基于VMD-MDE和ELM的柱塞泵微弱故障诊断

针对早期微弱故障信号易受噪声干扰、难以提取和识别的问题,提出一种基于变分模态分解(variational mode decomposition,简称VMD)多尺度散布熵(multiscale dispersion entropy,简称MDE)和极限学习机(extreme learning machine,简称ELM)的柱塞泵微弱故障诊断方法。首先,采集各状态的振动信号进行VMD分解,得到若干模态分量,根据各模态分量Hilbert包络谱中特征频率能量贡献率大小,提出以归一化特征能量占比(feature energy ratio,简称FER)为重构准则的变分模态分解特征能量重构法(variational mode decomposition feature-energyreconsitution,简称VMDF),对各模态分量进行信号重构;其次,计算重构信号的MDE,对各尺度散布熵进行分析,选择有效尺度散布熵作为特征向量;最后,将提取的特征向量输入ELM完成故障模式识别。柱塞泵不同程度滑靴端面磨损故障的实验结果表明,该方法不仅提高了模式识别效率,还可以更好地反映故障程度变化规律,具有较好的应用性。     

基于VMD的故障特征信号提取方法

变模式分解(variational mode decomposition,简称VMD)能够将多分量信号一次性分解成多个单分量调幅调频信号(variational intrinsic mode function,简称VIMF),但对噪声比较敏感。利用VMD对噪声的敏感特性,提出了一种基于VMD的降噪方法。利用排列熵定量确定VMD分解后各分量的含噪程度,对高噪分量直接剔除,对低噪分量进行Savitzky-Golay平滑处理,然后重构信号。运用该方法降噪后,对重构信号进行变模式分解,能够有效提取故障特征信号。仿真和实例分析表明,基于VMD的降噪方法的降噪效果优于小波变换降噪方法,VMD能有效提取故障特征信号。     

变分模态分解在转子故障诊断中的应用

针对转子故障诊断问题,提出一种基于变分模态分解(variational mode decomposition,简称VMD)的信号处理方法。该方法在获取分解分量的过程中通过迭代搜寻变分模型最优解来确定每个分量的频率中心及带宽,从而能够自适应地实现信号的频域剖分及各分量的有效分离,对各单分量信号进行希尔伯特变换,即可得到瞬时的频率和幅值信息。对仿真信号和典型转子故障信号进行VMD方法和经验模态分解(empirical mode decomposition,简称EMD)方法的分析比较,以验证所提方法的有效性。仿真信号的分解结果表明,变分模态能够准确分离出信号中的固有模态分量且不存在模态混叠;转子故障实验信号的分析结果表明,所提方法能够有效提取出明显的故障特征,从而准确诊断出转子存在的故障。     

基于VMD与KFCM的柴油机故障诊断算法

针对柴油机的故障诊断问题，提出了一种基于变分模态分解（variational mode decomposition，简称VMD）与核模糊C均值聚类算法（kernel fuzzy C-means clustering，简称KFCM）联合的故障诊断方法。首先，针对VMD算法中分解层数K的选择问题进行了自适应优化；然后，从优化VMD算法的分解结果中选取3个关键分量计算最大奇异值，并将其作为3维的特征向量输入KFCM算法中进行分类识别；最后，对仿真信号以及某型柴油机的模拟故障实验信号使用优化VMD、传统VMD和经验模态分解（empirical mode decomposition，简称EMD）方法分别进行分解与识别。结果表明，笔者提出的方法明显改善了模态混叠现象，提高了模式识别的诊断正确率，提出的联合算法具有更好的应用前景。     

基于SVM信号延拓改进的EEMD方法

为了抑制经验模态分解(empirical mode decomposition,简称EMD)中出现的端点效应和模态混叠现象,在信号组综合经验模态分解(ensemble empirical mode decomposition,简称EEMD)的基础上,从抑制信号干扰和噪声污染影响以及三次样条函数插值拟合误差逐级传播方面,提出利用信号支持向量机(support vector machines,简称SVM)延拓改进EEMD.通过对仿真和实测信号研究,比较了EMD和EEMD的分解,提出改进的EEMD方法不仅减少了虚假模态分量、避免了模态混叠,而且有效抑制了端点效应.与基于镜像延拓改进的EEMD方法比较表明,本研究方法的时频谱更加清晰,虚假模态分量更少,有效解决了端点效应引起的分解失真问题.     

盲VMD-Cepstral在轴承故障诊断中的应用

针对滚动轴承早期故障诊断困难的问题,从经验模态分解(empirical mode decomposition,简称EMD)以及包络谱出发,为解决EMD抗噪效果较差、具有端点效应等局限性,提出了盲变分模态分解(variational modal decomposition,简称VMD)-主成分分析(principal component analysis,简称PCA)-包络谱熵结合倒谱包络的轴承故障诊断方法。首先,对滚动轴承的振动信号进行了变分模态分解;其次,对分解得到的分量进行PCA去相关处理;然后,对分量计算包络谱熵,选择熵值小于其平均值的分量进行信号重构;最后,对重构的信号进行倒谱包络分析。实验结果表明,该方法能有效地提取出滚动轴承的故障频率,从而判断出滚动轴承的损伤位置,并且具有良好的抗噪能力。     

基于AVMD和二阶FWEO的滚动轴承故障诊断

针对滚动轴承振动信号中常包含有谐波、高斯白噪声和非周期性瞬态冲击成分,导致故障特征提取困难的问题,提出一种基于自适应的变分模态分解（adaptive variational mode decomposition,简称AVMD）和二阶频率加权能量算子（second-order frequency weighted energy operator,简称SFWEO）的滚动轴承故障诊断方法。首先,根据不同的信号自适应地确定模式数和惩罚因子,利用参数优化的变分模态分解（variational mode decomposition,简称VMD）对原始信号进行分解,得到多个本征模式函数（instrinsic mode function,简称IMF）;其次,计算每个IMF的时频加权峭度,根据时频加权峭度最大化准则选择最佳IMF;最后,采用二阶频率加权能量算子对最佳IMF进行解调。仿真和试验结果表明,所提方法克服了传统VMD算法分解精度受参数影响较大导致信号出现过分解或欠分解的问题,同时二阶频率加权能量算子对信号中的干扰成分具有很好的抑制作用,有效提高了诊断正确率。     

基于k值优化VMD的滚动轴承故障诊断方法

针对旋转机械中滚动轴承早期信噪比较低的故障特征提取困难问题,提出了一种基于能量的变分模式分解(variational mode decomposition,简称VMD)模态数k优化选取方法,用以提取滚动轴承早期故障特征,同时避免了信号分解过分或不足。首先,对振动信号进行VMD预分解,分别在不同k值条件下计算分量信号能量与原始信号总能量;其次,根据基于能量的模态数k选取准则,确定最佳模态数值对信号进行VMD分解;最后,通过峭度准则选择分量进行信号重构,对其进行包络分析,提取故障特征频率。将该方法运用到实际故障信号中,有效提取出滚动轴承内圈微弱故障特征,实现了早期故障特征判别,具有一定的应用价值和实际意义。     

基于VMD与Hilbert谱的旋转机械碰摩故障诊断方法

为了有效地诊断旋转机械中的碰摩故障,提出了基于变分模态分解(variational mode decomposition,简称VMD)与Hilbert谱分析的故障诊断方法。首先,利用VMD将碰摩故障信号自适应地分解为若干个不同频率段的本征模态函数(intrinsic mode function,简称IMF),并与集合经验模态分解(ensemble empirical mode dcomposition,简称EEMD)的处理结果进行对比分析;然后,在VMD分解的基础上,利用Hilbert谱对故障信号的时频特性进行分析。实验结果表明:与传统的频谱分析相比,该方法不但可以准确反映故障信号的频率成分,而且可以反映频率随时间的变化情况;与EEMD相比,该方法可以有效抑制模态混叠,更加准确地反映故障信息,从而验证了该方法的可行性与有效性。     

基于平均自相关和优化VMD的轴箱轴承故障诊断

针对动车组运行过程中轴箱轴承振动加速度信号非平稳特性以及较大的背景噪声导致故障特征难以提取的问题,提出一种平均自相关结合参数优化变分模态分解（variational mode decomposition,简称VMD）的轴箱轴承故障诊断方法。首先,利用平均自相关对原始信号进行降噪,增强故障周期性冲击信息;其次,以故障特征频率能量比相反数为适应度函数,利用哈里斯鹰优化算法（Harris hawks optimization,简称HHO）优化VMD的模态分量数和二次惩罚系数,实现对降噪信号的自适应分解并提取出最佳模态分量;最后,计算其平方包络谱进行故障诊断分析。仿真和试验结果表明：该方法能够有效地降低背景噪声的影响,稳定地提取出周期性故障冲击成分,实现轴箱轴承故障的准确诊断。     

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...     

On the Relation of Load to Average Gap in the Contact Between Surfaces with Longitudinal Roughness

A computer simulation model for the contact between longitudinally-oriented rough surfaces has been formulated. This model closely duplicates the actual surf ace contact deformation behavior by taking into account the elastic interactions between the asperities. There were no assumptions made about the shapes, or any deformation behavior of the asperities, except for their obeying the laws of elasticity. The plastic deformations on the high asperity peaks were taken into account by setting a ceiling on their contact pressures at the material hardness value. The simulations used real surface profiles which were digitized from unworn circumferentially ground steel surfaces. Each pair of these profiles was mathematically combined to form an equivalent rough profile pressing against an infinitely rigid flat and having the appropriately adjusted elastic modulus. A total of 28 different pairs of profiles were used in the simulations. Each contacting pair was subjected to 30 different load levels and the local contact pressures and deformations were calculated. The contact simulations yielded some important mathematical relationships between parameters, such as the real area of contact, average gap, and average asperity load through statistical curve fitting. Two analytical functions were generated to relate the average load to average gap and the real area of contact to load.     

三绕组变压器的双绕组等效建模及在Matpower中的应用

针对实际电网存在着大量的三绕组变压器,但国际上一些著名商业软件,如BPA仿真软件、Matpower这一权威潮流计算开源软件,均只提供双绕组变压器模型,限制了其在具有三绕组变压器的电力系统中的应用的问题,潮流计算是自主开发的电力系统各种应用软件的核心模块,因此依托国际权威开源程序进行二次开发,是一种较好的选择。对Matpower要求的数据格式进行了归纳,对变压器的一般的等值电路及带理想变压器的等值电路和带标幺值的等值电路进行了分析研究,提出了三绕组变压器转换为双绕组等效模型的建模方法,使得原先只适应双绕组变压器的潮流计算软件可以适用于三绕组变压器电网的潮流计算;最后以Matpower软件为例进行了案例计算,并用PSASP仿真软件进行对比验证。研究结果证明,所提出的建模方法是有效的。     

Quantum Cooperative Robotics and Autonomy

The intersection of Quantum Technologies and Robotics Autonomy is explored in the present paper.The two areas are brought together in establishing an interdisci...     

电站锅炉模糊风险评价方法研究与应用

针对电站锅炉风险等级评价问题,将模糊综合评价技术应用到电站锅炉风险等级评价中。开展了电站锅炉失效影响因素及模糊评价因素的重要程度分析,建立了一套科学合理适于在线评价的电站锅炉风险评价体系,提出了模糊综合评价技术与改进的模糊层次分析法相结合的模糊风险评价方法,利用改进的模糊层次分析法计算了指标体系中各层指标权重。对某一台电站锅炉的实际运行工况影响子因素进行了模糊风险评价,采用模糊合成算子进行模糊综合运算得到电了站锅炉运行工况影响子因素的评价向量。研究结果表明:电站锅炉的运行工况影响子因素的风险评价等级为第6级,失效可能性等级为小,该电站锅炉运行工况良好。     

考虑进油孔有限长滑动轴承油膜力的近似解析解

针对具有进油孔的有限长滑动轴承油膜力求解问题,采用变分原理和分离变量法,求得了有限长滑动轴承油膜压力分布的近似解析表达式。将油膜压力分布的近似解析表达式在油膜存在区域上进行积分,即得到了油膜力。将提出的计算有限长滑动轴承油膜力方法与无限长轴承模型、有限元方法的计算结果进行了比较,发现了提出的方法与有限元方法的计算结果很接近。最后,研究了进油孔位置和进油压力对油膜存在区域、油膜力等的影响,研究结果表明进油孔位置和进油压力对油膜存在区域和油膜力有较大的影响。     

Fifth International Summer School on Screw-Theory Based Methods in Robotics

正3-11 September,2014University of Bologna,Bologna,Italy www.summerscrews.org summerscrews2014.ing.unibo.it SUMMER 20SCREWS 14In 2014,our screw-theory school comes to the world's oldest university.In early September,Summer Screws'14 will gather six experts in the application of screw theory in robotics and up to 40 participants at the University of Bologna,Bologna,Italy.The school will teach attendees how to apply existing methods and empower them to develop new ones in their own research.The basic theoretical notions will be introduced in a rigorous manner,emphasizing examples,applications,and exercises.Scholarships are available.     

交通荷载作用下桥梁结构参数识别方法

应用动力节点加载法,将作用在桥梁上的交通荷载转化为等效节点荷载,再用两步构造法识别结构物理参数.第1步,用Newmark-β方法变换结构运动方程,并用结构的加速度响应求得变换空间内的位移、速度和加速度响应;第2步,基于最小二乘原理,构造出变换空间内求解结构参数的递推式,进行结构物理参数识别.数值模拟结果表明,在交通荷载作用下,该方法能够快速、准确地进行桥梁结构参数识别.     

INDUSTRIAL ENGINEERING AND VISUALISATION-A PRODUCT DEVELOPMENT PERSPECTIVE

Taking the actual project of teaching and researching process for example, the relationship between the industrial engineering and product development is discussed. And use the novel visualization technology to support the industrial engineering and product development. How to use the new computer modeling and simulating technologies to support the product development and industrial engineering, is introduced especially. The support includes both domestic products and industrial systems. The visualization and computer technologies take a very important role in some system or multi-direction modeling, those technologies mentioned above can help the industrial engineers study the effect of design on the whole life circle, including the producing steps. So the engineers can avoid making the wrong decision which may cause bad effects on the whole industrial engineering.     

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.