共查询到17条相似文献,搜索用时 437 毫秒
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Petri网的硬件实现 总被引:12,自引:1,他引:12
Petri网是异步并发现象建模的重要工具,Petri网的硬件实现将为并行控制器的设计提供有效的途径.给出了几种Petri网系统的硬件实现方法,包括带抑制弧和允许弧的C/E系统、P/T系统、T-时延Petri网系统;给出了硬件实现中非纯网的处理方法.首先讨论实现各种Petri网的逻辑电路;然后用ABEL语言对逻辑电路进行描述;最后给出了一个用解释Petri网描述的服务系统的例子,说明如何使用硬件(CPLD)实现的方法.实验结果表明了上述方法的正确性.这对于离散事件动态系统控制器的设计,尤其是片上并行控制器、多处理器芯片的设计都具有十分重要的意义. 相似文献
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可重构制造系统监督控制器的自动重构 总被引:2,自引:0,他引:2
提出了基于改进的网重写系统(Improved net rewriting system, INRS)的可重构制造系统(Reconfigurable manufacturing systems, RMS) Petri网监督控制器的自动重构方法, 以快速适应由市场需求变化所引起的制造系统构形的频繁变化. INRS解决了网重写系统存在的问题, 可动态调整给定Petri网模型的结构而不改变其行为属性. 以集合和图的组合形式定义了RMS的构形, 并提出了基于INRS的一类模块化、可重构的Petri网控制器的设计方法. 针对这类Petri网控制器, 提出了基于INRS的自动重构方法. 方法可将RMS构形的变化转变为INRS的图重写规则, 并作用于当前Petri网控制器, 使其快速、自动地重构为所求的新控制器. 所提出的Petri网控制器的设计与重构方法, 均从理论上保证了结果的正确性, 免校验. 仿真研究验证了方法的有效性. 相似文献
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提出了一种用于可重构制造单元故障恢复的策略与方法, 允许故障发生时, 通过对用于正常操作控制的Petri网形式的监督控制器进行局部、临时性的修改, 实现故障的恢复. 首先, 提出改进的网重写系统, 可用于动态改变Petri网模型结构. 然后,提出了基于改进的网重写系统的故障恢复方法, 其中改进的网重写系统用于操作、引导Petri网监督控制器由错误状态进入正确状态. 故障恢复后监督控制器的结构与期望属性维持不变. 最后, 以实例演示了该故障恢复方法的应用, 证实了方法的有效性. 相似文献
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首次研究离散制造装配系统的活性控制问题.建立了系统的工件加工过程Petri网模型.通过对系统Petri网模型的结构分析,提出了导致系统死锁的两类元素结构及活性特征.对一类离散制造装配系统提出了避免死锁的Petri网控制器,这类控制器容易实现,对系统的限制小,而且使得受控系统仍具Petri网模型.对一般离散制造装配系统提出了保证系统活性的控制策略. 相似文献
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自动制造系统异常情况Petri网控制器的形式化设计方法 总被引:1,自引:0,他引:1
CIMS,FMS等自动制造系统的控制器一般由有序控制器和异常情况处理控制器两个部
分组成.两者都可以用Petri网来实现.这里讨论用于异常情况处理的Petri网控制器的形
式化设计方法,其基本思想是利用状态表作为异常情况处理的规格说明语言,然后将状态表形
式化描述为MOORE自动机,最后给出构造与MOORE自动机行为等价的Petri网控制器
的形式化设计方法.并且用一个实例说明其设计过程.该方法也适用于Petri网的自动建
模. 相似文献
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基于P-不变量的Petri网并行化方法的研究 总被引:1,自引:1,他引:0
为使Petri网系统能够并行执行或模拟运行,提出了基于P-不变量的Petri网并行化方法.根据Petri网系统具有同步与并发的特点,给出基于P-不变量的Petri网模型分割、进程创建条件与并行化分析.在此基础上,提出并行进程创建条件拓展定理并给予证明和实例验证.给出实现并行化所需要解决的Petri网模型行为规范的形式化、P-不变量求解与基于P-不变量的Petri网并行化方法.实验结果表明,基于P-不变量的Petri网系统的并行化方法是可行和有效的. 相似文献
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死锁是柔性制造系统中容易发生的异常现象,如不加以消除,将会导致整个系统的瘫痪。文中通过Petri网模型对FMS的结构分析,揭示出导致FMS死锁的结构元素和活性特征,在此基础上,提出了FMS的无死锁Petri网控制器算法,并举例说明这种控制器算法在FMS中的应用。 相似文献
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Control Synthesis of Petri Nets Based on S-Decreases 总被引:8,自引:0,他引:8
Chen Haoxun 《Discrete Event Dynamic Systems》2000,10(3):233-249
A method for constructing a controller for a discrete event system modeled by a Petri net is presented in this paper. The control specification of the system is given by a set of linear inequality constraints defined on the marking of the net. The controller that forces the net to obey the constraints is an extended Petri net, which is synthesized based on minimal support S-decreases. The method can deal with general Petri nets with uncontrollable transitions, and then provides a systematic way for synthesizing net-based controllers for discrete event systems. 相似文献
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Deadlock must be prevented via the shop controller during the flexible manufacturing system (FMS) performing. Various models have been tried for the analysis and design of shop controller. Petri net is suitable to describe the dynamic behavior of the discrete event system , such as concurrency , conflict and deadlock , however , the verification of the system behavior needs ructure analysis with complex theoretical proof method. Temporal logic model checking has important advantages over traditional theorem prover. It is fully automatic and can produce possible unter- example which is particularly important in finding subtle error in complex transition systems. In this paper ,a new method for the deadlock prevention based on Petri net and Temporal Logic model checking is presented. The specification in the Temporal Logic is expressed according to some result of structure analysis of the Petri net . The model checking is employed to execute the formal verification ,which will conduct an exhaustive exploration of all possible behaviors. Finally ,an example is presented to demonstrate how the method works. 相似文献
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Deadlock must be prevented via the shop controller during the flexible manufacturing system (FMS) performing. Various models have been tried for the analysis and design of shop controller. Petri net is suitable to describe the dynamic behavior of the discrete event system, such as concurrency, conflict and deadlock, however, the verification of the .system behavior needs structure analysis with complex theoretical proof method. Temporal logic model checking has important advantages over traditional theorem prover. It is flatly automatic and can produce possible counter-example which is particularly important in finding subtle error in complex transition systems. In this paper, a new method for the deadlock prevention based on Petri net and Temporal Logic model checking is presented. The specification in the Temporal Logic is expressed according to some result of structure analysis of the Petri net. The model checking is employed to execute the formal verification, which will conduct an exhaustive exploration of all possible behaviors. Finally, an example is presented to demonstrate how the method works. 相似文献
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Lingxi Li Hadjicostis C.N. Sreenivas R.S. 《IEEE transactions on systems, man, and cybernetics. Part A, Systems and humans : a publication of the IEEE Systems, Man, and Cybernetics Society》2008,38(1):207-217
This paper proposes an approach for providing tolerance against faults that may compromise the functionality of a given controller modeled by a Petri net. The method is based on embedding the given Petri net controller into a larger (redundant) Petri net controller that retains the original functionality and properties, and uses additional places, connections, and tokens to impose invariant conditions that allow the systematic detection and identification of faults via linear parity checks. In particular, this paper considers two types of redundant Petri net controllers: 1) nonseparate redundant Petri net controllers have the same functionality as the given Petri net controller and allow for fault detection and identification, but do not necessarily retain the given controller intact; and 2) separate redundant Petri net controllers are a special case of the nonseparate redundant controllers that retain the given Petri net controller intact but enhance it with additional places to enable fault detection and identification. The work in this paper obtains complete characterizations of both types of redundant controllers along with necessary and sufficient conditions for them to be bisimulation equivalent to the given original Petri net controller. In addition, this paper discusses how each type of redundant controllers can be designed to have desirable fault detection and identification capabilities. When the bisimulation equivalence requirement is not directly enforced, nonseparate redundant controllers can potentially have advantages over separate ones (e.g., they can use fewer connections to detect and identify the same number of faults). An example of a Petri net controller for a production cell and its fault tolerance capabilities using separate and nonseparate embeddings is used to illustrate the approach. 相似文献
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Thomas O. Boucher Mohsen A. Jafari Glenn A. Meredith 《Computers & Industrial Engineering》1989,17(1-4):459-463
This paper discusses the Petri Net approach to real time production control. Petri nets were developed to model concurrent and asynchronous systems. Having modeled a machining cell or a production system as a Petri net, one can analyze the effects of controller behavior on the system before implementing the controller.
Petri net principles are illustrated for a machining cell being implemented in the Manufacturing Automation Laboratory at Rutgers University. Observations are made concerning the difference between a Petri Net Controller and a Programmable Logic Controller for the same application. 相似文献