基于时间延迟维修理论检查模型的比较研究

主要解决设备故障停机时间较长情况下如何修正基本检查模型并优化维修间隔期的决策问题.首先阐述了时间延迟概念及其原理,建立了基于时间延迟维修理论的单元件系统基本检查模型,该基本检查模型的建立是基于设备故障停机时间相对检查周期较短的情况,提出了缺陷在故障停机期间继续发生的假定条件,该假定条件并不适合故障停机时间较长的情况,为此提出了只有在设备运行期间才会发生缺陷的假定条件并修正了基本检查模型,根据修正后的检查模型估算出检查周期内故障次数期望值.通过案例比较基本检查模型与修正模型之间的差异,计算结果表明,修正后的模型在检查周期的确定、故障停机时间期望值的计算方面具有更高的精度.     

基于时间延迟理论的预防维修模型及案例研究

本文旨在解决设备维修决策过程中预防维修检查数据缺乏情况下如何确定出合理的维修间隔期问题。首先,通过预防维修技术经济分析,提出了有关维修间隔期和总的停机时间之间关系的预防维修模型。其次,根据时间延迟维修理论,利用故障记录数据和预防维修检查数据的估计值,建立了统计模型并用来计算维修间隔期内故障次数的期望值。计算机仿真检验证明统计模型正确后,采用最大拟然法估计有关参数,这些参数包括缺陷发生率、时间延迟分布、检查出缺陷的概率等。最后是案例分析,应用估计参数和预防维修模型,计算出最佳的维修间隔期。     

运用延迟时间理论建立汽车维修优化模型

本文在对车队维修现状及维修数据进行分析的基础上,阐述了包括缺陷、故障两个因素的时间延迟模型的概念以及延迟时间建模的原理,提出了检查的时间和次数影响汽车故障的关系,进而建立了汽车维修优化模型.在满足一些假定的检查原则下,这一模型能够确定设备的维修周期等重要维修保养要素.文中最后运用这一优化模型对汽车维修进行了实例研究,得出了优化的汽车维修周期.     

利用主观数据建立预防维修的优化模型

本文利用维修工程师的经验数据建立了一个较实用的预防维修模型.首先对预防维修进行技术经济分析,在此基础上建立了目标函数;然后阐述了用主观数据建立预防维修优化模型的原理,详细说明了缺陷发生率估计和延迟时间分布函数确定的方法.该模型描述了总停机时间与不同维修间隔期之间的关系,利用该模型求出合理的维修间隔期,使得单位时间内总的停机时间期望值最小.最后是案例分析.     

考虑故障停机的生产控制与维修计划联合决策模型

通过生产控制与维修计划协同决策,降低生产成本。首先描述生产过程,分析各项费用。其次,建立了考虑生产过程失控、故障率和故障停时间的生产过程控制、生产计划优化和维修管理联合优化决策的模型。通过模型求解,联合制定出生产过程检查策略、生产计划（经济生产批量、生产批次）以及维修计划（PM间隔期）,实现单位时间内总费用最低的目标。再次,案例研究,分析生产过程失控、故障率和故障停机时间对于经济生产批量、生产过程检查策略和生产系统维修计划的影响。该模型从理论上解决了生产过程控制、生产计划优化和维修管理联合优化决策难题,对于指导企业制定生产计划和生产系统的检修计划,进而提高产品质量、降低生产成本、确保准时交货都具有指导意义和实用价值。     

设备维修决策的仿真模型

本文就设备计划维修周期决策问题进行了探讨,建立了一个以设备的综合效益为目标的计算机仿真模型。讨论了模型中随机变量的生产算法及参数估计,通过一个实例,给出了该模型的逻辑框架及运行机制。     

制药设备维修管理优化系统初探

现代制药类企业的设备基本上采用的是连续工作的流程作业设备、自动化流水生产线设备以及联动设备中的主机、辅机及其配套设备等。而一些小型的制药企业大多数在建立生产作业线时,较少考虑设备的维护修理,或由于生产紧张没有对设备进行充分维护,经常导致设备故障频繁。为解决实际生产中设备的维修管理不影响生产的正常运作,笔者想从以下几点进行论述。     

考虑缓冲区库存不足情况下的设备维护与缓冲区库存联合优化研究

针对缓冲区库存不足的两设备流水线生产系统(2M1B系统)设备维护问题,提出了生产设备维护与缓冲库存联合优化模型。首先,采用指数分布描述设备故障规律,表达运行周期的总故障次数;其次,通过分析缓冲区库存量在达到额定库存后的变化,提出了利用条件概率改进库存充足和库存不足两种情况下的设备维护和缓冲库存模型,基于更新酬劳定理,以故障次数和额定库存为决策变量,以总费用为目标函数,建立缓冲区库存不足情况下的设备维护与缓冲库存联合优化模型,并且将生产系统的缺货费用集成到了总费用模型;最后,通过算例分析,计算故障次数和最优缓冲区额定库存量,进行了灵敏度分析,验证了模型有效性,丰富了考虑缓冲库存的设备理论。     

同步物流系统下准时化生产与配送调度问题研究

对于"加工-装配"行业而言,物流管理水平的高低直接决定了供应链绩效的好坏。本文以Supply Hub运作模式为背景,研究同步物流下装配系统中各节点的生产与配送调度问题。建立供应链各参与方的生产与配送模型,并通过规划求解得到供应商和制造商的最优生产周期、零部件的最优配送间隔以及零售商的最佳采购周期。最后,结合数值实验,对同步物流模式和传统物流模式下的供应链绩效进行了对比分析。研究结果表明:较之传统物流模式,基于同步化物流方式的装配系统总成本更低,这主要得益于库存成本的下降;由于采取拉动式的生产模式,因此同步物流系统下供应链中的生产和配送活动更加频繁;生产调整成本的增加提高了制造商的平均总成本,由此可见在同步物流系统下,供应商、制造商和零售商之间更需要相互协商和收益共享,从而实现多赢。     

设备状态管理探讨

先进的生产工艺和设备必须采用现代化的管理手段进行科学管理,才能使设备发挥其应有的效能,本文通过对设备运行状态管理业务和方法的介绍以及通过设备管理信息系统的应用,旨在提高日常设备状态管理的业务水平,减少设备故障时间,降低维修成本,确保设备稳定运行.     

风险质检行为下的模糊生产-库存决策

本文研究在风险质检行为下需求与生产率具有模糊属性的由一个制造商与一个零售商构成的生产-库存问题。在假设制造商生产的产品存在质量缺陷，零售商在质检过程中存在质检风险的基础上，分别建立了需求模糊下的生产-库存总成本模型，需求与生产率模糊下的总成本模型，运用符号距离法进行了逆模糊化处理，将模糊化的生产-库存总成本转化为确定性成本。证明了两类情形下的总成本均是关于最优订购量与最优缺货量的联合凸函数。数值分析结果表明：随着期望缺陷率的增加，最优订购量增加，最优缺货量减少，最优成本增加，且最优成本增加的速度越来越快。一类质检风险增大引起总成本增加，二类质检风险增大引起总成本减少。最优订购策略对质检一类风险敏感，对质检二类风险不敏感。     

具有隐藏故障的多状态竞争失效系统检测策略研究

复杂工业系统的故障中有40%属于隐藏故障,若隐藏故障得不到及时消除,则可能导致巨大的经济损失。本文针对具有隐藏故障的多状态竞争失效系统,在考虑不完全检测的基础上,对其进行了维修建模。首先,基于制定的视情维修策略,分析了系统的更新情形;然后,基于所推导出的各种系统更新情形的发生概率,建立了以期望成本率为目标函数,以检测间隔时间为决策变量的维修模型。最后,以电容器组为例对所构建维修模型的适用性和有效性进行了验证,研究结果表明,检测质量对检测策略的制定有重要影响,因此研究具有隐藏故障的多状态竞争失效系统的检测策略时,有必要考虑检测误差。本文提出的维修建模方法不仅能在一定程度上丰富多状态竞争失效系统的维修策略理论与方法,还能为工程实际中复杂工业系统的维修工作提供理论基础与决策依据。     

Integrated Order Scheduling and Packing

We consider an integrated production–distribution scheduling model in a make‐to‐order supply chain consisting of one supplier and one customer. The supplier receives a set of orders from the customer at the beginning of a planning horizon. The supplier needs to process all the orders at a single production line, pack the completed orders to form delivery batches, and deliver the batches to the customer. Each order has a weight, and the total weight of the orders packed in a batch must not exceed the capacity of the delivery batch. Each delivery batch incurs a fixed distribution cost. The problem is to find jointly a schedule for order processing and a way of packing completed orders to form delivery batches such that the total distribution cost (or equivalently, the number of delivery batches) is minimized subject to the constraint that a given customer service level is guaranteed. We consider two customer service constraints—meeting the given deadlines of the orders; or requiring the average delivery lead time of the orders to be within a given threshold. Several problems of the model with each of those constraints are considered. We clarify the complexity of each problem and develop fast heuristics for the NP‐hard problems and analyze their worst‐case performance bounds. Our computational results indicate that all the heuristics are capable of generating near optimal solutions quickly for the respective problems.     

Multi-product lot scheduling with backordering and shelf-life constraints

In this paper, we revisit the economic lot scheduling problem (ELSP), where a family of products is produced on a single machine, or facility, on a continual basis. Our focus is on the determination of a feasible production schedule, including the manufacturing batch size of each item. We assume that total backordering is permissible and that each of the products has a limited post-production shelf life. Several studies examining this problem have suggested a rotational common cycle approach, where each item is produced exactly once every cycle. To ensure schedule feasibility, we resort to the technique of reducing individual production rates and allow the flexibility of producing any item more than once in every cycle, in conjunction with appropriate timing adjustments. In order to solve this more generalized model, which is NP hard, we suggest a two-stage heuristic algorithm. A numerical example demonstrates our solution approach.     

Optimal Inspection of Imports to Prevent Invasive Pest Introduction

The United States imports more than 1 billion live plants annually—an important and growing pathway for introduction of damaging nonnative invertebrates and pathogens. Inspection of imports is one safeguard for reducing pest introductions, but capacity constraints limit inspection effort. We develop an optimal sampling strategy to minimize the costs of pest introductions from trade by posing inspection as an acceptance sampling problem that incorporates key features of the decision context, including (i) simultaneous inspection of many heterogeneous lots, (ii) a lot‐specific sampling effort, (iii) a budget constraint that limits total inspection effort, (iv) inspection error, and (v) an objective of minimizing cost from accepted defective units. We derive a formula for expected number of accepted infested units (expected slippage) given lot size, sample size, infestation rate, and detection rate, and we formulate and analyze the inspector's optimization problem of allocating a sampling budget among incoming lots to minimize the cost of slippage. We conduct an empirical analysis of live plant inspection, including estimation of plant infestation rates from historical data, and find that inspections optimally target the largest lots with the highest plant infestation rates, leaving some lots unsampled. We also consider that USDA‐APHIS, which administers inspections, may want to continue inspecting all lots at a baseline level; we find that allocating any additional capacity, beyond a comprehensive baseline inspection, to the largest lots with the highest infestation rates allows inspectors to meet the dual goals of minimizing the costs of slippage and maintaining baseline sampling without substantial compromise.     

MANAGING A FLOW LINE WITH SINGLE‐KANBAN,DUAL‐KANBAN OR CONWIP

To control the production of different parts on a single flow line, managers can choose between the Single‐kanban, Dual‐kanban, and Conwip. This paper therefore compares the three different systems. The results show that Conwip consistently produces the shortest mean customer wait time and lowest total work‐in‐process. Our results also contradict the finding of a previous study, which showed that Dual‐kanban performed better than Single‐kanban. The different findings can, however, be attributed to the use of a material transfer policy, which favors the Dual‐kanban modeled in the previous study. Our study shows that transferring replenished containers immediately to downstream stations, increasing the number of cards, and reducing the withdrawal cycle reduce the mean customer wait time significantly.     

Multi-product batch production on a single machine—A problem revisited

When several products are processed one at a time on a single machine, the conventional approach of computing the economic batch quantity for each product cannot apply. An example for six products is considered, where the total production capacity on regular time is inadequate, so that overtime has to be used at an extra cost. A simple method is described for solving this problem when each product is produced once during a production cycle, the objective being to minimize the total set-up and holding costs per day. Schedules which involve batch splitting can reduce these costs further, and a guideline is proposed for the construction of sub-cycles. The results compare favourably with lower bounds computed for the purpose.     

Production lot sizing with process deterioration and machine breakdown under inspection schedule

The paper develops integrated production, inventory and maintenance models for a deteriorating production system in which the production facility may not only shift from an ‘in-control’ state to an ‘out-of-control’ state but also may break down at any random point in time during a production run. In case of machine breakdown, production of the interrupted lot is aborted and a new production lot is started when the on-hand inventory is depleted after corrective repair. The process is inspected during each production run to examine the state of the production process. If it is found in the ‘in-control’ state then either (a) no action is taken except at the time of last inspection where preventive maintenance is done (inspection policy-I) or (b) preventive maintenance is performed (inspection policy-II). If, however, the process is found to be in the ‘out-of-control’ state at any inspection then restoration is done. The proposed models are formulated under general shift, breakdown and repair time distributions. As it is, in general, difficult to find the optimal production policy under inspection policy-I, a suboptimal production policy is derived. Numerical examples are taken to determine numerically the optimal/suboptimal production policies of the proposed models, to examine the sensitivity of important model parameters and to compare the performance of inspection and no inspection policies.