Fault detection based on robust characteristic dimensionality reduction

In this paper, a novel fault detection method is developed based on robust characteristic dimensionality reduction (RCDR). The time-constrained sparse representation (TCSR) method is firstly introduced by considering the space and time characteristics of industrial process monitoring data simultaneously. It can remove space-related outliers, time-related outliers and noises by solving an optimization problem. Then, a new RCDR method is proposed, which fully utilizes the constructed robust adjacency graph and considers the data characteristics. Its scatter matrices are specially designed by consideration of the data characteristics of fault detection. The within-class scatter matrix only characterizes normal data set with a classic covariance matrix, while the inter-class scatter matrix characterizes the separability between normal data and fault data through a pre-defined scatter matrix. It is worth mentioning that our method does not make Gaussian assumptions about the distribution of the fault data, and the number of projection directions is not limited as well. The TCSR is also embedded into our proposed dimensionality reduction method, enabling it to handle the fault detection problem under strong disturbances. Simulations on Tennessee Eastman process (TEP) and a case study of electric multiple unit (EMU) braking system of high-speed trains fully demonstrate the effectiveness and applicability of our proposed fault detection method.     

动车底部螺栓快速定位方法

动车底部闸瓦部位的螺栓是列车制动系统中的一个重要零件,对列车的安全制动和行驶起着关键作用。对于列车零部件的维护,传统的人工检修模式显然不再适应当前铁路运输领域中高效率、高质量的检修要求。随着计算机技术和电子技术的发展,基于机器视觉的在线检测系统在工业测量领域正在发挥着越来越重要的作用。在室外复杂环境下,通过图像处理和分析的方法对螺栓进行自动检测和识别,是一种行之有效的方法,但是充满了挑战。提出了一种基于特征提取和机器学习相结合的方法,实现了螺栓的快速定位和检测。通过实验验证,提出的算法对外界复杂环境,特别是光线的变化,具有较强的鲁棒性。     

基于压缩感知和深度小波网络的列车故障识别

针对列车走行部故障振动数据无监督特征学习的难点，提出了一种基于压缩感知和深度小波神经网络（CS-DWNN）的列车故障识别方法。首先，对采集得到的列车走行部振动信号利用高斯随机矩阵进行压缩采样；其次，构建以改进小波自编码器（WAE）为基础的深层小波网络，将压缩后的信号直接输入网络进行自动逐层特征提取；最后，用DWNN学习到的多层特征分别训练多个深度支持向量机（DSVM）和深度森林（DF）分类器，并将识别结果进行集成。该方法利用深层小波网络从压缩信号中自动挖掘隐藏的故障信息，受先验知识和主观影响较小，并且避免了复杂的人工特征提取过程。实验结果表明，CS-DWNN方法取得了99.16%的平均诊断正确率，能够有效识别列车走行部的3种常见故障，识别能力优于传统的人工神经网络（ANN）、支持向量机（SVM）等方法和深度信念网络（DBN）、堆栈降噪自编码器（SDAE）等深度学习模型。     

A new feature extraction approach based on one dimensional gray level co-occurrence matrices for bearing fault classification

ABSTRACT

Recently, precise and deterministic feature extraction is one of the current research topics for bearing fault diagnosis. For this aim, an experimental bearing test setup was created in this study. In this setup, vibration signals were obtained from the bearings on which artificial faults were generated in specific sizes. A new feature extraction method based on co-occurrence matrices for bearing vibration signals was proposed instead of the conventional feature extraction methods, as in the literature. The One (1) Dimensional–Local Binary Patterns (1D-LBP) method was first applied to bearing vibration signals, and a new signal whose values ranged between 0–255 was obtained. Then, co-occurrence matrices were obtained from these signals. The correlation, energy, homogeneity, and contrast features were extracted from these matrices. Different machine learning methods were employed with these features to carry out the classification process. Three different data sets were used to test the proposed approach. As a result of analysing the signals with the proposed model, the success rate is 87.50% for dataset1 (different speed), 96.5% for dataset2 (fault size (mm)) and 99.30% for dataset3 (fault type – inner ring, outer ring, ball) was found, respectively.     

基于Treelet变换的模拟电路故障诊断

针对模拟电路故障诊断中特征向量冗余的问题,提出一种基于Treelet变换的模拟电路故障诊断方法.Treelet变换是一种自适应的多尺度的数据分析方法,适用于对高维数据降维和特征选择。文中首先对被测电路的输出信号采样,将采集到的信号进行Treelet变换,提取故障特征向量,最后将得到的特征向量输入BP神经网络进行故障模式识别。仿真实验结果表明,该方法能够有效地提取电路故障特征。与其他故障特征提取方法相比较,基于Treelet变换的模拟电路故障诊断方法具有较高的故障诊断率和收敛速度。     

高速铁路列车追踪间隔时间优化研究

目前我国高速铁路在CTCS2/3级运行条件下,基本达到3min追踪间隔时间,为进一步缩短列车追踪间隔时间,基于线路坡度参数,对列车制动距离进行多阶段划分,通过建立列车混合优化模型和基于动态规划的多阶段决策模型,采用COADP算法(自适应动态规划协同优化算法)优化列车制动距离,得到各阶段的最优决策序列,以及列车制动距离的最优目标函数,对高速铁路列车追踪间隔时间进行优化,并对ADP算法(自适应动态规划算法)和COPADP算法的优化结果进行了仿真对比,结果表明COADP算法不仅有效避免了ADP算法的"维数灾"问题,而且对追踪间隔时间的优化作用更为明显,提升了高速铁路的通过能力。     

Diagnosis of multiple and unknown faults using the causal map and multivariate statistics

Feature extraction is crucial for fault diagnosis and the use of complementary features allows for improved diagnostic performance. Most of the existing fault diagnosis methods only utilize data-driven and causal connectivity-based features of faults, whereas the important complementary feature of the propagation paths of faults is not incorporated. The propagation path-based feature is important to represent the intrinsic properties of faults and plays a significant role in fault diagnosis, particularly for the diagnosis of multiple and unknown faults. In this article, a three-step framework based on the modified distance (DI) and modified causal dependency (CD) is proposed to integrate the data-driven and causal connectivity-based features with the propagation path-based feature for diagnosing known, unknown, and multiple faults. The effectiveness of the proposed approach is demonstrated on the Tennessee Eastman process.     

基于句法依存分析的图网络生物医学命名实体识别

现有的生物医学命名实体识别方法没有利用语料中的句法信息,准确率不高.针对这一问题,提出基于句法依存分析的图网络生物医学命名实体识别模型.首先利用卷积神经网络(CNN)生成字符向量并将其与词向量拼接,然后将其送入双向长短期记忆(BiLSTM)网络进行训练;其次以句子为单位对语料进行句法依存分析,并构建邻接矩阵;最后将Bi...     

Ridge regression-based feature extraction for hyperspectral data

Feature extraction based on ridge regression (FERR) is proposed in this article. In FERR, a feature vector is defined in each spectral band using the mean of all classes in that dimension. Then, it is modelled using a linear combination of its farthest neighbours from among other defined feature vectors. The representation coefficients obtained by solving the ridge regression model compose the projection matrix for feature extraction. FERR can extract each desired number of features while the other methods such as linear discriminant analysis (LDA) and generalized discriminant analysis (GDA) have limitations in the number of extracted features. Experimental results on four popular real hyperspectral images show that the efficiency of FERR is superior to those of other supervised feature extraction methods in small sample-size situations. For example, for the Indian Pines dataset, the comparison between the highest average classification accuracies achieved by different feature extraction methods using a support vector machine (SVM) classifier and 16 training samples per class shows that FERR is 7% more accurate than nonparametric weighted feature extraction and is also 9% better than GDA. LDA, having the singularity problem in the small sample-size situations, has 40% less accuracy than FERR. The experiments show that generally the performance of FERR using the SVM classifier is better than when using the maximum likelihood classifier.     

基于S域NMF的模拟电路故障特征提取新方法

针对提取的模拟电路故障特征向量信息不够充分的问题,提出了一种将S时频变换(ST,S-transform)和非负矩阵分解(NMF,non-negative matrix factorization)相结合的特征选取新方法.该方法先对模拟电路故障响应信号应用S时频变换建立时频图谱矩阵,再用NMF算法构造时频图谱数据集合的子空间基矩阵,有效降低了投影特征向量的维数,保留了足够多的故障隐含特征信息,进而提高模拟电路故障识别率.最后,在Sallen-Key高通滤波器电路中验证了文中方法的有效性.     

Generic form feature recognition and operation selection using connectionist modelling

For the purpose of enhancing the adaptability of computer-aided process planning systems, two connectionist modelling methods, namely neocognitron (i.e. neural network modelling for pattern recognition) and fuzzy associative memories (FAM), are applied to the phases of feature recognition and operation selection respectively in order to provide the system with the ability of self-learning and the ability to integrate traditional expert planning systems with connectionism-based models. In this paper, the attributed adjacency graph (AAG) extracted from a (B-Rep) solid model is converted to attributed adjacency matrices (AAM) that can be used as input data for the neocognitron to train and recognize feature patterns. With this technique, the system can not only self-reconstruct its recognition abilities for new features by learning without a priori knowledge but can also recognize and decompose intersection features. A fuzzy connectionist model, which is created using the Hebbian fuzzy learning algorithm, is employed subsequently to map the features to the appropriate operations. As the algorithm is capable of learning from rules, it is much easier to integrate the proposed model with conventional expert CAPP systems so that they become more generic in dealing with uncertain information processing and perform knowledge updating. mg]Keywords mw]Computer-aided process planning mw]feature recognition mw]neural networks mw]fuzzy neural networks mw]operation selection mw]connectionist model mw]fuzzy associative memories     

基于小波分析的高速列车车体运行状态估计

基于监测数据评估高速列车空气弹簧和横向减振器等关键部件的运行状态, 针对车体垂向加速度振动信号, 提出了小波包能量矩的列车状态估计方法。首先分析车体垂向振动特征, 对不同工况和不同速度下的信号进行小波包分解, 并重构能量较大的频带信号, 再计算各频带的小波包能量矩特征, 不同频带信号的小波包能量矩变化反映了列车运行状态的改变。将不同频带的小波包能量矩组成特征向量, 最后用支持向量机进行故障识别。实验数据仿真分析表明, 列车空簧失气故障和横向减振器失效故障识别率为100%, 说明该方法能很好地估计出高速列车的故障状态。     

基于维修日志的飞机设备故障原因判别方法

在飞机维修与保养过程中,航空维修公司已积累了大量经验性的维修日志数据.合理利用该类维修日志,结合机器学习方法,可以辅助维修人员做出正确的故障诊断决策.首先,针对维修日志的特殊性,提出一种迭代式的故障诊断基本过程;其次,在传统的文本特征提取技术的基础上,基于领域内信息,提出一种基于卷积神经网络（convolution neural network,简称CNN）的小样本文本特征提取方法,在样本量较少的情况下,利用预测目标将字向量作为输入,得到更为充分的文本特征;最后,使用随机森林（random forest,简称RF）模型,结合其他故障特征判别飞机设备的故障原因.卷积神经网络以故障原因为目标,预先对故障现象中的字向量进行训练,从而得到更能反映该领域的文本特征.与其他文本特征提取方法相比,该类方法在小样本数据上得到了更好的效果.同时,将卷积神经网络与随机森林模型应用于飞机设备的故障原因判别,并与其他文本特征提取方式和机器学习预测模型进行对比,说明了该类文本特征提取方式和故障原因判别方法的合理性和必要性.     

模糊预测-PID复合控制在高速列车制动中的应用

为解决高速列车的快速、准确、舒适停车问题,分析并建立了列车制动的牵引力模型;综合考虑列车制动过程中舒适度因素的影响,提出了带有舒适度约束条件的模糊预测-PID复合控制方法。该控制方法结合了模糊预测控制以及模糊PID控制的优点,使列车制动过程的控制没有死角,控制状况始终处于最优。在制动距离较大情况下采用模糊预测控制修正控制量,优化制动力,使制动过程满足舒适度要求;在距离较近的情况下,采用模糊PID实现列车的准确停车。仿真结果证明了该方法的可行性和有效性。     

高速列车牵引传动系统故障测试与验证仿真平台研究

牵引传动系统作为高速列车能量传递与转换的核心部分, 是保障高铁安全稳定运行的关键系统之一. 故障测试与验证平台是确保实时故障诊断技术在高速列车上有效应用的重要手段和途径. 围绕高速列车牵引传动系统故障测试与验证平台中面临的挑战性问题和关键技术, 本文从故障注入、仿真可信度评估、算法性能评估和仿真平台实现等方法和技术方面进行分析, 并针对上述难题概述了一些解决方案, 提出并构建了一种集高速列车实时仿真、故障运行行为逼真模拟以及随机故障测试和故障诊断算法评估于一体的牵引传动系统故障测试与验证实时仿真平台. 最后, 总结展望了高速列车安全监测验证平台未来研究方向.     

基于栈式自编码网络的风机叶片结冰预测

针对风电机组叶片结冰严重影响风机发电效率和安全性、经济性的问题，提出一种基于SCADA数据的栈式自编码（SAE）网络叶片结冰早期预测模型。该模型采用编码-解码的非监督方法对无标签的数据集预训练，再利用反向传播算法对有标签的数据集进行训练微调，实现了故障特征的自适应提取和状态分类，有效降低了传统预测模型的复杂度，同时避免了人为特征提取对模型效果的影响。利用SCADA系统采集的某15号风机的历史数据进行训练和测试，该模型测试结果准确率为97.28%。与支持向量机（SVM）和主成分分析-支持向量机（PCA-SVM）方法得到的建模分别为91%和93%的准确率进行对比分析，实验结果表明，基于栈式自编码网络的风机叶片结冰预测模型精确度更高。     

Two-dimensional supervised local similarity and diversity projection

This paper presents a novel manifold learning method, namely two-dimensional supervised local similarity and diversity projection (2DSLSDP), for feature extraction. The proposed method defines two weighted adjacency graphs, namely similarity graph and diversity graph. The affinity matrix of similarity graph is determined by the spatial relationship between vertices of this graph, while affinity matrix of diversity graph is determined by the diversity information of vertices of its graph. Using these two graphs, the proposed method constructs local similarity scatter and diversity scatter, respectively. A concise feature extraction criterion is then raised via minimizing the ratio of the local similarity scatter to local diversity scatter. Thus, 2DSLSDP can well preserve not only the adjacency similarity structure, but also the diversity of data points, which is important for the classification. Experiments on the AR and UMIST databases show the effectiveness of the proposed method.     

基于子树特征的中文实体关系抽取

基于核函数的实体关系抽取方法将信息隐含在核函数中,无法辨别有用和无用信息,会引入噪声。为此,提出一种基于子树特征的实体关系抽取方法。利用子树挖掘和特征选择得到有效子树,并将其作为特征模板构造特征向量。在中文语料库上进行的实验结果表明,该方法具有较好的分类效果。     

高速列车牵引系统故障诊断与预测技术综述

高速列车因其舒适、便捷、安全和准时, 已成为我国主流的城际间交通工具.CRH(China railway high- speed)动车组高速列车是一个大型复杂的机电耦合系统,作为其重要组成部分,牵引控制系统的可靠性对于高速列车的安全运行至关重要.随着在轨运行时间的增长,牵引控制系统中的很多部件都会发生不同程度的性能衰退,并引发各种故障,给高速列车的安全运行带来潜在的危险.鉴于此,针对牵引变压器、牵引变流器(整流器、逆变器)、牵引电机、转向架系统、牵引/制动控制单元等与高速列车牵引系统相关的重要部件和单元的故障诊断、容错控制与预测方法进行现状调研和分析,并对每种方法的基本思路、现阶段进展以及适用条件等进行了介绍,最后陈述了高速列车牵引控制系统故障诊断与预测领域尚待解决的问题.     

Adaptive diagnosis of DC motors using R-WDCNN classifiers based on VMD-SVD

Traditional fault diagnosis methods of DC (direct current) motors require high expertise and human labor. However, the other disadvantages of these methods are low efficiency and poor accuracy. To address these problems, a new adaptive and intelligent mechanical fault diagnosis method for DC motors based on variational mode decomposition (VMD), singular value decomposition (SVD), and residual deep convolutional neural networks with wide first-layer kernels (R-WDCNN) was proposed. First, the vibration signals of a DC motor were collected by a designed acquisition system. Subsequently, VMD was employed to decompose the raw signals adaptively into several intrinsic mode functions (IMFs). Moreover, the transient frequency means method, which can quickly and accurately obtain the optimal value of K, is proposed. SVD was applied to reduce the dimensionality of the IMF matrix for further feature extraction. Finally, the reconstructed matrix containing the main fault feature information was used to train and test the R-WDCNN. Based on residual learning, identification and classification of four types of vibration signals were achieved, while the R-WDCNN was optimized by the adaptive batch normalization algorithm (AdaBN). The recognition rate and the convergence were improved by this classifier. The results show that the method proposed in this paper has better adaptability and intelligence than other methods, and the R-WDCNN can reach a 94% recognition rate on unknown samples. Therefore, the proposed method is more intelligent and accurate than other methods.