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     

Protocol Representation with Finite-State Models

A three-layer model of a computer network is used to introduce the concept of interface and of end-to-end protocols. Using a simple interface protocol as example, finite state automaton and Petri nets are introduced. The idea of an interface machine is rejected and the problems related to the transmission medium are approached. End-to end protocols request a global model which includes two local models and a transmission medium model. However, the local model has to be generalized. This eventually leads to the association of the state of the automaton with a context. Petri nets have also to be expanded. Models presented here have been successfully used for modeling transport protocols.     

Stochastic Petri nets: Properties, applications and tools

This paper presents a survey on stochastic Petri nets. A stochastic Petri net is first and foremost a Petri net, whose places represent resources and transitions represent operations. Random time variables attached to transitions are associated with random operation durations. The stochastic behavior must be completely defined by a set of rules associated with the choice of the next transition to be fired in a given marking, the memory properties of the time already spent for a given operation. We introduce some of the main stochastic Petri nets classes, and we give theoretical results associated with conservation properties, ergodic properties and computational methods leading to exact and approximated solutions. From a practical point of view we present the modeling example of a bus allocation and existing software tools.     

Modeling and simulation of an electronic component manufacturingsystem using hybrid Petri nets

Modelling and analysis for the design and operation of manufacturing systems is a vital need. For semiconductor manufacturing systems, which are large scale systems, discrete Petri nets do not constitute an adequate tool for modeling and analysis. In fact, use of discrete Petri nets is confronted with tile state explosion and the high cost of simulation. In this paper, hybrid Petri nets are presented as powerful tools for modeling and simulation of semiconductor manufacturing systems. This model has been used for modeling and simulation of a real life electronic components manufacturing system. It provides an accurate and first simulation of this system     

Constructing and Refining Large-Scale Railway Models Represented by Petri Nets

A new method for rapid construction of large-scale executable railway models is presented. Computer systems for railway systems suffer from poor integration and lack of explicit understanding of the large amount of static and dynamic information in the railway. In this paper, we give solutions to both problems. It is shown how a component-oriented approach makes it easy to construct and refine basic railway models by effective methods, such that a variety of models with important properties can be maintained within the same framework. Basic railway nets are refined into several new kinds: nets that are safe, permit collision detection, include time, and are sensitive to its surroundings. Since the underlying implementation language is Petri nets, large expressibility is combined with simplicity, and in addition, the analysis of the behavior of railway models comes gently.     

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     

Microprogramming implementation of timed Petri nets

This paper describes a method to implement restricted timed Petri nets by microprograms. These timed Petri nets are used to represent control parts of VLSI systems to produce sequences of control signals that evoke the operations of a corresponding data part. The proposed method consists of a set of transformation algorithms which have been implemented as parts of CAMAD, an integrated design aid system. We have also studied the problem of microprogram optimization, for example, how to reconstruct the control structure of a VLSI system so as to produce better microprograms.     

基于层次实时有色Petri网的实时系统建模与分析方法研究

Petri网是一种基于图形进行模拟和分析的数学工具,能够描述系统的异步和并发行为,但是现有高级Petri网不能对嵌入式实时系统进行完整的模拟与实时性分析。该文首先通过扩展有色Petri网提出了层次实时有色Petri网模型,然后描述了嵌入式实时系统的建模和实时性分析方法。最后,将该文提出的方法应用于硬实时系统列车通信网络MVB总线控制器的建模和实时性分析过程,仿真和分析结果表明,该方法能够满足列车通信网络系统设计对MVB总线控制器的功能验证和实时性分析需求。     

A modeling framework to evaluate performability parameters ingracefully degrading systems

A systematic approach to modeling and assessing gracefully degrading systems, exploiting the formalism offered by Petri nets, is provided. The procedure followed is based on the definition of some fundamental modules, the composition of which allows a complete model of the system to be obtained. The model can then be solved by computer simulation or analytically by means of a class of Petri nets to obtain interesting performability parameters either at steady state or when the system is time-varying. A number of real cases are examined and the results obtained are described     

Comparing ladder logic diagrams and Petri nets for sequencecontroller design through a discrete manufacturing system

Design methods for sequence controllers play a very important role in advancing industrial automation. The increasing complexity and varying needs of modern discrete manufacturing systems have challenged the traditional design methods such as the use of ladder logic diagrams (LLDs) for programmable logic controllers. The methodologies based on research results in computer science have recently received growing attention by academic researchers and industrial engineers in order to design flexible, reusable, and maintainable control software. Particularly, Petri nets are emerging as a very important tool to provide an integrated solution for modeling, analysis, simulation, and control of industrial automated systems. This paper identifies certain criteria to compare LLDs and Petri nets in designing sequence controllers and responding to the changing control requirements. The comparison is performed through a practical system after introducing “real-time Petri nets” for discrete-event control purposes. The results reported in this paper will help: (a) further establish Petri net based techniques for discrete-event control of industrial automated systems; and (b) effectively convince industrial practitioners and researchers that it is worthy and timely to consider and promote the applications of Petri nets to their particular discrete-event control problems     

Design of industrial automated systems via relay ladder logicprogramming and Petri nets

For the past few decades, programmable logic controllers (PLCs) using relay ladder logic (RLL) programming have been the workhorse for controlling event-driven industrial automated systems. RLL proved to be flexible compared to the hardwired RLL control implementation, due to its feature of software implementation. As automated systems become more complex, they also become more difficult to understand and maintain. It takes tremendous effort to accommodate specification changes (which are becoming frequent) to meet today's flexible automation needs. Several methods are emerging to overcome the shortcomings of RLL. Petri nets (PNs), initially proposed as a modeling tool, have been developed as such a method. This paper adopts an industrial-scale system to compare RLL and PN design methods so that the advantages of PN-like approaches are fully recognized. The criteria are: (i) the understandability that relates to the ability to evaluate the programmed logic, to verify its correctness and to maintain the control system, and (ii) the flexibility that relates to the easy modification of logic when the specification changes. This network takes an existing industrial system, conducts discrete event control designs by using both RLL programming and PN methods, and performs a comparative study on them. Together with previous comparison results using small-scale systems, the results of this study support that PN-like advanced discrete event control design methods are better than RLL in terms of the understandability and flexibility of the resulting control design     

用Petri网对点击拨号业务的建模

该文提出一种将协议转换方法学和Petri网理论相结合来研究应用层协议转换的新方法。按照协议转换方法学的流程,对IIN(Internet Intelligent Network)模型中的点击拨号(CTD)业务进行分析。在用Petri网对CTD业务的建模过程中提炼出通用的Petri网模型协议转换耦合原则,丰富了协议转换方法学的内容。利用Petri网的分析能力分析了CTD业务协议转换模型的特性,达到了检错纠错的目的。 在该方法的指导下开发了业务控制网关(SCGF)和CTD业务,证明了这种新方法的可行性和适用性。     

Petri net as a modeling tool

Over the last decade, Petri nets have emerged as a most suitable, powerful and widely acceptable modeling tool for representing and studying the asynchronous concurrent hardware (or software) systems/processes. Petri nets can be viewed as formal automata or as an automation which can generate the formal languages or a model to analyse and synthesize various kinds of systems. The structure of Petri nets, their markings, extensions and subclasses are briefly discussed. Several examples of Petri net models of computer hardware and software are presented. Various applications of reachability concepts are also given.     

基于随机高级Petri网的ATM网络接纳控制过程模型

本文提出了一个ＡＴＭ网络的接纳控制过程模型，此模型是基于随机高级Ｐｅｔｒｉ网的层次模型方法。在复杂的ＡＴＭ网络的接纳控制过程模型中，使用了从顶向下的模型方法。在模型的性能分析中，则采用了从底向上的分解、压缩的方法。这种方法简化了复杂系统模型的状态空间爆炸问题。     

Modeling and Performance Evaluation of Inventory Systems Using Batch Deterministic and Stochastic Petri Nets

This paper presents our work on modeling and performance analysis of inventory systems using batch deterministic and stochastic Petri nets (BDSPNs). It addresses issues frequently raised by industrial companies, but did not receive enough attention by the Petri nets (PNs) community in spite of its important role in the study of discrete event systems. The BDSPN is a new class of PNs capable of describing the synchronization of discrete and batch token flows in discrete batch processes. Such processes appear in inventory systems or more general supply chains where materials are purchased in finite discrete quantities (batches of different sizes), and many operations such as inventory replenishment and customer order fulfillment are usually performed in a batch way because of the batch nature of customer orders and/or in order to take advantages of the economies of scale. In this paper, the BDSPN model is formally introduced, and its conflict resolutions of transitions and batch firing indexes are addressed. The model is then applied to the modeling and performance evaluation of various inventory systems. Analytic performance evaluation techniques are developed for the model with illustrative applications to the inventory systems. Our study shows that the model is powerful for both modeling and performance evaluation of the systems.     

A new formulation for state equation representation for Petri nets

A new algorithm for determination of state equations for Petri nets has been proposed. The proposed algorithm results in state equations similar to the state equations for linear sequential machines. All Petri nets may not be represented in the form of linear sequential machines. The resulting state equations are different from Petri net state equations and include output equations used in control theory literature.     

Differential Petri net models for industrial automation and supervisory control

Supervisory control systems play a central role in modern industrial automation. However, control theory has recently made significant advances in modeling mixed continuous/discrete event systems ("hybrid control systems"), whose typical instantiations include the industrial supervisory controller. This article shows how differential Petri nets, a model for hybrid control systems, can be used to represent industrial supervisory systems in a unified way. Typical industrial automation tests can be modeled, whereas the effect of communication protocols and software can be straightforwardly included using conventional Petri nets. Therefore, a global model for the operation of an industrial control system can be formed and its behavior analyzed.