FMS刀具流死锁控制策略与分派算法的研究

刀具流死锁控制及刀具分派问题是柔性制造系统(FMS)调度中的重要核心内容,为实现合理的死锁回避和刀具分派,在前期研究的基础上,通过建立刀具申请分配图,分析了死锁的相关性质,指出了FMS中刀具流死锁的两大根源是工件选择的不合理和刀具分派的不合理。提出了一种解决刀具流调度问题的两级死锁控制策略,建立了动态调度原理模型,给出了死锁检测算法和刀具分派算法。分析表明该策略与算法能够使得刀具流死锁的两大根源均得以回避,实现了刀具流死锁控制与刀具分派。     

基于刀具寿命约束的FMS刀具流死锁研究

刀具流死锁问题是柔性制造系统(FMS)调度中的重要核心内容,为实现合理的死锁回避,必须深入分析刀具流死锁的相关性质。在前期研究的基础上,分析了刀具寿命对刀具申请的影响,进一步建立了基于刀具寿命约束的刀具申请分配图,分析了死锁的相关性质,建立了在考虑刀具寿命的情况下的刀具流死锁判定定理,为下一步的深入分析死锁检测算法和死锁回避准备了基础。     

FMS刀具系统

<正> FMS投资大,但其单个单元不能象机床那样独立使用,这使得刀具管理工作难度大。但是,事实证明,在使用FMC实现自动化、无人化积累了一定经验之后,再渐渐向FMS发展是行之有效的,自然随之刀具管理形式也要发生变化。FMS拥有2000～3000把刀具不足为奇,但随着刀具数量的增加,刀具费用、管理面积也都成了问题。可见,开发出适用于FMS的刀具系统尤其重要,但要很好掌握这些刀具的情况却并非易事。下面介绍针对FMS开发的刀具与管理系统。     

应用遗传算法研究FMS刀具需求模型

针对柔性制造系统刀具需求模型及求解中存在的问题,提出以零件加工时间最短为优化目标,以刀具购买资金为约束,基于遗传法求解的新型柔性制造系统(FMS)刀具需求规划模型。通过比较分析,验证了该FMS刀具需求规划模型及其遗传算法求解需求问题的合理性和优越性。     

基于柔性制造系统(FMS)的刀具编码及刀具组装技术研究

在柔性制造系统(FMS)中,刀具编码技术和刀具组装是刀具管理的重要组成部分。该文研究了刀具的编码原理、基本构成和实现方法,在此基础上探讨了刀具在组装过程中遇到的一些问题,提出了相应解决办法,并应用SQL Server 2000数据库和Visual Basic 6.0进行了刀具管理信息系统的设计与开发。     

FMS刀具准备系统研究

围绕刀具准备系统的研究与开发 ,论述了刀具准备系统的总体结构和刀具寿命管理、刀具贮备管理、GT概念下刀具分配策略三个功能模块 ,利用相对磨损率来衡量刀具的磨损程度 ,从而对刀具寿命进行优化 ;根据从 MRP和 MPS得到的信息以及刀具的使用数据 ,生成基于成本优化的刀具补充策略 ;并将成组技术、遗传算法及虚拟刀具库思想 ,应用于刀具分配 ,解决FMS中刀具的优化分配问题。     

FMS的刀具管理系统

具管理系统是FMS的有机组成部分,刀具管理水平的高低是影响FMS生产效率和柔性的重要因素。本文阐明了FMS刀具管理系统的一些基本概念,可供有关人员进行此方面设计时参考。     

刀具磨损在线检测及刀具寿命实时跟踪技术在FMS中应用

刀具磨损在线检测和刀具寿命实时跟踪是柔性制造系统(FMS)的关键技术之一,通过分析刀具磨损在线检测原理,形成了适合于FMS刀具磨损检测的方案和具体实施办法,通过探讨刀具寿命的主要影响因素,提出了使用雷尼绍NC4非接触式刀具磨损检测系统进行刀具寿命监控的措施,在此基础上,开发了刀具寿命跟踪管理系统。研究成果提高了刀具磨损检测和刀具寿命管理的准确性与控制效率,有效提升了FMS工件加工合格率和加工精度。     

考虑刀具剩余寿命的工件流-刀具流综合调度研究

为解决FMS中工件流-刀具流的调度优化问题,考虑刀具剩余寿命,以完成时间最短为优化目标,建立了工件流-刀具流综合调度模型,提出了改进和声-遗传算法,并对模型进行优化求解.设计了MSOS+TSOS编码方式和GS初始化方法,从而显著提高了算法的收敛性能和求解效率.算例结果表明,该模型能有效降低完工时间,并且算法的收敛速度和...     

FMS混合调度中的两种启发式规则

针对FMS混合调度系统中的工件选择和运刀小车的启发式调度问题,给出了两个新的启发式规则,即在机床选工件策略中建立了刀具外借量最少规则,在运刀小车任务调度策略中提出了目标机床当前工序完成时间最早规则,通过仿真实验验证了两种启发式规则的有效性。结果表明所提出的两种调度规则能够较好地改善FMS的各项性能指标。     

基于对象模型的FMS死锁检测

柔性制造系统的主要特点是多种不同类型的工件同时在系统中加工 ,这些工件竞争系统中的有限资源会导致死锁的发生 ,能够检查出 FMS运控软件中可能发生的死锁问题是系统能够正常运行的必要条件之一。本文首次基于面向对象模型 ,定义了死锁问题 ,并在此基础上提出了检测死锁的算法 ,此算法具有通用性和实用价值。     

The use of the Petri net reduction approach for an optimal deadlock prevention policy for flexible manufacturing systems

In a flexible manufacturing system (FMS) with multiple products, deadlocks can arise due to limited shared resources, such as machines, robots, buffers, fixtures etc. The development of efficient deadlock prevention policies, which can optimise the use of system resources, while preventing deadlocks from occurring, has long been an important issue to be addressed. In [1], an optimal deadlock prevention policy was proposed, based on the use of reachability graph (RG) analysis of the Petri net model (PNM) of a given FMS and the synthesis of a set of new net elements, namely places with initial marking and related arcs, to be added to the PNM, using the theory of regions. The policy proposed in [1] is optimal in the sense that it allows the maximal use of resources in the system according to the production requirements. For very big PNMs, the reachability graph of the PNMs becomes very large and the necessary computations to obtain an optimal deadlock prevention policy become more difficult. In this paper, we propose the use of the Petri net reduction approach to simplify very big PNMs so as to make necessary calculations easily in order to obtain an optimal deadlock prevention policy for FMSs. An example is provided for illustration.     

多用户操作系统避免死锁的矩阵搜索法

死锁问题是多用户操作系统的一个重要事件,本文对避免死锁的矩阵搜索法进行分析。     

自动小车存取系统中轨道导引小车环路死锁控制的研究

为防止自动小车存取系统中轨道导引小车环路死锁现象,提出了一种基于Petri网和有向图的死锁控制方法.该方法首先应用有色赋时Petri网建立了自动小车存取系统的动态模型,并结合有向图工具,阐述了导致环路死锁的原因.在此基础上,针对单一轨道双向运行的轨道导引系统,探讨了其环路死锁的主要表现形式,给出了轨道导引小车无死锁运行的充要条件,并提出了包含临界状态在内的死锁避免控制策略.最后,结合实例说明了环路死锁控制的有效性.     

Deadlock prevention using Petri nets and their unfoldings

Unfoldings of Petri nets (PN) provide a method for the analysis of concurrent systems without restoring the state space of a system. This allows one to overcome the state explosion problem. Many properties of the initial PN (boundedness, safety, persistency and hazards) can be checked by constructing the unfolding. A deadlock prevention procedure first detects deadlocks using an unfolding. Then, the first method reduces the unfolding to a set of deadlock-free subunfoldings that cover all live behaviours. The second method uses a direct transformation at the level of the original PN. The methods are implemented as subroutines in the Berkeley program SIS. Although the deadlock detection problem is known to be NP-complete, experimental results show that for highly parallel specifications deadlock prevention by unfoldings is typically more efficient than deadlock prevention based on symbolic BDD (binary decision diagrams) traversal of the corresponding reachability graph.     

An improved strategy to solve shop deadlock problem based on the study on existing benchmark recovery strategies

In this paper, we study the effect of various benchmark deadlock recovery strategies, and we find that each of these recovery strategies either results into another kind of deadlock or results into very high handling cost and long handling time. We also propose a new improved strategy in order to solve the shop deadlock problem through the use of both automated guided vehicle and a central buffer. To the best knowledge of the authors, till date, no research study has been performed to propose any such strategy in this regard or to study the effect of several deadlock recovery strategies altogether. Simulation result shows that the proposed strategy performs better than the existing benchmark recovery strategies and provides much improved solution to the shop deadlock problem, resulting into considerable reduction in handling time and cost and better handling of jobs in central buffer compared to various benchmark deadlock recovery strategies available in the literature.     

FMS中资源共享导致的死锁状态及其避免方法

针对FMS中多种操作对有限资源的竞争会导致死锁状态，采用Petrinet分析技术对其进行了研究。建立了FMS的PPN模型，并在此基础上给出了直接死锁和潜在死锁的定义；引入了死锁状态方程的概念并给出了其构造方法；描述了死锁状态和资源分布之间的内在联系，并提出了一种死锁避免方法。实例表明该方法能够简单有效地避免死锁的产生，并允许资源的最大利用。     

Real-Time Deadlock Detection and Recovery for Automated Manufacturing Systems

The deadlock problems of automated manufacturing systems (AMS) are discussed in this paper. A dynamic-edge graph (DEG) with double labels was designed to model the AMS, to identify distinct part flows, to represent the states and capture the concurrent behaviour of the AMS. In the AMS, we assume that each resource has its own unit-capacity buffer to which it can be transferred when a deadlock situation occurs. The motivation of this research was to define the state of each part and propose a simple, dynamic and adaptable approach, based on double labels and some basic concepts in graph theory, for detecting a deadlock in real time and resolving deadlocks in the AMS. Through this approach both the utilisation of resources and the overall throughput can be improved. The proposed algorithmic procedure, in accordance with the states arrived at and generated from the model, can serve as a functional module for the operation of an AMS without the need to revise the original control extensively. In addition, the proposed procedure can be used cooperatively with a dispatching controller and expanded with little modification. ID="A1"Correspondance and offprint requests to: Dr W.-C. Yeh, Department of Industrial Engineering, Feng Chia University, PO Box 67-100, Taichung, Taiwan 407. E-mail: wcyeh@fcu.edu.tw     

一种运用图论进行FMS无死锁调度的方法

在制造系统中 ,必须防止死锁的发生。本文提出一种在制造系统 (带有限缓冲区 )中搜索最优的无死锁调度算法。此算法建立在遗传算法的基础上 ,运用图论算法来保证无死锁调度结果。为了保证遗传算法生成的调度策略能够满足所要求的约束 ,运用图论方法选择无死锁个体 ,添加缓冲区 ,从而在保证了系统的主要性能指标的同时 ,得到系统可行的无死锁的调度结果。本文的主要创新之处在于提出了一种考虑系统缓冲区的无死锁调度方法。