某型火箭弹意外点火事故原因分析及启示

通过对某型火箭弹意外点火事故的全面分析,验证试验,找到了产生事故的原因,采取有效措施,保证了产品的检验试验安全,提出了事故处理的启示。     

七号信令在移动通信故障定位中的应用

7号信令是由ITU-T制定的全球电信业的标准。这个标准指定了在通信中各个网络点通过数字信令网交换信息的过程及协议。在以电路交换为基础的GSM网络中,信令流程是一切通信过程的基本。只有确实掌握MS呼叫、位置更新、切换等通信过程中各接口的信令流程,才能有针对性地对网络故障进行分析定位。文中重点分析了GSM网络中位置更新的信令流程,结合信令监测系统获取的有效信令信息,对故障实例进行了分析,建立了一般的故障处理流程。     

基于红外图像识别的电气设备故障诊断

红外图像在故障诊断方面有着广泛的应用,但所采集的图像往往存在边缘模糊,细节丢失等问题,很难准确获取故障点信息。针对该问题本文提出了一种图像增强的综合算法,首先应用大津法将电气设备作为目标区从背景图像中分割出来,再用改进后的直方图均衡法对目标区增强,最后与细节图像叠加,该算法使故障信息在红外图像中得到了有效识别。仿真结果验证了该算法的有效性。     

基于单片机的交通灯控制系统设计

本文设计了一种基于AT89C51单片机芯片的交通信号灯控制系统.该系统除具有交通灯控制功能外,增加了现场实时控制及交通信号灯故障检测功能,提高了交通灯的智能化、可靠性和实用性,可有效提高交叉口的车辆通行能力.     

Optimal fault margin in a computer system

This paper suggests a stochastic model how to determine a fault margin in a computer system, who fails when the total number of hidden faults exceeds a threshold level N of tolerance: A fault occurs at a non-homogeneous Poisson process, and (i) becomes system failure with probability p₁, (ii) becomes hidden fault with probability p₂ and is accumulated, or (iii) is removed with probability p₃. The expected cost rate to system failure is derived, and an optimal number N^* to minimize it is discussed. A numerical example is finally given.     

Probabilistic fault grading based on activation checking and observability analysis

A simplified probabilistic fault grading method is described. The concept of propagation probability is introduced in place of the sensitization probability of STAFAN, and the empirical parameters of STAFAN are eliminated. The division of input vectors into subsets is monitored by the activation or toggle rate. The accuracy of the method is examined for fault coverage estimation and for predicting the undetected faults.     

A hierarchical test generation methodology for digital circuits

A new hierarchical modeling and test generation technique for digital circuits is presented. First, a high-level circuit model and a bus fault model are introduced—these generalize the classical gate-level circuit model and the single-stuck-line (SSL) fault model. Faults are represented by vectors allowing many faults to be implicitly tested in parallel. This is illustrated in detail for the special case of array circuits using a new high-level representation, called the modified pseudo-sequential model, which allows simultaneous test generation for faults on individual lines of a multiline bus. A test generation algorithm called VPODEM is then developed to generate tests for bus faults in high-level models of arbitrary combinational circuits. VPODEM reduces to standard PODEM if gate-level circuit and fault models are used. This method can be used to generate tests for general circuits in a hierarchical fashion, with both high- and low-level fault types, yielding 100 percent SSL fault coverage with significantly fewer test patterns and less test generation effort than conventional one-level approaches. Experimental results are presented for representative circuits to compare VPODEM to standard PODEM and to random test generation techniques, demonstrating the advantages of the proposed hierarchical approach.     

存储器故障诊断算法的研究与实现

集成电路工艺的改进使存储器的测试面临着更大的挑战。文中从存储器的故障模型入手,着重描述了存储器常见的诊断算法。诊断算法和诊断策略要在诊断时间、故障覆盖率、面积开支之间进行权衡。因此要根据存储器的故障类型和测试需求来选择合适的诊断算法,才能达到比较满意的效果。     

定子绕组诊断的分离电压和电流正负序分量法

感应电机早期定子绕组故障表现不明显,并且受到电源和负载等外部条件的影响而难以准确检测,如瞬时功率分解法受转子转速、电流波动和电源频率影响较大;对称分量法处理定子绕组不对称问题的效果不理想;同步速坐标变换法计算复杂.为此引入了分离定子电压和电流正负序分量的方法来提取故障特征.采集到的数据先进行低通滤波处理,减弱高次谐波和噪声的影响.采用电源变换消除对负序分量来源的判断;Park 变换将信号从三维坐标转换到二维坐标中;Hilbert变换的频率相移特性可以分离信号的正负序分量.仿真结果表明:该方法可以消除其他非故障因素的影响,准确提取定子电压和电流的正负序分量,并可根据电源的不对称度,分别采用定子负序电流和负序阻抗来表征故障的严重程度.该方法解决了早期定子绕组故障检测的难题,可应用于实际工程中.     

基于平衡流形展开模型的涡扇发动机传感器容错控制

基于某型涡扇发动机平衡流形展开模型设计了一种传感器容错控制方案。首先,利用非线性系统平衡流形建模理论建立某型涡扇发动机性能仿真模型。然后,利用该模型在线估计传感器输出,并根据解析冗余方法,重构故障传感器的输出。最后,针对传感器常见典型故障进行了故障容错控制过程仿真。仿真结果表明,所研究的方法能及时、有效的检测到故障传感器,并实现容错控制,表明该方案的可行性。