自适应无参经验小波变换及其在转子故障诊断中的应用

为了实现经验小波变换中Fourier谱的自适应分割,提出了自适应无参经验小波变换(APEWT)方法。同时,为了克服希尔伯特变换解调的不足,更精确地估计信号的时频分布,提出了改进归一化希尔伯特变换(INHT)。通过分析仿真信号将APEWT和INHT方法与经验模态分解(EMD)、总体平均经验模态分解(EEMD)和局部特征尺度分解等方法进行对比,结果表明了APEWT和INHT方法的优越性。最后,将基于APEWT和INHT的时频分析方法应用于转子局部碰磨故障诊断,试验数据分析结果表明,所提出的方法不仅能够有效地诊断转子局部碰磨故障,而且诊断效果优于EMD和EEMD方法。     

Teager-Huang变换在齿轮裂纹故障诊断中的应用

提出了一种基于Teager-Huang变换的齿轮箱故障诊断方法,该方法综合利用了经验模态分解(empiricalmode decomposition,简称EMD)和Teager能量算子分析技术。由于EMD方法具有自适应的分析能力,首先利用EMD把时间序列信号分解成不同特征时间尺度的固有模态函数,然后用Teager能量算子计算各固有模态函数的瞬时幅值和瞬时频率,得到Teager-Huang变换时频谱。齿轮箱齿轮裂纹故障振动试验信号的研究结果表明:Teager-Huang变换时频谱优于Hilbert-Huang变换时频谱,能有效地识别齿轮的裂纹故障。     

基于CCWEEMDAN和包络谱熵的轴承故障诊断研究

完全互补小波噪声辅助集总经验模态分解(CCWEEMDAN)是经验模态分解(EMD)的改进算法,是一种噪声辅助的自适应非线性非平稳数据处理方法。噪声辅助能克服EMD方法处理间歇信号出现的"模态混叠"问题。而相比较互补集总经验模态分解(CEEMD),完全互补小波噪声辅助集总经验模态分解能实现更优的性能。在轴承故障诊断的应用中,这里的方法利用小波分解高频段噪声细节成分,添加到原始轴承故障信号中,提取出本征模态信号。利用包络谱熵判断轴承故障导致的冲击响应特征所在本征模态信号,通过对轴承外圈、内圈局部故障状态下的特征提取进行故障诊断,结果表明该方法能有效提取故障冲击响应特征。     

APEEMD及其在转子碰摩故障诊断中的应用

总体平均经验模态分解(ensemble empirical mode decomposition,简称EEMD)是抑制经验模态分解(empirical mode decomposition,简称EMD)模态混叠的有效方法,针对EEMD分解效果依赖于添加噪声的大小、筛分次数和总体平均次数等参数的选择及噪声残留大、分解不完备等问题,提出了自适应部分集成经验模态分解。该方法通过成对地向目标信号加入自适应噪声,并对每个内禀模态函数(intrinsic mode function,简称IMF)自动选择筛选次数,通过排列熵检测筛分出高频IMF,再对剩余信号进行EMD分解。将提出的方法应用于仿真和转子碰摩故障试验数据分析,结果表明提出的方法能够有效地应用于转子碰摩故障诊断,而且在分量的精确性、完备性和模态混叠的抑制等方面优于EEMD方法。     

基于EMD与倒谱分析的轴承故障诊断

提出了一种基于经验模态分解与幅值倒频谱分析的轴承故障诊断方法。该方法首先对外圈故障信号作传统的傅里叶幅值谱和幅值倒频谱分析,未能明显地找到故障特征;然后对故障信号做经验模态分解,并对分解出来的第一层本征模函数作倒频谱分析,有效地提取出了故障特征;最后,用该方法分别对具有内圈故障和滚动体故障的轴承故障信号作分析,也有效地提取出了故障特征。实验结果表明,通过联合经验模态分解和倒频谱分析,能有效并且准确地提取出轴承的故障特征频率。     

基于SVD与改进EMD的滚动轴承故障诊断

针对经验模态分解(EMD)存在的模态混叠问题,提出一种奇异值分解(SVD)和改进经验模态分解相结合的信号分析新方法。该方法首先对故障信号进行SVD降噪,以消除随机干扰,再根据信号特征加入高频谐波信号并进行EMD进行分解,有效地减少模态混叠现象,最后对EMD分解得到的高频本征模态分量(IMF)进行代数运算得到故障冲击成分,经Hilbert包络分析,提取出故障特征信息。仿真信号分析了这种方法的实施过程,并将该方法成功运用于滚动轴承内圈和外圈故障的诊断中。实验结果证明:该方法能够有效地提取滚动轴承故障特征信息,实现故障诊断。     

基于EMD/HHT的齿轮箱齿轮不对中故障信号分析

研究了经验模态分解(简称EMD)技术在齿轮箱故障诊断中的应用,并详细论述了EMD原理,对齿轮故障振动信号(简称故障信号)进行EMD,获取固有模态函数(简称IMF)分量,并通过HHT(Hilbert-Huang)变换,对IMF分量进行解调,对解调信号进行频谱分析,提取故障特征频率。研究结果表明,EMD方法能够有效降低信号的噪声,提高信噪比,突出信号的故障特征。     

均值优化经验模态分解及其在转子故障诊断中的应用

经验模态分解（Empirical mode decomposition,EMD）作为一种自适应的信号分解方法已经被广泛应用于诸多工程领域。为了提高EMD的分解性能,分别考虑从不同权值均值曲线的迭代筛分结果中选择正交性最小以及从每层内禀模态函数迭代结果中选择最优以保证整体分解最优,发展了两种均值优化经验模态分解（Mean-optimized empirical mode decomposition,MOEMD）算法。通过仿真信号分析,将MOEMD方法与EMD等现有信号分解方法进行了对比,结果表明,MOEMD方法在分解性能和分解精度方面比EMD等方法有显著提高。最后,将MOEMD方法应用于转子碰摩故障信号分析,并与EMD进行了对比分析,结果表明,MOEMD方法不仅能够有效地识别转子碰摩故障,而且识别效果优于EMD方法。     

基于自适应经验傅里叶分解的机械故障诊断方法

为了克服傅里叶变换、经验模态分解与傅里叶分解方法在分析非平稳信号方面的不足,提出一种适合非线性和非平稳信号分析的新方法——自适应经验傅里叶分解(Adaptive empirical Fourier decomposition,AEFD)。AEFD方法以快速傅里叶变换为基础,通过对变换系数进行分组重构,能够将一个非平稳信号自适应地分解为若干个瞬时频率具有物理意义的傅里叶本征模态函数(Fourier intrinsic mode function,FIMF)之和。研究了AEFD的分解正交性和精确性,通过仿真信号分析,将其与经验模态分解,变分模态分解和傅里叶分解方法等进行了详细对比,结果表明了AEFD的优越性。最后,为了提高故障诊断的精度和验证AEFD的有效性,将AEFD应用到转子碰摩和滚动轴承局部故障诊断中。试验数据分析结果表明,与经验模态分解等方法相比,AEFD不仅能够有效地诊断故障,而且诊断精度更高。     

基于角域经验小波变换的滚动轴承故障诊断

针对变转速条件下滚动轴承故障特征难以提取的问题,提出了一种基于角域经验小波变换的变转速滚动轴承故障诊断方法。该方法首先利用等角度重采样将变转速下非平稳的滚动轴承故障振动信号转化为角域平稳信号,然后应用经验小波变换(Empirical mode decomposition,EWT)对角域平稳信号进行自适应分解,得到若干个经验模态分量,最后选择峭度值最大的经验模态分量进行包络谱分析,提取出滚动轴承故障的阶比特征。为提高经验小波变换的分解效率,对其频谱分割方法进行了改进。滚动轴承故障诊断实例表明,该方法能够有效地抑制噪声等干扰成分的影响,精确提取滚动轴承故障的阶比特征,为变转速条件下的滚动轴承故障诊断提供一种有效方法。     

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.     

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。     

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....     

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.     

Limits of topographic measurement by the scanning tunnelling and atomic force microscopes

Parameters describing the topographic character of a surface (height, surface wavelength, slope and curvature) can be derived from equivalent sinusoidal profiles. The response of a surface-measuring instrument may be modelled in terms of instrument parameters such as stylus radius, and scanning range and resolution. The performance of the instrument may then be mapped as a zone in amplitude-wavelength (AW) space to show the sinusoidal profiles it is capable of measuring. In a first-order analysis the STM and AFM are considered as equivalent to contact-stylus instruments with a notional stylus radius equal to the tip radius plus the gap. Comparisons between different instruments and types of instrument are readily made by mapping in AW space. The error arising from convolution of the sinusoidal profile with that of the finite tip may be quantified and plotted as contours in AW space.