柔性制造系统活性分析与死锁控制

发布时间：2018-04-25 04:25

本文选题：柔性制造系统 + 死锁控制　；参考：《西安电子科技大学》2015年博士论文

【摘要】：作为当代制造业不可或缺的一部分,柔性制造系统(Flexible Manufacturing Systems-FMSs)具有传统制造过程所不具备的柔性和灵捷性。柔性制造系统通常是由数控机床、缓冲器、夹具、机器人、自动导向小车以及其它材料处理设备构成的计算机控制系统,其中一部分设备被视为柔性制造系统的共享资源。从形式化的角度来看,柔性制造系统属于资源分配系统。根据多变的产品规格,柔性制造系统可以动态地配置和分配资源。通过资源共享,柔性制造系统可以同时加工多个不同的原始工件,从而满足多品种小批量的生产需求。但由于并发系统中对有限资源的竞争,导致柔性制造系统中死锁的出现,进而引发一系列不良的后果。目前,针对自动制造系统中出现的死锁问题,已研发出了多种死锁控制策略,分析和控制柔性制造系统中的死锁问题势在必行。柔性制造系统无死锁意味着系统中的一个或者多个并发加工进程始终可以完成。此外,活性是柔性制造系统的一个重要性质。非活性是制造系统中不希望出现的一种状况。需要注意的是活性意味着无死锁,但非反之亦然。一旦系统不活,系统中某些事件可能永远无法执行,导致局部或全局死锁。对于一些与生命和基础设施安全密切相关的系统,一旦出现死锁,必将造成巨大的生命和财产损失。Petri网作为一类有力的数学工具,广泛应用于柔性制造系统的建模、分析和控制。Petri网模型的活性意味着在一个系统中,从任意状态开始的每一个操作都是可执行的,意味着不存在全局死锁或局部死锁。本文致力于研究Petri网建模的柔性制造系统的活性检测以及死锁控制问题。主要研究成果如下：1.对于一类加权的S3PR网,简称WS3PR,充分利用该类网的结构特性对其进行分析。通过研究资源库所标识与其输入输出弧权值之间的约束关系,给出了α-变迁和β-变迁的概念。根据强连通子网和树结构的相关性质,导出了资源库所标识与其相关输入输出弧权值之间的数值组合关系,进而提出了判断网活性的充分条件并给出了一种简单图示的活性检测算法。2.作为WS3PR活性检测方法的一种拓展和应用,针对S3PR网的一类子网-LS3PR,提出了一种通过资源配置保证网系统活性的方法。利用LS3PR网的结构特征以及资源子网的相关知识,通过分析资源库所标识与闲置库所标识之间的约束关系,进而对系统中的资源进行配置。在充分利用资源子网结构特性的基础上给出了计算LS3PR网中每个资源库所标识的算法,并证明所给出的算法是多项式复杂的。3.从技术角度来说,大多数死锁控制策略都是通过对Petri网状态空间分析或结构分析而提出的。本文给出一种基于资源重配以及控制器重构的死锁预防策略。首先给定一个网模型,对其中的每个资源库所的标识进行重新分配使其均为一,在此标识下的网模型的可达状态与原网相比大大减少,在此情况下利用区域理论设计该网的控制器。此后,将该控制系统当中的资源标识重新设置到最初给定值。在不需要改变控制器结构的情况下,通过逐步改变控制器的标识来实现原网的死锁控制进而使其为活。通过实例验证,所给出的死锁预防策略使系统的许可行为达到接近最优。4.针对S3PR网,首先给出了关键资源库所和与其相关的多路径资源持有库所的概念。通过分析关键资源库所和环资源子网的结构特性,给出了环资源子集导出严格极小信标的充分条件。根据该条件,可以计算出给定S3PR网中所有的严格极小信标。最后,在总结全文的基础上,对柔性制造系统活性分析与死锁控制的未来工作进行了展望。
[Abstract]:As an integral part of the contemporary manufacturing industry, the Flexible Manufacturing Systems-FMSs has the flexibility and agility that the traditional manufacturing process does not possess. Flexible manufacturing systems are usually computer controlled machine tools, buffers, clamps, robots, automatic steering cars, and other material handling equipment. System, some of which are regarded as shared resources of flexible manufacturing systems. From a formal point of view, flexible manufacturing systems belong to a resource allocation system. Flexible manufacturing systems can dynamically configure and allocate resources according to variable product specifications. Flexible manufacturing systems can process multiple different processes at the same time through resource sharing. The original workpiece meets the needs of many varieties and small batch production. However, due to the competition of the limited resources in the concurrent system, the occurrence of deadlock in the flexible manufacturing system leads to a series of bad consequences. At present, a variety of deadlock control strategies have been developed for the deadlock problem in the automatic manufacturing system, and the analysis and control of the deadlock problems have been developed. The deadlock problem in a flexible manufacturing system is imperative. A flexible manufacturing system without deadlock means that one or more concurrent processing processes in the system can always be completed. In addition, activity is an important nature of a flexible manufacturing system. Inactivity is a condition that is not expected in the manufacturing system. No deadlock, but not vice versa. Once the system is not alive, some events in the system may never be executed, leading to a local or global deadlock. For some systems closely related to life and infrastructure security, once the deadlock occurs, it will cause huge life and property loss.Petri network as a kind of powerful mathematical tool, which should be widely used as a kind of powerful mathematical tool. For the modeling of FMS, the analysis and control of the activity of the.Petri network model means that every operation starting from any state is executable in a system, which means that there is no global deadlock or local deadlock. This paper is devoted to the activity detection and deadlock control of a flexible manufacturing system modeled by Petri networks. The main research results are as follows: 1. for a class of weighted S3PR nets, referred to as WS3PR, we make full use of the structure characteristics of this type of network to analyze it. By studying the constraint relation between the identification of the resource base and the weight of the input and output arc, the concept of alpha transition and beta transition is given. The related properties of the strong connected subnet and the tree structure are given. This paper derives the numeric combination relation between the identification of the resource base and its related input and output arc weights, and then puts forward the sufficient condition to judge the activity of the network, and gives a simple graphical activity detection algorithm.2. as an extension and application of the WS3PR activity detection method, and proposes a kind of subnet -LS3PR for S3PR net. The method of resource allocation to guarantee the activity of network system. Using the structure characteristics of LS3PR network and the related knowledge of the resource subnet, by analyzing the constraint relation between the identification of the resource base and the identification of the idle library, the resources in the system are configured. On the basis of fully utilizing the structure characteristics of the resource subnet, the calculation of each LS3PR net is given. The algorithm identified by the resource base shows that the proposed algorithm is polynomial complex.3. from the technical point of view, most of the deadlock control strategies are proposed by the Petri network state space analysis or structural analysis. In this paper, a deadlock prevention strategy based on resource redistribution and controller reconfiguration is given. The network model reassigns the identifiers of each of them, and the reachable state of the network model is greatly reduced compared with the original network. In this case, the controller of the network is designed with the region theory. After that, the resource identification in the control system is rearranged to the initial value. In order to change the structure of the controller, the deadlock control of the original network is realized by changing the identity of the controller gradually. By example, the deadlock prevention strategy gives the permissive behavior of the system close to the optimal.4. for the S3PR network, and first gives the multi path resource holding of the key resource repository and its related resource. By analyzing the structure characteristics of the key resource base and the ring resource subnet, we give the sufficient conditions for the strict minimal beacon derived from the subset of the ring resources. According to this condition, all the strict minimal beacons in a given S3PR network can be calculated. Finally, on the basis of the full text, the activity analysis and deadlock of the flexible manufacturing system are analyzed. The future work of control is prospected.

【学位授予单位】：西安电子科技大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TH165

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