配电网故障定位与快速抢修系统研究

针对配电网发生故障后采用传统的人工巡线方式存在故障区段定位困难、抢修效率低的问题,设计了一种基于柱上故障定位监测终端的配电网故障定位与快速抢修系统。该系统采用柱上故障定位监测终端实时测量配电网数据,采用过流速断法判别短路故障、全电流法判别接地故障;当故障发生时,柱上故障定位监测终端通过GPRS无线通信模块将故障信息发送到监控主站,监控主站采用改进的矩阵定位算法实现故障区段的准确定位;故障类型及故障位置以短信方式通知相关工作人员并在监控主站界面上显示,从而可实现故障的快速抢修。仿真结果验证了该系统的可行性。     

试谈电脑主板不上电故障实例的维修

日常的电脑主板维修中,电脑主板不上电的故障比较常见,掌握正确的常规维修方法,维修思路清晰,维修时会准确快速方便.以联想品牌机不能开机的故障为例,介绍了主板不上电故障的维修思路和方法,对电脑主板不上电故障维修提供帮助和参考,准确查出故障部位,进行故障维修.     

一个通用的系统故障诊断模型

狭义上,故障诊断包括两层含义即故障检测和故障定位,前者是指测试一个系统,判断其是否存在故障,而后者则是指在前者的基础上进一步定位故障点。广义上,故障诊断的内容,除了包含要判断系统有无故障以及故障产生后找到故障部位,还包含对故障特性的分析以及所采取的措施,例如让系统     

基于故障链路缓存再利用的NoC容错路由算法

建立故障模型是进行片上网络容错研究的基础,传统的细粒度故障模型未能有效地区分链路故障和通道故障.为了进一步提高片上资源的利用率,构建了一种粒度更细的微粒度故障模型,并在该模型的基础上提出了基于故障链路缓存再利用的容错路由算法.该算法为每个通信节点增加4条自收发通道,并采用基于缓存再利用的透传机制,通过复用故障链路两端的正常缓存和通道来透传故障通道上的数据包,提高了数据包采用最优输出端口的概率.实验结果表明,文中算法在高故障比例的片上网络中优势明显,且能以相对较小的硬件开销换取平均吞吐量、平均延迟和数据包平均跳数等性能的大幅度提升.     

微机鼠标接口故障检修一例

机型:486DX4/100兼容机(联讯8449 PCI 主板)。故障现象:Windows 屏幕上不出现鼠标箭头光标。分析与维修:鼠标器本身或微机鼠标接口电路出现故障均可引起 Windows 屏幕上不出现鼠标箭头光标,更换一只好的鼠标器试验,故障依旧,因此确定为主板上鼠标接口电路故障。通常若486、586主板接口电路出现故障,可通过对系统BIOS 设置进行更改,将主板上的一些接口屏蔽掉,在主板上插接多功能卡,改用多功能卡上的端口进行工作,不必更换主     

双谱分析在旋转机械故障诊断中的应用

在球轴承中,故障90%发生在内圈与外圈上,其它故障则基本发生在滚动体上,本文利用双谱技术,对轴承振动信号进行研究,通过MATLAB图像分析及轴承各频段故障的特征不同,可以有效地监测出轴承何种故障。     

复杂网络上相继故障研究综述

在复杂网络上,由微小扰动引发的大规模相继故障会导致灾难性后果.为了满足人们对各种关乎国计民生的复杂网络的安全性和可靠性的要求,复杂网络上相继故障研究成为近年来复杂网络研究的热点分支.对相继故障的理论建模是分析、预防和控制相继故障的基础和关键.综述了复杂网络上相继故障的研究进展,主要包括几类相继故障模型及相关的研究结果,并指出目前研究中存在的问题及今后的发展趋势.     

基于现场可编程门阵列的SMS4故障检测实现

硬件实现的SMS4加密算法计算过程中容易出现故障,为防止攻击者利用故障信息进行故障攻击从而破解SMS4算法,提出一种针对SMS4算法的故障检测方案。该方案首先分析了硬件实现的SMS4算法出现故障的位置及其影响,然后在关键路径上建立了3个检测点,通过实时监测检测点来定位算法执行过程中出现的故障。一旦成功检测到故障,立即重新执行算法以保证攻击者难以获取有效的故障信息。将提出的方案和原无故障检测的算法分别在Xilinx公司的Virtex-7和Altera公司的Cyclone Ⅱ EP2C35F76C6两个现场可编程门阵列(FPGA)上综合实现,在Virtex-7上,提出的带故障检测的方案比原算法占用逻辑资源增加30%,吞吐量相当;在EP2C35F76C6上比原算法增加0.1%的硬件资源,吞吐量达到原来的93%。实验结果表明,在尽量不影响吞吐量的前提下,提出的方案占用硬件资源小,并且可以有效地检测出故障,从而避免SMS4算法受到故障攻击。     

基于路由选择能力的容错路由选择

本文基于路由选择能力的概念,建立了一个有效的路由选择算法,该算法在故障超立方上具有较强的容错性,并可在不连通的故障立方体或含有故障边的立方体上使用。     

两种打印机打印针故障的检测

在计算机系统的日常使用过程中,打印机是出现故障较多的外设之一,而打印机的故障又多出在打印头上,其中的故障现象又多表现在打印针上。 明显的打印针折断、磨损等故障一般比较容易查出,但是如果当一根打印针不是折断,而是因其他     

IDDQ test and diagnosis of CMOS circuits

Designers must target realistic faults if they desire high-quality test and diagnosis of CMOS circuits. The authors propose a strategy for generating high-quality I_DDQ test patterns for bridging faults. They use a standard ATPG tool for stuck-at faults that adapts to target bridging faults via I_DDQ testing. The authors discuss I_DDQ test set diagnosis capability and specifically generated vectors that can improve diagnosability, and provide test and diagnosis results for benchmark circuits     

A fault tolerance framework for cooperative robotic manipulators

The problem of fault tolerance in cooperative manipulators rigidly connected to an undeformable load is addressed in this paper. Four categories of faults are considered: free-swinging joint faults (FSJFs), locked joint faults (LJFs), incorrectly measured joint position faults (JPFs), and incorrectly measured joint velocity faults (JVFs). Free-swinging and locked joint faults are detected via artificial neural networks (ANNs). Incorrectly measured joint position and velocity faults are detected by considering the kinematic constraints of the cooperative system. When a fault is detected, the control system is reconfigured according to the nature of the isolated fault and the task is resumed to the largest extent possible. The fault tolerance framework is applied to an actual system composed of two cooperative robotic manipulators. The results presented demonstrate the feasibility and performance of the methodology.     

Design and fault diagnosis of Petri net controllers for Petri nets with uncontrollable and unobservable transitions

This paper presents a methodology for diagnosing faults of controllers which are modeled by Petri nets with uncontrollable and unobservable transitions. The inadmissible constraints with uncontrollable and unobservable transitions are transformed into admissible conditions in this method. And we can design controllers easily using reduction technique. In order to provide tolerance against faults in controllers, we embed the given Petri net controller into a larger Petri net controller that retains the functionality of original controllers, and encode the large Petri net controller. Separate redundant Petri net controllers using additional places, connections and tokens to impose invariant conditions allow the systematic detection and identification of faults via Hamming code. The proposed method is attractive because it can check faults (place faults, transition faults or mixed faults) easily. A manufacturing cell is taken as an example to illustrate the approach.     

Design and analysis of a fault isolation scheme for a class of uncertain nonlinear systems

This paper presents a unified fault isolation scheme for handling both process faults and sensor faults in a class of uncertain nonlinear systems. The proposed fault diagnosis architecture consists of a fault detection estimator and a bank of isolation estimators, each corresponding to a particular fault type. The design of the fault isolation decision scheme is based on the derivation of appropriate adaptive thresholds for each fault isolation estimator. Fault isolability conditions characterizing the class of process faults and sensor faults that are isolable by the proposed scheme are derived. A rigorous isolability analysis is presented via the use of the so-called fault mismatch functions, which are defined between pairs of possible faults. A simulation example is used to illustrate the proposed fault isolation scheme.     

Observer-based fault tolerant control for a class of nonlinear multi-agent systems with sensor faults

This article focuses on the robust fault tolerant control (FTC) problem for a class of Lipschitz nonlinear multi-agent systems(MASs) subject to sensor faults. Firstly, sensor faults are transformed into actuator faults via introducing a new intermediate auxiliary state variable, and a distributed adaptive fault estimation observer is designed to estimate the state information and the concerned faults by using the relative output estimation error. Then, the sufficient existence conditions for the observer to satisfy the robust performance index are given. Thirdly, based on the results of observer design, a new design method of dynamic output feedback controller is proposed to implement consensus of MASs and ensure the desired disturbance rejection performance. Finally, the simulation results are presented to illustrate the effectiveness of the proposed method.     

一种回归测试后的错误定位方法

测试和调试之间的关系是极端密切的。回归测试是软件测试和维护过程中的一个重要活动。在程序中找出错误是一个复杂的过程，它涉及到理解程序的用途、结构、语意和导致错误的测试的相关特征。本文提出了一种基于Chopping技术进行错误定位的方法。这种方法反复利用调试信息和回归测试结果，通过从程序中抽取出与特定的语句有关的、 、相对原来的程序小得多的语句集，实现准确、快速的错误定位。     

Using NUMA interconnects for highly available filers

The paper discusses the clustered failover configuration which connects two independent file-server appliances via a nonuniform-memory-access network. Combining NUMA interconnects and a proprietary, log-structured file system results in file service that survives hardware faults with minimal disruption to clients     

Asymptotic tracking control of uncertain MIMO nonlinear systems with extended condition for controllability

For uncertain multiple-inputs multi-outputs nonlinear systems, it is nontrivial to achieve asymptotic tracking due to the intrinsic coupling among inputs, while the controllability conditions in most existing methods are rather restrictive or even impractical especially when unexpected actuator faults are involved. In this article, we focus on extending such controllability condition by resorting to the existence (instead of a priori knowledge) of some feasible auxiliary matrix, upon which a robust adaptive control scheme is first presented in the absence of actuator faults that is not only able to achieve asymptotic tracking even in the presence of non-parametric uncertainties with all the closed-loop signals globally ultimately uniformly bounded, but also able to deal with a larger class of system models. Furthermore, for the case with intermittent actuator faults, we develop a fault-tolerant control scheme with extended condition for controllability that is able to accommodate such faults automatically without using any fault detection or fault diagnosis unit. The effectiveness and benefits of the proposed method are verified via simulation on robotic systems.     

基于状态的工控协议Fuzzing测试技术

针对传统Fuzzing测试应用于工控系统存在测试覆盖率和有效性低、异常监测手段受限等不足,提出了一种基于状态的工控协议Fuzzing测试方法。该方法采用XML脚本对协议状态机进行描述,设计了基于协议状态机的测试序列生成算法PSTSGM,对被测对象进行状态引导以求达到更高的命中率和覆盖率。提出了基于心跳的异常监测与定位方法HFDLM,采用心跳探测和循环定位的方式,对被测嵌入式设备进行异常行为监测和异常用例定位。设计并实现了基于中间人代理的模糊测试原型系统SCADA-Fuzz,对电力SCADA系统进行了测试。实验结果表明,利用状态引导的测试能够有效发现安全漏洞。