基于提升多小波的机电设备复合故障分离和提取

机电设备的复合故障往往同时或级联出现,其振动信号常表现为多故障特征的相互耦合。基于波形匹配的思想,兼备优良性质的多小波拥有多个尺度函数和小波函数,可以很好地匹配复合故障的各种特征波形,从而实现复合故障耦合特征的一次性分离与提取。基于提升框架的多小波构造方法不依赖于傅里叶变换,具有算法简单,运行速度快等优点。研究类似二代小波变换的多小波提升框架分解和重构算法。基于Hermite样条插值,构造了紧支、双正交、对称和4阶逼近阶的多小波,并给出其相应的前处理算法。针对机电设备复合故障问题,改进了多小波后处理流程,使得解耦的特征信息能够清晰地呈现于多小波分析结果的不同通道中。将提出的方法应用于轴承试验台和电力机车走行部复合故障诊断中,结果显示该方法可以有效地实现试验台轴承内圈故障和转轴不规则弯曲故障的分离和提取,并成功解耦出机车轴承外圈和滚动体损伤复合故障。     

基于改进谐波小波包分解的滚动轴承复合故障特征分离方法

为解决滚动轴承单通道振动信号中复合故障特征难以分离的问题,提出了基于改进谐波小波包分解的轴承复合故障特征分离方法。首先,改进了二进谐波小波包分解方法,提出了连续谐波小波包分解方法,克服了信号分解后子带个数和带宽范围受二进制划分的缺陷;然后,采用谐波窗分解提取信号中频率成分集中的频段,根据轴承各单点故障特征频率确定分解层数,进行连续谐波小波包分解,利用能量算子包络解调得到子带信号中各个单点故障的权重因子;最后,重构轴承各单点故障信号,实现复合故障的特征分离和提取。对仿真信号和实测轴承内、外圈复合故障信号分析的结果表明,该方法能将轴承单通道复合故障信号分解到不同的通道中,实现了复合故障特征的分离,具有一定的工程实用价值。     

LCD和SWT在滚动轴承故障诊断中的应用

针对强噪声背景下滚动轴承故障诊断中存在的非平稳非线性信号特征提取这一难题,提出一种基于局部特征尺度分解(Local Characteristic-scale Decomposition,LCD)和同步压缩小波变换的方法(Synchrosqueezing Wavelet Transform, SWT),该方法首先对信号进行LCD分解,将其分解成多个內禀尺度函数(Intrinsic Scale Component,ISC),选取包含有效频率成分的ISC作为SWT的输入信号,使用SWT对其作进一步分析,从而提取有效频率特征。对强噪声背景下提取的滚动轴承外圈故障信号、内圈故障信号以及滚动体故障信号进行分析的结果表明,相比局部特征尺度分解、同步压缩小波变换等方法,该方法能够有效抑制噪声,从强噪声背景下提取出有效信号频率特征,从而能够有效判断滚动轴承的运转状况。同时该方法能够有效重构信号。     

基于MWT和CNN的滚动轴承智能复合故障诊断方法

提出一种基于多小波变换(MWT)和卷积神经网络(CNN)的滚动轴承智能复合故障诊断方法。对滚动轴承的振动信号进行去除后处理的MWT,得到相应的多小波系数分支;用所得多小波系数分支构造特征图,建立CNN分类器组模型,以实现滚动轴承复合故障的智能诊断。基于人工轴承故障数据集进行了实验研究,同时对诊断方法作了优化改进,即对振动信号进行MWT,用所得多小波系数矩阵构造特征图,建立CNN分类器模型,并进行了对比实验研究。结果表明,该方法能有效识别滚动轴承的复合故障,改进的方法能有效提高故障识别率,降低训练成本。     

基于子小波布置和系数融合的轴承故障诊断

针对滚动轴承早期微弱故障特征难以提取的问题,提出一种基于子小波布置策略和小波系数融合的故障诊断方法。首先,布置子小波并进行小波变换;然后,根据峰度指标对多尺度小波系数进行融合集成;最后,运用自相关谱抑制噪声,突出故障信息。通过仿真信号和实际信号对该方法进行了验证,结果表明,该方法能够提取出微弱的故障特征,实现滚动轴承的早期故障诊断。     

载荷影响下的机电阻抗协整结构损伤识别方法

针对滚动轴承早期故障特征信息十分微弱难以提取以及可调品质因子小波变换(tunable Q-factor wavelet transform,简称TQWT)参数设置依赖使用者经验的问题,提出改进的TQWT的滚动轴承早期故障诊断方法。首先,设定Q因子的区间范围,利用TQWT对滚动轴承故障振动信号进行分解得到若干个分量;其次,对各分量进行包络导数能量算子解调,在能量谱中根据特征频率强度系数这一指标自适应地确定TQWT的最佳分解参数,实现对故障信号的最优分解;最后,通过对最佳分量的包络导数能量谱分析即可准确地提取到轴承故障特征信息。通过对仿真信号、实验数据以及工程案例分析表明,该方法能够有效提取滚动轴承早期微弱故障特征并准确判断出滚动轴承故障类型,具有一定的工程应用价值。     

滚动轴承故障特征的时间—小波能量谱提取方法

振动信号中的周期性冲击现象是诊断滚动轴承各元件故障的重要依据之一,针对滚动轴承故障特征,在小波变换理论基础上提出一种时间—小波能量谱信号处理方法,它能够有效地提取出振动信号中冲击成分的时域和频域特征。利用时间—小波能量谱方法分析正常、外圈故障、内圈故障、滚珠故障等四种状态下滚动轴承的振动信号,并与传统的包络解调分析方法进行对比分析。时间—小波能量谱不仅可以有效提取出冲击特征明显的滚动轴承外圈故障,还能提取出内圈、滚珠等信号特征微弱的滚动轴承故障,而包络解调分析方法只能提取出外圈故障特征而不能提取出滚珠故障、内圈故障特征。结果表明,时间—小波能量普比包络解调分析方法更能有效地提取出振动信号中的冲击信号成分。     

改进的TQWT在滚动轴承早期故障诊断的应用

针对滚动轴承早期故障特征信息十分微弱难以提取以及可调品质因子小波变换(tunable Q-factor wavelet transform,简称TQWT)参数设置依赖使用者经验的问题,提出改进的TQWT的滚动轴承早期故障诊断方法。首先,设定Q因子的区间范围,利用TQWT对滚动轴承故障振动信号进行分解得到若干个分量;其次,对各分量进行包络导数能量算子解调,在能量谱中根据特征频率强度系数这一指标自适应地确定TQWT的最佳分解参数,实现对故障信号的最优分解;最后,通过对最佳分量的包络导数能量谱分析即可准确地提取到轴承故障特征信息。通过对仿真信号、实验数据以及工程案例分析表明,该方法能够有效提取滚动轴承早期微弱故障特征并准确判断出滚动轴承故障类型,具有一定的工程应用价值。     

平移不变多小波相邻系数降噪方法及其在监测诊断中的应用

为了提取大型动力设备中被强背景噪声淹没的微弱故障特征,提出一种基于平移不变多小波的相邻系数降噪方法.多小波具有多个尺度函数和小波函数,具备单小波无法同时满足的优良性质,可以匹配信号中不同的特征信息,而平移不变多小波有效地消除了Gibbs现象且其中的平均过程具有优越的消噪性并保持了信号的光滑性.同时相邻系数降噪法考虑小波系数之间的相关性,克服一般阈值消噪的不足.将相邻系数降噪思想引入到平移不变多小波中.并将平移不变多小波相邻系数降噪方法应用于齿轮箱试验台和电力机车滚动轴承的诊断中.齿轮箱试验台和滚动轴承实例的诊断结果表明该方法可以有效地揭示出齿轮早期裂纹的微弱故障特征信息,并成功提取出机车滚动轴承外圈轻微擦伤故障特征频率.     

改进的共振稀疏分解方法及其在滚动轴承复合故障诊断中的应用

滚动轴承复合故障信号中各故障特征受到传输路径和其他干扰源的影响,在多缺陷共存条件下提取单个缺陷诱发的故障特征存在困难。提出一种基于双参数优化、子带重构改进的共振稀疏分解(RSSD)滚动轴承复合故障诊断方法：首先利用人工鱼群算法自适应选择RSSD的品质因子和分解层数以构造与故障特征匹配的最优小波基,获得包含瞬态冲击的低共振分量;然后依据提出的子带筛选准则选择并重构低共振分量中包含瞬态冲击成分的最佳子带;最后通过多点最优最小熵反卷积（MOMEDA）方法识别并提取重构信号中周期性故障冲击。仿真信号和轴承全寿命周期复合故障信号分析结果表明,与RSSD-MCKD方法相比,所提出方法能有效提取复合故障信号中各故障特征,精确实现轴承复合故障诊断。     

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.     

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.