Synthesis a Petri net based control model for a FMS cell

Petri nets have been recognised as a high level formal and graphical specification language for modelling, analysis, and control of concurrent asynchronous distributed systems. This paper presents a PN model, synthesised by an extended version of the knitting synthesis technique. This method, as an incremental design approach, establishes the conditions under which the fundamental behavioural properties of the synthesised systems are fulfilled and preserved. That is, the synthesised models are live, bounded, and reversible (cyclic). A Petri net with the aforementioned properties is called a well-behaved Petri net system which is guaranteed to operate in a deadlock-free, stable, and cyclic fashion. Well-behaved Petri net models, synthesised using the proposed method can be compiled into control codes and implemented as real-time controllers for flexible manufacturing systems. The significance of this paper is due to the application of an extended version of knitting synthesis technique to a real life example of a flexible manufacturing system.     

基于Petri网的IPv4到IPv6协议转换分析

应用Petri网原理分析IPv4-IPv6协议转换,并结合实际的系统和详细转换流程图,建立Petri网模型。通过此Petri网模型的有界性、可达性及活性等动态特性,证明此转换模型功能和安全上的可行性。     

基于Petri网的Web服务组合与分析

Web服务为互联网提供了一种新的应用环境。然而,Web服务还有许多需要进一步研究的问题。Web服务的组合及其验证就是需要深入研究的问题。本文针对通用构件描述语言（UCDL）提出一种Petri网模拟和验证方法,即对于Web服务的元活动和构件,提出相应的Petri网模型和建模方法。在此基础上进一步研究了Web服务系统Petri网的语言表达式生成算法,从而为Web服务系统的验证分析提供了有效工具。     

基于UML活动图和Petri网电子政务工作流建模研究

通过对电子政务系统中投诉管理子系统的描述,提出了一种基于UML活动图与Petri网的电子政务工作流建模方法。该方法具有完全图形化的表示和坚实的数学基础,是一种工作流建模和分析的理想工具。在建立电子政务工作流模型的基础上,对该方法进行了正确性论证,表明该方法对电子政务系统的实用性和有效性。     

基于SCPN的软件可靠性建模与分析

针对软件动态行为复杂难以建模,且可靠性难以评估的问题,提出一种基于随机有色Petri网SCPN(Stochastic Colored Petri Net)的软件可靠性建模与分析方法。在建立软件可靠性分析的元结构模型的基础上,分别建立软件可靠性分析的串联结构模型和并联结构模型,有效地描述了软件的静态结构和动态行为。以某工厂采购系统为目标系统,以Time NET4.0为平台,建立其基于SCPN的软件可靠性分析模型,仿真验证了所提方法的正确性和有效性。该方法可以为软件可靠性的早期评估提供理论指导。     

A distributed approach for fault detection and diagnosis based on Time Petri Nets

This paper proposes an algorithm for the model based design of a distributed protocol for fault detection and diagnosis for very large systems. The overall process is modeled as different Time Petri Net (TPN) models (each one modeling a local process) that interact with each other via guarded transitions that becomes enabled only when certain conditions (expressed as predicates over the marking of some places) are satisfied (the guard is true). In order to use this broad class of time DES models for fault detection and diagnosis we derive in this paper the timing analysis of the TPN models with guarded transitions. In this paper we also extend the modeling capability of the faults calling some transitions faulty when operations they represent take more or less time than a prescribed time interval corresponding to their normal execution. We consider here that different local agents receive local observation as well as messages from neighboring agents. Each agent estimates the state of the part of the overall process for which it has model and from which it observes events by reconciling observations with model based predictions. We design algorithms that use limited information exchange between agents and that can quickly decide “questions” about “whether and where a fault occurred?” and “whether or not some components of the local processes have operated correctly?”. The algorithms we derive allow each local agent to generate a preliminary diagnosis prior to any communication and we show that after communicating the agents we design recover the global diagnosis that a centralized agent would have derived. The algorithms are component oriented leading to efficiency in computation.     

Agent-based FMS control

Future manufacturing systems will be integrated into the networks of distributed resources, and at the same time, such systems will be capable of processing both knowledge and material. It will probably be required that manufacturing systems be agile, flexible, and fault-tolerant. Petri nets (PN) and object-oriented design (OOD) are used together in order to develop the integrated agent-based FMS control system. The flexible manufacturing system (FMS) consists of machines, workstations, and automated material handling system, distributed buffer storage sites and computer-based supervisory control, all which can be modeled as an agent in OOD with PN. This paper introduces the design of an agent-based FMS control system through PNs and evaluates the performance using timed placed Petri nets (TPPN). In order to do so, the agent control design, FMS structure has been evaluated in detail and the agent definitions have been submitted. The system includes the sharing and distribution of tasks among agents and the mentioned structure has been simulated by TPPN. The simulation procedure has been realized through Petri Net 2.0—MATLAB Demo Program [Mahulea CF, Motcovschi MH, Pastravanu O. Department of Automatic Control Industrial Informatics, Technical University “Gh. Asachi” of Iasi, Blvd., Mangeron 53A, 6600 Iasi, Romania, 〈http://www.ac.tuiasi.ro/pntool,pntool@ac.tuiasi.ro〉, 2004.]. Each case is modeled, and then the agent's machine processing time is considered in this program. As for the evaluation of the study, the system performance is assessed through the waiting time of the parts in queue and the task distributions.     

基于Poses++环境的Petri网仿真方法研究

由于Petri网存在“指数爆炸”和对外没有明确的输入输出接口的问题,限制了其在大型系统中的应用。Poses＋＋作为动态系统的仿真软件,充分体现了面向对象的编程思想。该文探讨了Petri网在Poses＋＋环境下的仿真方法,通过模块化处理和接口设计,解决了Petri网固有的对外没有输入输出接口的问题,并在一定程度上缓解了“指数爆炸”的难题,最后以机场系统为例,进行了建模、分析和仿真,仿真结果表明,模型正确,方法可行。     

工作流模型正确性验证过程中的模型简化问题

将工作流概念映射到Petri网后得到的工作流网的合理性验证过程比较复杂,容易出现状态空间爆炸的问题,需要对工作流模型进行简化。文章将工作流模型的简化过程分为两个步骤,首先将工作流模型转化为经典Petri网,再对经典Petri网进行简化。对于自由选择网可以采用自由选择语义的规约方法进行简化,而对于非自由选择网可以结合自由选择语义的规约方法和标准的Petri网简化方法进行简化。     

嵌入式系统协同设计中的扩展双变迁Petri网技术

在分析现有用于软硬件协同设计的Petri网技术的基础上，针对双变迁Petri网在描述数据操作方面存在的不足，给出了一种扩展双变迁Petri网，并结合实例进行了阐述。     

Compositional Petri Net Approach to the Development of Concurrent and Distributed Systems

In the paper, a formal model based on Petri nets is proposed in the context of a compositional approach to the development and analysis of complex concurrent and distributed systems. Mutlilabels of Petri nets are introduced allowing labeling a transition not only with a single symbol, but also with a multiset of symbols. Operations on multilabeled Petri nets—parallel composition and restriction—are defined. A definition of a Petri net entity is given based on the notion of multilabels. A Petri net entity is a Petri net with a set of multilabels, where each multilabel is regarded as an access point of the entity. The operation of entity composition is introduced. Equivalence of entities is defined based on bisimulation equivalence of Petri nets. It is shown that the equivalence relation is congruent with respect to entity composition. It is also demonstrated that the composition operation is commutative and associative.     

基于矩阵方法的有界Petri网系统的能观性分析

Petri网和有限自动机是离散事件动态系统的两类主要研究内容.而Petri网系统的能观性分析与判别是基于Petri网的实际系统设计、优化、监测及控制的重要基础.以往关于Petri网能观测性的研究缺乏定量化的充要判别条件.本文利用代数矩阵方法研究了带有输出的有界Petri网系统的能观性问题.首先,基于矩阵的半张量积,将带有输出的有界Petri网系统的动态行为以线性方程组的形式建立了数学模型.然后,针对初始标识和当前标识,介绍了两种能观性定义.最后,基于矩阵运算建立了关于有界Petri网系统能观性的几个充分必要条件,并给出严格证明.数值算例验证了理论结果.本文提出的方法实现了有界Petri网系统能观性的矩阵运算,易于计算机实现.     

基于Petri网的企业经营过程分析

本文首先对一般中小制造企业的经营制造过程进行分析,建立起企业从供应链到加工制造的基本框架,在此基础上,进一步建立起基于Petri网的系统模型。运用该Petri网模型,对企业的生产经营过程进行模拟和分析,根据分析结果可以对系统的经营过程进行优化和重新组合,降低企业生产成本,提高企业竞争力。     

有色Petri网的一种密码协议建模分析

密码协议是任何安全系统的基础,对它的设计越来越受到广大用户的关注.本文详细论述了文献[1]提到的一种密码协议,并使用有色Petri网对该协议建模分析,说明该设计的正确性.     

Petri网协议分析器

本文以基于Ｐｅｔｒｉ网的协议工作站为研究目标，阐述协议工程工作站的基本功能，简介ＥＰｒ／ＴＮ网系统，着重探讨作者实现的协议描述分析辅助工具ＰＥＳＡＴ的功能特点和实现技术，并以一个例子加以说明，最后作者指出ＰＥＳＡＴ的完善工作和理论协议工程工作站建立的前景。     

Petri网共享单链子网合成及其应用研究

本文针对多个企业共用一个加工厂加工某种产品这一类业务处理问题,提出了经由Petri网共享单链子网构成单链子网合成网的解决方案;给出了自由选择网（FC）,非对称选择网（AC）的共享单链子网合成网为各自相应网的充分条件;提出了共享单链子网合成Petri网保持结构活性的条件;本文的结果可为Petri网系统合成的静态和动态性质的考察提供有效途径,具有宽广的应用前景.     

基于矩阵模型的DEDS仿真

离散事件动态系统(DEDS)矩阵模型是一种逻辑运算与代数运算的混合系统。该矩阵模型给出了分析和仿真DEDS的严格框架,并用类似于控制理论状态方程的分析方法描述系统的动态行为。该文采用一种Petri网描述的适用于仿真的DEDS矩阵模型,用Matlab语言,对某炼钢厂炼钢连铸生产过程进行了实例研究。该方法比一般Petri网分析法简洁、完备,并有严密的数学描述和分析手段。