基于EEMD和关联维数的小电流接地故障选线方法

针对小电流接地系统发生单相接地故障时,各线路零序电流的非平稳、非线性等复杂特性,提出一种基于总体模态分解(EEMD)和关联维数相结合的选线方法.EEMD算法是在经验模态分解(EMD)的基础上加以改进,能够消除模态混叠现象,同时保留了经验模态分解具有的良好的时频特性;EEMD能根据信号本身的特点对瞬时出现的信号进行分析,并将信号分解成若干个固有模态函数(IMF)分量和一个剩余分量.利用关联维数不易受噪声干扰特点,对分解的IMF信号分量进行处理,采用G-P算法计算关联维数,通过比较关联维数的大小选出发生故障的线路.仿真结果表明,该选线方法可靠性高且效果较好.     

改进的EMD及其在风电功率预测中的应用

针对非平稳信号在经验模态分解(Empirical Mode Decomposition,EMD)过程中包络拟合时出现的过冲/欠冲问题,提出采用分段三次Hermite插值代替三次样条插值作为新的包络拟合算法.针对神经网络对非平稳性功率序列预测困难问题,采用EMD和神经网络相结合的方法对发电功率进行预测.使用改进的EMD对...     

EEMD方法在刀具磨损状态识别的应用

总体经验模态分解(EEMD)方法在EMD的基础上消除了模态混叠的现象,从而更能准确地揭露出信号特征信息。根据声发射信号的非稳态、非线性的特点,提出一种基于EEMD应用于刀具磨损状态识别的方法。通过EEMD获取无模态混叠的IMF分量;通过敏感度评估算法从所有IMF分量中提取敏感的IMF;提取敏感IMF的能量作为支持向量机(SVM)分类器的输入,将刀具分成正常切削、中期磨损和严重磨损3种状态。通过比较EEMD与应用EMD等方法的分类准确率,确立了基于EEMD的方法在提取刀具磨损状态特征信息的优势。     

基于CEEMD阈值和相关系数原理的MEMS陀螺信号去噪方法

针对经验模态分解（EMD）方法易产生模态混叠问题,而集成经验模态分解（EEMD）方法又存在重构误差较大的缺陷,提出了一种基于完备集成经验模态分解（CEEMD）阈值滤波和相关系数原理的MEMS陀螺信号去噪方法。首先通过CEEMD方法对陀螺信号进行有效完备的分解,并利用相关系数原理合理确定分解后噪声分量与有效分量的界限。在此基础上,通过借鉴小波阈值处理方式和EMD阈值设置方法,对信号进行阈值滤波去噪。对仿真信号和实际MEMS陀螺信号的研究结果表明,CEEMD阈值去噪方法的去噪效果要优于CEEMD、EEMD、EMD强制去噪方法和小波分析方法。这也充分体现了其在MEMS陀螺信号去噪应用中的可行性和有效性。     

The complex local mean decomposition

The local mean decomposition (LMD) has been recently developed for the analysis of time series which have nonlinearity and nonstationarity. The smoothed local mean of the LMD surpasses the cubic spline method used by the empirical mode decomposition (EMD) to extract amplitude and frequency modulated components. To process complex-valued data, we propose complex LMD, a natural and generic extension to the complex domain of the original LMD algorithm. It is shown that complex LMD extracts the frequency modulated rotation and envelope components. Simulations on both artificial and real-world complex-valued signals support the analysis.     

基于EEMD和二代小波变换的表面肌电信号消噪方法

为了更好地消除混杂在表面肌电信号(sEMG)中的噪声,提出了一种基于总体平均经验模式分解(EEMD)和二代小波变换的sEMG消噪新方法。首先对信号加入白噪声处理后进行经验模态分解(EMD),然后对高频的内蕴模式函数(IMF)分量进行二代小波阈值消噪处理,最后把处理后的高频IMF分量与低频IMF分量进行叠加,重构后的信号即为去噪信号。实验结果表明,该方法融合了二代小波与EEMD的优点,能更好的消除噪声,最大限度的保留有用信号,并具有更高的信噪比。     

A new short-term load forecasting method of power system based on EEMD and SS-PSO

Aiming to the disadvantages of short-term load forecasting with empirical mode decomposition (EMD) such as mode mixing and many high-frequency random components, a new short-term load forecasting model based on ensemble empirical mode decomposition (EEMD) and sub-section particle swarm optimization (SS-PSO) is proposed in this paper. Firstly, the load sequence is decomposed into a limited number of intrinsic mode function (IMF) components and one remainder by EEMD, which can avoid the mode mixing problem of traditional EMD. Then, through calculating and observing the spectrum of decomposed series, some low-frequency IMFs are extracted and reconstructed. Other IMFs can be forecasted with appropriate forecasting models. Since IMF1 is main random component of the load sequence, the linear combination model is adopted to forecast IMF1. Because the weights of the linear combination model are very important to obtain high forecasting accuracy, SS-PSO is proposed and used to optimize the linear combination weights. In addition, the factors such as temperature and weekday are taken into consideration for short-term load forecasting. Simulation results show that accuracy of the load forecasting model proposed in the paper is higher than that of BP neural network, RBF neural network, support vector machine, EMD and their combinations.     

基于EEMD的车辆微动信号提取及分类

针对轮式和履带式车辆微动信号的差异对目标车辆进行了识别分类,利用集合经验模式分解(EEMD)将原始信号分解为多个本征模函数(IMF),通过相关性分析,验证了EEMD能够有效克服EMD所带来的模态混叠问题.在此基础上,提取了4种特征,采用最近邻方法进行分类.实验结果表明:经EEMD所提取的特征是有效的,对目标速度,以及方位角的变化具有相当的稳健性.     

基于白噪声统计特性与EEMD的高速列车横向减振器故障诊断*

针对高速列车横向减振器故障信号非线性非平稳的特点,提出了基于白噪声统计特性与聚合经验模态分解（EEMD）相结合的故障诊断算法。首先,利用经验模态分解（EMD）对故障信号进行去噪,然后对去噪后的信号进行EEMD分解,最后对用相关系数求得的最能反映振动信号的本征模态函数（IMF）计算排列组合熵。在240km/h速度下,对高速列车横向减振器7种工况进行诊断,识别率达到91.8%。实验结果表明：与基于小波熵特征分析的算法相比,该算法具有更高的识别率和更强的抗噪性能。     

基于谱插值与经验模态分解的表面肌电信号降噪处理*

根据表面肌电(surface electromyography, sEMG)信号的噪声特性来探讨其降噪方法的应用问题。采用谱插值法来削弱工频干扰以避免工频处的肌电信息成分丢失,再选取通过经验模态分解(empirical mode decomposition, EMD)方法获得的内在模态函数(intrinsic mode function, IMF)分量作小波软阈值分析,并将部分明显的低频IMF干扰分量及冗余分量去除,然后对相应IMF分量进行重构便可得到降噪处理后的sEMG信号。仿真和真实信号的降噪实验结果     

EEMD分解在电力系统故障信号检测中的应用

针对经验模态分解(EMD)的希尔伯特-黄变换(HHT)在电力系统故障信号检测问题,应用存在的模态混叠会导致扰动信号检测失效,为此提出一种基于聚类经验模型分解(EEMD)的故障信号检测的方法。方法通过多次对目标数据加入随机白噪声序列以保证不同区域信号映射的完整性,并且克服了传统EMD分解造成的模态混叠问题,通过EEMD方法提取信号的固有模态函数(IMF),再进行Hilbert变换,利用Hilbert谱对故障暂态和扰动时刻进行检测,通过瞬时频率实现对故障暂态和扰动时刻的准确定位。通过数字仿真分析表明,方法是准确有效的。     

经验模态分解方法中端点问题的处理

经验模态分解方法可以有效提取非线性非稳定信号的瞬时特征,但是在利用样条插值获得信号上、下包络过程中存在着棘手的端点问题。有文献提出利用线性神经网络对信号进行延拓的方法,来解决经验模态分解方法中存在的端点问题。提出利用BP和RBF网络对信号进行延拓的方法解决该问题;并利用实验对三种网络的延拓效果进行比较,证明了RBF神经网络的有效性。     

EMD方法在汽车动态称重中的应用

给出经验模分解（Empirical mode decomposition, EMD）步骤,提出了抑制边缘效应的次端点极值法,结合汽车动态称重信号的特点,应用该方法对实测轴重信号进行了EMD分解,并对轴重信号分解结果进行了分析.结果表明EMD方法对汽车动态称重信号的处理是有效的,车速≤30 km/h时最大偏差为5%.     

基于EMD和SST算法的闪电电场信号去噪研究

为进一步减少噪声对闪电电场信号的干扰,提出了一种经验模态分解(EMD)和同步压缩小波变换(SST)相结合的组合去噪方法。利用EMD算法能够自适应分解信号和SST算法可将噪声压缩为点状噪声或颗粒状噪声并集中分布的特点,从而选用中值滤波达到对噪声的抑制。利用该方法对标准闪电波和自然闪电波信号分别进行去噪处理,并运用信噪比、相关系数和均方误差对去噪效果进行了定量分析。实验结果表明,所提去噪方法相比于传统小波阈值去噪法、单独用EMD算法和单独用SST算法均取得了较好的去噪效果。     

基于改进小波阈值-CEEMDAN算法的ECG信号去噪研究

Electrocardiogram (ECG) signal denoising has always been a hot research issue. In order to eliminate the noises in ECG signal, a denoising method based on adaptive complete set empirical mode decomposition (CEEMDAN) and wavelet improved threshold function is proposed. Firstly, this method firstly decomposes the ECG signal by CEEMDAN to obtain a set of intrinsic modal functions (IMFs) from high frequency to low frequency. CEEMDAN decomposition is performed on ECG signal to yield several modal components (IMF). Secondly, the correlation coefficient method is used to perform wavelet denoising with improved threshold on the high frequency IMFs. For the low frequency IMFs, by setting a fixed threshold, the IMFs below the threshold is considered to be the baseline drift signal and removed. Finally, the denoised IMFs and the retained IMFs are reconstructed. The experimental results show that the proposed method is more effective than the empirical mode decomposition (EMD) wavelet denoising, and the global average empirical mode decomposition (EEMD) wavelet denoising method.     

基于MCKD-EEMD近似熵和TWSVM的齿轮箱故障诊断

在复杂环境下齿轮箱信号往往会淹没在噪声信号中,特征向量难以提取;为了有效地进行故障诊断,提出了基于最大相关反褶积(MCKD)总体平均经验模态分解(EEMD)近似熵和双子支持向量机(TWSVM)的齿轮箱故障诊断方法;首先采用MCKD方法对强噪声信号进行滤波处理,在采用EEMD方法对齿轮箱信号进行分解,分解后得到本征模函数(IMF)分量进行近似熵求解,得到齿轮特征向量,最后将其输入到TWSVM分类器中进行故障识别;仿真实验表明,采用MCKD-EEMD方法能够有效地提取原始信号,与其他分类器相比,TWSVM的计算时间短,分类效果好等优点。     

Low-complexity sinusoidal-assisted EMD (SAEMD) algorithms for solving mode-mixing problems in HHT

In recent years, Hilbert–Huang Transform (HHT) is widely used to analyze nonlinear and non-stationary signals in various applications, such as seismic and biomedical signal processing. In HHT, the Empirical Mode Decomposition (EMD) is the key component for decomposing natural signals into intrinsic mode functions (IMFs). Since the EMD suffers from mode-mixing problem, in which some fast intermittent signals riding on a slow-oscillating wave, the Ensemble-EMD (EEMD) is proposed to solve this problem with the aids of noise. However, the EEMD requires high computational complexity in ensemble and is unsuitable for some real-time applications, such as ultrasound systems. In this paper, intermittent signals are modeled in mathematical forms for IMF decomposition. We then propose sinusoidal-assisted EMD (SAEMD) for efficient and effective HHT computation to solve mode-mixing problems. The type I of SAEMD (SAEMD-I) is initially proposed to solve the mode-mixing problem with very low computational complexity. However, if the maximum frequency of data is unknown in some real-world applications, the SAEMD-I may encounter estimation error caused by imprecise locations of extrema. For practical data, the type II of SAEMD (SAEMD-II) is proposed to solve the sampling rate issue. Compared with the ensemble-100 EEMD, the SAEMD-II can have 11–13 times improvement in terms of computation speed in El Niño application and comparable correlation coefficient (−0.95 at IMF 8). Hence, the proposed SAEMD-II scheme is a good candidate of implementing cost-effective HHT when computational complexity and real-time data processing are of major concern.     

基于EMD和奇异值分解技术的滚动轴承故障诊断方法

提出了基于EMD(Empirical mode decomposition)和奇异值分解技术的滚动轴承故障诊断方法。采用EMD方法将滚动轴承振动信号分解成若干个基本模式分量(Intrinsic mode function，IMF)之和，并形成初始特征向量矩阵。然后对初始特征向量矩阵进行奇异值分解得到矩阵的奇异值，将其作为滚动轴承振动信号的状态特征向量，通过建立Mahalanobis距离判剐函数判断滚动轴承的工作状态和故障类型。实验数据的分析结果表明，本文方法能有效地应用于滚动轴承故障诊断。     

二维经验模态分解边界效应抑制研究

二维经验模态分解中边界效应抑制是一个关键问题,现有方法主要讨论一维信号端点效应抑制,基本思想是信号延拓,不适合对二维信号进行边界效应抑制。提出一种二维图像边界效应抑制方法,该方法根据对称性、局部性原理和牛顿插值理论,对边界点进行插值,获取部分边界极值,采用这些极值对边界进行线性插值获取图像每个边界像素点的极大值和极小值。把这种边界效应抑制方法应用到二维经验模态分解中收到了较好的实验效果。     

改进EEMD-GRU混合模型在径流预报中的应用

为解决径流预测模型存在的预测精确度低、稳定性差、延时高等问题,结合门控制循环单元神经网络（gated recurrent unit, GRU）,集合经验模态分解（ensemble empirical mode decomposition, EEMD）的各自优点,提出一种基于改进EEMD方法的深度学习模型（EEMD-GRU）。该模型首先以智能算法对径流信号进行边界拓延,以解决EEMD边界效应。然后利用改进EEMD方法将径流信号分解为若干稳态分量,将各分量作为GRU模型的输入并对其进行预测。实验结果表明,与结合了经验模态分解的支持向量回归模型相比,并行EEMD-GRU径流预测模型的预测精准度、可信度和效率分别提高82.50%、144.67%和95.49%。基于EEMD-GRU的最优运算结果表明,该方法可进一步减少区域防洪的经济损失,提高灾害监管的工作效率。