Robust Fault Detection and Isolation Based on Finite-frequency H?/H∞ Unknown Input Observers and Zonotopic Threshold Analysis

This work proposes a robust fault detection and isolation scheme for discrete-time systems subject to actuator faults, in which a bank of H_?/H_∞ fault detection unknown input observers (UIOs) and a zonotopic threshold analysis strategy are considered. In observer design, finite-frequency H_? index based on the generalized Kalman-Yakubovich-Popov lemma and H_∞ technique are utilized to evaluate worst-case fault sensitivity and disturbance attenuation performance, respectively. The proposed H_?/H_∞ fault detection observers are designed to be insensitive to the corresponding actuator fault only, but sensitive to others. Then, to overcome the weakness of predefining threshold for FDI decision-making, this work proposes a zonotopic threshold analysis method to evaluate the generated residuals. The FDI decision-making relies on the evaluation with a dynamical zonotopic threshold. Finally, numerical simulations are provided to show the feasibility of the proposed scheme.      

Fuzzy Filter Design for ItÔ Stochastic Systems With Application to Sensor Fault Detection

The paper deals with the robust fault detection problem for Takagi–Sugeno (T--S) fuzzy ItÔ stochastic systems. Our aim is to develop a robust fault detection approach to the T--S fuzzy systems with Brownian motion. By using a general observer-based fault detection filter as a residual generator, the robust fault detection is formulated as a filtering problem. Attention is focused on the design of both the fuzzy-rule-independent and the fuzzy-rule-dependent fault detection filters guaranteeing a prescribed noise attenuation level in an ${{H}}_infty$ sense. Sufficient conditions are proposed to guarantee the mean-square asymptotic stability with an ${{H}}_infty$ performance for the fault detection system. The corresponding solvability conditions for the desired fuzzy-rule-independent and fuzzy-rule-dependent fault detection filters are also established. Finally, a numerical example is provided to illustrate the effectiveness of the proposed theory.      

具有多测量数据包丢失的线性离散时变系统故障检测滤波器设计

研究存在多数据包丢失现象的线性离散时变系统有限时间域内故障检测滤波器(Fault detection filter, FDF)设计问题. 在数据包具有时间戳标记的条件下, 设计基于观测器的FDF作为残差产生器, 构造两类FDF. 其一为H-/H∞-FDF或H∞/H∞-FDF. 定义故障到残差和未知输入到残差的广义传递函数算子, 将此类FDF设计问题转换为随机意义下H-/H∞ 或H∞/H∞性能指标优化问题. 其二为H∞-FDF, 将此类FDF设计问题转化为随机意义下的H∞滤波问题. 采用基于伴随算子的H∞优化方法, 通过求解递推Riccati方程, 得到上述两类FDF设计问题的解析解. 通过算例验证所提方法的有效性.     

Fault Detection for Uncertain Fuzzy Systems: An LMI Approach

This paper studies the problem of designing a robust fault-detection system for uncertain Takagi-Sugeno fuzzy models. The worst case fault sensitivity measure is formulated in terms of linear matrix inequalities. The existence of a robust fault detection system that guarantees i) the L₂-gain from a fault signal to a residual signal greater than a prescribed value and ii) the L₂-gain from an exogenous input to a residual signal less than a prescribed value is given in terms of the solvability of linear matrix inequalities. Numerical examples are used to illustrate the effectiveness of the proposed design techniques.     

基于X2统计检验的线性离散时滞系统故障检测

基于X2统计检验,研究了一类含状态时滞线性离散时变系统的故障检测问题. 与基于残差的传统故障检测方法不同, 本文直接应用测量输出构造残差评价函数, 并通过投影与新息分析, 得到了残差评价函数的Riccati递推解. 分析表明, 该方法有效降低了残差评价函数的计算量, 并且在无故障发生情况下服从X2分布. 进一步, 通过X2统计检验可以判断系统是否有故障发生. 最后,通过一算例验证了提出方法的有效性.     

基于特征气体SO2F2的SF6气体绝缘设备的过热性故障诊断

利用SF₆分解产物检测来判断GIS故障发展程度已成为一种有效手段,在搭建的实验平台上展开200℃~360℃局部过热模拟实验,研究SF₆热分解特性。当实验温度较高时(320℃~360℃),新增SO₂F₂、H₂S、COS三种产物。在绝缘设备充满大量SF₆子的背景下,分解产生的H₂和COS的含量极少,给气体检测带来了困难。文中提出将SO₂F₂作为设备故障进入严重状态的标志气体,同时用量子化学计算法在B3LYP/6-311G(+d,p)水平下对SO₂F₂生成机理和能量条件进行研究。发现SO₂F₂通过F₂碎片与气室内SO₂反应、F原子与SO₂F结合、SOF 4水解反应这三条途径得到,其中SO₂与F₂反应是SO₂F₂的主要来源。实验现象与理论计算均表明:SO₂F₂的形成机制与高温息息相关,SO₂F₂出现,标志着设备故障处温度较高,SF₆绝缘能力已遭到严重破坏。     

Fault Detection, Isolation, and Accommodation Control in Robotic Systems

In this paper, fault diagnosis and accommodation control are developed for robotic systems. First, a nonlinear observer in the proposed method is designed based on the available model. The fault detection is carried out by comparing the observer states with their signatures. Secondly, state observers are constructed based on possible fault function sets. Thirdly, the accommodation control design is developed using a normal controller plus a neural network compensator to capture the nonlinear characteristics of faults. Finally, if the fault isolation is completed successfully, the second fault accommodation controller is presented based on the fault information obtained by the isolation scheme.      

Efficient calculation of the space-time performance of the working set

The performance of working set memory management is often used as a benchmark against which other algorithms are compared. Efficient algorithms which can generate exact performance curves for the mean working set size and fault rate have appeared in the literature. These algorithms exploit the fact that the curve of fault rate or mean resident set size versus the working set parameter value may be computed by gathering various statistics during one pass across the reference string and then by substituting those statistics into relatively simple formulae.

This paper develops an efficient technique for the determination of the exact space time product versus parameter value curve. The usual simulation approach to compute a space-time performance curve exhibits worst case time complexity of O(nn²) where p is the number of pages referenced by the program and n is the total number of memory references generated by the program. The one-pass technique presented here requires O(pn) time. Given that n may be quite large in practice (10⁷ references is not unusual), this reduction in complexity is necessary for the practical determination of space-time performance of the working set.     

Multiple-edge-fault tolerance with respect to hypercubes

Previous works on edge-fault tolerance with respect to hypercubes Q_n are mainly focused on 1-edge fault and 2- or 3-edge fault with limited size of n. We give a construction scheme for 2-EFT(Q_n ) graphs and 3-EFT(Q_n) graphs, where n is arbitrarily large. In our constructions, approximately log n extra degree is added to the vertices of Q_n for 2-edge-fault tolerance, and one more degree for 3-edge-fault tolerance     

Sensor Placement for Fault Diagnosis

An algorithm is developed for computing which sensors to add to meet a diagnosis requirement specification concerning fault detectability and fault isolability. The method is based only on the structural information in a model, which means that possibly large and nonlinear differential–algebraic models can be handled in an efficient manner. The approach is exemplified on a model of an industrial valve where the benefits and properties of the method are clearly shown.      

Dynamic Output Feedback-Fault Tolerant Controller Design for Takagi–Sugeno Fuzzy Systems With Actuator Faults

This paper addresses the problem of robust fault estimation and fault tolerant control (FTC) for Takagi–Sugeno (T–S) fuzzy systems. A fuzzy-augmented fault estimation observer (AFEO) design is proposed to achieve fault estimation of T–S models with actuator faults. Furthermore, based on the information of online fault estimation, an observer-based dynamic output feedback-fault tolerant controller (DOFFTC) is designed to compensate for the effect of faults by stabilizing the closed-loop system. Sufficient conditions for the existence of both AFEO and DOFFTC are given in terms of linear matrix inequalities. Simulation results of an inverted pendulum system are presented to illustrate the effectiveness of the proposed method.      

Simultaneous stabilization and simultaneous pole-placement by nonswitching dynamic compensation

In this paper, motivated by questions in fault tolerance, we investigate the existence of a compensator which simultaneously renders a givenr-tuple of plants internally stable. Sufficient conditions are derived for simultaneous pole-assignability of the genericr-tuple by dynamic output feedback, which are also shown to be necessary (and equivalent to generic stabilizability) in the case where the number of either input or output channels is one. We also derive an upper bound on the order of a simultaneous pole-assigning compensator. Ifr = 1, this reduces to the condition derived by Brasch and Pearson, while ifr = 2, this contains the recent theorem by Vidyasagar and Viswanadham. The casesr geq 3are new.     

Provable improvements on branch testing

This paper compares the fault-detecting ability of several software test data adequacy criteria. It has previously been shown that if C₁ properly covers C₂, then C₁ is guaranteed to be better at detecting faults than C₂, in the following sense: a test suite selected by independent random selection of one test case from each subdomain induced by C₁ is at least as likely to detect a fault as a test suite similarly selected using C₂. In contrast, if C₁ subsumes but does not properly cover C₂, this is not necessarily the case. These results are used to compare a number of criteria, including several that have been proposed as stronger alternatives to branch testing. We compare the relative fault-detecting ability of data flow testing, mutation testing, and the condition-coverage techniques, to branch testing, showing that most of the criteria examined are guaranteed to be better than branch testing according to two probabilistic measures. We also show that there are criteria that can sometimes be poorer at detecting faults than substantially less expensive criteria     

MPE2S: 基于多路径纠删编码的无线传感器网络可靠传输策略

传输可靠性是衡量无线传感器(Wireless sensor networks, WSN)网络性能的一个重要指标. 针对节点故障会影响网络传输稳定性和可靠性的问题, 提出了基于多路径纠删编码的 无线传感器网络可靠传输策略(Multi-paths and erasure encoding strategy, MPE2S). 根据反映链路质量的最优最差蚂蚁系统的信息素归一化值, 在相邻等级节点间建立多条互不交叉的传输路径, 将源数据包经纠删编码的 数据片沿多条路径分配和传输以实现负载均衡和故障容错. 理论分析和仿真结果表明,MPE2S具有较高数据包接收率、数据准确率和能效性, 体现了良好的故障容错性、数据传输稳定性和可靠性.     

Development of a user friendly gate-level logic simulator

A design of a digital logic simulator is developed and presented. BASIC on an IBM Personal Computer using interactive graphics tools is employed to make the simulator easy to use. The simulator can handle gate level logic circuits, and can be used for both logic verification and fault testing.

Efficient and correct simulation in a user-friendly environment was the main design objective. Concepts of interactive computer graphics are extensively applied to enable the drawing of the circuit. Menu structures have been used to simplify the interaction of user and computer. The foundation has been laid for a simulator that uses pattern recognition for circuit data acquisition.

The simulator permits the verification of the logic of a circuit without fault. The design also includes provision for inserting delays and simulating to detect hazards. Test sequences to detect the presence of faults in the circuit can be generated using deductive simulation. The design provides a reliable basis for further research into logic simulation.     

光网络中基于小波变换的链路故障监测算法

针对光网络中传统故障监测方法误差大、速度慢等问题,提出一种基于小波变换的链路故障监测算法。在该算法中采用动态周期轮询的方法监测链路光功率,利用小波变换在时-频域上的良好局部特性提取监测值中的故障信息。算法对监测到的光功率值进行多尺度分解以降低噪声影响,从而提高故障监测的准确性。仿真结果表明,与时域的分析方法相比,基于小波变换的故障监测算法能够较好地克服噪声影响,漏警率减少到0,误警率降低了5百分点;而且实验环境下的故障监测时间为2.53~3.12ms,能够满足实时需要。     

Efficient march test for 3-coupling faults in random access memories

A new efficient march test algorithm for detecting the 3-coupling faults in Random Access Memories (RAM) is given in this paper. To reduce the length of the test algorithm only the 3-coupling faults between physically adjacent memory cells have been considered. The proposed test algorithm needs 38N operations. We have proved, using an Eulerian graph model, that the algorithm detects all non-interacting coupling faults. This paper also comprises a study about the ability of the algorithm to cover the interacting coupling faults.

Simulation results with regard to the coupling fault coverage of the march tests, obtained based on a fault injection mechanism, are also presented in this paper.     

Firing Sequences Estimation in Vector Space Over $Z_{3}$ for Ordinary Petri Nets

Event sequences estimation is an important issue for fault diagnosis of Discrete event systems, so far as fault events cannot directly be measured. This paper is about event sequences estimation with Petri net models. Events are assumed to be represented with transitions, and firing sequences are estimated from measurements of the marking variation. Estimation with and without measurement errors are discussed in $n$-dimensional vector space over alphabet $Z_{3} = {-1, 0, 1}$. Sufficient conditions and estimation algorithms are provided. Performance is evaluated, and the efficiency of the approach is illustrated on two examples from manufacturing engineering.