A Note On “Determination of Coordinated Maintenance Scheduling Frequencies For A Group Of Machines”

In this note we present a simpler total cost model when the repair work on a group of machines is coordinated. We demonstrate that coordination of repair work may not be economically beneficial under the generally accepted conditions. We suggest an improvement in the solution procedure in order to consider coordinated as well as uncoordinated repair policies for a group of machines.     

Maintenance Scheduling for Multicomponent Equipment

The problem investigated is the scheduling of preventive and opportunistic maintenance or replacement for equipment with more than one component under conditions of positive failure costs and increasing failure rates for all components. Dynamic programming models are presented for determining optimal policies for two and three component equipment. The resulting optimal policies are compared to commonly used policies and the often substantial diseconomies of such policies are illustrated. The (n,N) policies are found to be near-optimal under a wide range of opportunistic/preventive maintenance costs and failure rates for two and three component equipment. An approach for developing simple (n,N) policies for many component equipment is suggested.     

Gamma Approximation for Preventive Maintenance Scheduling

This paper presents an approximation model for determining minimum cost preventive maintenance schedules where accurate failure data are not available except the “average” (mean) and the “typical” value (mode) of the component lifetime.     

Dynamic Scheduling of a Robot Servicing Machines on a One-Dimensional Line

We examine the operation of a single robot servicing a finite set of machines lined up in succession. Each machine operates for a random time, gets blocked (or fails), waits for the robot, waits for the repair duration, starts operating again, and so on. We seek a dynamic decision rule which at any time, depending on the state of the whole system, will decide what action the robot should take: to repair the machine in front of it, or to move left or right, or to stop and wait. The objective is to maximize the average number of operating machines, over an infinite horizon. This problem arises in die practical context of a textile winding process.

We model this system as a Markov Renewal Decision Process, and present a computational approach, based on dynamic programming, to approximate an optimal decision policy, under the assumption of exponential times to failure. We consider the case in which the robot can stop and change direction anywhere, and the case where the robot can stop or change direction only in front of a machine. Since the optimal policies turn out to be very complex, we examine simpler suboptimal rules, and compare them to the optimal policy and to other previously proposed or commonly used decision rules. For the numerical examples that we have examined, our best suboptimal rules almost always take the optimal decision, and their costs differ from the optimum by a negligible amount. For the case where the robot can stop or change direction anywhere, we used computer simulation to compare the suboptimal rules and conclude that our proposed rules are in general better man those previously proposed or commonly used.     

基于RCM的港口机械关键设备的维修决策

以港口起重机械为对象,在为振华港机建立的以可靠性为中心的维修决策流程框架下,对所涉及的维修方式进行研究优化.结合故障率调整因子,探索了按有效度最大的原则确定港口机械的最佳预防维修周期的算法;基于P-F间隔,提出了基于RCM的状态维修检测周期算法.最后,开发了可靠性维护系统,通过程序开发,实现各项功能模块.为企业的设备维护提供科学的决策支持.     

Sequencing, Scheduling and Tooling Single-Stage Multifunctional Machines in a Small Batch Environment

Single-Stage multifunctional Machining Systems (SSMSs) are an important integral part of automated, flexible manufacturing systems. However, the SSMS frequently becomes the bottleneck of the entire manufacturing system by virtue of protracted internal set-up requirements. A key aspect of achieving full SSMS utilization is the ability to reduce as much as possible these demands at the expense of increasing external set-up. As of today, fixturing devices have not received much attention in the modeling literature. Nevertheless, fixturing devices are in some cases a limited resource which, may affect the shop scheduling decisions and the shop performance and as such can not be omitted. This study presents a {0–1} programming model which takes the fixturing device's limitation in to consideration when determining the weekly sequence of jobs to be produced. The model tries to minimize the non-productive machine time. Based on this model, a heuristic procedure is developed and tested using data of four production weeks obtained from a hi-tech company that produces medical imaging systems.     

工件带到达时间并具有成组约束的车间排序算法

针对模具制造过程的特点,在工件不同时到达的情况下,研究了前阶段带有成组约束的两阶段柔性同序加工车间的调度问题,建立了目标函数为最小化最大完成时间的调度数学模型．基于Potts的RJ’算法提出解决此类问题的启发式算法,并将该算法应用到轮胎模具企业的生产实例中,通过仿真说明数学模型和求解方法的可靠性和有效性．     

A Bayesian Approach to the Scheduling of Preventive Maintenance

This paper presents a Bayesian model for determining minimum cost rate preventive maintenance schedules where historical data are not available. Also, a model to determine appropriate maintenance budgeting policies is presented and discussed.     

湿式报警阀组的安装、调试及维护管理

湿式报警阀组是湿式自动喷水灭火系统最主要的设备之一,当火灾发生时能迅速地启动消防设备进行灭火,并发出报警信号的设备,它的安装、调试质量直接影响到整个系统能否正常运行.文章对湿式报警阀组的安装、调试,以及日常维护管理作了较详细论述.     

集成预防性维护计划的单机调度蚁群优化研究

尽管生产调度与预防性维护计划密切相关,且其共有目标都是提高机床的利用率,但是存在着调度优化上的冲突.为了综合考虑单机情形下的生产调度与预防性维护计划,提出了一种改进的蚁群优化算法,用于解决以总计作业加权完成时间和总计维护成本最小为双目标的生产调度与预防性维护计划的集成模型.同时进行了大量的仿真实验,比较结果表明提出的蚁...     

A Computer-Aided Graphical Procedure for Scheduling Preventive Maintenance of Electric Power Generating Units

This article attempts to show how computer graphics can assist in computerized development of project-type schedules as exemplified by preventive maintenance scheduling in the electric power industry. The method is equally applicable to the scheduling of maintenance activities in general or, with modification, to devising shift schedules for personnel such as police, nurses, and toll collectors who must provide 24-hour service with changing demand levels. A hand procedure currently used by electric utilities for creating preventive maintenance shutdown schedules for generator units is first described. A mixed integer programming model of the problem is given which is computationally intractable for any realistic-size problems. The same problem using man-machine interaction via a graphics terminal to overcome the computational limitations of the mathematical formulation is then described and illustrated. A proposed extension to improve the speed of solution is also described.     

基于瓶颈的制造单元两阶段群组调度程序与仿真

为解决具有瓶颈的制造单元调度问题,提出了一种以瓶颈为基础的两阶段群组调度方法.该方法充分运用瓶颈机器,使所有零件的最大完成时间最小化.为评估调度方法的绩效,文章建立了两阶段群组调度程序的5机制造单元仿真模型.仿真实验结果证明,本方法不仅平均总完工时间最短,而且是绩效表现最稳定的调度方法.     

Using Utility Functions for Aggregate Scheduling in Health Maintenance Organizations (HMO'S)

The multiple attributes and characteristics of the services provided by a health maintenance organization (HMO) are reduced to a common unit of measurement by means of utility functions. This reduction allows the development of a micro-economic aggregate planning model that can be used both for the short and the long term to make optimizing decisions on system inputs and resource allocations. The model is designed to deal with the common revenue- and budget-constrained situations and is directed to maximize the level of service provided by the HMO, according to the management's perceptions of the system characteristics. An empirical short term application of the model is presented and compared against actual management decisions. Data needs and implementation requirements are discussed, along with the managerial implications of this approach.     

A Resonant Cavity Approach for the Nondestructive Determination of Complex Permittivity at Microwave Frequencies

A nondestructive microwave cavity approach for measuring complex permittivities of materials in sheet form is described. The resonant cavity is a section of a rectangular waveguide terminated by a thin rigid and large flange containing a small rectangular iris opening. The iris is placed in firm contact with one side of the dielectric sample while the other side is backed with a highly conducting plate. Variations of the cavity resonant frequency and Q-factor caused by the dielectric can be related to its complex permittivity through the consideration of equivalent admittance of this open-ended dielectricloaded aperture at resonance. Experimental determination of aperture admittance of a loaded iris is made and the results compared with theoretical calculations. The validity of this technique is confirmed by evaluating the resonant cavity characteristics by loading it with dielectrics of known permittivities and comparing the results with theoretical results. The permittivity of a lossy dielectric slab is measured and the value obtained by this method is compared with those found by other techniques. In all these cases the agreement between theory and measurements is satisfactory. Utility of this technique in evaluating the local inhomogeneities of permittivity of sheets is demonstrated. Measurement errors and limitations of this technique are pointed out.     

局内同类机器加工任务排序问题的一种算法及仿真试验

对于局内同类机器加工任务排序问题设计了一种Space Preparation算法(简称SP算法),改进了经典LIST算法的平均执行效率．文中证明SP算法的竞争比为2,并通过仿真试验进行验证SP算法的执行效率。     

生产调度与维护集成的多目标Lorenz非劣遗传优化

研究了一种单机环境下集成生产和维护的双目标优化调度问题。机床的故障间隔时间和平均维修时间服从指数分布,同时结合加工序列相关准备时间。预防性维护活动不能与作业加工同时进行,但与准备时间不相冲突。调度目标是同时最小化作业总计完成时间和机床不可得性。在问题建模的基础上,构造了一种基于Lorenz非劣关系的分类遗传算法(表示为L-NSGA-Ⅱ),详细设计了算法的核心部分。最后,通过大量计算实验,将L-NSGA-II算法与NSGA-II算法进行了比较分析,说明了L-NSGA-II算法的有效性。     

Determination of Time for Conducting Preventive Maintenance Using Hybrid Analysis

It becomes a common practice to determine time for conducting preventive maintenance (PM) using a hazard function and an alarm limit on a specified failure rate. In this paper, the authors argue that using both hazard and reliability functious can improve the accuracy of the result, especially when the whole-life characteristic failure is modelled using different failure distributions. The PM time predicted bused on the hazard function should be checked against reliability.     

Simultaneous Optimization of Preventive Maintenance and Replacement Policy for Machines: A Modern Control Theory Approach1

The problem of machine replacement in a changing technological environment is formulated as a problem in modern control theory. The objective is to maximize the present value of all future net profits over a class of infinite chains of machines where each link in the chain represents a uniform length replacement cycle with identical preventive maintenance. The control is effected by varying (a) the length of the replacement cycle, and (b) the schedule of preventive maintenance. The optimal control is determined by applying the maximum principle of Pontryagin and resulting influence functions are provided economic interpretations.     

Frequencies of a hydroelastic rectangular system

The coupled hydroelastic frequencies of a liquid in a rectangular channel covered by a membrane or plate (beam in the here treated two-dimensional case) have been obtained for various boundary conditions. The coupled eigenvalues have been obtained and show a decrease for increasing length of the beam to liquid heigh ratio, while for increasing mass ratio of the beam mass per unit length to the liquid mass per unit length exhibit an increase of the coupled eigenvalue.