A Fault Detection Mechanism in Erasure-Code Byzantine Fault-Tolerance Quorum

Fault-tolerance is increasingly significant for large-scale storage systems in which Byzantine failure of storage nodes may happen. Traditional Byzantine Quorum systems that tolerate Byzantine failures by using replication have two main limitations： low space-efficiency and static quorum variables. We propose an Erasure-code Byzantine Fault-tolerance Quorum that can provide high reliability with far lower storage overhead than replication by adopting erasure code as redundancy scheme. Through read/write operations of clients and diagnose operation of supervisor, our Quorum system can detect Byzantine nodes, and dynamically adjust system size and fault threshold. Simulation results show that our method improves performance for the Quorum with relatively small quorums.

Selection of Minimal Test Points Set for Integer-Coded Fault Wise Table

Test points selection for integer-coded fault wise table is a discrete optimization problem. On one hand, traditional exhaustive search method is computationally expensive. On the other hand, the space complexity of traditional exhaustive is low. A tradeoff method between the high time complexity and low space complexity is proposed. At first, a new fault-pair table is constructed based on the integer-coded fault wise table. The fault-pair table consists of two columns： one column represents fault pair and the other represents test points set that can distinguish the corresponding faults. Then, the rows are arranged in ascending order according to the cardinality of corresponding test points set. Thirdly, test points in the top rows are selected one by one until all fault pair are isolated. During the test points selection process, the rows that contain selected test points are deleted and then the dimension of fault-pair table decreases gradually. The proposed test points selection algorithm is illustrated and tested using an integercoded fault wise table derived from a real analog circuit. Computational results suggest show policies are better than the exhaustive strategy.

Application of Rollout Strategy to Test Points Selection for Integer-Coded Fault Wise Table

Test points selection for integer-coded fault wise table is a discrete optimization problem. The global minimum set of test points can only be guaranteed by an exhaustive search which is eompurationally expensive. In this paper, this problem is formulated as a heuristic depth-first graph search problem at first. The graph node expanding method and rules are given. Then, rollout strategies are applied, which can be combined with the heuristic graph search algorithms, in a computationally more efficient manner than the optimal strategies, to obtain solutions superior to those using the greedy heuristic algorithms. The proposed rollout-based test points selection algorithm is illustrated and tested using an analog circuit and a set of simulated integer-coded fault wise tables. Computa- tional results are shown, which suggest that the rollout strategy policies are significantly better than other strategies.

Multiple fault diagnosis of down-hole conditions of sucker-rod pumping wells based on Freeman chain code and DCA

It is important to achieve continuous, stable and efficient pumping well operation in actual oilfield operation. Down-hole pumping well working conditions can be monitored in real-time and a reasonable production scheme can be designed when computer diagnosis is used. However, it is difficult to make a comprehensive analysis to supply efficient technical guidance for operation of the pumping well with multiple faults of down-hole conditions, which cannot be effectively dealt with by the common methods. To solve this problem, a method based on designated component analysis （DCA） is used in this paper. Freeman chain code is used to represent the down-hole dynamometer card whose important characteristics are extracted to construct a designated mode set. A control chart is used as a basis for fault detection. The upper and lower control lines on the control chart are determined from standard samples in normal working conditions. In an incompletely orthogonal mode, the designated mode set could be divided into some subsets in which the modes are completely orthogonal. The observed data is projected into each designated mode to realize fault detection according to the upper and lower control lines. The examples show that the proposed method can effectively diagnose multiple faults of down-hole conditions.

万曼VENTImotion2无创呼吸机Code16故障分析与排除

目的为降低医疗设备全生命周期管理中的使用成本,我们对万曼VENTImotion2无创呼吸机Code16错误代码的故障进行了查修与分析。方法以我院万曼VENTImotion2无创呼吸机为研究对象,在无技术手册条件下对Code16错误代码进行故障查找,对Code16故障代码下的2例维修进行分析。结果维修后设备检测正常,自查自修,降低了维修成本,提高了专业技术水平,在设备日常维护中针对相关问题进行改进。结论通过对万曼VENTImotion2无创呼吸机的自修,以及总结问题发生原因与可能后,我院无创呼吸机的维修费得到了下降,使用质量得到了提升。

Optimal selection of tests for fault detection and isolation in multi-operating mode system

The complex systems are often in the structure of multi-operating modes, and the components implementing system functions are different under different operation modes, which results in the problems that components often fail in different operating modes, faults can be only detected in specified operating modes, tests can be available in specified operating modes,and the cost and efficiency of detecting and isolating faults are different under different operating modes and isolation levels. Aiming at these problems, an optimal test selection method for fault detection and isolation in the multi-operating mode system is proposed by using the fault pair coding and rollout algorithm. Firstly,the faults in fault-test correlation matrices under different operating modes are combined to fault-pairs, which is used to construct the fault pair-test correlation matrices under different operating modes.Secondly, the final fault pair-test correlation matrix of the multioperating mode system is obtained by operating the fault pair-test correlation matrices under different operating modes. Based on the final fault pair-test correlation matrix, the necessary tests are selected by the rollout algorithm orderly. Finally, the effectiveness of the proposed method is verified by examples of the optimal test selection in the multi-operating mode system with faults isolated to different levels. The result shows that the proposed method can effectively mine the fault detection and isolation ability of tests and it is suitable for the optimal test selection of the multi-operating mode system with faults isolated to the replacement unit and specific fault.

电动汽车PMSM驱动系统车载诊断技术研究

驱动电机是电动汽车驱动系统的核心,车载诊断和失效保护技术是提高其可靠性的有效技术手段。介绍了汽车随车诊断系统对电驱动系统的各种故障判定方法,并运用案例分析了汽车PMSM驱动控制系统中最常见的故障之一驱动电机抖动故障,呈现出了车载诊断系统判定电机位置传感器不良的典型情况;对电机位置传感器故障进行了simulink仿真并讨论了无位置传感器容错控制方案及发展趋势。

一种DEFAULT密码算法抵抗差分故障攻击新方法

针对DEFAULT轻量级分组密码算法无法抵抗差分故障攻击的问题,利用横向混淆和线性码提出一种抵抗差分故障攻击的方法。该方法在算法实现冗余部分针对算法结构使用横向混淆(或纵向隐藏)的方式实现,并结合[10,4,6]线性码的1 bit纠错和4 bit检错能力对每个S盒进行防护。研究结果表明,该方法不仅提供了对算法半字节的纠错和所有比特位的检测能力,而且仅需要约25.08%的额外软件实现性能消耗。相较于已有的防护方法,该方法在通用性、故障检测效果及实现代价方面均有明显优势。

Simulation the Wind Grid Code Requirements for Wind Farms Connection in Kosovo Transmission Grid

This paper presents aspects of study and simulation approach for planned wind power projects in Kosovo Power System in relation with Grid Code requirements. All generators, connected to the Kosovo Transmission System are required to comply with the Grid Code. The Grid Code was originally developed with conventional synchronous generators. Since Wind Turbine Generators don’t have the same characteristics as synchronous generators, it was considered appropriate to develop a new set of Grid Code provisions specifically for Wind Farm Power Stations in relation with specific characteristic of Kosovo Power System. With high excepted penetration of wind power, a simultaneous loss of Wind Farms generation will put in the risk the security and reliability of Power System. Therefore, the main requirements for Wind farm power stations concern the fault ride through capability, frequency operation range, and reactive power capability of wind turbines. In the case of grid faults wind turbines have to supply a definite reactive power depending on the instantaneous voltage level of connection point and they must return quickly to normal operation.

基于稀疏编码的复杂机械振动信号盲分离方法

复杂机械振动信号激励源较多,故源信号之间互为相关源,且较难满足统计独立特性,导致传统盲源分离方法分离效果不佳。对此,提出一种基于信号稀疏编码的机械振动信号盲分离方法。盲源分离的关键在于对混合矩阵的精确估计,然而机械振源中相关成分的存在严重影响混合矩阵的估计。对此,首先对观测信号进行短时傅里叶变换,增加信号稀疏性;然后利用稀疏编码筛选出具备直线聚类特性的时频观测点,利用K均值(K-means)聚类法找到聚类中心;最后利用所提筛选规则找到估计的混合矩阵,重构出源信号。通过对往复压缩机故障数据的分析,验证了所提方法有效性。

基于特征基的GMC卷积稀疏机械故障特征解析方法

在机械设备的复杂工况下,监测信号易受多振动源及环境噪声干扰,导致故障特征微弱且呈现强耦合特性,这给设备故障诊断带来极大挑战。因此,提出了一种基于振动特性基的GMC增强卷积稀疏机械故障特征解析方法,实现微弱耦合故障特征解析。首先,构造了一种自适应单边衰减小波匹配算法以获取最优特征原子,将最优特征原子升维同时匹配故障周期,以得到具有周期特征的振动特征基。其次,提出基于GMC增强的卷积稀疏编码,结合振动特征基优化求解稀疏系数。此外,提出了一种基于平均峭度与谐波能量比的过程参数优化选择方法,克服了优化过程中关键参数难选取的问题。最后,提取包络谱主要特征与理论故障特征频率对比判断故障类型。通过仿真分析和试验台信号验证,并对比分析了基于谱峭度分解和可调变Q因子小波变换GMC稀疏增强等两种传统方法。实验结果表明,相较于上述两种传统方法,本文提出的方法可以有效地分离不同类型的故障特征信号,并实现故障特征的增强。

基于SSTDR的电缆故障定位方法

由于当前电缆大都铺设在地下,一旦发生故障,检修人员若不能及时发现,将影响电网正常供电,因此检修人员须要提前定位电缆故障发生的位置。文章提出了一种基于改进扩展频谱时域反射法(Spread Spectrum Time-Domain Reflectometry,SSTDR)的电缆故障定位方法。文章介绍了SSTDR在线检测电缆故障测距原理、定位原理、PN码的选取以及故障定位算法;提出了以Logistic混沌序列作为入射信号对电缆故障进行定位的方法。基于MATLAB/Simulink平台搭建调制电路模型进行仿真分析,根据所生成二值化的Logistic混沌序列以及电缆开路故障波形,文章验证了所提方法具有一定的工程应用价值。

配电网中的故障定位技术分析及应用

为降低电流状态分析异常带来的配电网故障定位误差问题,提出配电网中的故障定位技术分析及应用研究。结合故障电流方向与主电源电流流向之间的关系,对配电网故障电流进行编码后,以电流状态对于与配电网运行状态之间的适应度作为基准,确定配电网故障电流在当前编码下的适应度值,逐步缩小故障范围,实现定位。在测试结果中,设计基础定位精度最高,准确性最可靠,且与对照组相比,明显更加稳定。

动车组司控器编码故障优化策略

司控器是司机操控动车组的主令电器,司控器故障可能造成动车组无法正常启动。文章分析了CRH5型动车组牵引控制的基本原理,并结合实际故障案例介绍了2种可能造成司控器编码故障的原因:一是采集数字编码器输出信号的RIOM故障,二是数字编码器故障。针对司控器编码故障造成全列无牵引或牵引力不足问题,从列车网络控制系统的角度,提出了3种牵引控制逻辑的优化策略:增加数字编码器输出信号的冗余采集、诊断出数字编码信号故障后切换模拟编码信号、诊断出数字编码信号故障后切换为恒速控车模式。3种优化策略均在实车完成现车试验,试验结果达到预期。增加输出信号冗余采集可有效降低采集设备异常产生的影响,切换恒速控车或切换模拟编码器方案均可实现编码故障时维持车组自主运行的目标。相对而言,综合采用增加输出信号冗余采集和切换模拟编码器方案最优,一方面提高了系统的冗余性和可靠性,另一方面在检测到司控器编码故障时自动进行切换维持动车组控制和运行,可避免动车组救援,有效保障铁路运营秩序。

基于领域分析的结构线性静力软件串并行一致化方法

并行CAE软件的计算结果串并行一致性是其计算结果可信的必要条件。然而,软件研发时常引入串并行不一致缺陷,其形式众多,现象相互耦合,散布于海量代码中,成为实现CAE软件串并行一致性的挑战。文中以结构线性静力软件的串并行一致性需求为切入点,针对现有的“专家知识法”与“缺陷定位法”应用于CAE软件串并行一致化时存在的粒度粗、准度差、成本高和缺乏系统性问题,引入领域分析方法,并与专家知识和数据流状态比对结合,提出了一种适用于结构线性静力的串并行一致化方法,实现了结构线性静力软件串并行不一致缺陷的细粒度、高准度与低成本系统性识别与修复。基于前述方法形成相关工具,并将方法与工具应用于SSTA的串并行一致化,识别并修复其中8处串并行不一致缺陷,使其通过90余真实模型的串并行一致考核,并实现串并行结果严格一致;同时,该方法与工具还将串并行不一致缺陷定位耗时由平均大于两人天降低至数人时。

小型绝对式光电编码器误码自动检测系统

在批量生产光电编码器时,对光电编码器是否存在误码进行检测是一个重要的环节。现有的检测方法采用二进制灯排手动转动编码器用肉眼进行观测,存在手动检测慢、肉眼观测误差较大、检测结果受转动速度影响等缺点。在大批量生产的光电编码器,采用传统方法进行误码检测费时费力。为解决编码器生产及使用过程中对光电编码器的自动误差检测,本文设计了小型光电编码器误码自动检测系统。首先,在参照大量光电编码器生产经验的基础上,分析了编码器误码产生的主要原因;然后,提出了基于微分算法实现对光电编码器是否存在误码进行判断的误码自动检测方法;最后,以FPGA为主控芯片,设计了小型光电编码器自动误码检测系统。该系统能够实现对光电编码器的高速数据采集、数据处理与误码判断,并将误码判断结果通过LCD液晶显示。同时,可以根据需要将数据传输到计算机中作进一步分析。检测实验表明：本文所设计的误码检测系统成功实现了对15位串/并口光电编码器在高速和低速下进行数据采集及误码判断。系统可用于批量生产下光电编码器的误码自动检测,减少了人工操作,提高了自动化程度。系统具有智能便捷,移动性强,适用于实验室及各种工作场合下的误码检测等优点,检测速度较以往检测方法提高了3~5倍。

基于医疗过失分类编码的医疗风险管理方法研究

通过对医疗过失分类编码的研究,对医疗过失进行分析和总结,探索合理的医疗风险管理新方法。研究结果表明,医疗过失分类编码管理是临床进行医疗风险管理的有效手段。通过建立和完善医疗过失分类编码管理制度,可以在诊疗全过程进行医疗缺陷监管和医疗安全预警。

基于汉明纠错编码的AES硬件容错设计与实现

提出一种AES硬件容错设计可避免攻击者利用在AES设计环节中插入故障位实现攻击.在原有AES硬件设计中加入汉明码纠错电路,能自动纠正同一字节内的所有单比特故障,硬件仿真实验证明,故障发现率接近100%.针对不同AES设计结构和测试点配置对纠错电路的资源及速度进行了分析,实验结果表明我们提出的硬件容错设计有很强的可行性.

RAID-VCR:一种能够承受三个磁盘故障的RAID结构

提出了一种新RAID结构———RAIDVCR.这种结构仅需要3个额外的磁盘来保存校验信息,但是却能够承受任意模式的3个成员磁盘故障.与现有的其它RAID结构相比,RAIDVCR的容灾能力大幅提高,但是对磁盘空间利用率和系统吞吐量的影响却非常小.RAIDVCR的编码和解码过程都是基于简单的XOR操作,并且以明文方式保存了用户数据,从而可以高效地执行读操作.仿真实验结果表明,RAIDVCR的编码和解码性能较好,具有很好的应用前景.

基于故障树编码的火炮故障诊断方法研究

基于故障树的故障诊断方法核心在于故障原因的自动推理和快速定位。构建了故障自动推理编码规则,可将故障树转换成一系列可操作的且具有一定逻辑关系的编码,实现故障自动推理和诊断。通过某型火炮故障推理实例验证,表明该方法层次结构清晰,推理简单有效,能够实现装备LRU级分层故障诊断和故障原因的快速定位。