基于LMD和灰色相似关联度的轴承故障诊断方法

针对轴承故障振动信号的非线性、非平稳特点及振动信号的强噪声背景,提出一种基于局部均值分解(Local Mean Decomposition,LMD)和灰色相似关联度的轴承故障诊断方法。首先对信号进行局部均值分解,得到若干个PF(Product function,简称PF)分量,再选取包含主要故障信息的PF分量进一步分析,并提取特征向量,然后通过计算标准故障模式与待识别样本的灰色相似关联度对轴承故障类型进行判断。利用该方法对试验轴承故障振动信号进行了分析,结果表明,基于LMD和灰色相似关联度方法能够有效地识别轴承运行状态,实现对轴承的故障诊断。     

LMD及马氏距离敏感阈值的滚动轴承故障诊断

针对滚动轴承非平稳性的振动信号,提出了基于局部均值分解(Local Mean Decomposition,LMD)及马氏距离敏感阈值的滚动轴承故障诊断方法。首先,对振动信号进行LMD分解,获得一系列乘积函数(Production Function,PF),有的PF分量包含的故障信息多,有的包含的少,为此采用K-L散度法提取出主要PF分量;计算主要PF分量的时域参数指标,将其组合成特征向量,根据马氏距离提出马氏距离敏感阈值来表征不同的故障状态,取多组正常信号的特征向量均值作为标准特征向量,计算未知特征向量与标准特征向量的马氏距离敏感阈值,从而对其故障状态进行识别。试验结果表明,在不同转速下,该方法能够有效的对滚动轴承故障进行识别,且效果较EMD方法好。     

基于LMD-SVD和极限学习机的滚动轴承故障诊断方法研究

针对局部均值分解(LMD)得到的PF分量对于分类方法的输入而言过大,提出了一种基于局部均值分解(LMD)-奇异值分解(SVD)和极限学习机(ELM)的故障诊断方法.首先,通过LMD将非线性非平稳的原始振动信号分解为一系列乘积函数,从而得到具有物理意义的瞬时频率;然后,采用SVD处理PF分量以压缩特征向量尺度并获得更加稳定的特征向量值;最后,基于提取的特征向量,应用运算效率和分类精度更高的ELM对轴承故障状态进行分类.试验结果表明,该方法能有效的对风机轴承在变工况条件下进行自适应诊断.     

基于PCA和LMD分解的滚动轴承故障特征提取方法

局部均值分解(LMD)是一种自适应时频分析方法,并在轴承的故障诊断中成功应用,但是受噪声的影响比较大。为了最大程度地降低噪声的干扰,提出了主分量分析(PCA)与局部均值分解(LMD)相结合的故障诊断方法。该方法首先利用相空间重构将一维时间序列振动信号嵌入为等效的多维时间序列信号,然后利用主分量分析提取主要成分实现降噪,最后把降噪之后的信号进行LMD分解,分解成若干个乘积函数(PF)之和,对能量最高的PF1进行包络谱分析,提取出故障特征信息。通过仿真试验和轴承故障试验,结果表明该方法能够有效地提取出信号的故障特征,证明了该方法的有效性。     

基于MCKD和LMD的滚动轴承早期故障诊断方法

针对局部均值分解(Local mean decomposition,简称LMD)方法难以提取滚动轴承早期微弱故障的问题,提出了基于最大相关峭度解卷积(Maximum Correlated Kurtosis Deconvolution,简称MCKD)和LMD的滚动轴承早期故障诊断方法。首先采用MCKD方法对故障信号进行降噪处理,同时增强信号中的周期成分,然后进行LMD分解,将得到的PF分量与分解前信号的相关系数作为判断标准,剔除多余低频PF分量,最后,选取有效PF集进行频谱分析,提取故障特征。通过仿真数据和真实滚动轴承故障诊断实验数据表明,该方法可有效提取早期故障特征频率信息,具有一定可靠性。     

奇异值分解与LMD结合的滚动轴承故障诊断研究

针对滚动轴承故障信号具有的非线性和非平稳性,其故障特征难以提取的问题,提出一种奇异值分解(SVD)和局部均值分解(LMD)相结合的滚动轴承故障特征提取和诊断方法。首先,将轴承故障信号进行LMD分解得到若干PF分量;然后选取和原始信号相关度较大的PF分量,利用奇异值序列来构造其故障特征向量;最后,将得到的故障特征向量作为学习样本输入到支持向量机(SVM)中,对故障类型进行分类和识别。实验结果表明,LMD和SVD结合的故障特征提取方法,能有效提取滚动轴承不同状态下的故障特征,对不同故障状态做出准确分类。     

改进LMD和排列熵的滚动轴承故障诊断

针对滚动轴承故障振动信号的复杂特性和局部均值分解(Local Mean Decomposition,LMD)方法存在的端点效应问题,提出了基于振动信号自相似性对左右端点两侧延拓来抑制端点效应问题的改进LMD、排列熵(Permutation Entropy,PE)及优化K-均值聚类算法相结合的轴承故障诊断方法。首先通过改进LMD将非线性、非平稳的原始故障振动信号分解出一系列的乘积函数(Production Function,PF)分量,对包含主要故障信息的PF分量提取PE值作为故障特征分量,在提取特征量的基础上,最后采用优化后的K-均值聚类算法对故障类型进行识别分类。将该方法应用在滚动轴承实验数据,实验结果表明该方法可以准确、有效的实现滚动轴承的故障诊断。     

基于DLMD样本熵和模糊聚类的滚动轴承故障诊断

针对传统的局部均值分解(LMD)方法不能有效提取微弱高频信号成分的问题,提出了一种基于微分的微分局部均值分解(DLMD)方法,在此基础上,将DLMD、样本熵和模糊聚类分析相结合,提出了一种基于DLMD样本熵和模糊聚类的滚动轴承故障诊断方法。该方法首先对滚动轴承振动信号进行微分局部均值分解,得到若干具有物理意义的乘积函数(PF)分量,然后求取各PF分量的样本熵并将其作为特征向量,最后通过模糊聚类对特征向量进行识别分类。实验结果表明,基于DLMD样本熵和模糊聚类相结合的方法能够准确、有效地对滚动轴承故障信号进行识别分类。     

基于LMD-MS的滚动轴承微弱故障提取方法

轴承的早期故障信号属于微弱信号,其故障特征提取一直是旋转机械故障诊断的一大难点。笔者将掩膜法引入到局部均值分解(local mean decomposition,简称LMD)分解中,提出了一种基于LMD和掩膜法(mask signal,简称MS)的滚动轴承微弱故障提取方法。由于LMD在噪声背景下分解出的功能分量(product function,简称PF)存在模态混叠现象,很难辨别故障频率的真伪,所以引入了掩膜信号法对LMD分解出的与原信号相关性强的PF分量进行处理,抑制模态混叠现象,提取故障频率。文中以滚动轴承实际故障信号为对象进行分析,通过将掩膜信号法与LMD方法相结合的方式,对存在噪声的故障信号进行处理,将故障频率处的峭度值提高了8倍,同时将信噪比提高了19.1%,成功提取了故障信号,为故障特征提取提供一种新的诊断方法。     

基于LMD能量特征的滚动轴承故障诊断方法

针对滚动轴承故障振动信号的多载波多调制特性,提出一种基于局域均值分解(local mean decomposition,简称LMD)能量特征的特征向量提取方法,并与支持向量机相结合用于滚动轴承的故障诊断。首先,采用LMD方法将复杂调制振动信号分解为若干单分量信号乘积函数(production function,简称PF);然后,对反映信号主要特征的PF基于时间轴积分,得到各PF分量能量矩并构造特征向量;最后,将其输入多分类支持向量机中,用于区分滚动轴承的故障类型与故障程度。对滚动轴承内圈故障、外圈故障及滚动体故障振动信号的分析结果表明,该方法能有效提取滚动轴承各工作状态信号的故障特征,能准确识别故障类型,同时对故障程度的判断表现出较高的识别率。     

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.