系统可靠性预计与分配集成系统的设计与实现

文章对系统可靠性框图建模、可靠性预计、可靠性分配的过程及相互关系进行了分析，在此基础上给出了系统可靠性预计与分配集成系统的体系结构及系统的各主要模块的功能设计，介绍了系统的实现技术，同时提出了可靠性框图模型的数据结构。     

Optimal testing resource allocation during module testing considering cost, testing effort and reliability

Software reliability is one of the most important quality attributes of commercial software. During software testing, software reliability growth models (SRGMs) are commonly used to describe the phenomenon of failure occurrence and/or fault removal which consequently enhancements software reliability. Large software systems are developed by integrating a number of relatively small and independent modules, which are tested independently during module testing phase. The amount of testing resource available is limited which is desired to be consumed judiciously so as to optimize the testing process. In this paper we formulate a resource allocation problem of minimizing the cost of software testing under available amount of testing resource, given a reliability constraint. We use a flexible SRGM considering testing effort which, depending upon the values of parameters, can describe either exponential or S-shaped failure pattern of software modules. A systematic and sequential Algorithm is proposed to solve the optimization problem formulated. Numerical examples are given to illustrate the formulation and solution procedures. Sensitivity analysis is performed to examine the behavior of some parameters of SRGM with most significant influence.     

考虑系统调用和失效模式的软件可靠性模型

可靠性是软件系统质量需求中的一个重要指标,而软件可靠性建模为人们提供了一种评估软件可靠性的方法,能够在软件质量控制方面有效地提供决策依据。无论是曾经受到广泛关注的黑盒方法,还是现在大量研究的白盒方法,这些模型都试图越来越精确地刻画软件的可靠性。然而,这些模型都是将软件独立在运行环境之外,只是纯粹地、抽象地考虑软件本身,完全忽略了软件所依赖的操作系统和运行环境对可靠性的影响。将软件运行所依赖的系统调用纳入了考虑范畴,考虑了软件中的多种失效模式（内核态失效、用户态失效）,同时对系统中的错误传播行为进行了建模,经过对经典模型逐步扩展,建立了一个更加符合实际情况的软件可靠性模型。通过一个实例详细描述了该模型的如何应用。     

网络结构的软件系统可靠性分配方法

针对网络结构的软件系统,通过构造软件系统的ANP结构,结合用户和程序员的观点,对超矩阵的构造进行了改进,提出基于改进型ANP的模块重要度评估方法。以软件实用性最大化为目标函数、以可靠性下限和开发费用为约束条件,建立了可靠性分配模型。并以某工厂实力信息管理系统为例,对算法进行了验证。     

基于子系统综合因子的软件可靠性分配方法

针对拥有多个分配在不同配置硬件环境上的软件子系统的综合软件系统,介绍了一种基于各子系统综合因子的软件可靠性分配方法。综合因子的确定涉及到子系统利用率等诸多因素,它的数值可以是软件详细规划时计算给出,从而对整个系统进行可靠性预分配,也可以在实际开发扣测试进程中动态地确定,从而不断地重新修正分配数值。给出详细的实例运算过程,并与传统方法进行了比较。     

一种改进的发动机曲柄连杆机构的可靠性分配算法

为了对发动机曲柄连杆机构的可靠性进行更合理的分配,提出了一种改进的可靠性分配算法。在对曲柄连杆机构进行可靠性分析的基础上,根据可靠性工程中可靠性成本函数的规律,构建了发动机曲柄连杆机构的可靠性预估成本函数,建立了曲柄连杆机构可靠性的分配模型,并根据可靠性与成本的微分性质,构建了以重要度最大单元为搜索单元逐步迭代的算法,该算法简单、易用。最后结合一个实例,验证了模型和方法的有效性与可行性。     

基于差分进化的复杂软件系统动态可靠性分配

现有关于复杂软件系统可靠性分配的研究均基于结构固定的软件系统,而实际情况中软件系统结构往往不固定。针对这一矛盾,构建复杂软件系统动态可靠性分配优化模型,并基于差分进化设计复杂软件系统动态可靠性分配算法。在系统结构发生变化时,首先基于D-S证据理论对系统中各模块的全局权重重新进行评估,并考虑变化前后系统的关联性,在差分进化生成初始种群时保留了部分历史解。最后,通过仿真实验分析验证了所提方法的有效性。     

Statistical tolerance analysis of a hyperstatic mechanism,using system reliability methods

The quality level of a mechanism can be evaluated a posteriori after several months by following the number of warranty returns. However, it is more interesting to evaluate a predicted quality level in the design stage: this is one of the aims of statistical tolerance analysis. A possible method consists of computing the defect probability (P_D) expressed in ppm. It represents the probability that a functional requirement will not be satisfied in mass production. For assembly reasons, many hyperstatic mechanisms require gaps, which their functional requirements depend on. The defect probability assessment of such mechanisms is not straightforward, and requires advanced numerical methods. This problem particularly interests the VALEO W.S. company, which experiences problems with an assembly containing gaps. This paper proposes an innovative methodology to formulate and compute the defect probability of hyperstatic mechanisms with gaps in two steps. First, a complex feasibility problem is converted into a simpler problem. Then the defect probability is efficiently computed thanks to system reliability methods and the m-dimensional multivariate normal distribution Φ_m. Finally, a sensitivity analysis is provided to improve the original design. The whole approach is illustrated with an industrial case study, but can be adapted to other similar problems.     

嵌入式实时控制系统软件可靠性建模与应用

嵌入式实时控制系统(ERCS)广泛应用于各种控制系统中,其软件不同于普通软件,除满足实时性要求外,可靠性也是相当重要的。首先对嵌入式实时控制系统软件进行形式化抽象定义,然后对不可再分的软件模块进行可靠性建模,并应用Copula函数对软件系统进行建模,最后应用建立的模型,对具体的系统进行了软件可靠性计算。通过实例计算可知,用Copula函数建立的嵌入式实时控制系统软件可靠性模型,考虑了软件各个模块的相依性,进而得到嵌入式实时控制系统软件模块相依的可靠度较各模块独立时有所提高。     

On a generalized k-out-of-n system and its reliability

A consecutive-k-out-of-n system is a system with n components arranged either linearly or circularly, which fails if and only if at least k consecutive components fail. An (n,?f,?k) system further requires that the total number of failed components is less than f for the system to be working. Here we consider a more general system consisting of N modules with the ith module-composed of n _i components in parallel; the system fails if and only if there exist at least f failed components or at least k consecutive failed modules. In this paper, some formulae for the reliability of such a generalized k-out-of-n system are derived for both the linear and the circular cases. The recursive formulae established here can be easily computed. Many existing results are also shown to be special cases of the results obtained in this paper. Furthermore, we investigate some component importance properties.     

Cost-oriented task allocation and hardware redundancy policies in heterogeneous distributed computing systems considering software reliability

Task allocation policy and hardware redundancy policy for distributed computing system (DCS) are of great importance as they affect many system characteristics such as system cost, system reliability and performance. In recent years, abundant research has been carried out on the optimal task allocation and/or hardware redundancy problem, most of which took a reliability-oriented approach, i.e., the optimization criterion was system reliability maximization. Nevertheless, besides system reliability, other system characteristics such as system cost may be of great concern to management. In this paper, we take a cost-oriented approach to the optimal task allocation and hardware redundancy problem for DCS, which addresses both system cost and system reliability issues. A system cost model which could reflect the impact of system unreliability on system cost is developed, and by minimizing the total system cost, a satisfactory level of system reliability could be reached simultaneously. In the reliability modeling and analysis of DCS, we take both hardware reliability and software reliability into account. Two numerical examples are given to illustrate the formulation and solution procedures, in which genetic algorithm is used. Results show that based on the developed system cost model, appropriate decision-makings on task allocation and hardware redundancy policies for DCS could be made, and the result obtained seems to be a fairly good trade-off between system cost and system reliability.     

计算机通信与控制系统运行可靠性的提升对策探究

随着信息技术的发展,计算机通信技术与控制技术的应用空前广泛.计算机通信技术的可靠性日趋重要.本文分析计算机通信技术与控制技术的可靠性理论,探讨目前计算机控制技术和通信技术存在的问题并提出建议.     

一种求解软件可靠性分配的近似算法

在考虑开发成本约束的基础上,通过建立一种开发成本-可靠度-满意度三者平衡的软件可靠性分配和优化模型,将对软件可靠性最优分配问题转化为对模糊非线性规划问题的求解,从而为软件可靠性分配的最优化问题提供了一种新方法。为获得具有实际意义的数值解,提出一种沿着加权梯度方向进行变异的特殊遗传算法。最后结合实例,证明了该方法的有效性和合理性。     

Evaluating the reliability of the software of a switching system with a multi-variable model

In recent years reliability growth models have gained a dominant role in the evaluation of the reliability of software products. However, their application to the quality assurance process of the software of a highly complex system such as a telecommunications switching system often shows that it is then possible to get accurate results only when some months of operation have elapsed. It is then impossible to give an answer to the typical questions which arise during the quality assurance phase: ‘Is the software ready for release? How long will it take before it is ready?’. This paper describes a multi-variable (MV) model which was developed to overcome the above limitation by providing a better model of the quality assurance process. A case study is presented, and a comparison is made between the results obtained by applying existing reliability growth models and the MV-model to it. Besides attaining surprising accuracy in its predictions and in measuring the reliability of the product, the MV-model also tries to tackle a different kind of question: ‘How is it possible to improve the effectiveness of testing?’.     

航天载荷应用软件可靠性参数的分析与确立

航天载荷应用软件可靠性研究是开展航天载荷系统可靠性工程的重要组成部分.而软件可靠性参数的分析与确立是进行软件可靠性研究的前提.首先定义并解释了航天载荷应用软件可靠性,其次对航天载荷系统中常用的软件可靠性参数进行了计算与分析,最后依据软件可靠性参数选取的原则提出了一个航天载荷应用软件可靠性参数集.该参数集在开展航天载荷软件可靠性工程中具有一定的参考价值,也是进行航天载荷软件可靠性设计与分析的前提.     

计算机测控系统的故障分析以及抗干扰技术研究

针对计算机测控系统实际运行中故障问题,从软硬件可靠性与系统运行环境的角度分析了故障产生的原因,提出来了相应的抗干扰措施.抗干扰技术与系统可靠性是计算机测控系统开发不可忽视的两个重要内容,常用的抗干扰技术主要有硬件抗干扰和软件抗干扰.软件抗干扰措施是硬件抗干扰措施的一个补充和延伸,运用得法可以显著提高计算机测控系统的可靠...     

Geometrically nonlinear finite element reliability analysis of structural systems. I: theory

This article reviews the theory of finite element reliability analysis of geometrically nonlinear elastic structures (GNS) based on the total lagrangian formulation. It also provides computer implementation developments and establishes the basis of understanding of the applications presented in the second part of this investigation. Because of the slenderness of GNS, the structural responses are nonlinear even if the strains are within the elastic range. For this reason, the nonlinear relationships between strains and displacements should be considered. Since the failure surface is nonlinear, this study reviews the evaluation of structural reliability of GNS by using both first-order and second-order reliability methods. To evaluate the structural reliability, the linkage of system reliability analysis program RELSYS with the finite element analysis program (FEAP) is presented. The computer code RELSYS–FEAP is readily applicable to the evaluation of system reliability of GNS.     

Geometrically nonlinear finite element reliability analysis of structural systems. II: applications

This is the second part of an investigation on finite element reliability analysis of geometrically nonlinear elastic structures (GNS). This study concentrates on applications. The linkage code RELSYS-FEAP presented in the companion paper is used for finding both component and system reliabilities of GNS. Structural reliabilities are evaluated for both geometrically linear and nonlinear elastic behaviors. Two geometrically nonlinear applications are presented, including a truss and a suspended structure. The stress and displacement reliabilities of the truss are computed considering both geometrically linear and nonlinear elastic behaviors. The system reliability of a geometrically nonlinear suspended structure is evaluated. The structure is modeled as a series of parallel subsystems according to three system failure criteria. The effects of correlation between loads, correlation between resistances, and material behavior (brittle or ductile) are evaluated and discussed. Finally, displacement reliability indices of the suspended structure are computed.     

Architectural reliability analysis of framework-intensive applications: A web service case study

A novel methodology for modeling the reliability and performance of web services (WSs) is presented. To present the methodology, an experimental environment is developed in house, where WSs are treated as atomic entities but the underlying middleware is partitioned into layers. WSs are deployed in JBoss AS. Web service requests are generated to a remote middleware on which JBoss runs, and important performance parameters under various configurations are collected. In addition, a modularized simulation model in Petri net is developed from the architecture of the middleware and run-time behavior of the WSs. The results show that (1) the simulation model provides for measuring the performance and reliability of WSs under different loads and conditions that may be of great interest to WS designers and the professionals involved; (2) configuration parameters have substantial impact on the overall performance; (3) the simulation model provides a basis for aggregating the modules (layers), nullifying modules, or to include additional aspects of the WS architecture; and (4) the model is beneficial to predict the performance of WSs for those cases that are difficult to replicate in a field study.     

Software reliability prediction model based on support vector regression with improved estimation of distribution algorithms

Software reliability prediction plays a very important role in the analysis of software quality and balance of software cost. The data during software lifecycle is used to analyze and predict software reliability. However, predicting the variability of software reliability with time is very difficult. Recently, support vector regression (SVR) has been widely applied to solve nonlinear predicting problems in many fields and has obtained good performance in many situations; however it is still difficult to optimize SVR's parameters. Previously, some optimization algorithms have been used to find better parameters of SVR, but these existing algorithms usually are not fully satisfactory. In this paper, we first improve estimation of distribution algorithms (EDA) in order to maintain the diversity of the population, and then a hybrid improved estimation of distribution algorithms (IEDA) and SVR model, called IEDA-SVR model, is proposed. IEDA is used to optimize parameters of SVR, and IEDA-SVR model is used to predict software reliability. We compare IEDA-SVR model with other software reliability models using real software failure datasets. The experimental results show that the IEDA-SVR model has better prediction performance than the other models.