Algebras of discrete event models

The authors consider discrete event models (DEMs) that describe logical system behavior, i.e. mathematical models that represent the set of traces of sequences of events that the system can execute. Examples of DEM formalisms include state machines, Petri nets, and Hoare's communicating sequential processes. All these formalisms are algebras, i.e. a set of models together with operators that combine models to form other models in ways in which real systems are interconnected. A general approach toward constructing model algebras is proposed. The approach covers both deterministic and nondeterministic models, and it can be tailored to recover existing formalisms and to obtain model families     

有界Petri网等价性的判定算法

Petri网语言是系统行为分析的一种重要工具,为了分析有界Petri网的行为等价,借助于有限自动机的等价性问题和算法,研究了有界Petri网的等价性问题和算法.定义了带标注Petri网语言等价性,证明了带标注的有界Petri网到有限自动机的等价转化,给出了判定有界Petri网的等价性算法,为模拟系统的性能比较提供了处理方法.     

FunState-an internal design representation for codesign

In this paper, an internal design model called FunState (functions driven by state machines) is presented that enables the representation of different types of system components and scheduling mechanisms using a mixture of functional programming and state machines. It is shown how properties relevant for scheduling and verification of specification models such as Boolean dataflow, cyclostatic dataflow, synchronous dataflow, marked graphs, and communicating state machines as well as Petri nets can be represented in the FunState model of computation. Examples of methods suited for FunState are described, such as scheduling and verification. They are based on the representation of the model's state transitions in the form of a periodic graph. The feasibility of the novel approach is shown with an asynchronous transfer mode switch example     

一种基于逻辑Petri网的过程挖掘方法

逻辑Petri网是抑制弧Petri网和高级Petri网的抽象和扩展,可在过程挖掘中简洁准确的表示活动之间复杂的业务逻辑关系.本文在传统Petri网挖掘方法的基础上,为了进一步提高复杂系统挖掘模型的简洁度和拟合度,尤其是对并行活动间存在复杂与或关系的系统,提出了一种基于逻辑Petri网的过程挖掘方法,并给出了逻辑Petri网中逻辑变迁的挖掘算法.它可以充分挖掘活动之间的业务逻辑,并且业务逻辑可用逻辑表达式表示.通过与相应Petri网模型的实例比较分析,例证了本文方法的正确性和有效性,且逻辑Petri网模型更加适合日志行为.     

Combined use of finite-state machines and petri nets for modelling communicating processes

In order to model and verify systems of concurrent processes (such as those involved in communication protocols), finite-state machines and Petri nets can be used as local and global models, respectively. The problem of composing a set of communicating finite-state machines into a single global Petri net is considered in the letter with special attention to the case of more than two processes.     

模糊Petri网的推理式算法在雷达电子战装备效能评估中的应用

基于模糊Petri网，研究了约束条件下的推理算法，将模糊Petri网与矩阵运算相结合．给出了雷达电子战装备效能评估的形式化推理算法。推理过程采用矩阵运算实现，并充分利用了模糊Petri网的并行处理能力．最后利用MATLAB语言对仿真实例进行分析计算，结果表明孩方法简单、快速和有效．不仅能评估单台电子战装备的作战效能，还能对同类型的多台装备进行作战效能的优劣排序。     

Computation of Performance Bounds for Real-Time Systems Using Time Petri Nets

Time Petri nets (TPNs) have been widely used for the verification and validation of real-time systems during the software development process. Their quantitative analysis consists in applying enumerative techniques that suffer the well known state space explosion problem. To overcome this problem, several methods have been proposed in the literature, that either provide rules to obtain equivalent nets with a reduced state space or avoid the construction of the whole state space. In this paper, we propose a method that consists in computing performance bounds to predict the average operational behavior of TPNs by exploiting their structural properties and by applying operational laws. Performance bound computation was first proposed for timed (Timed PNs) and stochastic Petri nets (SPNs). We generalize the results obtained for Timed PNs and SPNs to make the technique applicable to TPNs and their extended stochastic versions: TPN with firing frequency intervals (TPNFs) and extended TPNs (XTPNs). Finally, we apply the proposed bounding techniques on the case study of a robot-control application taken from the literature.     

同步时序电路的增广Petri网分析

本文应用带抑制弧的增广Petri网建立了基本门电路和常用触发器的Petri网模型;并运用该模型描述了同步时序电路;提出了增广Petri网的授权矩阵、状态转移方程和触发器次态与变迁授权条件的关系。在此基础上可对同步时序电路描述和分析,并用实例证明了该方法的有效性。     

自适应OFDMA系统无线资源管理的CPN建模与仿真

基于自适应OFDMA系统,对多业务系统中基于总发射功率最小化的无线资源管理问题进行研究,并使用着色Petri网(CPN,coloured Petri nets)以及CPN分析工具CPN Tools对其进行建模。采用Monitor监控器对模型进行仿真分析,并将仿真结果与随机Petri网(SPN,stochastic Petri nets)模型以及基于吞吐量最大化的CPN模型进行比较,验证了该系统模型的正确性和优越性。     

基于直觉模糊Petri网的知识表示和推理

针对模糊Petri网存在隶属度单一的问题,将直觉模糊集理论与Petri网理论相结合,构建直觉模糊Petri网(Intuitionistic Fuzzy Petri Nets,IFPN)模型,用于知识的表示和推理.首先构建了IFPN模型,并将其应用于知识的表示,通过在模型中引入抑止转移弧,解决了否命题的表示问题.其次提出了基于矩阵运算的IFPN推理算法,通过修改变迁触发后token值的传递规则,解决了推理过程中的事实的保留问题;通过修改变迁的触发规则,抑制了变迁的重复触发.最后对推理算法进行了分析,并举例验证了提出的IFPN模型及其推理算法的可行性,结果表明IFPN是对FPN的有效扩充和发展,其对推理结果的描述更加细腻、全面.     

Modeling, analysis, simulation, scheduling, and control ofsemiconductor manufacturing systems: A Petri net approach

This paper presents a Petri net approach to modeling, analysis, simulation, scheduling, and control of semiconductor manufacturing systems. These systems can be characterized as discrete event systems that exhibit sequential, concurrent, and conflicting relations among the events and operations. Their evolution is dynamic over time. The system complexity is tremendous owing to the complex semiconductor manufacturing processes and test procedures. A formal approach such as Petri nets enables one to describe such complex discrete event systems precisely and thus allows one to perform both qualitative and quantitative analysis, scheduling and discrete-event control of them. This paper also serves as a tutorial paper. It briefly reviews applications of Petri nets in semiconductor manufacturing automation. It then introduces definitions and concepts of Petri nets. It proceeds with a discussion of basic Petri net modules in system modeling, a modeling method and a practical system's modeling example. Next, the paper presents their properties and their implications in manufacturing systems, as well as their analysis methods. Timed Petri nets are introduced for system simulation, performance evaluation, and scheduling purposes. An application-oriented case study is presented. Finally, the paper concludes with the active research areas in applying Petri nets to design of semiconductor manufacturing systems     

基于Petri网局部性的极大冲突集枚举算法

冲突是Petri网研究的重要主题.目前Petri网冲突研究主要集中于冲突建模和冲突消解策略,而对冲突问题本身的计算复杂性却很少关注.提出Petri网的冲突集问题,并证明冲突集问题是NP（Non-deterministic Polynomial）完全的.提出极大冲突集动态枚举算法,该算法基于当前标识的所有极大冲突集,利用Petri网实施局部性,仅计算下一标识中受局部性影响的极大冲突集,从而避免重新枚举所有极大冲突集.该算法时间复杂度为O（m²n）,m是当前标识的极大冲突集数目,n是变迁数.最后证明自由选择网、非对称选择网的极大冲突集枚举算法复杂度可降至O（n²）.极大冲突集枚举算法研究将为Petri网冲突问题的算法求解提供理论参考.     

Simplification of Boolean functions through petri nets

A technique exploiting the modern concepts of Petri nets for simplification of Boolean functions is proposed. The firing concept of Petri nets has been utilized to give a Petri net interpretation to certain properties of switching algebra. These Petri net interpreted properties are then used for the simplification process. Unlike the existing method, the proposed technique does not require the functions to be expressed explicitly in a canonical form. This alleviates the computational efforts. It is simple and amenable for computer programming implementation.     

Modeling, qualitative analysis, and performance evaluation of theetching area in an IC wafer fabrication system using Petri nets

Integrated circuit (IC) wafer fabrication systems can be characterized as discrete event systems. Petri nets are tools that have been successfully used to model and analyze such systems. This paper reports a project of applying Petri net methodologies to detailed modeling, qualitative analysis, and performance evaluation of the etching area in a real-world IC wafer fabrication system located in Taiwan's Hsinchu Science-Based Industrial Park, To tackle the problem of building a large and complex system model, a synthesis technique is used. The resultant extended net model is checked for important qualitative properties in manufacturing. A simple control policy for deadlock prevention is proposed. To obtain performance measures, simulation is used. The simulation result shows that except a small number of machines, the errors between the simulated and actual utilizations are less than 5%, The validated model can be used to answer many “what-if” questions, such as predicting the maximal throughput and bottleneck machines     

Scheduling of semiconductor test facility via Petri nets and hybridheuristic search

This paper proposes and evaluates two Petri net-based hybrid heuristic search strategies and their applications to semiconductor test facility scheduling. To reduce the setup time, such as the time spent to bring the test facilities to the required temperatures, scheduling multiple lots for each job type together is desirable. Petri nets can concisely model multiple lot sizes for each job, the strict precedence constraints, multiple kinds of resources, concurrent activities and flexible routes. To cope with the complexities for multiple lots scheduling, this paper presents two Petri net-based hybrid heuristic search strategies. They combine the heuristic best-first strategy with the controlled back tracking strategy based on the execution of the Petri nets. The obtained scheduling results are compared and analyzed through a small-size test facility. The better algorithm is also applied to a more sizable facility containing types of resources with a total of 79 pieces and 30 jobs. The future work includes the real-time implementation of the proposed method and scheduling results in real industrial settings     

随机Petri网同步并发行为的定量分析方法

传统的随机Ｐｅｔｒｉ网定量分析都是针对顺序行为的，而并发描述却是Ｐｅｔｒｉ网引以为骄傲的内容，这就形成Ｐｅｔｒｉ擅长描述并发，却没有在并发活动下分析系统的手段。本文研究同步并发机制下随机Ｐｅｔｒｉ网定量分析法，旨在改进传统的分析方法，使Ｐｅｔｒｉ网真正成为并发系统建模与分析的有力工具。     

非状态空间搜索的电路面积优化

文章给出了一个通过去除冗余的方法，实现了电路面积优化的算法。该算法通过电路网络结点值的计算来找到相容的冗余，可以避免由遍历状态空间造成的计算量呈指数增长，同时，所在被找到的冗余将在一次全部除掉。变换后的电路延迟将不会超过初始电路。算法将计算相容时序的冗余，并通过在电路中传播它们来简化电路。实验比较证明，这一算法对大电路是有效的。     

Modeling and performance analysis of cluster tools using Petri nets

The performance of cluster tools is gaining ever-increasing importance as the semiconductor industry migrates to larger wafer sizes, and smaller device geometries. Customers demand higher throughput-to-footprint ratios for semiconductor equipment. Cluster tool throughput is the outcome of complex interactions of various subsystems, and there is a critical need for appropriate tools that aid in understanding these interactions, and their effects on throughput. Current methods for throughput analysis are not very well oriented toward understanding the dynamics in cluster tool processing. In this paper we present a procedure to model cluster tools using Petri nets. These models help designers to comprehend the flow of wafers during processing. While Petri nets have been used extensively in the modeling and analysis of diverse manufacturing processes/systems, this to the best of our knowledge is the first attempt to specifically model cluster tools. A state cycle analysis is discussed next; this method enables equipment designers to extract steady state throughput information, as well as understand the interplay of subsystems during the wafer Row. Two example configurations are used to illustrate Petri net-based model building and analysts. These two examples encompass a variety of design features found in the industry today, e.g., sequential and parallel processing, single and dual end effector robots, anticipatory and simple scheduling     

A parallel framework for the analysis of metal-flangedrectangular-aperture arrays

Computer-aided design of horn arrays, even by using state-of-the-art electromagnetic (EM) formulations, requires a considerable numerical effort and is, therefore, an ideal candidate for parallelization. We introduce a rigorous methodology, based on Petri nets and recursive bisection, in order to migrate a standard integral equation code toward parallel multiprocessor machines, following a data-flow design and a multiple-level parallelism. Significant (quasi-linear) speed-ups are demonstrated