Developing a computer control system for a flexible manufacturing cell

This article focuses on the development of a computer control system for a flexible manufacturing cell. The paper outlines the various modules that are required for a computer control system and elaborates on the development of some of these modules. This is part of an ongoing research project at the University of the Witwatersrand. The aim of the project is to demonstrate the viability of flexible manufacturing systems to South African industry. Thus the main constraints of the project were cost, ease of implementation, and ease of maintainability. This necessitated the use of existing machinery and of computer systems and software that were readily available and already familiar to industry.     

晶圆制造物料运输系统性能分析建模方法

为在自动化物料搬运系统设计阶段快速有效地分析该系统的性能,提出一种扩展Markov模型的建模方法,该方法减少了自动化物料搬运系统性能分析模型的规模,避免了模型的状态空间规模爆炸.采用某晶圆制造企业的实际生产数据进行测试,并与仿真分析方法比较.结果表明,扩展Markov模型与仿真模型在自动化物料搬运系统搬运量、运输小车利用率和空载小车到达平均时间间隔等指标方面的相对误差值为96％,处于[-8％,10％]的区间范围;与仿真模型相比,扩展Markov模型的性能分析效率提高了600倍以上.由此验证了所提扩展Markov模型建模方法的有效性.     

On modeling the design of cellular manufacturing systems

A new optimization model is discussed for the design of cellular manufacturing systems. It is based on an integer programming formulation that updates some other models by eliminating redundant machine assignment and cost coefficients dependent on cell configuration. To reduce computational burdens, a simplified integer programming model and a decomposition algorithm are proposed. Several computer solutions were performed to evaluate the performance of the new model. The computational results are discussed.     

A parallel multiple Markov chain simulated annealing for multi-period manufacturing cell formation problems

Simulated annealing (SA) is a general purpose optimization technique capable of finding optimal or near optimal solutions in various applications. The major disadvantage of this technique is its slow convergence making it not suitable for solving many complex optimization problems. This limitation may be alleviated by parallel computing using a multiprocessor computer or a cluster of workstations. In this paper, we present an integer programming model for solving a multi-period cell formation problem in cellular manufacturing system. In order to solve the mathematical model efficiently, we developed a multiple Markov chain simulated annealing algorithm which allows multiple search directions to be traced simultaneously. Our computational results on a single processor machine showed that multiple Markov chain SA is much more efficient than a conventional single Markov chain SA. The parallel implementation of the multiple Markov chain SA further improves its computational efficiency in terms of solution quality and execution time.     

基于Arena RT的柔性制造单元控制系统仿真

从物理仿真模型型的控制逻辑和模型中资源的组织形式出发,提出了一种基于Arena RT的柔性制造单元仿真控制模型.采用Web服务技术设计了柔性制造单元控制实体之间的通讯模型,结合Arena RT模犁实时控制外部应用程序的特性,构建了基于Web服务和Arena RT的仿真控制软件体系结构.在此基础上,设计并实现了一种开放式、可视化,以及对柔性制造单元实时控制的仿真集成系统.以某军工单位的机加车间为例,验证了该仿真系统的实时控制性.     

Performance Analysis of Flexible Manufacturing Systems with a Single Discrete Material-Handling Device

We present an analytical model for performance prediction of flexible manufacturing systems (FMSs) with a single discrete material-handling device (MHD). This configuration of FMS is significant for many reasons: it is commonly found in industry, it simplifies material-handling control, it is amenable to analytical modeling, and it forms a building block for more complex systems.Standard queueing models are inadequate to analyze this configuration because of the need to take into consideration many nontrivial issues such as state-dependent routing, interference from the MHD, and the analysis of the MHD. To account for state-dependent routing, we develop an iterative method that is built around mean value analysis. To analyze the MHD interference, we use two queueing network models. In the first, we ignore queueing at the MHD but model the interference from the MHD by inflating the station service times. The second network models the queueing for the MHD and estimates the blocking (inflation) times needed for the first model. By iterating between the two networks, we are able to predict the performance of this configuration of FMS. Our analytical estimates are validated against discrete event simulation and shown to be quite accurate for initial system design.     

An event-based,robot-served flexible manufacturing cell modeller

The development is described of a flexible manufacturing cell (FMC) programming and simulation system called FMCPS, which generates robot programs for a 6-DOF industrial robot. The development of FMCPS is based on an FMC that is being developed at UMIST. The cell consists of a Fanuc 600 ARCmate industrial robot, a Takisawa MAC V3 CNC machining centre and an MHP MT-50 CNC turning centre. The software has been developed on a SUN 4/110 workstation running under the UNIX operating system, using three-dimensional SUNCORE interactive graphics and SUNVIEW window systems. An event-oriented robot-programming method is used in the FMCPS. This method divides the robot tasks into different events. The user needs to define the points of the robot gripper route and the corresponding data for each event. The Cartesian coordinates of the points in the robot gripper paths are then transformed to the six robot joint angles by a variant inverse kinematics iteration method. These robot joint angles are used in the simulation model which generates robot programs suitable for the Fanuc robot. A three-dimensional, wire-frame-based graphical model is used for simulation. The user can observe the simultaneous animation of the robot movement, and display machine tool paths in separate graphics windows on the screen simultaneously. The various activities in the cell are simulated in pseudo-parallel mode by taking advantage of the multi-tasking and piping features of UNIX. At the end of a simulation exercise, the user is provided with the facility to obtain a performance report for the FMC which gives information on total operation time and on robot and machine utilisation, in addition to the robot program.     

增/减材柔性制造及加工系统构成形式

将柔性制造的思想引入到增/减材制造中,形成增/减材柔性制造工艺。阐述了该工艺的内涵及加工范围,确立了增/减材柔性制造工艺流程,描述了各组成工序的特点,详细阐述了增/减材柔性制造中材料沉积、材料去除两工序内部及其之间的多种柔性加工方式。在此基础上,确立了增/减材柔性制造系统的设备构成及其相互关系,给出了加工设备的总体布局。为进一步研究该工艺的加工序列规划及各种构成设备具体结构形式等方面打下基础。     

Component-based modeling of enterprise architectures for collaborative manufacturing

Agility and collaboration are key factors in collaborative manufacturing. An enterprise architecture (EA) framework for collaborative manufacturing has to support agility and have the ability to increase opportunities for collaboration. In this paper, an architecture-unit-based enterprise architecture (AUEA) framework is introduced for collaborative manufacturing. It supports the agility and collaboration ability of the EA using architecture units (AUs) and semantics of the metamodel. Each AU is a business-driven minimum EA component which consists of the components in predefined reference models of specific domains and the associations between domains and domain drivers. Because AUs enable the easy composition of a business-driven EA, the AUEA framework is agile. The semantics of the metamodel in AUEA frameworks are modeled using object-oriented and fact-oriented methods. The semantics and AUs enhance opportunities for collaboration. As an example of an AUEA in collaborative manufacturing, an EA for a supply chain on the basis of the supply-chain operations reference (SCOR) model is implemented in this paper.     

面向订单制造的可重构制造系统中虚拟制造单元构建技术

为适应单件、小批、个性化和市场需求动态多变的特点.研究了多种不同交货期生产订单并存时的可重构制造系统中虚拟制造单元构建问题.构造了以连续加工产品间相似系数之和最大、工作加班时间最少、单元的封闭性最好(工件跨单元搬运次数最少)、制造系统重构成本最小及设备生产负荷均衡为目标的非线性多目标0-1整数规划模型.采用两阶段的求解策略进行求解.在第一阶段采用启发式方法对非瓶颈设备和工艺进行预处理,以缩小问题解的搜索空间;第二阶段采用一种基于网格计算的分布式平行协同多目标粒子群算法,随机搜索Pareto优化解集.最后,利用globus 4.0 工具箱搭建计算网格和Java语言实现了算法.从生产实际出发给出了算例,证明结果可行,从而验证了算法的有效性.     

Generation of optimal control policy for flexible manufacturing cells: A Petri net approach

For flexible manufacturing cells (FMCs), the major control problem is to determine the optimal part routeing and machines dispatching policy. In this research, we present a methodology for generating optimal operating strategies for FMCs. The methodology is built on two techniques: stochastic timed Petri net (STPN) and Markov decision process (MDP). The operating strategy devised with the proposed methodology is deadlock-free and provides the best performance given a set of system parameters (machines, parts, machining times, etc.). Generation of programmable logic controller (PLC) codes is greatly facilitated as the generated strategy can be mapped directly to a ladder diagram representing the PLC code. The objective of real-time optimal control could then be achieved with this type of controller. An example is provided to illustrate the methodology.     

Dispatching, routing, and scheduling of two automated guided vehicles in a flexible manufacturing system

This article presents a new approach for planning the dispatching, conflict-free routing, and scheduling of automated guided vehicles in a flexible manufacturing system. The problem is solved optimally in an integrated manner, contrary to the traditional approach in which the problem is decomposed in three steps that are solved sequentially. The algorithm is based on dynamic programming and is solved on a rolling time horizon. Three dominance criteria are used to limit the size of the state space. The method finds the transportation plan minimizing the makespan (the completion time for all the tasks). Various results are discussed. A heuristic version of the algorithm is also proposed for an extension of the method to many vehicles.     

Analysis of flexibility with rationing for a mix of manufacturing facilities

A major competitive advantage of a flexible manufacturing facility is its ability to cope with uncertainties in demand. At a strategic level, capacity-size decisions for a mix of flexible facilities (each not necessarily producing the same combination of products) are made based on aggregates of product types. Such an approach overlooks possible capacity-devouring by some products, arising at the operational level, when the aggregate demand for the period exceeds the available capacity. A rationing policy is required to ensure that the available aggregate capacity of the facilities is shared equitably. In this article, it is shown that such a rationing policy has an impact on the required capacity size and, therefore, must be integrated with the decisions at the strategic level. Several properties indicating the relative preferences of certain facility strategies are also established.     

基于多Agent的敏捷制造单元控制系统

针对敏捷制造的需求,本文提出了一种基于多Agent制造单元控制系统的总体结构,并对各Agent的功能与单元控制系统的实现过程进行了详细描述,简单介绍了Agent之间的通信机制.     

可重构制造系统中基于相似性理论的虚拟制造单元生成方法

为实现可重构制造系统的逻辑重构,应用相似性理论对多种工件的多工艺路线进行相似性分析,提出了基于工艺相似性理论的设备集合模式的概念。建立了基于设备集合模式、图论和集合论的虚拟制造单元生成的框架模型,以及生成的有关定义、规则及算法。生成的有关定义包括伪设备、例外设备、设备集合模式识别和工艺路线更新等;生成规则包括候选首末设备生成和侯选制造单元处理两类规则;生成算法包括初始输入数据处理、候选制造单元生成、工艺路线更新和例外设备处理4个子算法。用Visual C 实现了所给出的算法,并通过示例测试验证了算法的正确性。     

建材装备制造企业数字化管理平台设计与实现

针对建材装备制造企业产品制造过程中的信息化管理问题,在分析企业制造过程信息业务流程的基础上,构建了基于制作流、物料流和资金流的信息化管理三大主线,提出项目主导下的多层次视图进度监控模型和基于内控指标的资金流多级预警模型,并针对数字化管理平台下多主体制造过程的信息协同,给出了基于数据传输中间件的数据集成和基于权限与重构的流程重组等关键技术和实现方法。开发了针对建材装备制造企业的数字化管理平台并进行了工程应用,验证了方法的可行性。     

面向变批量生产的制造单元构建方法

为实现变批量生产特征下制造资源的优化利用,提出一种有效的制造单元构建方法。在构建制造单元框架模型中,提出应先对现有单元布局可用性进行分析的策略,并考虑现有单元布局对变批量生产的一种适应性。以单元布局的可用性和物料搬运成本最小化为目标,构建了目标函数和约束条件模型,集成考虑了设备聚类和单元布局问题,同时利用改进粒子群算法对问题进行求解,并对粒子进行二维实数编码,解决了粒子群算法求解离散空间优化问题。通过一个实例验证了所提方法的有效性。     

多目标免疫遗传算法性能分析及其在柔性作业车间调度中的应用

讨论了一种多目标免疫遗传算法的收敛性和多样性。首先,提出了一种集成免疫思想和遗传算法的多目标优化算法;接着,采用马尔可夫链对算法的收敛性进行了定量分析,证明该算法能以概率1收敛到Pareto最优解集;定性分析了算法的多样性保持策略。最后,结合某柔性车间调度问题的实例,验证了算法的良好收敛性和多样性。     

An efficient heuristic for scheduling batches of parts in a flexible flow system

Flexible manufacturing systems (FMSs) are a class of automated systems that can be used to improve productivity in batch manufacturing. Four stages of decision making have been defined for an FMS—the design, planning, scheduling, and control stages. This research focuses on the planning stage, and specifically in the area of scheduling batches of parts through the system.The literature to date on the FMS planning stage has mostly focused on the machine grouping, tool loading, and parttype selection problems. Our research carries the literature a step further by addressing the problem of scheduling batches of parts. Due to the use of serial-access material-handling systems in many FMSs, the batch-scheduling problem is modeled for a flexible flow system (FFS). This model explicitly accounts for setup times between batches that are dependent on their processing sequence.A heuristic procedure is developed for this batch-scheduling problem—the Maximum Savings (MS) heuristic. The MS heuristic is based upon the savings in time associated with a particular sequence and selecting the one with the maximum savings. It uses a two-phase method, with the savings being calculated in phase I, while a branch-and-bound procedure is employed to seek the best heuristic solution in phase II. Extensive computational results are provided for a wide variety of problems. The results show that the MS heuristic provides good-quality solutions.     

新型板式链自动装配机的设计与研制

从中国一些链条生产厂家的现有设备入手,在分析当前主流的链条装配机结构形式的基础上,提出使用气缸代替凸轮机构作为驱动执行的机构,并针对送料、定位机构提出了一些改进设计。改进后的设备不仅减小了体积,还具备了柔性装配的条件。最后对链条自动装配机的发展趋势进行了展望。