的方法来处理。利用现代信号分析理论从线性时频分析(小波减噪变换)、非线性时频分析(伪Wigner-Ville时频分布)和高阶谱(三阶谱)三方面对滚动轴承故障信号特征进行提取加以研究。研究结果表明,小波减噪方法在微弱信号检测方面具有较强的能力;伪Wigner-Ville时频分布图能有效地建立故障信息图谱,直观性更强;高阶谱可以很好的检测出非高斯故障信号的信息。     

一种轴承故障诊断的时频综合分析法

针对旋转机械中最常见的滚动轴承问题,提出了一种基于小波包分析和Hilbert包络分析的时频综合分析法对轴承进行故障诊断。首先利用小波包分析将轴承故障信号分解到不同的节点,然后求出各个频带的能量谱,确定故障频带范围并对其进行信号重构,最后采用Hilbert变换对故障频带的重构信号进行包络谱分析,从而诊断出轴承故障。通过对轴承外圈故障信号的分析验证了该方法在轴承故障诊断中的有效性。     

Wigner-Ville分布复小波相似性评价及应用

针对常规特征量对轴承早期故障不敏感问题,基于不同状态下振动信号时频分布的结构差异,融合WignerVille时频分析和复小波变换的优点,提出了基于复小波变换的Wigner-Ville时频分布相似性评价指数(WignerVille distribution-complex wavelet structural similarity,简称WVD-CWSS),实现时频分布相似性的定量评价,并用于轴承早期状态评估。首先,对振动信号进行Wigner-Ville时频分布;其次,进行复小波变换,获取不同状态下的二维时频分布结构相似性复小波指数;最后,对滚动轴承全寿命试验数据进行了对比试验。结果表明,所提取的WVDCWSS特征对滚动轴承的早期损伤更敏感。     

基于Teager-Huang变换的滚动轴承故障诊断方法

针对滚动轴承故障振动信号的非平稳特征,介绍了一种基于Teager-Huang时频谱和边际谱的滚动轴承故障诊断方法。详细阐述了Teager-Huang时频谱和边际谱的计算方法及物理意义。给出了该故障诊断方法的步骤,并对仿真和实际轴承的滚动体故障、内圈故障和外圈故障信号进行了分析和故障诊断。结果表明,基于Teager-Huang变换的故障诊断方法具有计算速度快,估计准确稳定的特点,是准确判断滚动轴承故障状态的一种有效新方法。     

6205-2RS轴承内圈故障特征时频分析

分析6205-2RS轴承内圈故障时变信号,提取故障特征。通过对短时傅里叶变换与Wigner-Ville分布数值仿真实验比较,明确了短时傅里叶变换与Wigner-Ville分布的时频分析优缺点。针对非平稳轴承振动信号,利用短时傅里叶变换,结合Wigner-Ville分布进行了故障特征提取。通过提高短时傅里叶变换汉明窗点数,结合Wigner-Ville分布参数调整与轴承部件的旋转频率计算,给出了6205-2RS轴承内圈故障特征结果。该方法能较准确地诊断轴承内圈的故障现象。     

Minimal Realization of Linear Graph Models for Multi-physics Systems

An engineering system may consist of several different types of components,belonging to such physical"domains"as mechanical,electrical,fluid,and thermal.It is t...     

INTEGRAL EQUATION METHOD＇S APPLICATION IN HOLE-EDGE STRESS OF COMPOSITE MATERIAL PLATE WITH DIFFERENT SHAPED HOLES

The strength of composite plate with different hole-shapes is always one of the most important but complicated issues in the application of the composite material. The holes will lead to mutations and discontinuity to the structure. So the hole-edge stress concentration is always a serious phenomenon. And the phenomenon makes the structure strength decrease very quickly to form dangerous weak points. Most partial damage begins from these weak points. According to the complex variable functions theory, the accurate boundary condition of composite plate with different hole-shapes is founded by conformal mapping method to settle the boundary condition problem of complex hole-shapes. Composite plate with commonly hole-shapes in engineering is studied by several complex variable stress fimction. The boundary integral equations are founded based on exact boundary conditions. Then the exact hole-edge stress analytic solution of composite plate with rectangle holes and wing manholes is resolved. Both of offset axis loadings and its influences on the stress concentration coefficient of the hole-edge are discussed. And comparisons of different loads along various offset axis on the hole-edge stress distribution of orthotropic plate with rectangle hole or wing manhole are made. It can be concluded that hole-edge with continuous variable curvatures might help to decrease the stress concentration coefficient; and smaller angle of outer load and fiber can decrease the stress peak value.     

Non-monotonic material contrast in scanning ion and scanning electron images

30 keV Ga⁺ focused ion beam induced secondary electron (iSE) imaging was used to determine the relative contrast between several materials. The iSE signal compared from C, Si, Al, Ti, Cr, Ni, Cu, Mo, Ag, and W metal layers does not decrease with an increase in target atomic number Z₂, and shows a non-monotonic relationship between contrast and Z₂. The non-monotonic relationship is attributed to periodic fluctuations of the stopping power and sputter yield inherent to the ion–solid interactions. In addition, material contrast from electron-induced secondary electron (eSE) and backscattered electron (BSE) images using scanning electron microscopy (SEM) also shows non-monotonic contrast as a function of Z₂, following the periodic behavior of the stopping power for electron–solid interactions. A comparison of the iSE and eSE results shows similar relative contrast between the metal layers, and not complementary contrast as conventionally understood. These similarities in the contrast behavior can be attributed to similarities in the periodic and non-monotonic function defined by incident particle–solid interaction theory.     

Short-Term Relay Quality Prediction Algorithm Based on Long and Short-Term Memory

The fraction defective of semi-finished products is predicted to optimize the process of relay production lines, by which production quality and productivity ar...     

End-to-End Multiview Gesture Recognition for Autonomous Car Parking System

The use of hand gestures can be the most intuitive human-machine interaction medium.The early approaches for hand gesture recognition used device-based methods....     

Application of Feature Extraction through Convolution Neural Networks and SVM Classifier for Robust Grading of Apples

This paper proposes a novel grading method of apples,in an automated grading device that uses convolutional neural networks to extract the size,color,texture,an...     

分布动态载荷识别的抗噪处理

针对正交多项式频域法在用多种响应对矩形薄板进行载荷识别中抗噪性较差的问题,综合运用平均法、矩阵预处理和奇异值截断法等方法对之进行改善,并引入空间映射的思想,将该方法的应用范围拓展为复杂的模型.利用仿真算例,证实了该方法具有较好的抗噪性.     

基于MELTAC-N平台的核电厂安全级DCS环网研究与测试

针对工程实践中环网通讯相关问题的处理缺乏理论基础及国产化安全级DCS平台的开发缺乏成熟经验借鉴问题,对基于MELTAC-N平台核电厂安全级DCS环网的软硬件实现进行了研究。提出了安全级DCS环网双环网冗余设计、光切换开关设计等硬件设计方法,以及以RPR协议为基础,采用全数据收发策略的软件设计方法。在CPR1000安全级DCS平台上对安全级DCS环网的可靠性及实时性进行了评价,并进行了容错能力、响应时间及响应时间稳定性测试验证实验。结果表明,基于MELTAC-N平台安全级DCS环网软硬件设计具有较好的容错能力及响应时间稳定性。     

The laboratory simulation of abrasive wear

Abrasive wear has long been recognised as one of the most potentially serious tribological problems facing the operators of many types of plant and machinery; several industrial surveys have indicated that wear by abrasion can be responsible for more than 50% of unscheduled machine and plant stoppages. Locating the operating point of a tribological contact in an appropriate operational ‚map’︁ can provide a useful guide to the likely nature and origins of the surface degradation experienced in use, though care must be exercised in choosing the most suitable parameters for the axes of the plot. Laboratory testing of materials and simulations of machine contacts are carried out for a number of purposes; at one level for the very practical aims of ranking candidate materials or surface hardening treatments in order of their wear resistance, or in an attempt to predict wear lives under field conditions. More fundamentally, tests may be aimed at elucidating the essential physical mechanisms of surface damage and loss, with the longer term aim of building an analytical and predictive model of the wear process itself. In many cases, component surface damage is brought about by the ingress of hard, particulate matter into machine bearing or sealing clearances. These may be running dry although, more usually, a lubricant or service fluid is present at the interface. A number of standardised wear test geometries and procedures have been established for both two- and three-body wear situations, and these are briefly described. Although abrasive wear is often modelled as following an ‚Archard’︁ equation (i.e. a linear increase in material loss with both load and time, and an inverse dependence on specimen hardness) both industrial experience and laboratory tests of particularly lubricated contacts show that this is not always the case: increasing the hardness differential in an abrasively contaminated lubricated pair may not always reduce the rate of damage to the harder surface.     

ANGULAR DISTORTION ALLOWABLE VALUE AND ASSESS METHOD OF WELD ON COKE TOWER

A graph as the new engineering method for estimate the safety of bulging deformation of coke tower is proposed. Through stresses analysis of circumferential weld of coke tower and comparing the stresses produced by pressure with heat stress of steady state, residual stress, bending stress produced by both itself weight and wind loads, it showed that the stresses produced by pressure on the angle distortion are the main factor of equivalent stress of the combined stress. After comparing four kinds of stress controlling conditions, the relation to stress with depth of angular distortion, grade of curvature of angular distortion and half of region of angular distortion has been inferred. Graph of deformation allowable value of coke tower for different condition by angular distortion and half of region of angular distortion has been plotted. The five steps for its engineering use have been explained. The lighter the grade of curvature is, the larger of bulge allowance, may be, and the bigger of depth of angular distortion may pose too. For the coke tower with a popular structure of Dg 5 400 mm×28 mm, the result by graph is nearly more than the result of two formulas formed by other research, the error is less than 7.0%. But, the graph can be easily applied to different size of angular distortion.