Fault diagnosis method of hydraulic system based on fusion of neural network and D-S evidence theory

According to fault type diversity and fault information uncertainty problem of the hydraulic driven rocket launcher servo system（HDRLSS） , the fault diagnosis method based on the evidence theory and neural network ensemble is proposed. In order to overcome the shortcomings of the single neural network, two improved neural network models are set up at the com-mon nodes to simplify the network structure. The initial fault diagnosis is based on the iron spectrum data and the pressure, flow and temperature（PFT） characteristic parameters as the input vectors of the two improved neural network models, and the diagnosis result is taken as the basic probability distribution of the evidence theory. Then the objectivity of assignment is real-ized. The initial diagnosis results of two improved neural networks are fused by D-S evidence theory. The experimental results show that this method can avoid the misdiagnosis of neural network recognition and improve the accuracy of the fault diagnosis of HDRLSS.

Application of Multi-sensor Information Fusion in the Fault Diagnosis of Hydraulic System

Aiming at the problem of incomplete information and uncertainties in the diagnosis of complex system by using single parameter, a new method of multi-sensor information fusion fault diagnosis based on BP neural network and D-S evidence theory is proposed. In order to simplify the structure of BP neural network, two parallel BP neural networks are used to diagnose the fault data at first; and then, using the evidence theory to fuse the local diagnostic results, the accurate inference of the inaccurate information is realized, and the accurate diagnosis resuh is obtained. The method is applied to the fault diagnosis of the hydraulic driven servo system （HDSS） in a certain type of rocket launcher, which realizes the fault location and diagnosis of the main components of the hydraulic driven servo system, and effectively improves the reliability of the system.

Application of the fault diagnosis strategy based on hierarchical information fusion in motors fault diagnosis

This paper has analyzed merits and demerits of both neural network technique and of the information fusion methods based on the D-S (dempster-shafer evidence) Theory as well as their complementarity, proposed the hierarchical information fusion fault diagnosis strategy by combining the neural network technique and the fused decision diagnosis based on D-S Theory, and established a corresponding functional model. Thus, we can not only solve a series of problems caused by rapid growth in size and complexity of neural network structure with diagnosis parameters increasing, but also can provide effective method for basic probability assignment in D-S Theory. The application of the strategy to diagnosing faults of motor bearings has proved that this method is of fairly high accuracy and reliability in fault diagnosis.

Study on Power Transformers Fault Diagnosis Based on Wavelet Neural Network and D-S Evidence Theory

>Transformer faults are quite complicated phenomena and can occur due to a variety of reasons.There have been several methods for transformer fault synthetic diagnosis,but each of them has its own limitations in real fault diagnosis applications.In order to overcome those shortcomings in the existing methods,a new transformer fault diagnosis method based on a wavelet neural network optimized by adaptive genetic algorithm(AGA)and an improved D-S evidence theory fusion technique is proposed in this paper.The proposed method combines the oil chromatogram data and the off-line electrical test data of transformers to carry out fault diagnosis.Based on the fusion mechanism of D-S evidence theory,the comprehensive reliability of evidence is constructed by considering the evidence importance,the outputs of the neural network and the expert experience.The new method increases the objectivity of the basic probability assignment(BPA)and reduces the basic probability assigned for uncertain and unimportant information.The case study results of using the proposed method show that it has a good performance of fault diagnosis for transformers.

INTELLIGENT FUSION FOR AEROENGINE WEAR FAULT DIAGNOSIS

Four common oil analysis techniques, including the ferrography analysis （FA）, the spectrometric oil analysis （SOA）, the particle count analysis （PCA）, and the oil quality testing （OQT）, are used to implement the military aeroengine wear fault diagnosis during the test drive process. To improve the precision and the reliability of the diagnosis, the aeroengine wear fault fusion diagnosis method based on the neural networks （NN） and the Dempster-Shafter （D-S） evidence theory is proposed. Firstly, according to the standard value of the wear limit, original data are pre-processed into Boolean values. Secondly, sub-NNs are established to perform the single diagnosis, and their training samples are dependent on experiences from experts. After each sub-NN is trained, diagnosis results are obtained. Thirdly, the diagnosis results of each sub-NN are considered as the basic probability allocation value to faults. The improved D-S evidence theory is applied to the fusion diagnosis, and the final fusion results are obtained. Finally, the method is verified by a diagnosis example.

Fault Isolation of Light Rail Vehicle Suspension System Based on D-S Evidence Theory and Improvement Application Case

This paper presents an innovative approach for the fault isolation of Light Rail Vehicle (LRV) suspension system based on the Dempster-Shafer (D-S) evidence theory and its improvement application case. The considered LRV has three rolling stocks and each one equips three sensors for monitoring the suspension system. A Kalman filter is applied to generate the residuals for fault diagnosis. For the purpose of fault isolation, a fault feature database is built in advance. The Eros and the norm distance between the fault feature of the new occurred fault and the one in the feature database are applied to measure the similarity of the feature which is the basis for the basic belief assignment to the fault, respectively. After the basic belief assignments are obtained, they are fused by using the D-S evidence theory. The fusion of the basic belief assignments increases the isolation accuracy significantly. The efficiency of the proposed method is demonstrated by two case studies.

基于加权D-S证据理论的旋翼故障诊断

旋翼作为直升机的升力面和操作面,其健康状态对直升机的安全至关重要。旋翼故障诊断技术仍是直升机健康与使用监测系统(Health and usage monitoring system, HUMS)领域的薄弱环节,开发旋翼故障诊断技术具有重要价值。基于信息融合技术,首先分析了旋翼故障的诊断机理,建立了旋翼故障模型,通过流固耦合仿真获取了不同故障下桨叶、轮毂和机身的故障特征信息,生成数据集进行网络训练和验证。然后,利用遗传算法反向传播(Genetic algorithm-backpropagation, GA-BP)优化神经网络诊断3种类型的直升机旋翼故障,即后缘调整片误调、变距拉杆误调和桨叶质量不平衡。3个逐级神经网络分别对旋翼故障类型、故障位置和故障程度进行了诊断识别。最后采用加权的Dempster-Shafer(D-S)证据理论对旋翼故障进行诊断和分析。结果证明基于改进D-S证据理论的旋翼故障诊断方法能够成功应用到旋翼故障诊断中,并具有良好的识别效果。

基于多传感器信息融合的水工闸门故障诊断

针对水工闸门安全检修困难、检修效率低的问题,提出了一种基于支持向量机(Support vector machine,SVM)和改进D-S证据理论的信息融合水工闸门故障诊断方法。该方法通过提取不同传感器诊断信号小波包信息熵特征构建特征子空间,然后在每个特征子空间构建诊断子网络,最后使用改进证据理论对每个诊断子网络的输入进行决策层融合,从而水工闸门的多信息融合诊断结果。闸门故障诊断实验结果显示,信息融合的闸门故障诊断方法可有效识别弧形闸门故障种类,其故障诊断准确率达到了98.33%,同时诊断可靠度高,各类故障的诊断不确定度均小于1%。实验结果验证了智能故障诊断方法用于水工闸门领域的可行性,对于改进水工闸门故障检修方式,推动水利工程智能化的发展具有重大意义。

面向多源不确定性数据的往复压缩机决策级融合诊断方法

为解决不确定性高的数据源使多源信息融合诊断模型精度降低的问题,提出1种面向不确定性数据的往复压缩机决策融合诊断方法。构建基于GRU-AlexNet网络的初步诊断模型,得到往复压缩机各传感器信号的初始诊断结果,并引入余弦相似度与置信熵的概念构建联合指标改进传统DS证据理论,结合初步诊断结果进行多源信号决策融合诊断。研究结果表明:在对往复压缩机故障的加速度、位移、压力信号(不确定性数据)融合诊断试验中,融合诊断准确率高达99.98%,相较于单一信号源诊断结果分别提高约9.27,5.13,48.30个百分点。该方法可在较大程度上降低不确定性信息对于融合诊断结果的影响,具有良好的容错性与稳定性,可有效提高往复压缩机使用过程中各类故障识别的准确性,进而提高设备的稳定性,保证其良好工作状态。研究结果对保障相关企业安全生产、提高设备产出能力具有重要参考意义。

Multisensor Data Fusion for Automotive Engine Fault Diagnosis

This paper describes mainly a decision-level data fusion technique for fault diagnosis for elec-tronically controlled engines. Experiments on a SANTANA AJR engine show that the data fusion method provides good engine fault diagnosis. In data fusion methods, the data level fusion has small data preproc-essing loads and high accuracy, but requires commensurate sensor data and has poor operational perform-ance. The decision-level fusion based on Dempster-Shafer evidence theory can process noncommensurate data and has robust operational performance, reduces ambiguity, increases confidence, and improves sys-tem reliability, but has low fusion accuracy and high data preprocessing cost. The feature-level fusion pro-vides good compromise between the above two methods, which becomes gradually mature. In addition, ac-quiring raw data is a precondition to perform data fusion, so the system for signal acquisition and processing for an automotive engine test is also designed by the virtual instrument technology.

基于多维信息融合的电力变压器故障诊断方法研究

考虑到现有变压器故障诊断方法仅针对单一故障特征,难以对电力变压器的实际情况做出准确、全面的判断。在电力变压器多维信息融合的基础上,提出了一种改进极限学习机和改进D-S证据理论相结合的故障诊断方法。通过后验概率映射优化极限学习机的输出,得到不同标签的概率,使用改进的证据理论来融合概率分配矩阵。通过试验对诊断方法优化前后进行对比分析,验证了该方法的优越性。结果表明,与优化前的故障诊断方法相比,该方法具有更高的故障识别准确率,准确率达到96.50%,能准确识别出电力变压器的各种故障,可为状态检修提供决策依据。

多信息融合特征下的发动机故障自动化诊断研究

发动机工作过程的复杂性以及其故障诊断信息的繁杂性使得单一传感器难以较好识别与诊断故障问题。故研究对数据层、特征层以及诊断层进行多信息融合,并基于最大信息特征和主成分分析提出诊断模型。实验结果表明,模型对不同故障类型的数据提取偏差值低于5%,且其误差性能(<0.06%)和测试精度明显优于其他对比算法。多信息融合特征诊断算法能有效对发动机设备进行故障诊断,并提供新维修思路。

Dynamic Fault Diagnosis Using the Improved Linear Evidence Updating Strategy

The majority of the existing fault diagnosis methods using Dempster-Shafer(DS) evidence theory(DST) all provide the "static" fused results by combining several pieces of diagnosis evidence, which only reflect the current running status of monitored equipment. This paper presents the dynamic diagnosis strategy by using recursively the improved linear evidence updating rule. Its updated result can synthesize the diagnosis evidence collected at historical, current and future time steps by dynamically adjusting the proposed smoothing linear combination weights. The diagnosis examples of machine rotor show that the proposed method can provide more reliable and accurate results than the diagnosis methods based on the classical updating strategies.

小波熵证据的信息融合在电力系统故障诊断中的应用

电力系统中快速准确的故障诊断是事故后隔离故障元件、恢复系统正常运行的首要前提,具有重要意义。该文从信息融合的角度出发,提出利用多种小波熵测度的融合来解决电力系统故障诊断问题。小波熵测度由于结合了小波变换和信息熵理论的优势,能快速准确地提取线路故障特征,但由于故障的不确定性和多样性,依靠单一的小波熵测度诊断故障可能出现诊断困难或诊断失真等问题,因此提出采用D-S证据理论对多种小波熵进行信息融合,并采用范数加权平均的方法来建立基本可信度分配,以基本可信数的决策方法来实现故障模式诊断。基于EMTDC和Matlab的仿真证明,该方法能提高对故障诊断结果的支持度及故障诊断的准确性和实时性,是故障模式定量诊断的一种可行性新方法。

传感器多故障诊断的信息融合方法研究

提出了基于证据理论的在不同识别框架下的多传感器多故障诊断的信息融合方法。利用多个传感器在空间或时间上的冗余或互补信息,为故障的检测和分离提供诊断依据。采用模块化的径向基函数状态识别网络来获得传感器状态的证据,即发挥了神经网络的优点,又解决了因输入参数改变而不可用的缺点。提出了一种在不同识别框架下的证据组合规则,采用精细和粗化运算,可充分利用传感器的冗余或互补信息,减少传感器状态的不确定性。仿真结果表明该方法可以对传感器的单故障和多故障进行有效的诊断。

多传感器信息融合基本原理及应用

全面系统地阐述了多传感器信息融合技术的信息融合理论、模型、算法和应用,并对目前信息融合在机器人、故障诊断、图像处理等领域的应用现状进行了剖析。信息融合技术虽然发展迅速,但由于信息融合技术理论尚待完善,在融合算法、融合模型以及关联的二义性等方面还存在问题。信息融合理论在多传感器分布检测、异类多传感器融合以及建立信息融合数据库和知识库等方面将有进一步发展。

基于Dempster-Shafer证据理论的信息融合在设备故障诊断中应用

给出了一种基于神经网络的基本概率分配构造方法和诊断决策规则,提出了一种基于Dempster-Shafer证据理论的多故障特征信息融合的故障诊断方法,并以旋转机械故障诊断为例,详细说明了该方法的具体实现步骤.结果表明,经过多故障特征信息融合,诊断结论的可信度明显提高,不确定性明显减小,因此充分显示了该诊断方法的有效性.

基于随机集理论的并发故障诊断信息融合方法

为了诊断并发故障,提出一种基于随机集理论的信息融合方法。首先构造包含并发故障的论域,并在此论域的超幂集上定义扩展型随机集。基于该随机集和广义集值映射给出证据组合规则的随机集模型,用其构造可以同时适用于单发和并发故障诊断的新型组合规则。此外,根据传感器提供的故障信息构造故障样板模式与待检模式的模糊隶属度函数,利用模糊集的随机集表示以及随机集似然测度,获得两种模式匹配的程度作为待融合的诊断证据。最后通过在电机柔性转子平台上的试验,证明了所提方法可有效地减少单一传感器信息诊断的不确定性,显著提高转子系统故障诊断的精度。

基于证据理论的数字化变电站继电保护容错方法

在数字化变电站时代,过程层采样值信息的网络化传输和共享使得利用冗余信息快速识别错误数据成为可能。本文提出了一种对多源互感器数据进行综合分析以辨识错误数据,并防止继电保护装置误动的新方法。在介绍新方法基本原理的基础上,分析了证据的生成法则、融合信息的选取以及算法流程等关键问题,并对算法的有效性和实时性进行了仿真分析。仿真结果表明,所提方法可有效地防止错误数据引起的继电保护误动,信息融合算法与继电保护算法的时间相当,可形成并行处理。此外,该方法还可对数据采集系统进行在线监测和诊断。

D-S证据理论在多传感器故障诊断中的改进及应用

为了解决在多传感器信息融合处理故障诊断过程中,传统证据理论对含有冲突证据的处理结果与实际相悖的问题,介绍了传统D-S证据理论的基本构架,分析了其在处理含有高冲突的证据融合过程中将高信任度分配给小可能故障源的不足,提出了一种新的基于模糊成员函数和证据平均距离的证据调整方法,该模糊成员函数充分考虑了专家知识对基本概率分配函数的影响,证据的平均距离给证据分配的权重系数可降低冲突证据的可信度,增加其未知程度.运用证据的充分性系数及利用证据平均距离得到的证据重要性系数,重新分配概率指派函数.实验结果表明,改进后的方法可以提高故障诊断结果的准确性,在一定程度上提高了诊断系统的性能.