具有自重置功能的两部件温贮备可修系统的可靠性分析

该文讨论具有自重置功能的两部件温贮备可修系统.系统有两种修理策略,一是每个部件都有自重置功能,即通过自动错误检测从故障中自动恢复;二是通过修理工修理故障的部件.该文首先研究该系统稳态和瞬时可靠性指标,然后讨论了系统各参数对系统可靠性的影响.     

带启动时间和可修服务台的M/M/1/N工作休假排队系统

分析带有启动时间、服务台可故障的M/M/1/N单重工作休假排队系统.在该系统中,服务台在休假期间不是完全停止工作,而是处于低速服务状态.假定服务台允许出现故障且当出现故障时,服务台停止为顾客服务且立即进行修理.服务台的失效时间和修理时间均服从指数分布,且工作休假期和正规忙期具有不同的取值;同时,从关闭期到正规忙期有服从指数分布的启动时间.建立此工作休假排队系统的有限状态拟生灭过程(QBD),使用矩阵几何方法得到QBD的各稳态概率相互依赖的率阵,从而求得稳态概率向量.通过有限状态QBD的最小生成元和稳态概率向量得到系统的基本阵和协方差矩阵,求解出系统方差、系统稳态可用度、系统吞吐率、系统稳态队长、系统稳态故障频度等系统性能.数值分析体现了所提出方法的有效性和实用性,通过敏感性分析将各参数对系统性能的影响进行了初探,为此模型的实际应用提供了很好的理论依据.     

修理工带休假的单部件可修系统的可靠性分析

考虑修理工带有单重休假的单部件可修系统,系统发生故障时可能因修理工的休假而 得不到立即修理,因此系统可处于工作、等待修理和修理三种状态.利用全概率分解技术和拉普 拉斯或拉普拉斯--司梯阶变换工具,讨论了系统的可靠度、瞬时可用度和稳态可用度,以及 (O,t]时间中系统的平均故障次数和稳态故障频度,得到了关于系统的可靠度、瞬时可用度和稳 态可用度,以及(O,t]时间中系统的平均故障次数和稳态故障频度等可靠性指标的重要结果.     

离散时间单重休假冷储备系统的可靠性分析

利用离散向量Markov过程方法研究了离散时间单重休假两同型部件冷储备可修系统。在部件寿命服从几何分布,修理时间和修理工休假时间服从一般离散型概率分布的假定下,引入修理时间和休假时间尾概率,求得了系统的稳态可用度、稳态故障频度、待修概率、修理工空闲概率和休假概率,以及首次故障前平均时间等可靠性指标。     

带工作休假和工作故障的M/M/1/N排队系统性能分析

本文在可修M/M/1/N排队系统中引入了启动时间、工作休假和工作故障策略.在该系统中,服务台在休假期间不是完全停止工作,而是处于低速服务状态.设定服务台在任何时候均可发生故障,当故障发生时立刻进行维修.且当服务台在正规忙期出现故障时,服务台仍以较低的服务速率为顾客服务.服务台的寿命时间和修理时间均服从指数分布,且在不同的时期有不同的取值.同时,从关闭期到正规忙期有服从指数分布的启动时间.本文建立此模型的有限状态拟生灭过程(QBD),使用矩阵几何方法得到系统的稳态概率向量,并应用基本阵和协方差矩阵理论,计算出系统稳态可用度、系统方差、系统吞吐率、系统稳态队长及各系统稳态概率等系统性能指标.同时,通过数值实验对各系统参数对系统性能的影响进行了初探.文中的敏感性分析体现了这种方法的有效性和可用性.实验表明,文中提出的模型,可有效改善仅带有工作休假或工作故障策略排队模型的系统性能.     

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.     

两部件系统视情维修与生产调度的联合优化模型

为了解决生产调度过程中由系统维护维修产生的资源闲置和时间成本增加问题,将系统维修与生产调度联合建模.在众多学者将系统作为整体进行生产调度与维修研究的基础上,考虑系统内各组成部件之间的复杂关系.针对具有经济相关性的两部件系统,以调度作业加工顺序、预防性维修阈值、机会维修阈值作为决策变量,考虑到两部件同时维修比单部件独立维修更为经济,将机会维修引入到建模之中,制订机会维修、预防性维修、故障后更换的视情维修与生产调度结合的联合策略,通过劣化状态空间划分法给出生产调度过程中所有维修组合及其对应维修概率,推导出联合概率密度函数,建立以最小化总加权期望完成时间为目标的联合优化模型.通过数值实验和灵敏度分析验证所提出的策略及模型的有效性.     

考虑维修优先权的多状态温贮备系统可靠性模型

针对工程应用中装备维修和保养两类活动具备不同优先级这一问题,考虑单一维修台可进行维修和保养两类工作,其中维修具有优先权.以多状态温贮备系统为研究对象,采用可近似拟合任意分布的Phase-type(PH)分布构建一种描述能力更强的系统可靠性模型,得出系统稳态可用度、系统故障率、平均故障间隔时间等一系列可靠性指标的解析表达式.最后利用算例验证PH分布的适用性,演示系统可靠性函数随时间的变化趋势,并讨论维修台工作速率对系统故障率、稳态可用度、维修台忙期稳态概率和平均故障间隔时间的影响.算例结果表明,所提模型具有较广泛的应用价值.     

基于故障树-贝叶斯网络的受电弓系统可靠性评估

受电弓是城市轨道交通车辆重要电气设备,其稳定性直接影响车辆受流稳定性,受电弓的良好性能是车辆安全运营的保证之一.针对受电弓系统可靠性评估故障树分析法的局限性,将故障树分析法与贝叶斯网络相结合进行受电弓系统可靠性的分析研究.该方法不但能计算出受电弓系统可靠性指标,还可以对系统失效时各部件失效的条件概率进行求解,进而得到各个部件对系统的可靠性影响程度,进行正反推理诊断,找出受电弓系统可靠性的薄弱环节,提高了其可靠性分析的效率.为地铁车辆受电弓系统的可靠性评估及其故障检修提供理论依据.     

基于Markov模型的可维修双机热备系统可靠性分析

为了综合考虑维修性、故障检测率及共因失效对双机热备系统可靠性的影响,利用马尔可夫模型对可维修双机热备系统进行可靠性分析.由系统状态转移关系建立双机热备系统的状态转移图,由于备用单元发生不可测失效时不能及时对其进行维修,提出在状态转移图中增加一个状态来区分此种降级工作状态.根据状态转移图得到系统状态转移方程并借助Matlab对其进行求解,得到故障检测率、失效率、维修率与共因失效因子为不同取值时的系统状态概率图.分析结果表明,维修率对可维修双机热备系统达到平稳状态所需时间贡献较大,系统工作状态概率值与故障状态概率值则由故障率与修复率的比值、故障检测率及共因失效等因素共同决定.     

A batch arrival queue under randomised multi-vacation policy with unreliable server and repair

This article examines an M^[x]/G/1 queueing system with an unreliable server and a repair, in which the server operates a randomised vacation policy with multiple available vacations. Upon the system being found to be empty, the server immediately takes a vacation. If there is at least one customer found waiting in the queue upon returning from a vacation, the server will be activated for service. Otherwise, if no customers are waiting for service at the end of a vacation, the server either remains idle with probability p or leaves for another vacation with probability 1???p. When one or more customers arrive when the server is idle, the server immediately starts providing service for the arrivals. It is possible that an unpredictable breakdown may occur in the server, in which case a repair time is requested. For such a system, we derive the distributions of several important system characteristics, such as the system size distribution at a random epoch and at a departure epoch, the system size distribution at the busy period initiation epoch, and the distribution of the idle and busy periods. We perform a numerical analysis for changes in the system characteristics, along with changes in specific values of the system parameters. A cost effectiveness maximisation model is constructed to show the benefits of such a queueing system.     

Optimization analysis of an unreliable multi-server queue with a controllable repair policy

This article deals with an infinite-capacity multi-server queueing system, in which the servers are assumed unreliable and may fail at any time. To conserve energy while delivering reliable service, a controllable repair policy is introduced. With such a policy, the failed servers will be sent to the repair facility only when the number of failed machines in the system arrives at a preset threshold value. A quasi-birth-and-death process is used to model the complex system and the stability condition is examined. The rate matrix is calculated approximately and steady-state stationary distributions are obtained by a matrix-analytic approach. The closed-form expressions of important system characteristics are presented. A cost model is constructed to determine the optimal repair policy, the optimal value of service rate and the optimal value of repair rate. Three heuristic algorithms are employed to deal with the optimization problem. Some numerical results are provided to compare the efficiency of two methods.     

Sensitivity analysis of the machine repair problem with general repeated attempts

In this paper, we propose a machine repair problem with constant retrial policy, wherein if a failed machine finds the repairman busy upon arrival, it enters into an orbit. The machines in the orbit form a single waiting line, and only the one at the head of the orbit repeats its request for repair. The failure times of operating machines and the repair times of failed machines follow exponential distributions. It is assumed that retrial times are generally distributed. We used the supplementary variable technique to obtain explicit expressions for the steady-state probabilities of the number of failed machines in the orbit. We performed sensitivity analysis of the machine availability and operative efficiency with respect to system parameters and the number of machines in operation. The analysis of the busy period and the waiting time were also presented. Finally, we developed a cost model and formulated a cost minimization problem.     

Availability of a repairable retrial system with warm standby components

In this paper, we study a repairable K-out-of-(M+W) retrial system with M identical primary components, W standby components and one repair facility. The time-to-failure and time-to-repair of the primary and standby components are assumed to be exponential and general distributions, respectively. The failed components are immediately for repair if the server is idle, otherwise the failed machines would enter an orbit. It is assumed that the retrial times are exponentially distributed. We present a recursive method using the supplementary variable technique and treating the supplementary variable as the remaining repair time to obtain the steady-state probabilities of down components at arbitrary epoch. Then, a unified and efficient algorithm is developed to compute the steady-state availability. The method is illustrated analytically for the exponential repair time distribution. Sensitivity analysis of the steady-state availability with respect to system parameters for a variety of repair time distributions is also investigated.     

具有优先权的M/G/1重试可修排队系统

在服务台忙的情况下, 到达服务台的顾客以概率 q 进入无限位置的优先队列而以概率 p 进入无限位置的重试轨道 (orbit), 并且按照先到先服务 (FCFS) 规则排队, 假定只有队首的顾客允许重试, 同时考虑服务台可修的因素, 证明了系统稳态解存在的充要条件. 利用补充变量法求得稳态时两个队列与系统的平均队长、顾客等待时间、服务台的各种状态概率以及可靠性指标.     

Stochastic manufacturing system with process deterioration and machine breakdown

This paper presents a realistic manufacturing inventory model with process deterioration and machine breakdown. In economic manufacturing quantity model, process usually starts with ‘in-control’ state and produces items of good quality. After some random point of time, process may deteriorate and shift to ‘out-of-control’ state due to occurrence of assignable cause. From that point, process produces some percentage of non-conforming items. Further process deterioration after machine shift may result in machine breakdown at any random time during the production period. If machine breakdown occurs during the production period, then corrective (emergency) repair is performed immediately otherwise preventive (regular) repair is performed at the end of production period. The proposed model is formulated assuming that the time required for production facility shifting from ‘in-control’ state to ‘out-of-control’ state, time when machine breaks down, corrective and preventive repairing time and demand of items follows probability distribution. We have derived analytically the optimal production time which minimises the total expected production cost annually for machine breakdown and no machine breakdown cases. The solution procedure is illustrated with the help of numerical examples for different probability distributions. Sensitivity of the optimal solution with respect to different parameters are also analysed.     

On solving unreliable planar location problems

In this paper, we generalize conventional P-median location problems by considering the unreliability of facilities. The unreliable location problem is defined by introducing the probability that a facility may become inactive. We proposed efficient solution methods to determine locations of these facilities in the unreliable location model. Space-filling curve-based algorithms are developed to determine initial locations of these facilities. The unreliable P-median location problem is then decomposed to P 1-median location problems; each problem is solved to the optimum. A bounding procedure is used to monitor the iterative search, and to provide a consistent basis for termination. Extensive computational tests have indicated that the heuristics are efficient and effective for solving unreliable location problems.Scope and purposeThis paper addresses an important class of location problems, where p unreliable facilities are to be located on the plane, so as to minimize the expected travel distance or related transportation cost between the customers and their nearest available facilities. The unreliable location problem is defined by introducing the probability that a facility may become inactive. Potential application of the unreliable location problem is found in numerous areas. The facilities to be located can be fire station or emergency shelter, where it fails to provide service during some time window, due to the capacity or resource constraints. Alternatively, the facilities can be telecommunication posts or logistic/distribution centers, where the service is unavailable due to breakdown, repair, shutdown of unknown causes. In this paper, we prescribed heuristic procedures to determine the location of new facilities in the unreliable location problems. The numerical study of 2800 randomly generated instances has shown that these solution procedures are both efficient and effective, in terms of computational time and solution quality.     

A deteriorating repairable system with stochastic lead time and replaceable repair facility

In this paper, a deteriorating repairable system with stochastic lead time and replaceable repair facility is studied. We assume that the spare system for replacement is available only by an order and the lead time for delivering the spare follows exponential distribution. Moreover, we also suppose that the repair facility may be subject to failure during the repair period. Under these assumptions, by using the geometric process and the supplementary variable technique, some important reliability indices such as the system availability, rate of occurrence of failure (ROCOF) and the probability that the system is waiting for replacement are derived. An ordering policy N − 1 and a replacement policy N based on the number of failures of the system are also considered. Furthermore, employing several Lemmas, the explicit expression of the average cost rate is derived. Meanwhile, the optimum value N^∗ for minimizing the average cost rate could be determined numerically.