基于EMD-SVD-BIC的机械振动源数估计方法

提出了一种复合EMD-SVD-BIC(经验模态分解,empirical mode decomposition,简称EMD;奇异值分解,singular value decomposition,简称SVD;贝叶斯信息准则,bayesian information criterion,简称BIC)的机械振动源信号数量估计方法,解决卷积混合的机械振动源在观测数小于振动源数情况下的源数估计问题。应用EMD方法获得信号的本征模函数,对两观测信号的本征模函数复合矩阵的相关矩阵进行奇异值分解,获得反映源数信息的特征值分布;再采用BIC信息准则,判断源信号的数目。仿真和试验结果表明,该方法可以在观测数小于振动源数的情况下正确获取信号源数,为机械振动故障诊断中的振动源分析及其源信号的正确分离提供了方法保障。     

大跨径桥梁实时动态挠度信号的分离

由于经验模式分解(empirical mode decomposition,简称EMD)将非线性非平稳信号分解成为一系列线性、平稳的本征模函数(intrinsic mode function,简称IMF)信号,针对单通道大跨径桥梁挠度信号分离问题,结合盲源分离和经验模式分解各自优点,提出基于经验模式分解的盲源分离方法。利用奇异值分解(singular value decomposition,简称SVD)估计信号源数目,根据源信号数目将单通道挠度信号和其本征模函数重组为多通道输入信号,应用独立分量分析（independent component analysis,简称ICA）理论中的快速独立分量分析（fast independent component analysis,简称FastICA）算法对输入信号进行分解,实现桥梁挠度信号各分量的分离。仿真研究表明,该方法能较好地解决ICA模型源数估计和单通道挠度信号盲源分离难题。     

大跨径桥梁实时动态挠度信号的分离

由于经验模式分解(empirical mode decomposition,简称EMD)将非线性非平稳信号分解成为一系列线性、平稳的本征模函数(intrinsic mode function,简称IMF)信号,针对单通道大跨径桥梁挠度信号分离问题,结合盲源分离和经验模式分解各自优点,提出基于经验模式分解的盲源分离方法。利用奇异值分解(singular value decomposition,简称SVD)估计信号源数目,根据源信号数目将单通道挠度信号和其本征模函数重组为多通道输入信号,应用独立分量分析(independent component analysis,简称ICA)理论中的快速独立分量分析(fast independent component analysis,简称FastICA)算法对输入信号进行分解,实现桥梁挠度信号各分量的分离。仿真研究表明,该方法能较好地解决ICA模型源数估计和单通道挠度信号盲源分离难题。     

VMD⁃SVD在机械故障信号欠定源数目估计中的应用

针对在观测信号数目小于机械故障振动信号源数目的欠定情况下,源信号的个数难以估计的问题,提出一种变分模态分解(Variational mode decomposition,VMD)和奇异值分解(Singular value decomposition,SVD)相结合的盲源数目估计方法.首先利用VMD对振动信号进行分解,得到若干本征模态函数分量(Intrinsic mode function,IMF),然后对IMF进行重新组合得到多维观测信号的协方差矩阵,最后依据奇异值分解的结果来对信号源数目进行最终确定.仿真信号分析验证了该方法的有效性,将该方法运用到轴承复合故障振动信号中,分析结果表明,该方法能够实现欠定情况下源数目的可靠估计.     

基于经验模式分解的单通道机械信号盲分离

盲源分离是机械设备复合故障诊断的一种有效方法,经验模式分解是非平稳信号分析的有力工具,它将非线性、非平稳信号分解成为一系列线性、平稳的本征模函数信号。在机械故障信号盲分离中,单通道机械信号盲分离是一个病态问题。针对单通道机械信号盲分离的困境,综合盲源分离和经验模式分解各自的优点,提出基于经验模式分解的单通道机械信号源数估计和盲源分离方法。针对单通道机械观测信号进行经验模式分解,并将单通道信号和其本征模函数组成多维信号,利用奇异值分解估计机械源数目,根据源信号数目重组多通道机械混合信号,并利用FastICA算法实现机械信号的盲分离。将该方法应用于轴承和齿轮的仿真研究,正确分离出轴承和齿轮源信号,仿真研究表明,它能很好地解决单通道机械信号的源数估计和盲源分离难题。     

基于形态奇异值分解和经验模态分解的滚动轴承故障特征提取方法

针对随机噪声和局部强干扰影响经验模态分解(Empirical mode decomposition,EMD)质量的问题,提出一种形态奇异值分解滤波消噪方法,并将其与EMD相结合形成一种新的故障特征提取方法。该方法首先对原始振动信号进行相空间重构和奇异值分解(Singular value decomposition,SVD),根据奇异值分布曲线确定降噪阶次进行SVD降噪,再形态滤波,最后把消噪后的信号进行EMD分解,利用本征模模态分量(Intrinsic mode function,IMF)提取故障特征信息。对仿真信号和实际轴承故障数据的应用分析表明,该方法能有效地提取轴承故障特征,诊断轴承故障,还可以减少EMD的分解层数和边界效应,提高EMD分解的时效性和精确度。     

基于流形学习的滚动轴承故障盲源分离方法

滚动轴承的故障信号是一种典型的非线性非平稳信号,其信号中常常混有噪声信号及其他干扰成分。提出了一种基于流形学习的滚动轴承故障盲源分离方法,首先,利用经验模态分解(empirical mode decomposition,简称EMD)对单通道模拟信号进行分解,对得到的多通道信号构造其协方差矩阵,计算矩阵的奇异值下降速比得到原始信号数目;其次,利用峭度等指标选择最优观测信号,利用核主成分分析(kernel principal components analysis,简称KPCA)提取信号的流形成分;最后,利用快速独立成分分析(fast independent component analysis,简称Fast ICA)还原得到源信号。该方法不但解决了故障信号的欠定盲源分离问题,还提出了最优观测信号的确定准则,并通过实例验证了方法的有效性。     

基于EMMD和BSS的单通道旋转机械故障诊断方法

针对在欠定的观测信号情况下,传统基于矩阵的盲源分离算法效果比较差的问题,提出一种基于极值域均值模式分解和盲源分离的单通道旋转机械信号故障特征提取方法,并应用于实际的故障诊断中.该方法先通过极值域均值模式分解法分解观测信号,把得到的固有模态函数和原观测信号一起组成新观测信号,从而实现了信号升维,使欠定问题转化为正定问题;然后,由奇异值分解和贝叶斯准则进行源数估计;最后,利用基于四阶累积量的特征矩阵联合对角化方法实现信号的盲分离.通过仿真,验证了该方法对旋转机械故障信号进行盲源分离的可行性.将提出的方法应用到齿轮和轴承系统的故障诊断中,进一步证明了该方法的有效性.     

基于源数估计的旋转机械源盲分离

在传统的源数估计方法基础上引入聚类分析思想，提出了一种基于奇异值分解的聚类不相关源数估计新方法。应用该方法，可以估计系统中独立源数的上界，并籍此获得足够维数的传感观测信号，保证盲源分离方法在实际应用中的正确实施。仿真以实验的结果证明了所提出的整体解决方案的可行性和有效性。     

基于EMD和奇异值差分谱理论的列车齿轮箱故障诊断研究及实现

针对列车齿轮箱故障频率难以提取的情况,提出了一种基于EMD和奇异值差分谱理论的故障诊断方法。通过EMD分解齿轮原始振动加速度信号,得到若干个本征模函数;从频谱图中提取某个含有故障特征信息的本征模函数,对该分量构造hankel矩阵并对其进行奇异值分解,差分谱消噪,信号重构和希尔伯特包络解调,从而确定故障频率,准确实现列车齿轮箱的故障诊断。通过实验证明了该方法的可行性和有效性,为列车运行状态监控、故障诊断和运行安全自动防护提供理论和实践参考。     

开关稳压电源的原理及发展

本文简述了开关稳压电源的基本原理,以及开关电源与线性电源、相控电源相比较的优劣性。介绍了数字开关稳压电源的发展前景。     

Application of similar source method for noise source identification

Similar source method (SSM) has been developed to describe interior and exterior sound field by Too et al. [G.-P.J. Too, TK Su, Estimation of scattered sound field via nearfield measurement by source methods, Appl. Acoust. 58 (1999) 261–281]. The application can be used for arbitrary boundary conditions in terms of acoustic impedance. In the present study, a modified version of SSM is developed to describe the sound pressure distribution in a planar surface. In addition, a signal processing procedure is developed to identify noise source locations. This procedure contains a power spectrum analysis and acoustic holographic analysis to identify different source locations. Several test examples are shown to verify this approach.     

基于恒流源激励的远距离高精度电子秤

介绍基于恒流源激励的远距离高精度电子秤，这种电子秤克服了基于恒压源激励的电子秤在远距离传榆信号时，信号不稳定而造成的精度下降问题，同时实践证明基于恒流源激励的电子秤在温度系数上也低于基于恒压源的电子秤。     

混合信号振声源分离与多机组故障诊断

针对机房设备混合信号难以提取有用信息,提出了多参数的振声诊断方法。应用最小互信息梯度下降的盲分离算法,通过展开边缘熵和修正四阶累积量估计值的方法改善算法性能,在故障源数量未知且可能大于传感器数量的情况下,根据信息源之间的独立性测度关系依次提取最显著的特征值。仿真结果证明,改进算法估计误差减小且算法可靠。在诊断实例中,首先,分离机房内的混合噪声信号以确定主要故障来源;然后,采集故障源的振动信号进行非线性盲分离,提取热泵机组压缩机不对中、齿轮啮合不良和碰磨的故障特征;最后,根据分离的振源信号特征识别故障类型,建立基于盲源分离算法的大空间设备群的振声诊断方法。     

‘Collapsing rings’ on Schottky electron emitters

The electron beam in systems that use a Schottky emitter as the electron source can display periodic fluctuations when the emitter is operated at an extraction voltage that gives a relatively low field strength at the tip. In the past, these fluctuations have been associated with the so-called “collapsing rings” without much further information. In this paper, the tip’s geometry changes associated with these beam instabilities are investigated in more detail by recording the evolution of the emission pattern of a Schottky emitter showing ‘collapsing rings’ for different operating conditions. Scanning electron microscope (SEM) images of different Schottky emitters have been used to support the interpretation.     

“二次源”法阻抗估值算法和数据处理程序设计

针对现有“二次源”法在参考管道上传感器距离是压力波波长整数倍时,泵源估值精度较低,且整个数据处理过程繁琐复杂、费力耗时,导致其不适于工业应用的问题,提出泵源阻抗估值算法优化模型,并应用Matlab/GUI模块编写一套“二次源”法数据处理平台软件,在提高泵源流量脉动的测试精度的同时简化“二次源”法数据处理过程。介绍柱塞泵标准“二次源”法的测试原理,对比几种泵源阻抗估值方法的特点,应用Matlab/GUI模块开发优化的“二次源”法数据处理软件,并进行试验验证。结果表明,相比分布参数法,线性衰减技术能够估测全频率处柱塞泵泵源阻抗,估值效率提高了70%;在保证测试精度的情况下,“二次源”法测试软件简化了标准“二次源”法数据处理过程并节省了80%的计算时间,为“二次源”法的工业应用提供技术支撑。     

三种典型油源液压系统传动效率分析

基于理论分析和仿真,对变量泵油源(VD油源)、变频调速油源(INV油源)、启停式油源(ACC油源)三种不同油源组成的液压系统传动效率进行了分析计算。计算过程中,设定三系统均选用了同功率的定量泵,考虑各部件的效率和管路的压力损失,对VD油源、INV油源做了直接的效率分析和计算;针对ACC油源液压系统,对其核心元件——蓄能器的充放液过程作了仿真,并做了效率计算。最后从效率、主要部件的成本、频响等各方面综合比较了三种液压系统。理论计算表明,ACC油源液压系统由于利用了蓄能器储存的能力,有效地提高了液压系统效率。     

Design and implementation of a new modified sliding mode controller for grid-connected inverter to controlling the voltage and frequency

As the output power of a microgrid with renewable energy sources should be regulated based on the grid conditions, using robust controllers to share and balance the power in order to regulate the voltage and frequency of microgrid is critical. Therefore a proper control system is necessary for updating the reference signals and determining the proportion of each inverter in the microgrid control. This paper proposes a new adaptive method which is robust while the conditions are changing. This controller is based on a modified sliding mode controller which provides adapting conditions in linear and nonlinear loads. The performance of the proposed method is validated by representing the simulation results and experimental lab results.     

Characteristics of a high brightness gaseous field ion source employing tungsten-carbon doped NiAl needles

We report on the characterization of a high brightness gaseous field ion source using an emitter made of a NiAl needle containing tiny spherical tungsten-carbon precipitates. By field evaporation of such a multiphase alloy, a surface protrusion is formed out of a precipitate, which can act as a small source size field ion emitter. The emission current-voltage characteristics of this emitter were recorded for a variety of parameters. The results obtained suggest that its application as a stable ion source is possible even on long term operation.     

Continuous acoustic source tracking for tangible acoustic interfaces

The challenge in human computer interaction is to create tangible interfaces that will make digital world accessible through augmented physical surfaces like walls and windows. In this paper, two continuous acoustic source tracking methods are proposed which have the potential to covert a physical object into a tracking sensitive interface. The spatial likelihood method has been used to locate an acoustic source in real time. The source location is obtained from searching the maximum in the likelihood map. The Kalman filter is used to improve the trajectory estimation by predicting the location based on the previous source location and the current measurement of the source location. Finally a Linear Positioning algorithm is proposed for acoustic source tracking. This method is independent on the spatial size of the tangible object and thus applicable on large interactive surfaces without additional computation cost. Promising results have been achieved experimentally for the application of acoustic tangible interfaces.