Analysis of superheater's pipe wall overtemperature by fault tree diagnose

After research on a 2000t/h subcritical forced-circulation balanced ventilation were applied boiler and the structure and operation of its auxiliary system builds up this heat transfer model of a superheater's pipe wall and analyze the effect of primary factors on the overtemperature of the pipe wall. Fault tree structure was used to uncover the multiplayer logic between the overtemperature of the superheater's pipe wall and the faults.

Study on Method of Fault Vibration Diagnose for Roller Overrunning Clutch

Fault diagnose of the roller overrunning clutch is a headache problem in engineering at home and abroad. This paper introduces a new method to solve the problem by using the wavelet transform to separate fault si gnal and further analyzing the impact frequency. The signal local singularities under the wavelet transform are studied. According to the propagation features of modulus maximums of the fault signal and the noise under the wavelet transfor m different on the scales, and by use of the signal wavelet decomposition-recon struction algorithm, the clutch shell vibration acceleration signal is decompose d, denoised, and reconstructed.The signal-to-noise of the monitored signal imp roved greatly.The fault characteristic signal on time domain is positioned.The f ault characteristic frequency is picked up. Experiment shows that it is quite effective.

Evaluation of fault diagnosability for nonlinear uncertain systems with multiple faults occurring simultaneously

Up to present,the problem of the evaluation of fault diagnosability for nonlinear systems has been investigated by many researchers.However,no attempt has been done to evaluate the diagnosability of multiple faults occurring simultaneously for nonlinear systems.This paper proposes a method based on differential geometry theories to solve this problem.Then the evaluation of fault diagnosability for affine nonlinear systems with multiple faults occurring simultaneously is achieved.To deal with the effect of control laws on the evaluation results of fault diagnosability,a design scheme of the evaluation of fault diagnosability is proposed.Then the influence of uncertainties on the evaluation results of fault diagnosability for affine nonlinear systems with multiple faults occurring simultaneously is analyzed.The numerical simulation results are obtained to show the effectiveness of the proposed evaluation scheme of fault diagnosability.

Application of Single Channel Blind Separation Algorithm Based on EEMD-PCA-RobustICA in Bearing Fault Diagnosis

Aiming at the problem that ICA can only be confined to the condition that the number of observed signals is larger than the number of source signals;a single channel blind source separation method combining EEMD, PCA and RobustICA is proposed. Through the eemd decomposition of the single-channel mechanical vibration observation signal the multidimensional IMF components are obtained, and the principal component analysis (PCA) is performed on the matrix of these IMF components. The number of principal components is determined and a new matrix is generated to satisfy the overdetermined blind source separation conditions, the new matrix input RobustICA, to achieve the separation of the source signal. Finally, the isolated signals are respectively analyzed by the envelope spectrum, the fault frequency is extracted, and the fault type is judged according to the prior knowledge. The experiment was carried out by using the simulation signal and the mechanical signal. The results show that the algorithm is effective and can accurately diagnose the location of mechanical fault.

Fault Diagnosing System of Steam Generator for Nuclear Power Plant Based on Fuzzy Neural Networks

All kinds of reasons are analysed in theory and a fault repository combined with local expert experiences is establishedaccording to the structure and the operation characteristic of steam generator in this paper. At the same time, Kohonen algo-rithm is used for fault diagnoses system based on fuzzy neural networks. Fuzzy arithmetic is inducted into neural networks tosolve uncertain diagnosis induced by uncertain knowledge. According to its self-association in the course of default diagnosis. thesystem is provided with non-supervise, self-organizing, self-learning, and has strong cluster ability and fast cluster velocity.

Petri net model for diagnosis of permanent faults of a hydraulic system

Petri net model is applied to diagnose the permanent fault of hydraulic system within the framework of interpreted Petri net. The permanent fault is described as redundant structure of the model. A definition and a theorem are proposed to determine the diagnosability of the hydraulic system. The relations bwtween the diagnosability and other structure properties are also discussed. An example of actual hydraulic system is presented and its permanent fault can be diagnosed by the proposed method efficiently.

Restricted-Faults Identification in Folded Hypercubes under the PMC Diagnostic Model

System-level fault identification is a key subject for maintaining the reliability of multiprocessor interconnected systems. This task requires fast and accurate inferences based on big volume of data, and the problem of fault identification in an unstructured graph has been proved to be NP-hard （non-deterministic polynomial-time hard）. In this paper, we adopt the PMC diagnostic model （first proposed by Preparata, Metze, and Chien） as the foundation of point-to-point probing technology, and a system contains only restricted-faults if every of its fault-free units has at least one fault-free neighbor. Under this condition we propose an efficient method of identifying restricted-faults in the folded hypercube, which is a promising alternative to the popular hypercube topology.

THEORY ON THE DIAGNOSABILITY OF THE FAULT CLASSIFICATION APPROACH

This paper describes, by means of a Voronoi hypersphere, the nearest neighbor relations of all the feature submatrices in the fault classification space and analyses the deviation disturbance angles between fault feature submatrices and a k-dimension unitary matrix of the measured voltage change matrix. With the above two concepts, this paper discusses the diagnos-ability in the fault classification approach. The paper also classifies and defines the fault diagnosis problems. Finally, the paper derives the corresponding necessary and sufficient conditions for correct location of faults.

An Improved Approach to Test Diagnosability of Bounded Petri Nets

For bounded Petri nets, Cabasino et al. propose a diagnosability test method that is based on the analysis of a modified basis reachability graph and a basis reachability diagnoser. However, its complexity is exponential in the number of nodes of the basis reachability diagnoser. In order to reduce the complexity of their method, this paper presents a new diagnosability test approach for bounded Petri nets. We present the concept of an extended basis reachability graph and prove that our approach is of polynomial complexity in the number of nodes of extended basis reachability graphs. An example is given to illustrate the application of the presented approach. © 2017 Chinese Association of Automation.

基于贝叶斯网络的卫星通信设备故障诊断研究

卫星通信作为保障平台遂行任务时重要的通信保障手段,使得卫星通信设备需在出现故障时能快速定位问题并解决问题具有重要意义。论文基于贝叶斯网络进行卫星通信设备故障诊断,构建故障诊断模型,并使用贝叶斯工具Neti-ca软件对该模型进行了分析,得出卫星通信设备出现故障时设备部件可能发生故障的概率,结果表明该方法可为卫星通信设备故障的快速定位提供依据,提升卫星通信设备故障诊断效率,支撑任务顺利遂行。

基于DTW时序距离的故障可诊断性评估方法

对装备中具体故障进行可诊断性评估,可以量化地表明故障被诊断的难易程度。针对故障可诊断性评价方法中存在的不客观及度量方法选择不恰当的问题,提出一种基于动态时间规整(Dynamic Time Warping,DTW)的时序距离度量方法。定义可诊断性评估模型,从实际系统中抽取系统的结构、信号、测试、故障模式4种要素,为故障可诊断性评估工作的开展打下基础。摒弃传统的从信号中提取特征进行相似性度量的做法,将信号看做时序序列,基于DTW方法衡量不同状态下各信号之间的相似程度,作为故障可诊断性的评估依据。使用动量轮系统对新方法进行仿真实验,仿真结果表明新方法在进行可诊断性评估方面具有客观性和有效性。

Y-Δ接法分数槽永磁电机断相故障电流特征分析与诊断方法研究

星-三角(Y-△)接法的分数槽永磁电机(fractional-slot permanent magnet machine,FS-PMM)因其谐波分量低、转矩脉动小等优点在电动汽车领域具有较好的应用前景。但由于该电机中的△接绕组位于电机内部,其电流无法直接测量,故障时难以被及时发现。该文针对Y-△接法的FS-PMM内层△接绕组单相断相故障,提出一种基于电流三次谐波幅值的故障诊断方法。首先,建立△接绕组单相断相故障下的数学模x相故障的检测与故障相定位。经实验验证,所提方法能够实时准确地实现△接绕组单相断相故障诊断,且具有良好的鲁棒性。

基于故障敏感度学习和集成学习的可诊断性设计方法

对系统进行可诊断性设计,能优化诊断方案、提升诊断方案与系统的契合程度,对于准确检测或隔离系统故障具有重大意义。为此提出一种基于故障敏感度学习和集成学习的可诊断性设计方法。对于采集到的不同状态下的系统测试点信号进行特征提取,结合系统的可诊断性评价结果,提出特征贡献度量化算法,对信号中不同特征对故障诊断的贡献度进行评估,使用改进的D-S证据理论算法对不同信号的特征进行融合,确定适用于故障检测与隔离的故障敏感特征集合;采用集成学习方法对基分类器的诊断效果进行加强,最终获得对当前系统的诊断方案。仿真实验结果表明,采用新的可诊断性设计方法设计出来的针对系统的诊断方案,可以对系统故障进行良好的诊断,其中与未进行故障敏感度学习环节相比,故障诊断的错误率由5.33%下降到2.66%,与未进行集成学习环节相比,故障诊断的错误率由16.22%(基诊断器的平均值)下降到2.66%。在与其他诊断方案的对比实验中,新方法的故障诊断错误率相较于对比方法的平均值下降了3.34%。

考虑噪声影响的基于Wasserstein测度的可诊断性评价方法

针对可诊断性评价中区分度不足以及评价结果难以解释等问题,提出了一种基于Wasserstein测度的可诊断性定量评价方法。该方法以系统在不同状态下测点的量测信号为基础,将信号视作随机变量,使用2-Wasserstein测度作为衡量变量之间相似程度的手段,来实现对系统的可诊断性评价,同时分析了量测信号对于可诊断性评价结果的影响。使用双带通滤波电路对所提方法进行验证,结果表明,相较于基于K-L散度和D矩阵的可诊断性评价方法,所提方法在进行评价故障可诊断性方面更具客观性和科学性。

笼型异步电机故障诊断实验台设计

异步电机是最常见的电气设备,在国民生产活动中占有重要的地位,电机故障诊断能够有效降低事故发生率和企业运行成本,对其进行研究有着重要的意义。为此以常用的笼型异步电机故障为对象,在完成电机及负载的选择、故障设置和电气系统设计的基础上,以电压、电流作为基本分析信号,完成了故障诊断实验台的开发。在该实验台上设置了气隙偏心、转子断条和匝间短路等三种故障,通过对输出电流信号进行了傅里叶变换和Park变换,对其故障特征进行了对比分析。结果表明,当电机存在气隙偏心故障时,在25Hz及75Hz频率点附近出现特征分量,当存在转子断条故障时,分别在频率为44.9Hz、45.9Hz、54.1Hz及55.1Hz处出现特征分量,当存在匝间短路故障时,Park轨迹图的椭圆形扁平程度会随着故障程度的增加越来越高。

柴油机故障诊断技术的现状及展望

柴油机作为—种复杂动力机械 ,其运行状态监测和故障诊断技术越来越受到人们的关注。在柴油机故障诊断领域 ,信号处理、故障特征提取及识别方法已初具雏形 ,但离实用化还有一定距离。笔者分析了柴油机常见故障及影响因素 ,综述了现代柴油机故障诊断技术中常用的各种基于振动信号的时频分析法、瞬时转速波动法、铁谱及光谱分析法、灰色系统理论诊断法、神经网络诊断法及专家系统诊断法的原理、特点及不足 ,最后指出了柴油机故障诊断的难点和发展方向。

基于故障树的模糊故障诊断方法

随着电 -气、电 -液控制系统在工程车辆上的广泛运用 ,解决其控制电路的故障诊断日趋重要 .虽然采用数字电路是其应用主流 ,但仍有大量模拟电路正在使用中 ,探讨其有效的故障诊断方法有实际意义 .考虑到故障诊断方法及检测效果的差别 ,提出一种结合故障树与模糊诊断的新方法 .通过分析故障树结构 ,提取征兆集和故障集 ,利用权矩阵得出故障隶属度输出 ,根据判断法则确定某工程车辆模拟控制电路的故障位置 ,提供了维修人员所需的诊断参考数据 ,并给出诊断流程图 .

基于分形理论的斯太尔汽车发动机故障诊断的研究

研究了斯太尔汽车发动机气缸在不同状态下的关联维数，给出了获得反映其真实状态的关联维数方法。研究结果表明：该发动机气缸振动的时间序列在不同状态下关联维数不同，可以将其关联维数作为识别其状态的特征量，给出了利用分形理论判断斯太尔汽车发动机气缸状态的判椐。

裂纹碰摩耦合故障转子系统诊断分析

采用有限元方法分析了裂纹碰摩耦合故障转子系统的响应,研究裂纹碰摩耦合故障转子系统在动态特性方面和单一裂纹故障、单一碰摩故障的区别及耦合故障的诊断方法。由于当碰摩比较严重时,响应信号中碰摩特征比较明显,容易掩盖裂纹特征,使基于信号分析的诊断方法只能诊断出碰摩,难以诊断出裂纹故障,因此本文利用裂纹引起的等效弯矩现象,通过基于模型的诊断方法,区别碰摩裂纹耦合故障和碰摩故障,该方法不仅能诊断裂纹的有无,还能诊断裂纹的位置。最后通过试验验证了仿真结果。

汽轮发电机转子绕组匝间短路故障诊断新判据

该文分析了发生转子绕组匝间短路时,汽轮发电机的电磁特性及导致的相关电气参量的变化,提出了在转子发生匝间短路故障时,励磁电流增加而无功输出量却相对减少的特征。根据确定的故障特征,找到一种利用故障前后励磁电流相对变化率作为识别故障的方法,从而建立了在线识别转子匝间短路故障的判据。该判据可以反映故障的严重程度,最后利用动态模拟试验机组进行了相关的实验,得到了与理论分析相吻合的结论。