Cold vs. hot standby mission operation cost minimization for 1-out-of-N systems

It is well recognized that using the hot standby redundancy provides fast restoration in the case of failures. However the redundant elements are exposed to working stresses before they are used, which reduces the overall system reliability. Moreover, the cost of maintaining the hot redundant elements in the operational state is usually much greater than the cost of keeping them in the cold standby mode. Therefore, there exists a tradeoff between the cost of losses associated with the restoration delays and the operation cost of standby elements. Such a trade-off can be obtained by designing both hot and cold redundancy types into the same system. Thus a new optimization problem arises for the standby system design. The problem, referred to in this work as optimal standby element distributing and sequencing problem (SE-DSP) is to distribute a fixed set of elements between cold and hot standby groups and select the element initiation sequence so as to minimize the expected mission operation cost of the system while providing a desired level of system reliability. This paper first formulates and solves the SE-DSP problem for 1-out-of-N: G heterogeneous non-repairable standby systems. A numerical method is proposed for evaluating the system reliability and expected mission cost simultaneously. This method is based on discrete approximation of time-to-failure distributions of the system elements. A genetic algorithm is used as an optimization tool for solving the formulated optimization problem. Examples are given to illustrate the considered problem and the proposed solution methodology.     

Reliability of repairable redundant systems in nuclear generating stations

Markov models are presented to assess the reliability performance of redundant standby systems in nuclear generating stations. These systems are inactive during the normal station operation. However, they are required to operate for a specified period after the loss of normal power supply during emergency. The estimated probabilities of system failure are useful in deciding on the best combination of standby units and repair facilities. The proposed models are applicable to such systems as combustion turbine units in emergency service (Class III power system, emergency power supply system), and pumps in emergency coolant injection system.     

开关寿命连续型n部件冷贮备系统的可靠性分析

为了讨论由n个同型部件和一个转换开关组成的冷贮备不可修系统的可靠度,假设部件的工作时间和转换开关的寿命均服从指数分布、所有随机变量均相互独立,首先根据系统的特征和可靠度的定义研究并求出三部件冷储备系统可靠度的解析式,然后在三部件冷储备系统可靠度研究的基础上建立了n部件冷贮备系统的可靠性关于部件个数n的递推关系式,最终得到系统的可靠度的解析表达式.计算过程对其他多部件系统可靠度的推导有一定的借鉴作用,计算结果具有一定的理论价值.     

STRUCTURES OF SYSTEMS WITH EXPONENTIAL LIFE DISTRIBUTIONS

Abstract. Structures of monotone systems and cold standby systems with     

Reliability analysis of two-unit cold standby repairable systems under Poisson shocks

This paper analyses the reliability of a cold standby system consisting of two repairable units, a switch and a repairman. At any time, one of the two units is operating while the other is on cold standby. The repairman may not always at the job site, or take vacation. We assume that shocks can attack the operating unit. The arrival times of the shocks follow a homogeneous Poisson process and their magnitude is a random variable following a known distribution. Time on repairing a failed unit and the length of repairman’s vacation follow general continuous probability distributions, respectively. The paper derives a number of reliability indices: system reliability, mean time to first failure, steady-state availability, and steady-state failure frequency.     

修理工带休假的两同型部件冷贮备可修系统

假定部件工作寿命,修理时间和修理工休假时间均服从一般分布,利用马尔可夫骨架过程理论,研究了修理工带休假的两同型部件冷贮备可修系统的可靠性。     

带有一个冷贮备部件的两部件串联系统机会维修策略

针对带有一个冷贮备部件的两部件串联系统,本文首先提出一种预防维修与机会维修相结合的维修策略,运用更新报酬定理求得长期运行情况下的单位时间期望维修成本函数的表达式,然后研究最优的机会维修阀值,运用微分学理论求解最优解,最后用实例验证理论的正确性,从实际例子说明本文提出的维修策略可明显节约维修成本,为相应的带有冷贮备的多部件串联系统的维修策略分析提供参考,对企业设备的维修有实际指导意义。     

n个同型部件k个修理设备的冷贮备可修系统的可靠度研究

在设定元件的工作寿命和维修时间的分布都是负指数分布,全部随机变量都互相独立,发生故障的元件能够修成新的前提下,对由n个同种型号的元件和k(k≤n)个设备修理构成的冷贮存可修体系的可靠性方面进行分析,构建关于此体系的数学模型,获得了n个同种型号元件的冷贮存体系在k个设备修理的情况下的可靠度,且探讨在修理设备k值不相同的情况的可靠度,并针对n=3的情况下,分析修理设备数不相同情况下的可靠度。     

具有修理延迟的两不同部件冷贮备系统的可靠性分析

研究了有修理延迟的两个不同部件和两个修理工组成的冷贮备系统.假定部件的工作寿命服从一般分布,故障后的延迟修理时间和修理时间均服从指数分布.利用马尔可夫更新过程、拉普拉斯变换和拉普拉斯-司梯阶变换工具,得到了系统的首次故障前时间、可用度和平均故障次数等可靠性指标.     

Reliability analysis of a renewable multiple cold standby system

We present a general reliability analysis of the basic multiple cold standby system attended by a single repair facility. The particular case of deterministic repair provides some explicit results for the survival function illustrated by computer-plotted graphs.     

基于马尔科夫过程的储备系统稳态性能分析

由于储备系统组成部件在存储期间的失效概率各不相同,当部件状态趋于稳定时,各个状态对系统性能的影响也存在差异。为了识别关键部件及其状态对系统性能的影响程度,本文以重要度为主要指标,应用马尔科夫过程研究储备系统在稳态时的性能变化模式。首先基于综合重要度研究系统性能的变化规律,并结合冷储备系统和温储备系统的状态转移矩阵推导出马尔科夫过程中稳态值的计算方法;其次基于稳态综合重要度获得系统稳态时的性能变化模式;最后以双臂机器人为例,分析部件处于不同状态时对系统性能的影响模式,比较了不同部件综合重要度的变化,验证了提出方法的有效性。     

Reliability analysis of a single warm-standby system subject to repairable and nonrepairable failures

An n-unit system provisioned with a single warm standby is investigated. The individual units are subject to repairable failures, while the entire system is subject to a nonrepairable failure at some finite but random time in the future. System performance measures for systems observed over a time interval of random duration are introduced. Two models to compute these system performance measures, one employing a policy of block replacement, and the other without a block replacement policy, are developed. Distributional assumptions involving distributions of phase type introduce matrix Laplace transformations into the calculations of the performance measures. It is shown that these measures are easily carried out on a laptop computer using Microsoft Excel. A simple economic model is used to illustrate how the performance measures may be used to determine optimal economic design specifications for the warm standby.     

有优先权且工作故障与贮备故障后的修理时间不相同的温贮备系统的可靠性分析

为了解决开关寿命为连续随机变量且部件工作故障的修理时间与贮备故障后的修理时间各不相同的问题,利用Markov过程理论和Laplace变换方法,研究了有优先权的两不同型部件和两不同修理工组成的温贮备可修系统.假定部件的工作寿命、贮备寿命、工作故障的修理时间和贮备故障的修理时间均服从不同的指数分布,得到了该系统的可靠度Laplace变换和系统的首次故障前平均时间的解析表达式.     

泊松冲击下单部件混合贮备系统可靠性分析

研究的是泊松冲击下由三同型部件组成的单部件混合贮备系统可靠性.在系统三部件分别为工作部件、温贮备部件和冷贮备部件假定下,且假定三部件在工作过程中都是接着工作、修理、冷贮备、温贮备、工作依次进行状态转移,同时假设部件寿命和维修时间都服从指数分布,利用基本概率理论和马尔可夫过程理论分别对不可修和可修两类系统进行讨论得到相关可靠性指标.     

N个部件冷贮备可靠性模型的扩散估计界

本文对Ｎ个同型部件冷贮备的可靠性模型首次提出了一类扩散估计的近似算法理论，利用这个近似算法，首先给出了系统的一个基本循回过程的向前扩散偏微分方程，然后得到了这个偏微分方程在格占 上的近似瞬态解和稳太上的近似瞬态解和稳态解，最后给出了系统稳态可靠性指标的上下估计界，算便表明这个近似算法简便易行，对大系统的可靠性研究是有效的。     

A redundant repairable system with imperfect coverage and fuzzy parameters

This paper proposes a procedure to construct the membership functions of the system characteristics of a redundant repairable system with two primary units and one standby in which the coverage factor is the same for an operating unit failure as that for a standby unit failure. Times to failure and times to repair of the operating and standby units are assumed to follow fuzzified exponential distributions. The α-cut approach is used to extract from the fuzzy repairable system a family of conventional crisp intervals for the desired system characteristics, determined with a set of parametric nonlinear programs using their membership functions. A numerical example is solved successfully to illustrate the practicality of the proposed approach. Because the system characteristics are governed by the membership functions, more information is provided for use by management, and because the redundant system is extended to the fuzzy environment, general repairable systems are represented more accurately and the analytic results are more useful for designers and practitioners.     

泊松冲击下冷贮备可修系统的可靠性分析

本文研究了一类由有限个同质部件和一个修理工组成的冷贮备可修系统在随机冲击下的可靠性问题。假设冲击以泊松过程到达。当冲击到达时,它会独立地对系统中工作的部件产生影响,而不会对冷贮备部件产生影响。每次冲击的量都服从某一确定的分布,受冲击的部件以一定的概率发生故障,其故障概率是冲击量的函数,当工作的部件发生故障时,下一个冷贮备部件立即开始工作,当所有部件故障时,系统故障,故障部件按故障顺序进行修理,修理时间服从指数分布,故障部件能被修理如新。本文显式给出了系统首次故障前平均时间、稳态可用度、稳态故障频度等可靠性指标。     

具有四类故障可修系统解的存在惟一性

研究了具有四类故障且有两个热备器 (Warm Standby)的可修系统模型 .首先对用微分——积分方程描述的模型转换为 6维空间的积分方程形式 ,运用泛函分析 Banach空间下的算子理论 ,证明了此系统非负解的存在惟一性     

Optimal maintenance policy in a multistate deteriorating standby system

An optimal maintenance policy for a multistate deteriorating standby system is proposed in this study. Traditionally, a system could only presume two operational states: success or failure, and the maintenance policy is to determine the optimal number of standby components, subject to factors such as maintenance capability, cost of the standby items, etc., so as to minimize the operational cost. This study considers a more general production system in which progressive deterioration is incurred during the operating time, hence resulting in degrading performance. By modeling the system as a multistate deteriorating system, an optimal maintenance policy is obtained by determining the optimal number of standby components required in the system and the optimal state in which the replacement of deteriorating components shall be made.     

N-控制策略且温储备失效M/G/1可修排队的可靠性指标

本文研究N-门限值进入控制策略且温储备失效M/G/1可修排队系统, 其中系统在处于温储备失效的状态下最多容许N(1)个顾客进入系统。 运用全概率分解技术和拉普拉斯变换工具, 对服务台第一次失效前的寿命概率分布、不可用度、(0,t]时间内的平均失效次数以及处于温储备失效而等待修理的概率等可靠性指标进行了讨论, 并给出了其稳态结果表达式。 最后, 通过数值实例分析了服务台因温储备故障的稳态不可用度和稳态故障频度随一些参数的变化情况。