不可"修复如新"的两相依部件的并联系统的可靠性分析

研究了两相依部件的并联可修系统,在部件的故障分布服从二维指数分布、两个维修分布 为一般分布、且故障部件不能"修复如新的假设下",利用几何过程和补充变量法求出了该系统 的主要可靠性指标.     

存在故障相关及不完备检测的主辅并联系统可靠性建模与维修策略

主辅部件并联普遍存在于机电系统中, 部件间存在故障相关性等因素使得针对系统的可靠性建模和维修策略优化尤为困难. 本文以部件间存在I类和III类故障相关性及因检测系统的不完备引起主部件累积损伤速率分布改变的主辅并联系统为对象, 通过对系统退化过程的分析建立其可靠性模型. 依据所建模型和观测的辅助部件的故障次数及系统的运行时间, 建立(T, N)预防性更换策略优化模型. 通过案例分析检测系统的完备性、累积损伤速率等参数对系统可靠性及预防性维修策略的影响.     

神威太湖之光可靠性及可用性设计与分析

随着系统规模与集成度的快速增加,可靠性与可用性问题成为构建E级计算机系统所面临的重大挑战.针对神威太湖之光超级计算机可靠性与可用性设计与实现开展全面的分析.首先概要描述神威太湖之光超级计算机系统结构.其次,系统提出神威太湖之光超级计算机可靠性增强技术以及故障预测、主动迁移、任务局部降级等主被动容错技术,建立神威太湖之光超级计算机多层次主被动协同的容错系统.再次,根据系统故障统计信息,分析失效分布及主要失效来源,结合指数、对数正态与韦布尔3种典型寿命周期分布,对神威太湖之光系统故障间隔时间分布进行数据拟合分析.最大似然估计与K-S(Kolmogorov Smirnov)检验结果表明,对数正态分布与系统失效经验数据取得了最好的拟合度,建立神威太湖之光系统失效分布模型,并计算得出系统平均无故障时间.通过系统运行统计与实际应用测试,分析了故障预测精确度以及主动迁移、局部降低等容错技术的时间开销与容错效果.最后,在神威太湖之光超级计算机可靠性与可用性分析的基础上,提出E级计算机系统高可靠与高可用技术发展建议.     

复杂失效分布下的动态检查点设置

检查点技术是保障计算机系统可靠性的一种常用方法.通常假定系统失效的发生服从泊松分布,因此检查点是等间隔设置的.但近几年公布的现场数据表明以上假定不合实际.因此,首先利用现场失效数据对固定检查点间距方法的适应性进行分析,并提出两种检查点动态设置方法,它们根据系统前个阶段的失效信息动态地设置下一个检查点.模拟实验结果表明,所提出的方法在复杂失效分布下所获得的效果达到或者优于最优固定检查点的水平.     

连接函数下部件相依可修系统的可靠性分析

将Copula函数应用到部件相依可修系统的可靠性分析中,刻画出两相依部件组成的串联系统的寿命分布,实现单部件可修系统的虚拟化;利用增加变量法将虚拟单部件可修系统转化为马尔可夫可修系统,计算出系统的可靠性指标。通过算例验证了所讨论思路的有效性。     

考虑多维修台异步多重休假的温贮备冗余系统可靠性模型

考虑多维修台保障多个系统时维修力量存在调度与分配的情况,引入多维修台异步多重休假策略;以温贮备冗余系统为研究对象,针对以往研究利用指数分布等典型分布导致模型约束条件过于严格的问题,采用连续phase-type(PH)分布描述系统中工作部件寿命、温贮备部件寿命以及维修台休假时间和维修时间,建立通用性更好的系统可靠性解析模型,给出系统可靠度、系统稳态可用度等冗余系统可靠性指标和稳态忙期维修台数量等维修台稳态指标;利用算例验证模型适用性,演示了维修台数量、系统温贮备部件数量变化以及修理工休假速率、维修速率变化对系统各可靠性指标和维修台稳态指标的影响.算例计算结果表明,所提出的可靠性模型能够有效复现多维修台调度对冗余系统可靠性的影响,从而为维修台数量的合理安排及系统部件数量的优化配置提供理论基础和实践参考.     

基于故障树的系统可靠性仿真分析

如何推断系统的寿命分布,是目前可靠性工程领域的一个重要问题.文章应用改进的故障树分析法建立系统的仿真模型,利用蒙特卡洛法在计算机上产生等价于基本部件寿命实现值的随机数,将其代入到系统的仿真模型中,经过逻辑运算得到等价于系统寿命实现值的随机数.这个过程重复多次,便得到足够多的代表系统寿命的实现值的随机序列.在概率图中对随机序列进行统计推断,从而得到系统的寿命分布.此方法简单易行,计算结果精度高,对系统的可靠性分析有重要意义.     

可靠性试验图分析法的研究及应用

产品失效分布的检验是可靠性工程中的重要问题，本文通过对各种常用分布概率图法检验的研究，实现了计算机检验失效分布的过程，并对外设产品进行了应用实例分析。     

数控机床功能部件可靠度建模与维护预警系统开发*

为了提高机床可靠性,深入分析了机床功能部件故障数据,研究了采用两重威布尔分段模型建立机床功能部件可靠度分布模型的方法与极大似然方法确定模型参数的过程。提出了基于可靠性分析的机床维护预警系统开发,阐述了预警系统原理设计过程与功能模块设计方法。系统的实例应用表明,该方法对机床预防维护非常合理有效。     

电子元器件加速退化寿命评估方法研究

基于退化轨迹的评估方法是退化型产品进行可靠性评估的主要方法,适合于对具有退化失效机理的高可靠长寿命产品进行可靠性评估;基于退化轨迹的可靠性评估方法首先选取合适的退化轨迹模型,利用退化数据对退化轨迹进行模型拟合得到模型参数,然后根据退化轨迹外推得到伪失效寿命,最后基于伪失效寿命利用最小二乘法进行统计分析确定产品的失效分布,并通过假设检验的方法选择拟合度最优的分布;本文以大功率开关的加速退化试验数据为例进行了分析和说明.     

A reliable multi-objective control strategy for batch processes based on bootstrap aggregated neural network models

This paper presents a reliable multi-objective optimal control method for batch processes based on bootstrap aggregated neural networks. In order to overcome the difficulty in developing detailed mechanistic models, bootstrap aggregated neural networks are used to model batch processes. Apart from being able to offer enhanced model prediction accuracy, bootstrap aggregated neural networks can also provide prediction confidence bounds indicating the reliability of the corresponding model predictions. In addition to the process operation objectives, the reliability of model prediction is incorporated in multi-objective optimisation in order to improve the reliability of the obtained optimal control policy. The standard error of the individual neural network predictions is taken as the indication of model prediction reliability. The additional objective of enhancing model prediction reliability forces the calculated optimal control policies to be within the regions where the model predictions are reliable. By such a means, the resulting control policies are reliable. The proposed method is demonstrated on a simulated fed-batch reactor and a simulated batch polymerisation process. It is shown that by incorporating model prediction reliability in the optimisation criteria, reliable control policy is obtained.     

SRM: a staged reliability model for Web service

SOA (Service-oriented Architecture) is becoming the major architecture for building complex Web service systems. In SOA, the lifecycle of Web services consists of four stages: service publication, service discovery, service binding and service execution. Faults may occur in any stage and cause a failure of service. The reliability of services depends on not only the faults of the remote services itself, but also the faults that may occur in any SOA stage. Designing an effective and accurate reliability prediction model for Web services has become an important and necessary task. This study first proposes a staged reliability model for atomic services, which structures the reliability estimation based on the faults that may occur at each stage. Then, the reliability of composite services or service systems can be estimated based on this staged model. An experiment is conducted to study the influence of failures at each stage on the reliability of atomic services and a case study is designed to demonstrate the reliability of composite services using our staged model. In addition, the accuracy of our approach is investigated by comparing it against CBRM (component-based reliability model). Sensitivity analysis is also performed to identify critical service. Experimental results show that our staged model can obtain higher reliability prediction accuracy and is more suitable for Web services than traditional model.     

Gompertz software reliability model: Estimation algorithm and empirical validation

Gompertz curve has been used to estimate the number of residual faults in testing phases of software development, especially by Japanese software development companies. Since the Gompertz curve is a deterministic function, the curve cannot be applied to estimating software reliability which is the probability that software system does not fail in a prefixed time period. In this article, we propose a stochastic model called the Gompertz software reliability model based on non-homogeneous Poisson processes. The proposed model can be derived from the statistical theory of extreme-value, and has a similar asymptotic property to the deterministic Gompertz curve. Also, we develop an EM algorithm to determine the model parameters effectively. In numerical examples with software failure data observed in real software development projects, we evaluate performance of the Gompertz software reliability model in terms of reliability assessment and failure prediction.     

Reliability Growth Modeling and Optimal Release Policy Under Fuzzy Environment of an N-version Programming System Incorporating the Effect of Fault Removal Efficiency

Failure of a safety critical system can lead to big losses.Very high software reliability is required for automating the working of systems such as aircraft controller and nuclear reactor controller software systems.Fault-tolerant softwares are used to increase the overall reliability of software systems.Fault tolerance is achieved using the fault-tolerant schemes such as fault recovery (recovery block scheme),fault masking (N-version programming (NVP)) or a combination of both (Hybrid scheme).These softwares incorporate the ability of system survival even on a failure.Many researchers in the field of software engineering have done excellent work to study the reliability of fault-tolerant systems.Most of them consider the stable system reliability.Few attempts have been made in reliability modeling to study the reliability growth for an NVP system.Recently,a model was proposed to analyze the reliability growth of an NVP system incorporating the effect of fault removal efficiency.In this model,a proportion of the number of failures is assumed to be a measure of fault generation while an appropriate measure of fault generation should be the proportion of faults removed.In this paper,we first propose a testing efficiency model incorporating the effect of imperfect fault debugging and error generation.Using this model,a software reliability growth model (SRGM) is developed to model the reliability growth of an NVP system.The proposed model is useful for practical applications and can provide the measures of debugging effectiveness and additional workload or skilled professional required.It is very important for a developer to determine the optimal release time of the software to improve its performance in terms of competition and cost.In this paper,we also formulate the optimal software release time problem for a 3VP system under fuzzy environment and discuss a the fuzzy optimization technique for solving the problem with a numerical illustration.     

一种嵌入式系统的可靠性测试与评价方法

使用Markov模型进行嵌入式系统的可靠性测评,能够明显地节约计算时间,并保证可靠性测评的准确性,因而越来越受到人们的关注。在Markov模型中,可以使用敏感性因子描述嵌入式系统可靠性,建立敏感性因子和测试资源的关联,为系统模块分配可靠性指标,把嵌入式系统的可靠性测试,转化为相应的优化问题。文中介绍了一种基于Markov模型的嵌入式系统可靠性测试与评价方法,包括测评框架、设计指标分配和敏感性分析等内容,说明如何依照可靠性测评框架对嵌入式系统进行可靠性测评。     

具有错误修复的非齐次马尔可夫模型

软件可靠性工程是对软件的质量进行管理和控制的实用性学科,而软件可靠性模型又是软件可靠性工程的基础之一,为了保证靠性模型的估测精度,好的软件可靠性模型应该包括对测试覆盖的说明,并且能够反映的错误修复过程。本文在基于测试覆盖的ＮＨＰＰ模型的基础上,讨论了一有反映软件错误修复过程的非齐次马尔可夫模型。     

一种满足可靠度期望的网构软件优化方法*

Internet环境下网构软件的开发是一个构件组装过程,传统的软件可靠性技术在其应用过程中面临着新的挑战。建立了网构软件的抽象模型和物理模型,介绍了可靠性的形式化定义及五种构件组装结构的可靠性度量方法,提出了一种满足可靠度期望的网构软件优化方法。该方法将复杂的网构软件结构进行串行化,以抽象构件、链路的可靠度期望阈值过滤无效分支,以网构软件的可靠性期望筛选较优路径,应用一种改进的蚁群优化算法求解,从而实现了网构软件抽象模型与物理模型的映射。实验仿真及分析表明,该方法适用于解决开放式环境下网构软件的可靠性优化问题,相对于传统方法,它具备较好的执行性能。     

Confidence-based reliability assessment considering limited numbers of both input and output test data

Simulation-based methods can be used for accurate uncertainty quantification and prediction of the reliability of a physical system under the following assumptions: (1) accurate input distribution models and (2) accurate simulation models (including accurate surrogate models if utilized). However, in practical engineering applications, often only limited numbers of input test data are available for modeling input distribution models. Thus, estimated input distribution models are uncertain. In addition, the simulation model could be biased due to assumptions and idealizations used in the modeling process. Furthermore, only a limited number of physical output test data is available in the practical engineering applications. As a result, target output distributions, against which the simulation model can be validated, are uncertain and the corresponding reliabilities become uncertain as well. To assess the conservative reliability of the product properly under the uncertainties due to limited numbers of both input and output test data and a biased simulation model, a confidence-based reliability assessment method is developed in this paper. In the developed method, a hierarchical Bayesian model is formulated to obtain the uncertainty distribution of reliability. Then, we can specify a target confidence level. The reliability value at the target confidence level using the uncertainty distribution of reliability is the confidence-based reliability, which is the confidence-based estimation of the true reliability. It has been numerically demonstrated that the proposed method can predict the reliability of a physical system that satisfies the user-specified target confidence level, using limited numbers of input and output test data.     

最小通路法在通信保密装备可靠性建模中的应用

针对通信保密装备可靠性建模难度大的问题,提出了一种新的适用于复杂系统的可靠性建模方法一最小通路法。通过在系统拓扑结构图上搜索出所有能够使系统正常工作的最小通路,建立系统的可靠性模型。该方法基于广义的网络拓扑结构,因此网络的源节点和目标节点不必局限于严格的定义,可以随意指定,具有很大的灵活性。实例证明,该方法可行有效。