自动化空中交通管制系统软件可靠性评估研究

文章提出了评估自动化空中交通管制系统(AATCS)软件可靠性的一种新方法—基于PCR的软件可靠性评估。经操作员和软件支持业务人员(SSF)现场测试,对发现、过滤的软件故障进行确认,生成S2级的软件系统问题变更报告(PCR)。采用CROW-AMSSA(NHPP)模型进行系统的可靠性增长计算,通过极大似然估计法确定模型的参数,经过计算得到AATCS的S2级失效强度和可靠性预测趋势。     

基于总线耦合器的变电站监控系统设计

详细阐述了基于软PLC软件TwinCAT和Beckhoff总线耦合器的变电站监控系统的实现方案,描述了系统的硬软件配置及主要技术特点,介绍了软PLC技术的有关概念并描述了软PLC的实现。经过实践证明,基于总线耦合器的变电站监控系统提高了供配电的安全性和可靠性,并且系统的抗干扰能力强,组态灵活,应用前景非常广泛。     

模糊故障树在列车运行时故障开门中的应用

故障树是对系统进行可靠性分析的最普遍的方法.针对传统故障树分析法在进行故障率计算时存在着未考虑基本事件故障发生率不精确的问题,提出运用模糊故障树算法进行故障率计算.模糊故障树将故障发生率作为模糊数据来处理,将基本事件的不精确性加入计算.将此方法应用于列车运行时故障开门中,结合FCSI (fuzzy cut-set importance)法、FFVI (fuzzy fussell-vesely importance)法和FUI (fuzzy uncertainty importance)法对基本事件跟最小切割进行计算.结果表明该方法可行有效,能为改进列车车门系统提供一定的科学依据.     

微机软故障的分析与处理

在微机工作过程中,软件故障率要比硬件故障率高得多.常见的软件故障可概括为以下四种情况:(1)系统软件出错引起的故障;(2)应用软件出错引起的故障;(3)用户对微机系统的各参数的不正确设置造成的故障;(4)计算机病毒对软件的侵害引起的故障.下面通过一些实例分析上述四处软故障的发生原因及排除方法.故障1故障现象:系统加电后,硬件自检通过,由硬盘引导操作系统时,系统进入ROM BASIC.故障分析与处理:引导操作系统失败而进入ROM BASIC,一般故障发生在硬盘主引导记录上.     

基于FSK调制的契斯软判决纠错译码方法

介绍契斯软判决纠错译码原理,提出基于FSK调制的解调器输出量化方法,不完备契斯译码方法.给出硬译码器及软判决译码的软件实现方法,最后提供不完备契斯译码过程示例.在FSK调制数字通信系统中引入契斯软判决纠错译码,使码的纠错能力至少提高一倍,提高了系统通信性能和可靠性.用软件实现调制解调及软判决纠错译码,降低了数字通信系统成本,拓宽了计算机的应用范围.     

一种软件可靠性增长模型选择与综合方法

软件可靠性增长模型可以预测软件在将来某个时刻的可靠性,以此作为软件是否发布的依据.而目前常见的各种模型对不同失效数据集的预测能力并不一致.提出了一种软件可靠性增长模型选择和应用的框架,利用可靠性模型评价准则,对特定的失效数据集选择优选模型集,根据优选模型集利用神经网络较好的学习预测能力计算可靠性.利用此方法对实际软件项目中的失效数据进行了分析,并验证了它的有效性.     

对多信号模型中故障模式建模方法的改进研究

多信号模型是一种简单而有效的系统建模表示方法,已被美国QSI公司引入其TEAMS(测试性工程和维修系统)软件中用于系统测试性分析和预计、可靠性分析以及故障诊断等.论文分析了TEAMS软件中多信号模型故障模式建模和故障-测试相关性分析中存在的问题,提出了将故障模式由组元节点的构成层次变更为与组元作用信号相关联的组元节点属性的解决方案.通过分析表明,新的故障模式建模方法能够明显提高测试性建模与分析的准确性且易于计算,并有利于扩展和增强故障分析功能.     

改进的J-M模型及其在软件安全性评估中的应用

分析了软件可靠性和安全性之间的关系;针对安全软件测试剖面和操作剖面有不同的故障检测率,以及软件故障剔除时有引入新故障的可能,通过改变Jelinski-Moranda(J-M)可靠性模型相关假设及参数,提出了一个既能描述安全软件测试剖面与操作剖面不同,又能描述故障引入率的软件安全性评估模型;并给出了该安全性评估模型的性能度量.最后,对同一组铁路信号控制安全软件的失效数据进行分析,结果表明改进后的J-M评估模型比原J-M模型有着更好的拟合能力和预测能力.     

软件可靠性模型选择的理论研究

为了预测软件中残留的故障,帮助发布软件做出决定,人们建立了各种软件可靠性预测模型.在工程实践中,有一类被称为软件可靠性增长模型(SRGMs)的模型被证明很有价值.然而,现有的模型通常建立在对于开发环境、失效性质、错误发生概率等的一系列特定假设的基础上.这就使得对于一个实际项目,选择恰当的模型存在很多困难.本文中我们采用了一种具有较广泛适用性的方法从理论上对如何在实际项目中选择合适的模型进行了研究.通过实际的例子描述了所提出的选择模型的理论与策略,并解释了为什么我们的方法能够动态地选择出最恰当的模型.分析结果和案例研究都说明了所提方法的有效性,这种方法对于测试阶段选择合适的可靠性模型具有一定的指导意义.     

运用MATLAB进行军用软件可靠性评估

军用软件的可靠性已成为影响武器装备系统质量的关键因素。介绍了非齐次泊松过程类软件可靠性增长模型的原理以及如何运用MATLAB绘制软件故障数据曲线、模型参数估计及分布拟合检验,进而建立可靠性增长模型,进行可靠性评估。     

Effect of System Workload on Operating System Reliability: A Study on IBM 3081

This paper presents an analysis of operating system failures on an IBM 3081 running VM/SP. We find three broad categories of software failures: error handling (ERH), program control or logic (CTL), and hardware related (HS); it is found that more than 25 percent of software failures occur in the hardware/software interface. Measurements show that results on software reliability cannot be considered representative unless the system workload is taken into account. For example, it is shown that the risk of a software failure increases in a nonlinear fashion with the amount of interactive processing, as measured by parameters such as the paging rate and the amount of overhead (operating system CPU time). The overall CPU execution rate, although measured to be close to 100 percent most of the time, is not found to correlate strongly with the occurrence of failures. The paper discusses possible reasons for the observed workload failure dependency based on detailed investigations of the failure data.     

Software architecture reliability analysis using failure scenarios

With the increasing size and complexity of software in embedded systems, software has now become a primary threat for the reliability. Several mature conventional reliability engineering techniques exist in literature but traditionally these have primarily addressed failures in hardware components and usually assume the availability of a running system. Software architecture analysis methods aim to analyze the quality of software-intensive system early at the software architecture design level and before a system is implemented. We propose a Software Architecture Reliability Analysis Approach (SARAH) that benefits from mature reliability engineering techniques and scenario-based software architecture analysis to provide an early software reliability analysis at the architecture design level. SARAH defines the notion of failure scenario model that is based on the Failure Modes and Effects Analysis method (FMEA) in the reliability engineering domain. The failure scenario model is applied to represent so-called failure scenarios that are utilized to derive fault tree sets (FTS). Fault tree sets are utilized to provide a severity analysis for the overall software architecture and the individual architectural elements. Despite conventional reliability analysis techniques which prioritize failures based on criteria such as safety concerns, in SARAH failure scenarios are prioritized based on severity from the end-user perspective. SARAH results in a failure analysis report that can be utilized to identify architectural tactics for improving the reliability of the software architecture. The approach is illustrated using an industrial case for analyzing reliability of the software architecture of the next release of a Digital TV.     

硬软件交互的可靠性建模及其应用

开发了一种统一的可靠性模型,该模型对系统的硬件失效、软件失效和软硬件交互失效都可以作出解释。硬软件失效可以由熟知的建模方法来解决。而提出了一套利用马尔可夫过程来捕获硬软件交互失效的建模方法论,通过将其应用到真实的通信系统来说明该硬软件混合的建模方法。     

软硬件综合AADL可靠性建模及分析方法

目前嵌入式系统广泛应用于航空电子、远程医疗、汽车电子等具有高可靠性要求的系统中。随着嵌入式系统的复杂度越来越高,为了保障系统的高可靠性需求,需要在系统开发的早期设计阶段对系统的可靠性进行分析评估,以提高系统的开发效率。嵌入式系统中软件、硬件功能的失效都会对系统可靠性产生影响,而AADL的可靠性模型缺乏对硬件构件错误的影响及传播机制进行刻画分析的能力。本文综合考虑软、硬件错误发生失效后对系统可靠性的影响,提出了一种面向系统架构级别的软硬件综合可靠性分析方法。该方法基于电子电路设计中事务级建模方法,扩展了AADL事务级错误模型的语法和语义,来支持AADL对硬件构件错误传播的硬件功能行为建模,在此基础上,利用AADL模型实例化机制实现对嵌入式系统可靠性建模,刻画了错误行为在硬件构件之间、软硬件构件之间的传播与影响。同时,定义了AADL硬件构件事务级错误模型到广义随机Petri网模型的映射规则,实现了系统软、硬件综合的可靠性行为仿真计算模型组合,支持嵌入式系统的软硬件综合可靠性分析。论文开发了软硬件综合可靠性建模与分析工具原型,并以某型飞机空气增压系统为例,在航空电子系统架构设计中进行尝试,验证了该方法在复杂嵌入式系统设计中进行软硬件综合可靠性分析的可行性与优越性。     

基于概率影响图的软件体系结构安全风险分析*

针对传统安全分析方法过于复杂的问题,提出将概率影响图引入体系结构的安全性风险分析中。该方法首先基于用例识别出系统功能故障,建立以系统安全性为目标节点的初级影响图;再对系统功能故障进行分解,确定各构件功能故障模式,并从构件内部失效及输入失效两方面进行考虑;最后根据这些事件的相关性建立从系统安全风险到构件失效的概率影响图,并开发了相应的基于概率影响图的辅助分析工具。     

Fault-tolerant control of paper machine headboxes

This paper presents a model-based fault detection and fault-tolerant control technique for the pressurized headbox of a paper machine. A bank of Kalman filters is constructed corresponding to all the possible sensor failure modes. The possibility that each failure mode hypothesis is true is calculated using measurement innovation processes. The sensor failures are detected and located based on the calculated possibilities of the hypotheses. The controller and state estimator are automatically reorganized subsequent to the occurrence of failures to ensure the stability and good performance of the closed-loop system. The issues of system hardware redundancy and computational burden as well as implemental complexity are taken into account in the system design. Simulation results have shown satisfactory performance of the headbox control system after applying the presented technique.     

Modeling of correlated failures and community error recovery inmultiversion software

Three aspects of the modeling of multiversion software are considered. First, the beta-binomial distribution is proposed for modeling correlated failures in multiversion software. Second, a combinatorial model for predicting the reliability of a multiversion software configuration is presented. This model can take as inputs failure distributions either from measurements or from a selected distribution (e.g. beta-binomial). Various recovery methods can be incorporated in this model. Third, the effectiveness of the community error recovery method based on checkpointing is investigated. This method appears to be effective only when the failure behaviors of program versions are lightly correlated. Two different types of checkpoint failure are also considered: an omission failure where the correct output is recognized at a checkpoint but the checkpoint fails to correct the wrong outputs and a destructive failure where the good versions get corrupted at a checkpoint     

基于POOSL的系统性能建模与性能分析

本文介绍了面向对象的并行描述语言(POOSL,ParallelObject-OrientedSpecificationLanguage)的基本语义语法及相关的建模工具,并通过对一个基本的包交换系统的建模和分析,说明了利用POOSL进行软硬件系统的性能建模和性能分析的基本方法。     

Human factors risk assessment: An integrated method for improving safety in clinical use of medical devices

Medical devices play a critical role in care and treatment. The human-related failures can significantly affect the safety of patients in clinical use of medical devices. This study develops a comprehensive risk assessment model for identification and evaluation of failures which may occur in the clinical use of medical devices. First, the “Swiss cheese” model and SHEL model (the acronym of software, hardware, environment, and liveware) are integrated to comprehensively identify the potential human errors. Then, a new failure mode and effects analysis (FMEA) approach improved by rough set theory and grey relational analysis is developed to assess the risk of the identified failures. The proposed method integrates the strengths of the “Swiss cheese” and SHEL model in identifying human failures from both the vertical and horizontal perspectives of the system, and the advantages of the improved FMEA approach in flexibly manipulating vague information in risk evaluation without much priori information. Finally, the proposed method is applied in clinical use of respirator to verify its efficiency and effectiveness.     

Software health management with Bayesian networks

Software health management (SWHM) is an emerging field which addresses the critical need to detect, diagnose, predict, and mitigate adverse events due to software faults and failures. These faults could arise for numerous reasons including coding errors, unanticipated faults or failures in hardware, or problematic interactions with the external environment. This paper demonstrates a novel approach to software health management based on a rigorous Bayesian formulation that monitors the behavior of software and operating system, performs probabilistic diagnosis, and provides information about the most likely root causes of a failure or software problem. Translation of the Bayesian network model into an efficient data structure, an arithmetic circuit, makes it possible to perform SWHM on resource-restricted embedded computing platforms as found in aircraft, unmanned aircraft, or satellites. SWHM is especially important for safety critical systems such as aircraft control systems. In this paper, we demonstrate our Bayesian SWHM system on three realistic scenarios from an aircraft control system: (1) aircraft file-system based faults, (2) signal handling faults, and (3) navigation faults due to inertial measurement unit (IMU) failure or compromised Global Positioning System (GPS) integrity. We show that the method successfully detects and diagnoses faults in these scenarios. We also discuss the importance of verification and validation of SWHM systems.