Approach to the production environment design task within factory coordination

In a discrete parts batch manufacturing environment, there are different data flows concerning the design of products and manufacturing facilities, customer orders, purchase of materials, production control and delivery of orders. Traditionally, because of the functional allocation of tasks within an organization, there is little integration of information between the production control task and the design of manufacturing facilities. One of the objectives of the design of manufacturing facilities tasks is to efficiently organize a production environment to manufacture a range of products. With a greater relationship between these two tasks, we feel that the complexity of the production control task is reduced. This reduction in complexity arises from a reduction in the range of possible problems that can occur and an increase in the predictability of events through more effective organization of a production environment. Factory coordination is part of an approach to shopfloor control which recognizes this principle by establishing a relationship between the design of a production environment and the control of product flow throughout a factory. This relationship is established through a modular architecture for factory coordination. The production environment design element of the architecture for factory coordination is concentrated on. Using a methodology for describing systems, known as SADT, three main tasks associated with this approach are described; process planning, maintenance of a cellular layout, and manufacturing systems analysis.     

Integrating Flexible Process Plans with Scheduling in Flexible Manufacturing Systems

This paper highlights the importance of integration between process planning and scheduling in flexible manufacturing systems (FMS). An effective integration increases the potential for enhanced system performance and enhanced decision making A framework that integrates flexible process plans with off-line (predictive) scheduling in FMS is presented. The flexibility in process planning, including process flexibility, sequence flexibility, and alternative machine tools, is discussed. The proposed framework consists of four integrated stages with the objective of reducing the completion time. The integrated stages include: 1. Machine tool selection. 2. Process plan selection. 3. Scheduling. 4. Re-scheduling modules. In addition, the paper proposes a new approach, namely the Dissimilarity Maximisation Method (DMM), for selecting the appropriate process plans for a part mix where parts have alternative process plans. The recursive structure of the framework provides a different approach, namely overlapping schedules, which considers a longer scheduling period as comprising several short scheduling periods. Knowing that neither the process plans nor the planned (predicted) schedules are truly followed on the shop floor, the related literature and the corresponding approaches are compared in order to envisage new approaches for closing the gap between process planning and scheduling.     

The computer-aided design of modular fixturing systems

The flexibility of modular fixturing systems can be exploited to significantly enhance the productivity of computer integrated manufacturing facilities. A major impediment to the implementation of this philosophy is the absence of viable methodologies for the automated design and assembly of these fixturing systems. This paper addresses this technological void by proposing a CAD/CAM tool for the automated design and robotic assembly of modular fixturing systems which can form the basis for a fully automated design system. The development of automated flexible fixturing technologies that transcend the traditional time-consuming and expensive practice of manual assembly would significantly contribute to the evolution to the factory-of-the-future.     

Near optimal manufacturing flow controller design

Flow control of flexible manufacturing systems (FMSs) addresses an important real-time scheduling requirement of modern manufacturing facilities, which are prone to failures and other controllable or stochastic discrete events affecting production capacity, such as change of setup and maintenance scheduling. Flow controllers are useful both in the coordination of interconnected flexible manufacturing cells through distributed scheduling policies and in the hierarchical decomposition of the planning and scheduling problem of complex manufacturing systems. Optimal flow-control policies are hedging-point policies characterized by a generally intractable system of stochastic partial differential equations. This article proposes a near optimal controller whose design is computationally feasible for realistic-size systems. The design exploits a decomposition of the multiple-part-type problem to many analytically tractable one-part-type problems. The decomposition is achieved by replacing the polyhedra production capacity sets with inscribed hypercubes. Stationary marginal densities of state variables are computed iteratively for successive trial controller designs until the best inscribed hypercubes and the associated optimal hedging points are determined. Computational results are presented for an illustrative example of a failureprone FMS.     

模块化的可重构制造系统研究

随着市场经济全球化的发展,可重构制造系统必将成为未来制造系统发展的新趋势,而可重构制造系统这个概念的提出是源于模块化机床和开放式体系结构控制器两种技术的日臻成熟。在分析了可重构制造系统和刚性制造系统、柔性制造系统区别的基础上,针对可重构制造系统的模块化特点及划分原则进行了详细分析,并对可重构制造系统的关键技术进行了研究。     

Coloured adaptive structured petri-net a tool for the automatic synthesis of hierarchical control of flexible manufacturing systems

Based on the authors' last results concerning a methodological approach for the analysis and the synthesis of flexible cells in manufacturing, this paper presents some basic ideas on which the authors are currently working for the automatic design of hierarchical control of flexible manufacturing systems (FMS). The approach is based both on the use of coloured adaptive structured Petri-nets (in order to describe the scheduling of manufacturing tasks) and artificial intelligence concepts to design such a net and to describe metarules for the control strategy. The paper is in two parts.     

A methodology to define a reconfigurable system architecture for a compact heat exchanger assembly machine

Due to the unexpected, fast, and constant changes of market requirements and the hypercompetency, robust manufacturing systems are needed that adjust easily to operational variability and the customized product supply. The simply substitution of components, software, hardware, and/or their adaptation by parameters resetting are an attractive option to face this challenge. Short product life cycles are an undeniable consequence and evidence of this. For this reason, to develop products or services profitably in the product manufacturing field, it is common to use the product family concept, which involves sharing components, functional features, and manufacturing process, both to make a cheaper product development process and to obtain customized products. A new generation of manufacturing systems that deploy characteristics such as adaptability and flexibility responding to the market dynamics called reconfigurable manufacturing systems (RMS) are required by market according to manufacturing experts. The manufacturing systems with modular architecture are the best way to meet flexible and adaptable RMSs because they allow reconfiguration by a simple module substitution or by resetting module operation parameters. This paper presents a design methodology developed to obtain modular RMS. The method integrates the utilization of modular architecture principles, selection algorithms (analytical hierarchical process), clustering algorithms (average linkage clustering algorithm), family product features and functional system analysis in the classical product design process. The methodology proposed allows defining the most adequate modular system architecture and the modular definition of the reconfiguration variables that are needed to reach the flexibility required. A real study case about a heat exchanger assembly machine is presented where this methodology is applied in order to present an evidence of its usefulness.     

Dynamic control of flexible manufacturing systems

Flexible manufacturing systems (FMSs) are a relatively new technological and organisational approach to helping companies respond to real-time marketing conditions for their production. Under a proposal of the National Bureau of Standards the FMSs are subdivided into virtual manufacturing cells in a dynamic manner, on the basis of group technology.A method of dynamic optimisation for the design of manufacturing processes, capacity balancing and checking, and also production scheduling or rescheduling in virtual manufacturing cells is described. It can be used during real-time production control in FMSs.     

客户需求驱动的模块化产品配置设计

现代企业面临着用有限的生产成本为客户提供多品种、高质量产品的压力,合理地实施面向大规模定制的模块化产品配置设计方法是解决问题的关键。在模块化产品设计的基础上,以提高定制产品的性能与客户需求相关度最大为目标,建立了相应的优化数学模型;利用模拟退火算法得到了产品的性能和成本之间的平衡点--最优的变量配置方案:最后以波轮式洗衣机为验证实例,仿真结果及系统实现表明了提出方法的合理性和有效性,解决了ATO生产模式下的模块组合优化问题,为面向大规模定制的模块化产品配置设计理论提供了另一种实用工程数值计算方法。     

组合夹具计算机三维智能组装系统

将CAD和人工智能技术引入组合夹具设计中，可以提高生产效率、减轻劳动强度、缩短生产准备周期和加快产品上市时间。介绍了组合夹具计算机辅助设计的发展情况和研制的智能型组合夹具计算机辅助组装系统的结构及其功能，重点对系统中的智能模块做了阐述。     

MAS-based production scheduling system for manufacturing cell-based workshop

The task of production scheduling is to determine the detailed machining path, time, machine tool, etc., for every work piece, according to the production objective and constraints. It is also an important part of the manufacturing system. In this paper, the manufacturing cell-based workshop is described and its scheduling system structure is established based on MAS (multi-agent system) technology. Through the negotiation and communication of each agent, the machining path is determined and the machining sequence and start time are calculated by GA (genetics algorithm). The communication among agents uses the CORBA (common object request broker architecture) technology of the OMG (Object Management Group). The CORBA-based architecture of the communication is designed and some interfaces for the communication are listed. For the genetics algorithm, chromosome coding, fitness function, parameters selection, and the basic genetics operation including selection, crossover and aberrance, are described. The scheduling system also can deal with some abnormal conditions, such as machine tool failure and urgent tasks. Finally, two scheduling examples are given.     

Solving a multi-objective overlapping flow-shop scheduling

In flow-shop manufacturing scheduling systems, managers attempt to minimize makespan and manufacturing costs. Job overlaps are typically unavoidable in real-life applications as overlapping production shortens operation throughput times and reduces work-in-process inventories. This study presents an ant colony optimization (ACO) heuristic for establishing a simple and effective mechanism to solve the overlap manufacturing scheduling problem with various ready times and a sequentially dependent setup time. In the proposed approach, the scheduling mechanism and ACO heuristics are developed separately, thereby improving the performance of overlapping manufacturing flow by varying parameters or settings within the ACO heuristics and allowing for flexible application of manufacturing by altering scheduling criteria. Finally, the experimental results of the scheduling problem demonstrate that the ACO heuristics have good performance when searching for answers.     

Integration of process planning and scheduling in a job shop environment

Today’s manufacturing systems are striving for an integrated manufacturing environment. To achieve truly computer-integrated manufacturing systems (CIMS), the integration of process planning and production scheduling is essential. This paper proposes a framework for integration of process planning with production scheduling in a job shop environment for axisymmetric components. Based on the design specifications of incoming parts, feasible process plans are generated taking into account the real time shop floor status and availability of machine tools. The scheduling strategy prioritizes the machine tools based on cost considerations.     

A grid-based scheduling system of manufacturing resources for a virtual enterprise

In this paper, a scheduling system of manufacturing resources for a virtual enterprise is built up based on grid technology. The scheduling system is composed of an exterior grid and an interior grid in the architecture, while the scheduling procedure of manufacturing resources in a virtual enterprise consists of two stages – distributed scheduling and local scheduling. The exterior grid is utilized to implement the distributed scheduling and the interior grid is used to accomplish the local scheduling. This paper illustrates the manufacturing system of a virtual enterprise based on an exterior grid and the manufacturing subsystem of a member enterprise based on an interior grid. Subsequently, the scheduling procedure of manufacturing resources within the virtual enterprise is described for a particular example. Finally, a case of collaborative production of a customized artificial joint (CAJ) in a virtual enterprise is applied to demonstrate the implementation of the scheduling system of manufacturing resources for the virtual enterprise. With grid technology, the efficiency of manufacturing resource scheduling in the virtual enterprise has been improved greatly.     

Design of integrated manufacturing planning, scheduling and control systems: a new framework for automation

The automation and integration of manufacturing planning, scheduling and control functions have, for a long while, been targeted in computer-integrated manufacturing (CIM) and artificial intelligence (AI) approaches. Current systems, however, are human-based and they can only be characterised as decision support systems (DSS) rather than automated systems. Global competition and the need for improved responsiveness, particularly in low-volume, high-variety manufacturing industries, necessitate further integration and automation in planning, scheduling and control functions. We consider that, to achieve automation, the concepts and techniques from operations research (OR), control theory (CT), and computer science (CS) should be integrated, enriched and unified to provide a platform for automation. This paper presents a fresh perspective for understanding the design issues involved and proposes a new framework for the automation and integration of planning, scheduling and control functions. A fully automated flow shop production system is presented to illustrate the applicability of the new framework.     

DESIGN OF RECONFIGURABLE MANUFACTURING SYSTEMS WITH STRONGLY COUPLED NATURE

Today's manufacturing environment forces manufacturing companies to make as many product variations as possible at affordable costs within a short time. Mass customisation is one of most important technologies for companies to achieve their objectives. Efforts to mass customisation should be made on two aspects: ① To modularize products and make them as less differences as possible; ② To design manufacturing resources and make them provide as many processes variations as possible. This paper reports our recent work on aspect ②, i.e. how to design a reconfigurable manufacturing system (RMS) so that it can be competent to accomplish various processes optimally; Reconfigurable robot system (RRS) is taken as an example. RMS design involves architecture design and configuration design, and configuration design is further divided in design analysis and design synthesis. Axiomatic design theory (ADT) is applied to architecture design, the features and issues of RRS configuration design are discussed, automatic modelling method is developed for design analysis, and concurrent design methodology is presented for design synthesis.     

Reconfigurable modular automation systems for automotive power-train manufacture

This paper describes research towards the realization of reconfigurable modular automated machines and the associated engineering methods and tools necessary to support their lifecycle needs. UK-based research, in collaboration with the Ford Motor Company and several machine builders, has resulted in the development of full-scale prototype reconfigurable modular automation systems for both engine assembly and machining applications. The implementation of an assembly system is featured in this paper. An engineering environment and associated reconfigurable component-based control system architecture have been created aimed at supporting the lifecycle needs of a new generation of agile automated systems, i.e., providing reconfigurable, easily scalable automated machinery. This approach has the potential to fit within a wider collaborative automation strategy where manufacturing systems are implemented as a conglomerate of distributed, autonomous, and reusable units.     

企业制造系统敏捷化技术与可重配置制造的研究

对企业制造系统实施单元化改造 ,符合敏捷制造生产模式下企业的组织建设思想。采用可重配置的设备和单元控制系统 ,可以使制造单元具有敏捷性。提出采用模块化的设备和开放式数控系统 ,实现单元设备的可重配置的策略 ,给出了一种具有可重配置能力的单元控制系统体系结构。分析了可重配置制造这种新的生产制造模式的特点 ,指出了其关键使用技术。     

Optimization and implementation of cellular manufacturing system in a pump industry using three cell formation algorithms

In recent years cellular manufacturing has become an effective tool for improving productivity. Attainment of full benefits of cellular manufacturing depends firstly on the design of the machine cells and part families and secondly on the method of operation which take full advantages of cell properties. Inappropriate methods of loading and scheduling can even lead to the failure of cellular manufacturing systems (CMS), however efficiently the cell is designed. This paper examines three array-based clustering algorithms, namely rank order clustering (ROC), rank order clustering-2 (ROC2) and direct clustering analysis (DCA) for manufacturing cell formation, with a real-life example to demonstrate the effectiveness of various clustering algorithms. The machine cell formation methods considered in this comparative and evaluative study belongs to the cluster formation approach of solving the MCF problem. The most effective method is selected and used to build the cellular manufacturing system. The comparison and evaluation are performed using four published performance measures and compares the improvements with the existing conventional system and the cellular manufacturing system. The above algorithms were written in the C++ language on an Intel/Pentium III-PC-compatible system.