Optimal production run length and maintenance schedule for a deteriorating production system

This study considers manufacturing cost, inventory holding cost, system setup and maintenance costs, restoration cost, and warranty cost to a deteriorating production system whose state can be classified into in-control or out-of-control state at any time. This study develops a framework of simultaneous determination of optimal production run length and maintenance schedule and shows that there exists a unique optimal production run length and scheduled maintenance policy that minimize the expected total cost per item. The mathematical conditions to the optimal production run length and scheduled maintenance policy for a production cycle are deduced.     

考虑设备维修与维护的装配作业车间动态生产仿真研究

装配作业车间生产调度的关键是动态协同产品各零件的生产进度以满足产品的齐套需求。设备的随机故障将会扰乱已有的生产计划,给各零件之间的进度协同带来更高的挑战。预防性维护能够提高设备的可靠度以减少故障的发生,但过度的维护又会减少生产加工的时间。从调度规则构成属性的角度分析设备故障将带来的影响,并提出一种考虑设备故障的改进型调度规则。通过仿真试验分析了企业常见的3种预防性维护策略对车间性能的影响和7种代表性调度规则的性能。试验结果表明:预防性维护策略对车间有明显的影响;且考虑了设备故障的调度规则有一定的改进效果。     

Data-driven modeling of truck engine exhaust valve failures: A case study

Exhaust valve is an essential part of truck engine. Dynamic and unpredictable thermal and mechanical stress cause valves to wear prematurely, leading to increased maintenance costs. In this paper, a data-driven approach is presented to predict failures of exhaust valves of truck engines. The failure datasets of exhaust valves recorded from 13 truck engines are divided into three groups: First failure, second failure, and third or more failures. The Kaplan-Meier estimator is selected to express the distribution of survival probability of the three groups of failures. In order to find the hazard indicator, two data-mining algorithms, a wrapper and a boosting tree are applied to select parameters highly relevant to the hazard rate. A Cox proportional hazard model is used to conduct regression analysis on each selected parameter. Based on the derived hazard ratio, the time-dependent baseline hazard rate is computed. Five parametric reliability models are selected to capture the baseline hazard rate for the three groups. The value-at-risk for each group of failures is computed to express the risk at different confidence levels. Life circle of truck engine exhaust valves can be estimated.     

Joint control of production, overhaul, and preventive maintenance for a production system subject to quality and reliability deteriorations

This research investigates the case of an unreliable manufacturing system subject to quality and reliability deterioration. In particular, we conjecture that the deterioration of the system leads to a continuous increase in the intensity of failures and a decrease on the quality of the parts produced. As such, deterioration implies a twofold effect on the manufacturing system. When the machine fails, minimal repair is conducted, leaving the machine at the same level of deterioration before failure. Hence, the quality of the parts produced and the failure intensity remain unchanged with this repair. Meanwhile, an overhaul refers to a perfect repair that completely restores the quality of the parts and the failure intensity of the machine. This option completely counters all the effects of the deterioration. Preventive maintenance may also be conducted, but it reduces the level of deterioration only partially, improving the quality of the units produced and the failure intensity just in part. This set of characteristics yields to the formulation of a new control model that simultaneously determines the optimal production plan, the overhaul, and preventive maintenance strategies. Such a joint control policy minimizes the total cost including the inventory holding, backlog, overhaul, preventive maintenance, and defective costs over an infinite planning horizon. Since the dynamics of the system change as a function of the level of deterioration, it is necessary to use its history for a proper formulation; therefore, a semi-Markov decision process is used. Numerical methods are applied to determine the control policy, and numerical examples are conducted as illustrations. An extensive sensitivity analysis is presented in order to confirm the structure of the control policy obtained and examine the effect of several parameters.     

基于系统可靠性的生产与维护计划联合决策

为准确构建生产系统中批量生产与设备维护之间的关联关系,以并行机系统产能受限批量计划问题为基础,提出并引入基于系统可靠性的预防性维护策略与成组维护策略,建立了以生产与维护总成本最小化为目标的生产计划与预防性维护联合决策模型,从而在保证系统生产效益的前提下优化系统的维护频率、减少系统中生产与维护的总成本。模型的求解采用基于产能约束松弛的拉格朗日松弛算法框架,并设计了基于移动平滑方法的构造启发式算法,以获得问题的可行解并协同优化系统生产和维护计划。数值实验表明,该模型能充分发挥并行机的协调能力,有效避免设备过度维护问题,从而降低生产与维护总成本,所设计的算法具有较好的求解性能。     

生产系统维修策略和控制图经济设计研究综述

在生产系统的产品质量保证过程中,设备维修管理与统计过程控制是两种常用手段和方法。在分析设备维修管理和统计过程控制对生产系统的产品质量和经济成本影响基础上,重点从经济性角度按照维修策略经济设计、控制图经济设计,以及维修策略和控制图联合经济设计三个知识模块,对生产质量保证管理系统的经济性设计研究现状进行了梳理与评述,并提出了未来研究的努力方向。     

基于造价和维修费用的系统可靠性指标分配方法

可靠性指标分配是人力、物力统一调度和合理运用的一个工程决策问题，是与工程系统造价、维修费用密切相关的。因此，在进行系统可靠性分配时，必须同时考虑工程系统的造价和维修费用。本文给出了工程系统造价与可靠度的关系式和系统维修费用期望值与可靠度的关系式，建立了考虑造价与维修费用的系统可靠性模糊优化分配数学模型，从一而提出了基于造价和维修费用的系统可靠性指标分配方法，并给出了该方法的工程应用算例。结果表明：本文方法科学合理、简单实用，具有一定的工程应用价值。     

Automation and parameters optimization in production line: a case of study

A metal-forming production line was automated and the critical parameters of the process of feeding to the press were determined using experiments designed to optimize production with a minimum number of tests. In order to carry out a factorial design of experiments, we registered the level of lubricant, the speed of the feeder, the advance of raw material, and the pressure of the lubrication to be taken as experimental factors. The results of the experiment design showed that the advance of raw material and the interactions between the level of lubricant and the pressure of the lubricant and between the feeder speed, the level of lubricant, and the pressure of the lubricant are the main parameters for feeding to the press for production optimization. Several tests were carried out and the production in the automated and optimized process increased more than 400 % with respect to the artisan process. This paper demonstrates that optimization of the feed to the press in a production line is very important for high operational efficiency and for maintaining a factory competitive and sustainable.     

考虑处置和服务水平影响的混合系统库存决策

为确定最优的制造与再制造策略,对混合系统进行了研究。在该系统中,因再制造能力不足,返回的旧产品仅有一部分用于再制造,其余的被处置。用于再制造的旧产品构成了可翻新品库存。顾客需求恒定且由服务性产品库存来满足,该库存由制造新品与再制造品组成。顾客允许延迟交货,但企业的最大缺货量受其服务水平制约。在两类策略下分别构建了库存决策模型,即一次制造准备和至少一次再制造准备策略与至少一次制造准备和一次再制造准备策略,并利用消元思想和差分函数对模型求解,得到了最优的制造与再制造批量等求解公式。结果表明,能找到最优的制造与再制造策略,并存在一个最优的服务水平控制点。     

基于质量约束的生产调度与设备维护联合优化模型分析

本文主要研究车间生产管理中设备维护维修、生产调度、质量控制三者联合优化问题.在质量控制成本约束下,研究生产调度和设备维护维修联合优化模型,旨在通过优化工艺过程质量控制成本函数参数与预防性维护时间变量,获得单位时间预期成本最小值.通过采用启发式算法,得出最优质量控制成本函数参数与预防维护时间参数组合,与生产调度计划相结合...     

Cell adhesion and the immune system: a case study using earthworms

In the earthworm's immune system, cell adhesion, which occurs by putative receptors on leukocytes, is essential after recognition of self vs. non-self. Confrontation with foreign antigens is a normal event in the environment, replete with microbial pathogens that pose a threat to survival. To better understand what happens when an effector cell first recognizes a foreign target followed by its adhesion to it, isolated leukocytes, in sufficient quantities to be subjected to various analyses, have been extremely beneficial. In vitro approaches when accompanied by biochemical, immunological, and molecular technologies, have opened up new vistas concerning the immune response of earthworms and other invertebrates. The most recent discovery includes the preliminary identification of cell differentiation (CD) markers that play vital roles in recognitive and adhesive events. Certain leukocyte effectors show characteristics of natural killer (NK) cells that may act differently depending upon their source, whether autogeneic, allogeneic, xenogeneic, or expressed under normal or varying environmental conditions including exposure to xenobiotics. At the level of earthworm evolution, there is apparently a dissociation of phagocytosis from the process of killing by NK-like effectors. There are at least three future challenges. First, it is essential to determine the precise nature of the CD markers with respect to their molecular structure. Second, once their molecular and biochemical characteristics have been defined, the role of these markers in cellular and humoral mechanisms must be clarified in order to define effector cell products and resulting immune responses. Third, there is a need to differentiate between the several lytic factors that have been found in earthworms with respect to molecular structure, and biochemical and functional characterization.     

制造执行系统中基于状态的关键设备预防性维护研究

阐述了制造执行系统中基于状态的关键设备的预防性维护和车间作业计划管理。提出了多台关键设备预防性维护与车间作业计划管理的同步与协调模型。假设关键设备的失效概率服从威布尔分布,结合设备的失效时间估计及关键设备的预防性维护时间与车间作业计划决策,得出多台设备利用率最高的决策目标函数。     

A study on fault diagnosis and maintenance of CNC-WEDM based on binary relational analysis and expert system

The paper presents a binary relational analysis and expert system base module for maintenance and fault diagnosis of CNC wire EDM. The module proposes a framework of integrated maintenance and fault diagnosis system. The study explores the binary coded matrix system, which plays an important role in prediction and diagnosis of wire electrical discharge machining (WEDM) faults on the spot by expert guidance. In this study, 15 inputs were considered to observe eight probable causes with the help of the forward and backward propagation algorithms. Inputs and output matrices were considered in the form of a square matrix. To explain the fault diagnosis and to realize the importance of maintenance through advice, the detection of faults is investigated through forward and back propagation of matrix transformation on the spot. It is an integrated backup that can be individually focused when input and output parameter do not match. It is a time saving, knowledge acquisition, easy to maintain, and capable of self-learning system. To verify the developed framework, 120 data sets were generated for proper analyzing of acquired output through graphical representation. The paper also presents some of the important features of maintenance schedule and probable causes of wire breakage with remedial actions in tabular form. The developed system can help the operators, trainees, and manufacturing engineers in achieving trouble free machining through quick detection of faults and proper maintenance of machines in actual practice.     

A study on fault diagnosis and maintenance of CNC-WEDM based on binary relational analysis and expert system

The paper presents a binary relational analysis and expert system base module for maintenance and fault diagnosis of CNC wire EDM. The module proposes a framework of integrated maintenance and fault diagnosis system. The study explores the binary coded matrix system, which plays an important role in prediction and diagnosis of wire electrical discharge machining (WEDM) faults on the spot by expert guidance. In this study, 15 inputs were considered to observe eight probable causes with the help of the forward and backward propagation algorithms. Inputs and output matrices were considered in the form of a square matrix. To explain the fault diagnosis and to realize the importance of maintenance through advice, the detection of faults is investigated through forward and back propagation of matrix transformation on the spot. It is an integrated backup that can be individually focused when input and output parameter do not match. It is a time saving, knowledge acquisition, easy to maintain, and capable of self-learning system. To verify the developed framework, 120 data sets were generated for proper analyzing of acquired output through graphical representation. The paper also presents some of the important features of maintenance schedule and probable causes of wire breakage with remedial actions in tabular form. The developed system can help the operators, trainees, and manufacturing engineers in achieving trouble free machining through quick detection of faults and proper maintenance of machines in actual practice.     

Optimization of the number of clusters: a case study on multivariate quality control results of segment installation

When encountering too many records, each of which has several attributes, clustering of the data is an important issue on mining and classification. Recently many advances on clustering algorithms have been made such that clustering of data is done precisely and quickly. Clustering algorithms use optimization algorithms which simultaneously provide the number of clusters as default. These algorithms cluster the data so that those which belong to a cluster have maximum similarity and those in different clusters have minimum similarity. The k-means algorithm is a traditional algorithm for clustering problems. One of the most important difficulties of clustering algorithms is determining the number of clusters before starting the algorithm. In other words, by having knowledge on distribution of data, the number of clusters should be estimated and then imported to the problem as an input. In this paper, the data collected on quality control of mechanized tunneling are analyzed. They consist of measurements of 16 characteristics for 200 initial installed rings of segments on the tunnel walls inspected by the quality control team. A dynamic validity index is used and combined to the k-means algorithm for clustering the data so that the optimal number of clusters can be determined simultaneously. The application of the algorithm shows that the total installed rings can be clustered into four clusters. These four classes of quality can best describe the total installed rings on the tunnel in comparison of other number of classes (or clusters). Furthermore, this approach helps the quality team to determine the most effective or best performance executive team whom their installed rings have best class and minimum variations.     

采用Flexsim的生产系统建模与仿真研究

以生产线中一个典型的组成部分(两个机器一个暂存区)为例,介绍Petri网建模方法及其性能分析过程,将变迁实施时间为指数分布的Petri网模型转换成马尔科夫链(MC),得到了其性能指标的计算公式.由于Petri网模型理论计算复杂,提出了一种新的Petri网仿真方法,即利用Flexsim软件对Petri网模型进行仿真分析.通过与Geshwin[2]研究结果的比较,验证了此仿真分析方法的有效性.     

Model for production planning and control decisions at cell level: a case study

Many computer integrated manufacturing systems exist today. The full benefits of these systems have not yet been fully achieved, partly due to the bespoke or proprietary nature of the systems. Integrating such systems creates bigger islands of automation, but these islands soon become less beneficial. Companies having achieved this hardware integration, and some communication among software, often feel this to be the end of their integration. This would be so for the achievement of short-to-medium-term benefits, but for long-term reconfigurability of the system, information is necessary. A basis for such a reconfiguration is a generic model for Production Planning and Control (PP&C) systems. A generic model for PP&C systems at the cell level has been developed. The model has a Functional Model, an Information Model and a set of Generic Commands. It is intended that, although the model is application-independent, during model implementation it can be adapted for specific applications.     

A study on squeal noise reduction considering the pad shape of the disc brake system for urban railway vehicles

Journal of Mechanical Science and Technology - In this paper, to help reduce the squeal noise produced during the braking of urban railway vehicles, the shape of the disc brake pad was investigated...