模拟电路软故障诊断的研究

分析了模拟电路软故障诊断的重要性及现有的各种软故障诊断方法。对模拟电路软故障诊断字典法中基于支路屏蔽原理、电路参数随元件参数变化轨迹、节点电压灵敏度序列守恒定理和节点电压增量关系方程的四个研究方向各自的基本原理和优缺点进行了探讨;介绍了基于神经网络,结合模糊理论、小波变换的现代模拟电路软故障诊断的两个方向的研究现状;同时从通用的软故障诊断方法、大规模模拟电路的诊断策略和数模混合集成电路的诊断需求三方面指出了模拟电路软故障诊断的发展趋势和亟待解决的问题。     

Dynamic effects in the detection of bridging faults in CMOS ICs

Dynamic effects in the detection of bridging faults in CMOS circuits are taken into account showing that a test vector designed to detect a bridging may be invalidated because of the increased propagation delay of the faulty signal. To overcome this problem, it is shown that a sequence of two test vectors < T ₀, T ₁ >, in which the second can detect a bridging fault as a steady error, can detect the fault independently of additional propagation delays if T₀ initializes the faulty signal to a logic value different from the fault-free one produced by T ₁. This technique can be conveniently used both in test generation and fault simulation. In addition, it is shown how any fault simulator able to deal with FCMOS circuits can be modified to evaluate the impact of test invalidation on the fault coverage of bridging faults. For any test vector, this can be done by checking the state of the circuit produced by the previous test vector.     

基于小波高频系数统计特征的电路故障诊断

对故障电路进行特征提取与分类是模拟电路诊断的两个重要环节。现有方法多对时域响应信号进行小波变换以提取故障特征,并用神经网络或支持向量机方法实现对故障进行分类。为提高模拟电路故障诊断率,提出一种新的特征选取方法:在模拟电路的时域响应中对其进行小波变换,并对变换得到的高频细节系数统计平均值、标准偏差、峭度、熵和偏斜度等统计特征,并建立以支持向量机为分类器的故障诊断系统。以两种常见电路为例,实验结果表明,提出方法对常见电路进行故障诊断,准确率得到提升,精度达到99%以上,优于传统单纯小波系数分析方法,适用于模拟电路的故障诊断。     

Switch fault detection and diagnosis in space vector modulated cascaded H-bridge multilevel inverter

This article investigates the development and online implementation of the power switch open-circuit fault detection and diagnosis in symmetric cascaded H-bridge multilevel inverter. A mathematical modelling technique is presented to understand the effect of the fault on the bridge voltages and output voltage. The modelled values of the output voltage, simulation results and experimental results indicate that the fault diagnostic methods based on the output voltage as the diagnostic feature have certain ambiguity in identifying the fault switch, since the output voltage waveform and its features remain the same for a group of switches under the fault condition. In order to overcome this, fault detection and diagnosis method based on the mean values of the bridge voltages is proposed in this article, which identifies the faulty switch pair and H-bridge in which the fault has occurred. Further, this method has been experimentally validated on a five-level space vector modulated symmetric cascaded H-bridge multilevel inverter.     

子网络级模拟故障诊断的神经网络实现

利用容差模拟电路节点电压灵敏度序列守恒定理,得到了模拟电路元件的软、硬故障统一样本。然后利用统一样本集训练BP神经网络,并将神经网络用于子网络级模拟故障诊断。实例验证表明,软、硬故障统一样本集使得用于神经网络训练所需样本数目大大减少,但经过训练的神经网络可以诊断容差模拟电路的全部软、硬故障,而且诊断正确率较高。     

基于学习向量量化的传感器免疫网络诊断模型

为克服传感器免疫网络连接权值获取困难,提出了一种基于学习向量量化的传感器免疫网络诊断模型.该模型将学习向量量化(LVQ)的概念引入到传感器免疫网络模型中,在训练模式下,LVQ用于提取传感器正常工作下的相关性;在诊断模式下,根据LVQ获取的知识即可以确定传感器之间的检测结果,同时给出了诊断模型的性能优化算法.航空发动机传感器的仿真结果表明,所提出的方法能够准确获得网络节点之间的连接权值,保证免疫网络具有较高的检测灵敏度.     

改进的基于故障特征平面的双星故障识别算法

针对基于识别门限的奇偶矢量法等双星故障识别算法存在较大误警率、漏检率以及故障偏差抵消致使双星故障正确识别率较低的问题,提出了一种改进的用于双星故障识别的接收机自主完好性监测算法.在奇偶矢量法的基础上,构造故障特征平面和改进奇偶矢量,分析二者之间的几何特征与卫星故障的关系,并设计相应算法识别故障卫星.该算法不受识别门限的影响,避免了由识别门限引起的识别率较低的不足.半物理仿真结果显示：改进后的算法故障识别率达到90%以上,与直接利用奇偶矢量法相比,可以显著提高双星故障识别率.     

Differential Fault Attack on the Stream Cipher LIZARD

In this paper, we try to give a security evaluation of LIZARD stream cipher in regard to fault attacks, which, to the best of our knowledge, is the first fault analysis on LIZARD. We design a differential engine of LIZARD to track the differential trail of the keystreams. It is shown that the distributions of the keystream differences are heavily biased. Utilizing this characteristic, we propose an improved method to identify the fault location for LIZARD whose success probability approaches 1. Then we use the fault-free keystream and faulty keystreams to generate system of equations in internal state variables and solve it by SAT solver. The result shows that with 100 keystream bits, only 6 different faults are needed to recover the internal state. Finally, the comparison between LIZARD and Grain v1 shows that LIZARD is more resistable than Grain v1 in regard to fault attacks.     

基于支持向量机和振动场的故障诊断方法

故障样本量是制约智能故障诊断发展的关键因素之一,然而实践中往往难以获取充足的故障样本。支持向量机是一种新型的机器学习和模式识别方法,在解决小样本、非线性及高维模式识别问题中表现出优越的性能。本文将欧氏距离分类引入到支持向量机解决支持向量机多类分类问题,提出了基于支持向量机和振动场的故障诊断方法。实验结果表明,该方法在故障诊断上计算速度和准确度令人满意,为类似的研究提供了借鉴意义和参考。     

基于探测圈覆盖的光突发交换网络故障定位

针对光突发交换(Optical Burst Switching,OBS)网络在干扰告警信息情况下定位率低的问题,在最短长度m2圈算法的基础上,提出了相应的故障定位机制。首先,故障探测阶段收集由故障触发的告警信息,并组成相应的二进制告警相关矩阵,然后,故障定位阶段利用告警矩阵进行快速定位,找到可能的故障设备集合。     

Fault tolerance in Clos–Knockout multicast ATM switch

In this paper, we propose a new architecture for multicast ATM switches with fault tolerant capability based on the Clos–Knockout switch. In the new architecture, each stage has one more redundant switch module. If one switch module is faulty, the redundant module would replace the faulty one. On the other hand, under the fault‐free condition, the redundant modules in the second and third stages will provide additional alternative internal paths, and hence improve the performance. The performance analysis shows that the cell loss probability is lower than the original architecture when all modules are fault free, and the reliability of the original architecture is improved. Copyright © 2002 John Wiley & Sons, Ltd.     

Fault diagnosis and its prediction in wireless sensor networks using regressional learning to achieve fault tolerance

Due to the wide range of critical applications and resource constraints, sensor node gives unexpected responses, which leads to various kind of faults in sensor node and failure in wireless sensor networks. Many research studies focus only on fault diagnosis, and comparatively limited studies have been conducted on fault diagnosis along with fault tolerance in sensor networks. This paper reports a complete study on both 2 aspects and presents a fault tolerance approach using regressional learning with fault diagnosis in wireless sensor networks. The proposed method diagnose the different types of faulty nodes such as hard permanent, soft permanent, intermittent, and transient faults with better detection accuracy. The proposed method follows a fault tolerance phase where faulty sensor node values would be predicted by using the data sensed by the fault free neighbors. The experimental evaluation of the fault tolerance module shows promising results with R² of more than 0.99. For the periodic fault such as intermittent fault, the proposed method also predict the possible occurrence time and its duration of the faulty node, so that fault tolerance can be achieved at that particular time period for better performance of the network.     

高压单芯电缆外护套故障的定位及修复

针对高压单芯电缆在敷设施工后出现的外护套耐压试验通不过的故障,分析了外护套故障产生的原因和故障定位的几种方法。基于高压电桥定位法,给出了相关故障的查测经验和技巧。同时介绍了电缆外护套故障的修复方法。     

含光伏系统的微网并入配电网的故障区段定位研究

为解决传统配电网继电保护故障定位系统难以应对含光伏系统的微网并网运行的问题,提出了一种集中与分布式相结合的故障区域检测与隔离的保护方法。根据配电网的拓扑结构和假定的网络功率流向形成网络描述矩阵,在配电系统发生短路故障时,根据被保护线路故障的电压、电流分量的相位关系确定故障正方向,并形成故障信息矩阵。以故障信息矩阵对网络描述矩阵进行修正而形成故障判断矩阵,利用故障定位判据逐一查询故障判断矩阵即可快速准确地定位出故障位置,从而发出跳闸命令切除故障。     

Failure Analysis of VLSI by IDDQ Testing

A method for enhancing the popular failure techniques has been presented. The method was built on three principles: CMOS devices only draw power during switching operation; fault defects, both floating and stuck will consume power if properly conditioned; bridging fault model test programs combined with the combinational logic designs, the elevated power state should surface at some vector point prior to the location of the falling vector. A system was constructed by making use of an older vintage emission microscope. The system was configured so that direct docking to existing production hardware is possible. Using this system, five case studies were presented. The case studies proved that quiescent current signature scan analysis was successful at locatingthe defects within the failing units after conventional failure analysis techniques had been exhausted. Both bridging faults and floating faults were detected.     

压差式光纤矢量水听器声压相位灵敏度研究

该文介绍了压差式光纤矢量水听器及其基元的工作原理,并分析了光纤层等效处理对仿真结果的影响。基于有限元法对压差式光纤矢量水听器的基本性能进行了仿真分析,根据仿真模型所选定的参数研制压差式光纤矢量水听器样品,并对样品在频率为20～1 000 Hz时进行了测试。测试结果表明,声压相位灵敏度的仿真计算结果与实验测试结果基本一致,平均差值约为1.0 dB。研究结果表明,采用有限元法对压差式光纤矢量水听器的声压相位灵敏度进行仿真具有可行性。     

基于网格搜索的改进SVM模拟电路故障诊断方法

针对模拟电路故障识别与诊断问题,提出了一种基于K最近邻的一对一SVM分类器(KNN-OSVM)的故障诊断方法。将K最近邻算法与用网格搜索法优化后的一对一SVM模型相结合,建立KNN-OSVM模型,有效解决了SVM因存在不可分域造成的误分问题,提高了故障诊断率。采用小波分析法提取输出端电压信号作为故障特征值,采用网格搜索对核函数、惩罚参数寻优。采用两个模拟电路进行仿真实验,并将改进的SVM与传统SVM进行对比。结果证明了该故障诊断方法的可行性。     

基于KPCA-LSSVM的单向阀故障诊断研究

针对高压隔膜泵单向阀的故障振动信号特征难以提取及诊断的问题,文中采用KPCA和LSSVM相结合的方法进行故障诊断研究。对单向阀各状态信号运用双稳SR方法和DEMD算法进行信号预处理,并利用K-L散度选择分解后的主分量进行时频域特征参数的提取以构建特征向量集。运用KPCA对向量集进行二次特征提取,并将提取的特征向量输入到LSSVM诊断系统中,以完成单向阀故障诊断及分类。经实验验证,该方法的故障诊断率可达到90%,能够较好的诊断出单向阀故障特征。     

模拟电路故障诊断的结点电压灵敏度比值法

在证明线性电路中结点电压变化量比值等于结点电压灵敏度比值的基础上,提出了结点电压灵敏度比值法,通过结点电压变化量比值和结点电压灵敏度比值的比对确定电路的故障元件。理论分析和实验结果表明,该方法算法简单、诊断速度快,在可测点受限条件下具有较高的诊断精度,特别适合大规模线性模拟电路的故障诊断和测试。     

AON中基于网络编码的单链路故障定位机制

文章提出了一种AON(全光网络)中基于网络编码理论的单链路故障定位机制.利用网络编码在信息处理和融合上的优势,可使从单个信源发出的信息经过不同的探测通路后得到不同的处理.若经过每条链路的探测通路的集合互不相同,则可以根据目的节点接收到的探测信息定位故障链路.仿真结果表明,该机制能够在保证定位准确性的同时有效地降低故障定...