Flexible and reconfigurable manufacturing systems paradigms

Reconfigurable Manufacturing System (RMS) is a new manufacturing systems paradigm that aims at achieving cost-effective and rapid system changes, as needed and when needed, by incorporating principles of modularity, integrability, flexibility, scalability, convertibility, and diagnosability. RMS promises customized flexibility on demand in a short time, while Flexible Manufacturing Systems (FMSs) provides generalized flexibility designed for the anticipated variations and built-in a priori. The characteristics of the two paradigms are outlined and compared. The concept of manufacturing system life cycle is presented. The main types of flexibility in manufacturing systems are discussed and contrasted with the various reconfiguration aspects including hard (physical) and soft (logical) reconfiguration. The types of changeability and transformability of manufacturing systems, their components as well as factories, are presented along with their enablers and compared with flexibility and reconfigurability. The importance of having harmonized human-machine manufacturing systems is highlighted and the role of people in the various manufacturing paradigms and how this varies in pursuit of productivity are illustrated. Finally, the industrial and research challenges presented by these manufacturing paradigms are discussed.     

可重构单元模块化及其结合面动特性的研究

通过对可重构制造系统(RMS)关键技术的研究，分析讨论了单元模块化对RMS的重要意义，指出了模块化设计在具体实现过程中存在的问题。给出了可重构制造单元模块的定义以及阐明了最小运动模块的具体划分。为管理、配置模块，给出了模块的组合数学模型，这有助于模块分类、排列以及组合。根据模块组合数学模型，总结出可重构单元模块接口即结合面的特点。运用分形技术，对模块结合面接触刚度的研究，得到了重构后结合面表面粗糙度与分形维数的关系原型以及接触刚度，为研究模块重构后形成的装备的动态特性、精度以及可靠性奠定基础。     

基于智能聚类算法的产品粒度确定方法

通过分析当前的聚类算法在产品模块划分过程中普遍存在的局限性,结合产品配置的特点,对模糊C均值算法所构建的具有片面性的目标函数和爬山法寻优模式的缺点进行了改进,并用于产品的模块化结构规划。提出了一种利用演化细胞学习自动机与改进后的模糊C均值聚类算法相结合的智能聚类算法进行产品粒度划分。在分析影响配置设计主要因素的基础上,建立需求满意度、装配复杂度和变型设计复杂度等三个量化指标,对不同粒度层次下模块划分结果的合理性与有效性进行评价,进而确定出最佳的粒度大小和模块数量。最后,通过实例验证说明了所提方法的可行性。     

Effect of reconfiguration costs on planning for capacity scalability in reconfigurable manufacturing systems

In a globally competitive market for products, manufacturers are faced with an increasing need to improve their flexibility, reliability, and responsiveness to meet the demands of their customers. Reconfigurable manufacturing systems (RMS) have become an important manufacturing paradigm, because they broadly encompass the ability to react efficiently to this environment by providing the exact capacity and functionality needed when needed. This paper studies how such new systems can manage their capacity scalability planning in a cost effective manner. An approach for modeling capacity scalability planning is proposed. The development of the model is based on set theory and the regeneration point theorem which is mapped to the reconfigurable manufacturing paradigm as the capacity scalability points of that system. The cost function of the model incorporates both the physical capacity cost based on capacity size and costs associated with the reconfiguration process which referred to as the scalability penalty cost and scalability effort cost. A dynamic programming (DP) approach is manipulated for the development of optimal capacity scalability plans. The effect of the reconfiguration costs on the capacity scalability planning horizon and overall cost is investigated. The results showed the relation between deciding on the optimal capacity scalability planning horizon and the different reconfiguration costs. Results also highlighted the fact that decreasing costs of reconfiguration will lead to cost effective implementation of reconfigurable manufacturing systems.     

基于图论的可重构制造系统重构策略

可重构制造系统(RMS)是针对零件族设计的既具有定制的柔性,又具有高生产率的制造系统。RMS通过重构来适应市场需求的变化。RMS的设计目标是基于重构条件下寻求制造系统在全生产周期内的系统成本最优。首先建立RMS的各生产周期成本模型、重构成本模型与全生产周期成本模型,构建RMS在各生产周期的组态有向图,利用Dijkstra算法与双向扫视算法求得RMS在各生产周期的最优成本组态与K-1个次优成本组态。根据所求得各生产周期的最优成本组态与K-1个次优成本组态,重构成本模型与全生产周期成本模型,计算上下生产周期各组态间的重构成本,并构建RMS全生产周期的重构策略有向图,再次利用Dijkstra算法与双向扫视算法求得 RMS全生产周期的最优重构策略与K-1个次优重构策略。最后用实例验证了方法的有效性与可行性。     

Investigating optimal capacity scalability scheduling in a reconfigurable manufacturing system

Responsiveness to dynamic market changes in a cost-effective manner is becoming a key success factor for any manufacturing system in today’s global economy. Reconfigurable manufacturing systems (RMSs) have been introduced to react quickly and effectively to such competitive market demands through modular and scalable design of the manufacturing system on the system level, as well as on the machine components’ level. This paper investigates how RMSs can manage their capacity scalability on the system level in a cost-effective manner. An approach for modeling capacity scalability is proposed, which, unlike earlier approaches, does not assume that the capacity scalability is simply a function of fixed increments of capacity units. Based on the model, a computer tool that utilizes a genetic algorithm optimization technique is developed. The tool aids the systems’ designers in deciding when to reconfigure the system in order to scale the capacity and by how much to scale it in order to meet the market demand in a cost-effective way. The results showed that, in terms of cost, the optimal capacity scalability schedules in an RMS are superior to both the exact demand capacity scalability approach and the approach of supplying all required capacity at the beginning of the planning period, which is adopted by flexible manufacturing systems (FMSs). The results also suggest that the cost-effective implementation of an RMS can be realized through decreasing the cost of reconfiguration of these new systems.     

A methodology for facilitating reconfiguration in manufacturing: the move towards reconfigurable manufacturing systems

The launch of new products to the market is essential for companies in order to remain competitive. Products are constantly being replaced for others that fulfil the changing requirements of the customers. For achieving this, companies have to adapt their production system to the new requirements of the new products by adding or removing machines, changing the lay-out, etc. Normally, this reconfiguration implies a high investment. Reconfigurable manufacturing systems (RMSs) arise for facilitating the reconfiguration of the production system, being considered as the next step in manufacturing. This paper deals with the development of a methodology based on RMSs that allows a feasible reconfiguration of production systems. This methodology is based on the ALCA algorithm from group technology, and takes into account five requirements of products on RMSs: modularity, commonality, compatibility, reusability and demand. The selection of the product families is obtained with a mathematical model specifically formulated for this purpose.     

面向产品族的制造单元聚类规划研究

为了支持用户的个性化需求 ,在分析产品族的模块化结构及其零部件构成比例等特点的基础上 ,提出了支持生产线布局规划的面向产品族的制造单元聚类规划方法 ,给出了聚类规划过程、聚类规划算法描述 ,并进行了应用分析。构建了零部件与工艺路线间的关联量化矩阵。利用聚类规划方法 ,获得了零部件的聚集分类及相关的聚集工艺需求、与零部件聚集相对应的制造单元的加工需求能力分配比例指标和制造单元间的交流等信息。最后在企业制造资源和工艺环节映射关系的支持下 ,形成了面向产品族的基于制造单元的生产线布局规划方法。本研究为企业的大规模定制生产模式下生产系统的规划提供了可行的思路     

敏捷制造链的快速构造与运行控制策略

针对未来产品异地设计、加工、装配等制造全过程中的组织、管理、信息、决策与控制方式,提出了一种基于Internet、采用具有多智能体机制的敏捷制造快速构造与运行控制的技术体系与总体方案,探索了有关异地制造过程中技术信息交换平台、制造链统一建模、资源配置、多边协商、异地监控等技术路线与关键技术,该方案在充分考虑我国现有国情的基础上,突出了系统性、可操作性与实用性。     

Production planning and performance optimization of reconfigurable manufacturing systems using genetic algorithm

To stay competitive in the new dynamic market having large fluctuations in product demand, manufacturing companies must use systems that not only produce their goods with high productivity but also allow for rapid response to market changes. Reconfigurable manufacturing system (RMS) is a new paradigm that enables manufacturing systems to respond quickly and cost effectively to market demand. In other words, RMS is a system designed from the outset, for rapid changes in both hardware and software components, in order to quickly adjust its production capacity to fluctuations in market demand and adapt its functionality to new products. The effectiveness of an RMS depends on implementing its key characteristics and capabilities in the design as well as utilization stage. This paper focuses on the utilization stage of an RMS and introduces a methodology to effectively adjust scalable production capacities and the system functionalities to market demands. It is supposed that arrival orders of product families follow the Poisson distribution. The orders are lost if they are not met immediately. Considering these assumptions, a mixed integer nonlinear programming model is developed to determine optimum sequence of production tasks, corresponding configurations, and batch sizes. A genetic algorithm-based procedure is used to solve the model. The model is also applied to make decision on how to improve the performance of an RMS. Since there is no practical RMS, a numerical example is used to validate the results of the proposed model and its solution procedure.     

Capacity reconfiguration management in reconfigurable manufacturing systems

During a manufacturing operation, exceptions may occur dynamically and unpredictably. Their occurrence may lead to the degradation of system performance or, in the worst case scenario, may interrupt the production process. The research proposes a multi-agent architecture for the capacity reconfiguration problem in a reconfigurable manufacturing system (RMS). A policy to manage capacity exchange among manufacturing lines based on due date performance is proposed. The Multi-Agent architecture was built in a simulation environment developed in ARENA^® package and it is compared with a dedicated manufacturing and flexible manufacturing systems. The simulations are conducted in several demand scenarios to test the approach in a static and dynamic context. The simulation environment developed can support the planner to decide among the different manufacturing systems by the evaluation of the manufacturing performance. The simulation results, in dynamic environment, showed that the proposed approach leads to similar performance to flexible manufacturing system.     

基于 CPS 的可重构制造系统在互联工厂的应用

为了解决个性化定制与大规模生产的矛盾,应用 CPS 技术和模块化制造单元,建立了完整的可重构制造系统,实现大规模个性化定制产品生产流程的高效协同。在研究了面向大规模个性化定制可重构系统特性的基础上,构建了基于 CPS 的可重构制造系统架构,研究了可重构系统的关键核心技术。建立的系统可以将生产制造的复杂行为转换为实际数据信息,通过重构分析、智能决策和动态优化调整模块化制造单元,使整个生产环节的制造资源处于有序可控状态。通过在互联工厂展开应用落地验证,结果表明了该系统的可行性和有效性。     

可重组制造系统

可重组制造系统是一种能够快速响应新的生产环境的新型制造系统，在快速响应市场变化和个性化生产方面具有重要的意义。阐述了可重组制造系统的发展历史、概念、分类、重组特性及其特点，评述了目前可重组制造系统的研究现状，讨论了可重组制造系统的关键技术，并提出了可重组制造系统应用研究的发展方向。     

A Schema for Flexile Equipment Control in Manufacturing Systems

In this work a methodology is proposed for increasing the flexibility of the control software of Flexible Manufacturing Systems (FMSs). This greater flexibility is required due to factors such as uncertain product demand, uneven distribution of shop load, and machine or cutting tool unavailability. In the proposed framework the following modules were developed: (a) an automated process planning module which generates non-linear process plans for a given part, considering the shop floor resource availability; the non-linear plans include both material handling and material processing information; (b) a planning module that linearises the process plan aiming at minimising the total manufacturing time of the parts; (c) a NC program generation module, which generates the NC program for the chosen CNC machine(s). In order to increase the flexibility of the control software even more, a resource model was devised and implemented, which provides the necessary resource information for the above modules. Each of these modules is described within this paper, and details about the part and process plan representation necessary for this implementation are also given. A case study is presented in order to show the capability of the methodology.     

A systematic approach for green design in modular product development

In response to the changing market trend of having large varieties within a small production, green design and modular design have assumed significant roles in the product development process. This research applied quality function deployment (QFD) to achieve the goal of analyzing customers' needs. It also applied design structure matrix (DSM) based on the modular concept to group different design parts together to obtain optimized module efficiency. A balance between product development and ecological (ECO) friendliness can be achieved in advance if green QFD (GQFD) and DSM were introduced during the early design and manufacturing stages. Furthermore, using the result of GQFD, we proposed the analysis of DSM to find the result of coupled tasks. A pairwise comparative algorithm and loop analysis algorithm in DSM were utilized to decrease the number of module groups and find the most suitable clustering approach for further green design consideration. In this research, an electronic translator was used as a case study for the integration of green design with modularity. The main goal of this paper is to sort the importance weight values for green consideration by QFD during product development. These results can then be applied to finish modular grouping by DSM for subsequent green assembly and disassembly considerations of the products.     

可重构制造系统工艺路线与系统布局设计研究

为使可重构制造系统的重构过程更加快速有效,提出了一种工艺路线和系统布局设计的方法.首先,基于图论构建了可重构制造系统工艺路线的有向网络模型,并采用Dijkstra算法和双向扫视算法,进行最优工艺路线和备选工艺路线的选择;然后,以工艺路线为基础,依据排队论中的相关理论,对制造系统的布局进行优化设计,以获得可重构制造系统布局方案.实例表明,该设计能够适应可重构制造系统快速多变的特征,提高对制造系统已有资源的利用率.     

A task-oriented modular and agent-based collaborative design mechanism for distributed product development

The rapid expansion of enterprises makes product collaborative design （PCD） a critical issue under the distributed heterogeneous environment, but as the collaborative task of large-scale network becomes more complicated, neither unified task decomposition and allocation methodology nor Agent-based network management platform can satisfy the increasing demands. In this paper, to meet requirements of PCD for distributed product development, a collaborative design mechanism based on the thought of modularity and the Agent technology is presented. First, the top-down 4-tier process model based on task-oriented modular and Agent is constructed for PCD after analyzing the mapping relationships between requirements and functions in the collaborative design. Second, on basis of sub-task decomposition for PCD based on a mixed method, the mathematic model of task-oriented modular based on multi-objective optimization is established to maximize the module cohesion degree and minimize the module coupling degree, while considering the module executable degree as a restriction. The mathematic model is optimized and simulated by the modified PSO, and the decomposed modules are obtained. Finally, the Agent structure model for collaborative design is put forward, and the optimism matching Agents are selected by using similarity algorithm to implement different task-modules by the integrated reasoning and decision-making mechanism with the behavioral model of collaborative design Agents. With the results of experimental studies for automobile collaborative design, the feasibility and efficiency of this methodology of task-oriented modular and Agent-based collaborative design in the distributed heterogeneous environment are verified. On this basis, an integrative automobile collaborative R＆D platform is developed. This research provides an effective platform for automobile manufacturing enterprises to achieve PCD, and helps to promote product numeralization collaborative R＆D and management development.     

Development of a computer numerical control (CNC) modular fixture — Machine design of a standard multifinger module

This paper presents the first phase of our ongoing development of a computer numerical control (CNC) modular fixture involving the machine design of a standard multifinger module. The aim is to develop a modular fixture which consists of only one type of standard multifinger CNC module which can provide locating, supporting and clamping functions. The module consists of four fingers with eight degrees of freedom to conform to any arbitrary workpiece surfaces. The eight motions of the four fingers are controlled by one motor through the use of two transmission and clutch systems. Different fixture layouts or reconfigurations can be made by different combinations of a multiplicity of such modules for major product family changes; while adjustments to finger positions of individual modules can be made by direct computer numerical control for minor product changes within a product family. The machine design and operation of the module are presented in the paper. A prototype was built and tested and satisfactory performance was achieved. Finally, two examples are provided to illustrate the flexibility and use of the standard multifinger module.     

Improved net rewriting system-based approach to model reconfiguration of reconfigurable manufacturing systems

This work aims at presenting a method for rapidly reconfiguring Petri net (PN) models of reconfigurable manufacturing systems (RMS). We start with introducing the model of improved net rewriting systems (INRS), which supports dynamic structural changes in a PN model without losing its important behavioral properties, i.e., liveness, boundedness (or safeness), and reversibility. Based on INRS, the method for rapid reconfiguration of Petri net models for RMS is proposed and an implementation algorithm is designed as well. In our method, changes in a RMS configuration adjusted with production demands can be rapidly formalized into graph rewriting rules of an INRS called model reconfigurator whose underlying Petri net is the existing Petri net model. Subsequently, by applying these rewriting rules, the existing Petri net model can be reconfigured rapidly into a new one for the RMS with a new configuration. Validity of the resulting Petri net model can be guaranteed naturally throughout the whole reconfiguration process and thereby there is no need for verification. A case study is provided that demonstrates the reconfiguration process of a Petri net model for a reconfigurable manufacturing cell. The given case study shows that the proposed method is capable for reconfiguring PN models of RMS in a rapid and successive manner, without requiring verification.     

基于扩展随机Petri网的可重组制造系统建模与分析方法

可重组制造系统(Reconfigurable manufacturing system,RMS)可根据市场变化进行组态调整和组元升级,系统的建模与分析方法必须能适应上述特点。提出基于扩展随机Petri网(Extended stochastic Petri nets,ESPN)的模块化建模方法,将RMS不同的加工资源对应于相应的ESPN基本模块,并通过过渡变迁合成ESPN模型,该模型能适应任意分布的制造系统,可更加精确地反映生产过程。在此基础上采用基于行为表达式的分析方法,得到系统性能指标,该分析方法可不必画出可达图而直接得到系统性能关系函数,使分析过程更加直观、简洁。可重组电动机生产线的实例证明了该建模与分析方法的有效性。