基于分层Petri网的半导体生产线建模

论文提出了一种分层Petri网模型用于半导体生产线建模。首先,总结了Petri网在半导体生产线建模中的应用,继而给出了分层Petri网的定义及其建模过程。最后以一个典型的半导体生产线为例,进行该方法的应用研究。     

军用装备维修保障系统面向对象Petri网建模

Petri网模型是离散事件动态系统(DEDS)建模的有利工具，但传统的Petri网模型存在模型结构复杂、缺少时间描述等不足。该文在装备维修保障系统建模中，结合应用面向对象技术和有色Petri网、赋时Petri网理论，提出了将面向对象思想与赋时Petri网相结合进行装备维修保障系统建模的方法，并应用该方法对已有的空军通信导航装备维修保障系统Petri网模型进行了对象化和赋时改造，使得新建模型结构更加简约、直观，有利于扩展和仿真实现，并且具备时间描述功能。     

模糊时间Petri网及扩展的模糊时间Petri网

网络实时系统对时间和QoS有严格要求，因此对设计、实现和测试的技术和工具都有很高的要求。模糊时间Petri网是将模糊集合理论用于不确定的或主观的时间信息的表示，在每个变迁上添加时间间隔约束对模糊时间Petri网进行扩展得到扩展的模糊时间Petri网，它是一种对网络实时系统进行建模和分析的形式化模型，Petri网数学理论基础能保证并发系统的可靠性和正确性。本文详细地介绍了模糊时间Petri网及可扩展的时间Petri网，可扩展的时间Petri网的网精简方法，使用design／CPN仿真，及使用EFTN对多媒体同步建模，并探讨了进一步研究的方向。     

面向对象的Petri网建模技术的研究

将面向对象的概念引入到Petri网建模技术中，对网进行分类与抽象，给对象模型的消息和方法赋予新的含义，并将Petri网扩展成具有输入与输出的开放式系统，从而形成了面向对象的Petri网建模技术（简称OPNe技术）。给出的OPNet建模技术的一般方法具有较大的实际意义。     

基于Petri网与SimEvents的半导体晶圆生产线建模与仿真

SimEvents与Petri网相结合是一种很好的复杂生产线建模仿真方法,应用这一方法建立了一条300mm晶圆生产线的仿真模型.描述了其Petri网模型建立的总体流程和各个详细步骤,以及在SimEvents环境下实现Petri网模型并进行仿真的关键技术.在此基础上,对晶圆生产的不同调度方案分别进行了仿真,并把仿真结果进行了比较,从而验证了仿真建模方法的正确性.     

基于流随机Petri网模型的可重入生产线稳定性分析

可重入生产线是作为芯片制造生产线模型被研究的，其特点是具有“可重入性”。该文基于流随机Petri网(Fluid Stochastic Petri Net,FSPN)对可重入生产线进行建模，并得到了一些相关的稳定性结论。     

神光Ⅲ控制系统的故障建模与分析

应用混合随机Petri网对神光Ⅲ控制系统的故障进行了建模，并应用Visobj Net对建立的故障模型进行了仿真分析。网络化控制系统是一个离散和连续相结合的混合动态系统，具有动态、并发及同步等特征；神光Ⅲ控制系统就是网络化控制技术在武器装备上的一个典型应用；对于复杂系统的建模和分析，Petri网是一个非常有效的工具。Petri网已经被证明是离散事件或异步系统很好的建模和分析工具，混合随机Petri网是Petri网的一个扩展，具有强大的建模功能。仿真结果表明，所建立的模型是正确的。     

基于Petri网的电子政务工作流模型研究

设计了一种基于Petri网扩展的、用于复杂工作流模型设计的建模方法及其相关规则。并且通过电子政务系统的网上审批子系统为例,详细阐述了用此方法及其相关规则构建Petri网工作流模型的过程。最后通过Petri网理论对模型进行了正确合理性分析,并对网上审批子系统的资源分配情况进行了定量分析。此建模方法简化了Petri网的建模过程,并保证了正确性和合理性资源分配的分析结果对合理的进行资源分配有指导作用。     

基于扩展混合Petri网的晶圆制造系统建模

提出了一种扩展的面向对象混合Petri网（EOHPN）的建模方法：针对晶圆制造系统的复杂性，在EOHPN模型中融入了面向对象的抽象机制；为了减少系统建模的复杂性，引入混合Petri网并用面向对象建模技术作了扩展。在定义EOHPN模型的基础上，作了对象模型的拓展。用实例描述了基于EOHPN的晶圆制造系统的建模过程，验证了模型在处理系统建模时的有效性。     

基于Petri网的Stateflow建模方法的研究与应用

以输送机器人生产线控制系统设计为例,提出将基于Petri网的Stateflow建模仿真方法应用于PLC控制软件的开发过程中。首先利用Petri网对系统控制功能进行分析,结果表明系统在运行时序上存在并行冲突,采用Petri网的数学建模功能协调冲突后,通过可达图验证了此Petri网模型是安全无死锁的;其次在上述基础上将Petri网与Stateflow组成元素相对应并进行转换;最后利用Simulink构建模型进行系统仿真分析,证明输送机器人生产线控制逻辑正确,状态转移有效。     

Optimal deadlock avoidance Petri net supervisors for automated manufacturing systems

Deadlock avoidance problems are investigated for automated manufacturing systems with flexible routings. Based on the Petri net models of the systems, this paper proposes, for the first time, the concept of perfect maximal resourcetransition circuits and their saturated states. The concept facilities the development of system liveness characterization and deadlock avoidance Petri net supervisors. Deadlock is characterized as some perfect maximal resource-transition circuits reach their saturated states. For a large class of manufacturing systems, which do not contain center resources, the optimal deadlock avoidance Petri net supervisors are presented. For an general manufacturing system, a method is proposed for reducing the system Petri net model so that the reduced model does not contain center resources and, hence, has optimal deadlock avoidance Petri net supervisor. The controlled reduced Petri net model can then be used as the liveness supervisor of the system.     

Optimal deadlock avoidance Petri net supervisors for automated manufacturing systems

Deadlock avoidance problems are investigated for automated manufacturing systems with flexible routings. Based on the Petri net models of the systems, this paper proposes, for the first time, the concept of perfect maximal resource-transition circuits and their saturated states. The concept facilitates the development of system liveness characterization and deadlock avoidance Petri net supervisors. Deadlock is characterized as some perfect maximal resource-transition circuits reaching their saturated states. For a large class of manufacturing systems, which do not contain center resources, the optimal deadlock avoidance Petri net supervisors are presented. For a general manufacturing system, a method is proposed for reducing the system Petri net model so that the reduced model does not contain center resources and, hence, has optimal deadlock avoidance Petri net supervisor. The controlled reduced Petri net model can then be used as the liveness supervisor of the system.     

A generalized Petri net modeling approach for the control of re-entrant flow semiconductor wafer fabrication

Re-entrant flow manufacturing lines, such as occur in semiconductor wafer fabrication, are characterized by a product routing that consists of multiple visits to a workstation or group of workstations during the manufacturing process. In this paper, a modeling approach is based on the use of generalized Petri nets for a re-entrant flow manufacturing line is presented. Specifically, three Petri net models representing a re-entrant flow line with three work centers and six machines are modeled. How these models may be used to represent a variety of queuing disciplines and work release policies is discussed.     

A Petri-Net Approach to Modular Supervision With Conflict Resolution for Semiconductor Manufacturing Systems

In a semiconductor manufacturing system, particular human operations may violate desired requirements and lead to destructive failure. For such human-in-the-loop systems, this paper proposes a supervisory framework which guarantees that manual operations meet required specifications so as to prevent human errors in operation using Petri nets. Moreover, a modular technique with an intersection mechanism is proposed in order to cope with the state-space explosion problem of large-scale systems. A rapid thermal process in semiconductor manufacturing systems is provided to show the practicability of the proposed approach. Note to Practitioners - This work was motivated by the requirement of remote monitoring and supervision of semiconductor manufacturing systems. In such human-in-the-loop and large-scale systems, certain human operations may violate desired safety requirements and result in catastrophic failure. Moreover, the overall complexity of most existing Petri net modeling and analysis approaches significantly increases with the size of the considered systems. This paper suggests a modular supervisory scheme for modeling and synthesis of supervisory agents using Petri nets. The proposed method contributes a promising tool for preventing abnormal operations from being carried out to semiconductor manufacturing systems which, if appropriately modified, may be also applied to other types of discrete event systems.     

离散制造装配系统的活性控制1)

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.     

离散制造装配系统的活性控制

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.     

一种制造系统模型及其简化

本文采用随机Petri网的方法,建立制造系统基本单元模型。在保持系统可靠性等特性的前提下,对单一加工制造单元、串行加工系统这两种基本系统模型进行有效变换,从而最大程度地简化模型,降低模型的复杂度。     

Combining flow control techniques with Petri nets methodologies for real-time control of FMS

This paper focuses on the combination of the flow control techniques with Petri net methodologies. The flow control techniques are improved in order to handle multiple routing. A general and unified Petri net formalism is introduced. The integration of the flow control techniques with an interpreter based on this new Petri net formalism is discussed. Results for simulation of a very flexible manufacturing system are provided.     

A deadlock prevention approach for flexible manufacturing systems with uncontrollable transitions in their Petri net models

Deadlocks are a highly undesired situation in a fully automated flexible manufacturing system, whose occurrences are tied to the existence of shared resources that are competed by different production processes. In the last two decades, a fair amount of research has been done on deadlock analysis and control for flexible manufacturing systems, leading to a variety of strategies in the literature. Petri nets are a promising mathematical tool to handle deadlock problems in flexible manufacturing systems. However, most deadlock control policies based on a Petri net formalism assume that all the transitions in a plant model are controllable. However, uncontrollability of events are a natural feature in a real‐world production system. This paper proposes a deadlock prevention policy for a class of Petri nets by considering the existence of uncontrollable transitions. Deadlocks are prevented by adding monitors to a plant Petri net model, whose addition does not inhibit the firings of uncontrollable transitions. Linear programming techniques are employed to find transitions to which a monitor points in order that a more permissive liveness‐enforcing Petri net supervisor can be found. A number of manufacturing examples are used to demonstrate the proposed methods. Copyright © 2011 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society