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 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.     

可重构制造系统研究与发展

在竞争日益激烈的环境下，制造企业必须能够快速地响应市场需求的变化，可重构制造系统可以达到这一目的。本文从可重构制造系统的定义和特点、可重构制造系统与现有制造系统的对比、可重构制造系统研究的现状等方面综述了可重构制造系统研究的进展。     

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。     

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.     

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.     

面向多品种变批量的可重构制造系统的设计方法研究

可重构制造系统的设计目标是要确定各种零件的生产周期、各种零件之间的生产顺序与加工各种零件所用的组态。建立了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。由各种零件的批量确定加工各种零件的标准生产周期，分析系统成本冗余，得到了多组偏差生产周期，求出了各种生产周期下各种零件之间所有生产排序的K-优组态路径。通过比较所求得的组态路径，可以获得一条最优与多条次优组态路径。用案例验证了所提出的方法。     

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.     

An adaptive agile manufacturing control infrastructure based on TOPNs-CS modelling

In this paper, an infrastructure for adaptive production control in an agile manufacturing environment is proposed. With this infrastructure, Virtual Production Systems (VPSs), each of which takes care of the production of a specific customer ordered product, can be dynamically and flexibly constructed. This can be achieved logically by product workflow and physically by the resources in one or more manufacturing systems, e.g. job shops. To respond to changes and disturbances to a VPS, architecture for the adaptive controller of a VPS is designed based on adaptive control principles and Temporised Object-Oriented Petri Nets with Changeable Structure (OPNs-CS) modelling. A case study is used in this paper to illustrate how adaptive production control of VPS functions can be conducted to cope with changes and disturbances to the production system.     

可重构制造系统创新软件的研究

对可重构制造系统的几个典型软件系统进行了研究,包括制造系统性能分析、系统资源的管理分配、经济模型的寿命周期、可重构机器设计程序、生产量管理、工厂范围的可重构控制,讨论了这些软件的应用情况和发展趋势。     

Development of reconfigurable machines

This paper summarizes our survey on the development of reconfigurable machines (RMs). The goals of this survey were to (i) clarify the needs and drivers to develop the RMs, (ii) define the academic and practical issues involved in the development of RMs, (iii) learn the state of the art of the R&D on design methodologies of the RMs, and (iv) identify future research directions, which benefit the manufacturing industries in short and long terms. The survey has concluded that reconfigurable manufacturing systems (RMSs) are advantageous in dealing with changes and uncertainties in the ever-changing environment; while RMs are essential components to implement an RMS. RMs should be designed to meet a variety of task requirements via its reconfigurability. It has been found that few existing RMs can achieve this objective. The survey has concluded that the obstacles of the development of RMs include (i) the difficulties to identify and generalize design requirements since an RM is application-oriented and the design requirements have to be defined from an actual application; and in fact, some requirements are very difficult to be quantified; (ii) the lacking of efficient automated robot programming tools despite that the robots are essential components for most of the RMs; (iii) the lack of effective technologies that can be used to support system reconfigurations; (iv) no international organization that serves for standardizing the modular components for manufacturing and assembly processes; (v) the lack of the effort in implementing a heterogeneous system consisting of different types of RMs. The survey has suggested some future research works to overcome these obstacles.     

制造系统的物能资源流模型

指出制造系统中物能资源问题的重要性，从制造系统的主要运行环节和制造系统的物料流等两个方面的分析制造系统中物能资源消耗状态的影响因素，最后建立了一种制造系统的能资源模型。     

An Information Modelling Framework to Support Intelligent Concurrent Design and Manufacturing of Sheet Metal Parts

Sharing of information is an important issue in supporting integrated and rapid product development. The use of information modelling technology is a promising approach for solving the problems of the intensive sharing of information in a concurrent and rapid product development cycle. This paper explores the definition and the structure of a framework of information modelling for the concurrent design and manufacturing of sheet metal parts. This framework aims to build an information bridge to fill the gap between the sheet metal part design and manufacturing systems. It is based on abstract handling principles of entities called zero thickness and zero bend radius principles. Based on this framework, information models can be built for information sharing by different systems. Knowledge bases that support intelligent concurrent design and manufacturing can also be created. In this paper, a two-branch tree based stepping-structure information modelling methodology for sheet metal parts is described, and a case study is given.     

Design principles of reconfigurable machines

Reconfigurable machines form a new class of machines that are designed around a specific part family of products and allow rapid change in their structure. They are designed to allow changes in machine configuration according to changes in production requirements. The reconfiguration may be related to changes in machine functionality or its scalability, i.e., the change in production volumes or speed of operation. Reconfigurable machines represent a new class of machines that bridges the gap between the high flexibility and high cost of totally flexible machines and the low flexibility and low cost of fully dedicated machines. The design principles of reconfigurable machines follow a similar philosophy, which was derived for reconfigurable manufacturing systems, and present an approach for the design of machines to be used mainly in high-volume production lines. This paper introduces design principles for reconfigurable machines, which may be applied in different fields of manufacturing. Based on these design principles, three types of reconfigurable machines were designed for various types of production operations such as: machining, inspection and assembly. This paper shows how the suggested design principles were utilized in the design of several full-scale machine prototypes and tested experimentally.     

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.     

Real-time software methodologies: Are they suitable for developing Manufacturing control software?

Computer-Integrated Manufacturing (CIM) systems may be classified as real-time systems. Hence, the applicability of methodologies that are developed for specifying, designing, implementing, testing, and evolving real-time software is investigated in this article.The paper highlights the activities of the software development process. Among these activities, a great emphasis is placed on automating the software requirements specification activity, and a set of formal models and languages for specifying these requirements is presented. Moreover, a synopsis of the real-time software methodologies that have been implemented by the academic and industrial communities is presented together with a critique of the strengths and weaknesses of these methodologies.The possible use of the real-time methodologies in developing the control software of efficient and dependable manufacturing systems is explored. In these systems, efficiency is achieved by increasing the level of concurrency of the operations of a plan, and by scheduling the execution of these operations with the intent of maximizing the utilization of the devices of their systems. On the other hand, dependability requires monitoring the operations of these systems. This monitoring activity facilitates the detection of faults that may occur when executing the scheduled operations of a plan, recovering from these faults, and, whenever feasible, resuming the original schedule of the system.The paper concludes that the set of surveyed methodologies may be used to develop the real-time control software of efficient and dependable manufacturing systems. However, an integrated approach to planning, scheduling, and monitoring the operations of these systems will significantly enhance their utility, and no such approach is supported by any of these methodologies.     

A specification language for planning and fault recovery in manufacturing systems

This paper presents the syntax and semantics of a component-oriented rule-based language for specifying the formal models of manufacturing systems. A model captures the state of a component of the system in a set of first-order logic predicates, and it captures the semantics of the operations performed by this component in a set of rules that determine the preconditions and postconditions of an operation. The models are then used to plan the sequence of operations of each class of jobs to be manufactured by these systems. A plan-oriented fault detection and correction strategy is proposed. This strategy can automatically handle any combination of faults that may occur when monitoring the operations of manufacturing systems. A fault-tree is consulted prior to executing the scheduled operations of a plan, and the faults that affect the execution of these operations are handled subsequently. Resuming the original cyclic schedule is attempted, whenever feasible. As a proof of concept, a prototype implementation of both the main constructs of the component-oriented rule-based language and the planning and fault-recovery algorithms presented in this paper have been completed. This prototype is implemented on a Unix-based system in the Ada programming language. The specification of a manufacturing system is first expressed in the proposed language. These statements are then translated into Ada code. This code is next compiled by a Verdix Ada compiler and is executed in order to create and populate the model data structure of the system. A detailed plan of execution and a set of fault-recovery plans may then be derived for a job to be manufactured on this system.     

A review on artificial intelligence applications to the optimal design of dedicated and reconfigurable manufacturing systems

Reconfigurable manufacturing systems (RMS) are considered the future of manufacturing, being able to overcome both dedicated (DMS) and flexible manufacturing systems (FMS). In fact, they provide significant cost and time reductions in the launch of new products, and in the integration of new manufacturing processes into existing systems. The goals of RMS design are the extension of the production variety, the adaption to rapid changes in the market demand, and the minimization of the investment costs. Despite the interest of many authors, the debate on RMS is still open due to the lack of practical applications. This work is a review of the state-of-the-art on the design of cellular RMS, compared to DMS, by means of optimization. The problem addressed belongs to the NP-Hard family of combinatorial problem. The focus is on non-exact meta-heuristic and artificial intelligence methods, since these have been proven to be effective and robust in solving complex manufacturing design problems. A wide investigation on the most recurrent techniques in DMS and RMS literature is performed at first. A critical analysis over these techniques is given in the end.     

大口径非球面系统的共基准加工与检验

针对大口径离轴非球面系统加工与装调的难点,提出了非球面光学系统共基准加工与检测的方法,对该方法的基本原理和实现过程进行了分析和研究。当光学系统的主镜和第三镜面形的RMS值优于λ/10(λ=632.8nm)时,对主镜和第三镜进行共基准装调和测试,并进行背板一体化装嵌,然后利用离子束对其进行一体化共基准加工。结合工程实例,对一大口径非球面系统口径为724mm×247mm的非球面主镜和口径为632mm×205mm的第三镜进行了共基准加工与检测,最终利用离子束共基准一体化精抛光得到主镜和第三镜面形的RMS值分别为0.019λ和0.017λ,满足光学成像。     

对地观测微小卫星主承力结构的优化设计与试验

为降低对地观测小卫星单机安装点加速度响应均方根值,提出了一种使加速度响应均方根值最小化的微小卫星主承力结构拓扑优化方法。首先对整星方案进行了有限元分析,分析显示整星Z向某些单机安装点的随机振动加速度响应均方根值过大。对系统进行了灵敏度分析,确定了卫星主承力结构底板是影响随机振动加速度响应均方根值大小的关键因素。以卫星单机安装点的加速度响应均方根值为目标函数,以体积作为优化的约束条件,应用连续体结构拓扑优化思想对卫星有限元模型进行拓扑优化设计,得到了一种单机安装点加速度响应均方根值满足指标要求的卫星主承力结构。最后,通过有限元分析与振动试验,证明了本文所设计的小卫星主承力结构力学性能参数均满足设计要求,其中整星的星敏感器、蓄电池、电源控制器等关键器件安装点的加速度响应均方根值相比优化前分别降低了23.3%、10.6%、11.3%,得到的结果验证了本文优化方法的有效性。