Real-Time Manipulation of Alternative Routeings in Flexible Manufacturing Systems: A Simulation Study

This paper presents the results of a simulation study of a typical flexible manufacturing system (FMS) that has routeing flexibility. The objective is this study is to test the effectiveness of the dissimilarity maximisation method (DMM) for real-time FMS scheduling. DMM is an alternative process plan selection method developed for routeing selection in off-line FMS sched-uling. An integrated framework that consists of a computer simulation model, which mimics a physical system, a C++ module, and a linear program solver is used to evaluate the effects of various operational control rules on the system performance. The hypothetical FMS employed in this study consists of seven machining centres, a loading and an unloading area, and six different part types. Owing to the existence of identical machining centres in the system, the part types have alternative routeings. For selecting an incoming part and later routeing it to a machining centre for its next operation, three control rules, namely, first-in first-out/first available (FIFO/FA), equal probability loading (EPL), and dissimilarity maximisation method/first-in first-out (DMM/ FIFO) are used. In this study, DMM is 1. Used as a real-time decision-making tool to select routeings for the parts that are in the system. 2. Tested and benchmarked against FIFO/FA and EPL. The results show that DMM/FIFO outperforms FIFO/FA and EPL on system throughput. Other measures such as average waiting time, average transportation time, and percentage utilisation rates are also investigated to provide insights for the effectiveness of the DMM rule for real-time FMS control applications.     

FMS调度与控制的统一建模与集成设计

分析了FMS调度与控制统一建模与集成设计的必要性，从FMS运行过程的IDEF0功能建模入手，建立了基于模块化彩色赋时Petri网（CTPN）的FMS调度与控制的统一模型。该模型不仅可描述FMS的调度问题，而且能表达FMS的运行控制逻辑与仿真，从而为FMS控制系统的集成设计奠定了基础。为简化FMS控制系统的设计，提出了虚拟工作站的概念与方法，将FMS控制器的部分控制功能下放到低层的工作站控制层。基于上述CTPN统一模型，开发了FMS调度与控制的集成设计原理和方法。     

A Dynamic Tool Requirement Planning Model for Flexible Manufacturing Systems

Despite their strategic potential, tool management issues in flexible manufacturing systems (FMSs) have received little attention in the literature. Nonavailability of tools in FMSs cuts at the very root of the strategic goals for which such systems are designed. Specifically, the capability of FMSs to economically produce customized products (flexibility of scope) in varying batch sizes (flexibility of volume) and delivering them on an accelerated schedule (market response time) is seriously hampered when required tools are not available at the time needed. On the other hand, excess inventory of tools in such systems represents a significant cost due to the expensive nature of FMS tool inventory. This article constructs a dynamic tool requirement planning (DTRP) model for an FMS tool planning operation that allows dynamic determination of the optimal tool replenishments at the beginning of each arbitrary, managerially convenient, discrete time period. The analysis presented in the article consists of two distinct phases: In the first phase, tool demand distributions are obtained using information from manufacturing production plans (such as master production schedule (MPS) and material requirement plans (MRP)) and general tool life distributions fitted on actual time-to-failure data. Significant computational reductions are obtained if the tool failure data follow a Weibull or Gamma distribution. In the second phase, results from classical dynamic inventory models are modified to obtain optimal tool replenishment policies that permit compliance with such FMS-specific constraints as limited tool storage capacity and part/tool service levels. An implementation plan is included.     

An Intelligent Decision Support System for Part Launching in a Flexible Manufacturing System

The effective control of flexible manufacturing systems (FMS) poses a major challenge to designers and the research community. In this paper, the framework of a unique decision support system to assist in the control of a FMS through intelligent part-launching is introduced. The proposed system makes usr of a new heuristic method based on the pull concept, and a neural network trained with data from a system simulation model, which in turn provides a desision about choosing a part to be launched into the FMS. The performance of the proposed heuristic method was tested against another popular heuristic method normally used in existing FMS via discrete event simulation models. Data sets from the simulation program of the proposed system were used to train the neural network, which can be used on the shop floor for realtime decision support. The output from the trained neural network is based on the same principle as the proposed heuristic method used in the simulation program. Therefore, the descision support provided by the neural network can be used for improved shop floor control.     

精益生产在某涂装设备车间的应用

运用精益生产理论与方法对某起重机生产企业的涂装车间进行规划研究。在对该企业涂装车间现状及存在的问题进行分析的基础上,对现有的生产线平衡、喷漆工艺路线进行了一系列的改善。对企业实施精益生产后的结果进行了系统分析,对提高企业技术水平和适应当前的市场竞争有较强的指导意义。     

Integrated Manufacturing System for Precision Press Tooling

The press tooling industry, characterised by many small-scale job-shops, is facing an increasingly competitive global market. This comes at a time when there is a shortage of experienced process planners and unavailability of affordable CAD/CAM systems that could provide an integrated solution for manufacturing sheet metal tooling. Many commercially available CAD/CAM systems are either too expensive or too narrow in scope, in the sense that they provide only point solutions. The design of press tools and its manufacturing functions are highly specialised and knowledge-intensive in nature. This paper presents a framework and the implementation details of an integrated system that has been developed for a local sheet metal tooling company specialising in precision punches and dies. A PC-based system has been implemented on an AutoCAD platform using the Autolisp programming language.     

Optimal configuration selection for Reconfigurable Manufacturing Systems

The selection of Reconfigurable Manufacturing Systems (RMS) configurations that include arrangement of machines, equipment selection, and assignment of operations, has a significant impact on their performance. This paper reviews the relevant literature and highlights the gaps that exist in this area of research. A novel “RMS Configuration Selection Approach” is introduced. It consists of two phases; the first deals with the selection of the near-optimal alternative configurations for each possible demand scenario over the considered configuration periods. It uses a constraint satisfaction procedure and powerful meta-heuristics, real-coded Genetic Algorithms (GAs) and Tabu Search (TS), for the continuous optimization of capital cost and system availability. The second phase utilizes integer-coded GAs and TS to determine the alternatives, from those produced in the first phase, that would optimize the degree of transition smoothness over the planning horizon. It uses a stochastic model of the level of reconfiguration smoothness (RS) across all the configuration periods in the planning horizon according to the anticipated demand scenarios. This model is based on a RS metric and a reconfiguration planning procedure that guide the development of execution plans for reconfiguration. The developed approach is demonstrated and validated using a case study. It was shown that it is possible to provide the manufacturing capacity and functionality needed when needed while minimizing the reconfiguration effort. The proposed approach can provide decision support for management in selecting RMS configurations at the beginning of each configuration period.

现代制造系统控制研究发展

制造系统控制是制造系统研究的重点之一,对提高制造系统自动化和智能化水平有重要作用。综述了控制结构、控制模型和调度方法的研究内容、现状和发展趋势,指出了协调分布自组织控制结构、基于多Agent的Petri网控制决策模型和基于多Agent的软计算调度算法是今后制造系统控制研究的重点。     

A cost-based algorithm for design of Cellular Manufacturing Systems

This paper describes a cost-based algorithm that deals with the design problems of Cellular Manufacturing Systems (CMS) associated exceptional parts and bottleneck machines. The developed algorithm employes explicitly the main elements of manufacturing costs, such as the fixed machine cost, the production cost, the setup cost, and the material handling cost. The algorithm is based on the minimization of sum of these costs, and considers three alternatives to solve exceptional issues. The first alternative is to try to eliminate the maximum number of intercellular movements from the presently configured manufacturing system by buying and installing extra bottleneck machines into the appropriate cells. The second alternative considers the alternative process plans available and tries to complete the job using the overtime basis in the small machine cells. The third alternative considers the possibility of subcontracting the processing operations of exceptional part(s) to outside vendors to reduce the overall cost for the manufacturing system. The total costs of the three cases are compared and the best alternative for any given problem is identified. In order to illustrate performance of the algorithm developed, a test example is provided.     

三牙轮钻头牙掌生产用FMS数控程序设计及质量控制

通过牙掌结构特征分析，编程方法的选择，提出ＦＭＳ最佳数控程序结构。结合加Ｌ误差分析，指出严格控制各项静态误差，保存各项动态误差，是确保ＦＭＳ产品质量，实现柔性生产的基本条件。     

基于竞争机制的FMS分布式控制系统

分析比较ＦＭＳ的计算机监控系统不同结构形式的特点,重点研究分布式控制系统在ＦＭＳ中的应用及存在的主要问题,提出引入“竞争机制”的方法来改善分布式系统整体性能的思想,并举例简要介绍有关竞争规划及算法的建立。     

An Object-Oriented Approach for Flexible Manufacturing Control Systems Analysis and Design Using the Unified Modeling Language

In reacting to global competition and rapidly changing customer demands, industrial business organizations have developed a strong interest in flexible automation. The aim of flexible automation focuses on achieving agility in handling uncertainties from internal or external environments. Modeling complex structures, promoting reuse, and shortening the development time cycle are particularly significant aspects in the analysis and design of CIM systems, where heterogeneous elements have to be integrated in a complex control architecture. The design methodology for FMS control software involves the abstraction of an FMS and the estimation of the system performances. The aim of this activity is to suggest the optimal configuration of an FMS for given specifications, through simulation tools. In the software engineering field, object-oriented (OO) approaches have proven to be a powerful technique with respect to such aspects. The unified modeling language (UML), by using OO design methodologies, can offer reusability, extendibility, and modifiability in software design. Also, it bridges the gap that exists between the OO analysis and design area and the area of OO programming by creating an integrative metamodel of OO concepts. The specific goal of this paper is to formulate a new methodology for developing reusable, extendible, and modifiable control software for an FMS in an object-oriented environment. It is demonstrated that, with few diagrams, UML can be used to model such systems without being associated with other modeling tools.     

制造业信息技术应用之间的协同效应分析方法

应用信息技术是企业提高其竞争能力的重要手段之一。企业实施的各种信息技术应用通过信息集成组成企业的信息技术应用组合系统 ,各子系统相互配合而产生协同效应 ,使得系统总体功能可以大于各子系统功能之和。协同效应分析对于信息技术应用的可行性分析和企业信息技术应用水平的正确评价具有重要意义。本文给出的协同效应分析方法以计算机排样为例 ,首先通过信息技术应用的功能原理分析绘制待考察的应用与其它各种信息技术应用之间的数据流表 ,然后根据信息流表对协同系数进行估计 ,根据协同系数计算该信息技术的权数。最后说明了协同效应分析方法的应用价值。     

A Graph Representation Scheme for Process Planning of Machined Parts

A new generic graph representation scheme for process planning is presented. It has been specifically developed to facilitate the planning and control of geometric dimensions and tolerances. Relationships between cut, location, and datum surfaces and machining operations are represented by a graph consisting of connected boxes. A box is a multi-terminal node that corresponds to a machine set-up. Machining operations are depicted as arrows inside the box. These connect input nodes, representing datum and location surfaces, to output nodes, representing machined surfaces. External connectors join boxes together to form a directed graph. The main purpose of these connectors is to indicate the surfaces (from prior set-ups) that are used as location and datum surfaces for later set-ups. The representation covers cutting operations and non-cutting operations, such as surface finishes and coatings. The paper concludes with an example that illustrates the application and power of the scheme.     

Image Processing Applied to Brick Quality Control

The results from an investigation into the feasibility of using image processing in the quality control system at a particular brickworks is reported. Methods were developed that allowed the identification and measurement of cracks and surface inden-tations and protrusions, and the measurement of the area of uniform pink on the surface of the particular brick type considered. It is concluded that the methods used could be developed relatively easily into a commercial real-time quality control system, which could result in considerable cost savings. It is also concluded that quality control measurements additional to those considered could easily be incorporated into such a system.     

Towards an Integration of Process Planning and Production Planning and Control for Flexible Manufacturing Systems

This introduction article attempts to present some major issues relating to the integration of process planning and production planning and control (PPC) for flexible manufacturing systems (FMSs). It shows that the performance of an FMS can be significantly improved and FMS capabilities more effectively utilized by integrating process planning and PPC functions. The various types of flexibility to be planned and provided for in process planning and manufacturing are summarized in the article, as well as emerging conceptual frameworks for integration, along with their implementation requirements and problems. Distinctive elements that differentiate these frameworks, such as the extent of integration of process planning and PPC activities, number of alternative process plans, and the time at which numerical control programs are generated, are discussed, followed by a brief summary of the articles compiled for this special issue.     

Modelling and Simulation of Integrated Operations and Information Systems in Manufacturing

This paper presents a novel method to determine the relative impact on logical interactions and interrelationships between operations and information systems within a manufacturing environment by formulating an integrated model, in which both operational function and information processing function are modelled and simulated to predict system behaviour and to obtain an optimal solution that maximises system performances. To achieve this, modelling and simulation of a flexible printed circuit board assembly (PCBA) system has been implemented. The research has shown that applying this approach is valuable for analysing a wide range of manufacturing systems (CIM, FMS, dynamic process control systems, etc.).     

汽车装备制造企业产品管理研究

介绍了汽车装备制造企业生产现状,从生产、产品复杂多样性及产品创新等方面论述了汽车装备制造企业进行产品管理的重要性,从提高项目管理水平、建设制度化与标准化管理体系、建立任职资格与薪酬激励体系等方面分析了汽车装备制造企业提高产品管理水平的措施.     

虚拟环境下制造设备模型建立方法的研究

制造设备模型的数字化是构成虚拟环境的关键 ,根据物理设备的结构与功能特征 ,对物理设备进行了层次化、模块化分解 ,分析了虚拟设备行为控制的方法 ,提出了能够表达物理设备功能特性及其形状特性的虚拟设备模型 ,利用面向对象的建模方法实现了虚拟设备模型     

A Part Scheme in Single-Stage Multimachine Systems

In current manufacturing environments, manufacturing orders are often characterised by unstable market demand, short product life cycles, carieties of products, and shory production lead times. In order to fulfil such manufacturing orders, a recent trend in flexible manufacturing systems (FMS) is to use versatile machines with fast tool delivery devices. In contrast to a conventional FMS that mainly focuses on part flows, tool flow control is important in single-stage multimachine systems (SSMS), which consist of versatile machines and fast tool delivery devices. This study proposes a part release scheme for SSMS, which considers the projected tool competition at the part release stage. This scheme can be applied to a real environment to improve system performance. The effectiveness of the scheme is demonstrated through a series of simulation experiments. Interpretations of the results are also presented.