提升小波在木材颜色特征提取上的应用

在总结以往研究的基础上,结合图像分块理论,提出一种新的木材颜色特征提取方法.该方法基于提升小波变换提取木材表面的颜色信息,最终形成12个特征参数.为了验证特征提取的有效性,采用了径向基函数神经网络、概率神经网络和支持向量机三种分类器,最终实验仿真的分类效果很好,验证了这种新的颜色特征提取方法的有效性.     

基于快速提升小波变换的语音特征提取方法

为提高语音识别系统对环境噪声的鲁棒性,在快速提升小波的基础上,结合感知频域上的滤波与倒谱均值归一化技术,提出一种语音特征参数提取方法．仿真实验表明,与传统方法相比,噪声鲁棒性显著提高;在语音信号的信噪比相近情况下,与传统小波方法相比,该方法计算简便、易于编程、计算速度快．     

Nonlinear feature selection using Gaussian kernel SVM-RFE for fault diagnosis

Feature selection can directly ascertain causes of faults by selecting useful features for fault diagnosis, which can simplify the procedures of fault diagnosis. As an efficient feature selection method, the linear kernel support vector machine recursive feature elimination (SVM-RFE) has been successfully applied to fault diagnosis. However, fault diagnosis is not a linear issue. Thus, this paper introduces the Gaussian kernel SVM-RFE to extract nonlinear features for fault diagnosis. The key issue is the selection of the kernel parameter for the Gaussian kernel SVM-RFE. We introduce three classical and simple kernel parameter selection methods and compare them in experiments. The proposed fault diagnosis framework combines the Gaussian kernel SVM-RFE and the SVM classifier, which can improve the performance of fault diagnosis. Experimental results on the Tennessee Eastman process indicate that the proposed framework for fault diagnosis is an advanced technique.     

Improved wavelet feature extraction using kernel analysis for text independent speaker recognition

A text independent speaker recognition system based on improved wavelet transform is proposed. Learning of the correlation between the wavelet transform and the expression vector is performed by kernel canonical correlation analysis. Kernel canonical correlation analysis is a nonlinear extension of canonical correlation analysis. Moreover, we also propose an improved kernel canonical correlation algorithm to tackle the singularity problem of the wavelet matrix. The identification model underlying the Gaussian mixture model is presented; in particular, an expectation-maximization algorithm is also proposed for adjusting the parameters. The experimental results on the TALUNG database and KING database illustrate the effectiveness of the proposed method.     

基于小波提升与Sobel膨胀特征提取的零水印版权认证方案*

为了对数字媒体作品的版权信息进行有效的保护,在Chen和Chang提出的零水印版权认证系统方案的基础上,利用基于提升算法的Haar整数小波变换和带有膨胀操作的Sobel特征检测方法,对零水印签名和验证过程的特征提取方式进行了改进。通过适当选取阈值参数,对比三种算法在不同种类信号处理攻击下的性能,改进的零水印系统方案对于模糊、噪声、有损压缩、剪切、锐化、旋转和缩放等攻击模式具有良好的鲁棒性。仿真结果进一步验证了算法的有效性能。     

Energy and entropy-based feature extraction for locating fault on transmission lines by using neural network and wavelet packet decomposition

The aim of this paper is to estimate the fault location on transmission lines quickly and accurately. The faulty current and voltage signals obtained from a simulation are decomposed by wavelet packet transform (WPT). The extracted features are applied to artificial neural network (ANN) for estimating fault location. As data sets increase in size, their analysis become more complicated and time consuming. The energy and entropy criterion are applied to wavelet packet coefficients to decrease the size of feature vectors. The test results of ANN demonstrate that the applying of energy criterion to current signals after WPT is a very powerful and reliable method for reducing data sets in size and hence estimating fault locations on transmission lines quickly and accurately.     

一种用于机械故障特征提取的多尺度稀疏滤波网络

针对传统稀疏滤波网络缺乏多尺度特征提取能力,难以充分挖掘故障信息的问题,提出一种多尺度稀疏滤波网络.该网络包括5层:多尺度粗粒度层,以获取多尺度信号;样本分段层,对每个尺度的信号分段;局部特征提取层,计算每个片段的特征向量;特征平均化层,将单个尺度下所有片段的特征向量池化以得到输入信号在该尺度下的表征;特征堆叠层,将所...     

自适应提升小波变换及飞机发动机故障分析

小波提升方案通过改变预测器和更新器构造出所需要的小波,这为机械设备故障特征分析中小波基函数的选择提供了方便。为了能在每个尺度上自适应选择与机械振动信号特征匹配的小波基函数,提出了一种更新器和预测器同时自适应地提升小波变换方法。在此方法中,采用先更新后预测的提升方案,分别通过信号的局部梯度大小和最小化预测误差来实现自适应更新和预测。将此方法应用在某飞机发动机故障分析中,实验结果表明,与经典小波变换相比该自适应提升小波变换分离的故障特征更明显效果更好。     

提升小波变换在煤矿轴承故障诊断中的应用研究

针对煤矿关键设备中滚动轴承故障诊断问题,提出将提升小波变换应用到煤矿轴承故障诊断中,介绍了提升小波变换原理,并设计了自适应提升小波预测器和升级滤波器。仿真结果表明,轴承故障信号实际测量值与理论值平均误差小于3%,说明利用提升小波变换能够实现噪声条件下轴承故障信号的准确识别。     

AKSNet: A novel convolutional neural network with adaptive kernel width and sparse regularization for machinery fault diagnosis

Convolutional kernels have significant affections on feature learning of convolutional neural network (CNN). However, it is still a challenging problem to determine appropriate kernel width. Moreover, some features learned by convolutional layers are still redundant and noisy. Thus, adaptive selection of kernel width and feature selection of feature maps are key techniques to improve feature learning performance of CNNs. In this paper, a new deep neural network (DNN) model, adaptive kernel sparse network (AKSNet) is proposed to extract multi-scale fault features from one-dimensional (1-D) vibration signals. Firstly, an adaptive kernel selection method is developed, where multiple branches with different kernels are used to extract multi-scale features from vibration signals. Channel-wise attention is developed to fuse features generated by these kernels to obtain different informative scales. Secondly, a spatial attention is used for dynamic receptive field to focus on salient region of feature maps. Thirdly, a sparse regularization layer is embedded in the deep network to further filter noise and highlight impaction of the feature maps. Finally, two cases are adopted to verify effectiveness of AKSNet-based feature learning for bearing fault diagnosis. Experimental results show that AKSNet can effectively extract features from multi-channel vibration signals and then improves fault diagnosis performance of the classifier significantly. AKSNet shows better recognition performance in comparison with that of shallow neural networks and other typical DNNs.     

An MRF-based kernel method for nonlinear feature extraction

Nonlinear kernel-based feature extraction algorithms have recently been proposed to alleviate the loss of class discrimination after feature extraction. When considering image classification, a kernel function may not be sufficiently effective if it depends only on an information resource from the Euclidean distance in the original feature space. This study presents an extended radial basis kernel function that integrates multiple discriminative information resources, including the Euclidean distance, spatial context, and class membership. The concepts related to Markov random fields (MRFs) are exploited to model the spatial context information existing in the image. Mutual closeness in class membership is defined as a similarity measure with respect to classification. Any dissimilarity from the additional information resources will improve the discrimination between two samples that are only a short Euclidean distance apart in the feature space. The proposed kernel function is used for feature extraction through linear discriminant analysis (LDA) and principal component analysis (PCA). Experiments with synthetic and natural images show the effectiveness of the proposed kernel function with application to image classification.     

基于小波包和神经网络的瓦斯传感器故障诊断

针对瓦斯传感器常见的故障,提出了基于小波包和神经网络的故障诊断方法.通过对瓦斯传感器的输出信号进行三层小波包分解,得到8个不同频段的分解信号,再对其进行特征提取得到一个八维的特征向量,作为故障样本对三层神经网络进行训练,建立故障类型分类器,对瓦斯传感器故障进行诊断.仿真结果表明:该方法可以准确地诊断出故障类型.     

基于小波包与SOM神经网络的传感器故障诊断

研究传感器实时故障诊断问题.首先采用MATLAB2015仿真得到传感器各种典型工作状态下的运行数据样本;其次将这些故障样本作3层小波包分解,分别求出第3层小波包基对应的各频率段的能量,利用这些能量值与正常工作时各频段的能量值之比构造出传感器故障诊断的特征向量;最后构建基于3×3的SOM神经网络的传感器故障诊断算法.测试证明了所提算法的有效性和准确性.     

A deep feature alignment adaptation network for rolling bearing intelligent fault diagnosis

Fault diagnostic methods based on deep learning achieve impressive progress recently, but most studies assume that signals from the source domain and target domain share a similar probability distribution. However, the domain shift phenomenon is often unavoidable in practical engineering because of changeable conditions, which hinders the performance of some intelligent methods in fault diagnosis. To tackle the above issue, an unsupervised domain adaptation approach called Deep Feature Alignment Adaptation Network (DFAAN) is proposed in this paper to raise the domain adaptability of fault diagnosis. Firstly, the latent distributions of the two domains are aligned indirectly guided by a Gaussian prior to create a common latent space, which can promote the feature alignment across different domains. Secondly, to better narrow the discrepancy of the feature distribution with the Gaussian prior, a novel discriminative reconstruction distance based on the mechanism of the autoencoder is introduced. Thirdly, an entropy minimum technique is incorporated in the objective function to further increase the transferability of the adaptation method. Diagnostic experiments are conducted on two bearing datasets to illustrate the effectiveness of the proposed approach. The results reveal the superiority of the proposed approach over other typical methods and validate the versatility in multiple diagnostic tasks.     

A novel approach to wavelet selection and tree kernel construction for diagnosis of rolling element bearing fault

A novel methodology for early diagnosis of rolling element bearing fault is employed based on continuous wavelet transform (CWT) and support vector machine (SVM). CWT is especially suited for analyzing non-stationary signals in time–frequency domain where time information is retained as well as frequency content. To better approximate non-stationary vibration signals from rolling element bearing, a wavelet choice criterion is established to select an appropriate mother wavelet for feature extraction. The Shannon wavelet is picked out of several considered wavelets. The classification tree kernels (CTK) are constructed to address nonlinear classification of the characteristic samples derived from the wavelet coefficients. By using Fuzzy pruning strategy, a large variety of classification trees are generated. The trees with diverse structures can effectively explore intrinsic information among samples. Then, the tree kernel matrices can be acquired through ensemble statistical learning, which eventually reveal the similarity of samples objectively and stably. Under such architecture of kernel methods, a classification tree kernel based support vector machine (CTKSVM) is proposed to identify bearing fault. The performance of the methodology involving CWT and CTKSVM (CWT–CTKSVM) is evaluated by cross validation and independent test. The results show that the CWT–CTKSVM totally is superior to other SVM methods with common kernels. Therefore, it is a prospective technique for detection and identification of rolling element bearing fault.     

Bilinear analysis for kernel selection and nonlinear feature extraction.

This paper presents a unified criterion, Fisher + kernel criterion (FKC), for feature extraction and recognition. This new criterion is intended to extract the most discriminant features in different nonlinear spaces, and then, fuse these features under a unified measurement. Thus, FKC can simultaneously achieve nonlinear discriminant analysis and kernel selection. In addition, we present an efficient algorithm Fisher + kernel analysis (FKA), which utilizes the bilinear analysis, to optimize the new criterion. This FKA algorithm can alleviate the ill-posed problem existed in traditional kernel discriminant analysis (KDA), and usually, has no singularity problem. The effectiveness of our proposed algorithm is validated by a series of face-recognition experiments on several different databases.     

A fast method of feature extraction for kernel MSE

In this paper, a fast method of selecting features for kernel minimum squared error (KMSE) is proposed to mitigate the computational burden in the case where the size of the training patterns is large. Compared with other existent algorithms of selecting features for KMSE, this iterative KMSE, viz. IKMSE, shows better property of enhancing the computational efficiency without sacrificing the generalization performance. Experimental reports on the benchmark data sets, nonlinear autoregressive model and real problem address the efficacy and feasibility of the proposed IKMSE. In addition, IKMSE can be easily extended to classification fields.     

Investigation of engine fault diagnosis using discrete wavelet transform and neural network

An investigation of a fault diagnostic technique for internal combustion engines using discrete wavelet transform (DWT) and neural network is presented in this paper. Generally, sound emission signal serves as a promising alternative to the condition monitoring and fault diagnosis in rotating machinery when the vibration signal is not available. Most of the conventional fault diagnosis techniques using sound emission and vibration signals are based on analyzing the signal amplitude in the time or frequency domain. Meanwhile, the continuous wavelet transform (CWT) technique was developed for obtaining both time-domain and frequency-domain information. Unfortunately, the CWT technique is often operated over a longer computing time. In the present study, a DWT technique which is combined with a feature selection of energy spectrum and fault classification using neural network for analyzing fault signal is proposed for improving the shortcomings without losing its original property. The features of the sound emission signal at different resolution levels are extracted by multi-resolution analysis and Parseval’s theorem [Gaing, Z. L. (2004). Wavelet-based neural network for power disturbance recognition and classification. IEEE Transactions on Power Delivery 19, 1560–1568]. The algorithm is obtained from previous work by Daubechies [Daubechies, I. (1988). Orthonormal bases of compactly supported wavelets. Communication on Pure and Applied Mathematics 41, 909–996.], the“db4”, “db8” and “db20” wavelet functions are adopted to perform the proposed DWT technique. Then, these features are used for fault recognition using a neural network. The experimental results indicated that the proposed system using the sound emission signal is effective and can be used for fault diagnosis of various engine operating conditions.     

基于小波神经网络的空调系统传感器故障诊断

详细阐述了小波神经网络(WNN)的原理、结构,并对传统的BP算法进行了改进。以空调系统传感器故障检测问题为目标,提出了基于WNN的故障诊断方法。通过采集天津博物馆中的传感器数据,对训练好的WNN进行了传感器故障诊断能力的验证,对温度传感器的1℃偏差故障、0.05℃/s速率漂移故障、完全故障、与不同方差下的精度等级下降故障进行了仿真,结果表明:这种方法对传感器故障具有很好的诊断效果。     

小波神经网络在滚动轴承故障诊断中的应用

结合小波变换和神经网络的优势给出小波神经网络的结构模型,研究了小波神经网络的学习算法;针对传统算法收敛速度慢等问题,从学习率和引入动量项两个方面对算法进行改进。应用小波网络对滚动轴承的典型故障进行实例诊断。以7216圆锥轴承在实验台上所测取的数据进行网络训练。用振动信号为网络输入向量,给出训练结果。仿真实例表明,采用小波神经网络能够很好地对故障进行分类,其收敛速度明显要快于相同条件BP神经网络,有效地实现了滚动轴承的故障诊断。