Polynomial Approach to Optimal One-wafer Cyclic Scheduling of Treelike Hybrid Multi-Cluster Tools via Petri Nets

A treelike hybrid multi-cluster tool is composed of both single-arm and dual-arm cluster tools with a treelike topology. Scheduling such a tool is challenging. For a hybrid treelike multi-cluster tool whose bottleneck individual tool is process-bound, this work aims at finding its optimal one-wafer cyclic schedule. It is modeled with Petri nets such that a onewafer cyclic schedule is parameterized as its robots' waiting time. Based on the model, this work proves the existence of its onewafer cyclic schedule that features with the ease of industrial implementation. Then, computationally efficient algorithms are proposed to find the minimal cycle time and optimal onewafer cyclic schedule. Multi-cluster tool examples are given to illustrate the proposed approach. The use of the found schedules enables industrial multi-cluster tools to operate with their highest productivity.      

基于混合法的叶片FMS控制系统研究

本文基于Ｐｅｔｒｉ网建模的混合法，建立了叶片ＦＭＳ控制系统活的、安全和可逆的Ｐｅｔｒｉ网模型，应用该模型开发了叶片ＦＭＳ控制系统仿真器，可成功地避免叶片ＦＭＳ的死锁产生。     

自动组合装置赋时有色Petri网模型的建立分析

半导体制造中的自动组合装置是半导体制造的关键设备和瓶颈设备.对其性能进行量化的直观的分析对于半导体制造的效率和成本预测具有重要意义.文章阐述了如何利用Aarhus大学开发的CPN Tools对单臂双处理仓的自动组合装置建立赋时有色的佩特里网模型.文中按照不同建模思想建立起抽象型和具象型两个结构不同的模型,通过比对进行验证,最后利用CPN Tools自带的仿真功能进行仿真得出模拟运行的结果.文中的研究方法和结论对于复杂的自动组合装置的有色佩特里网的分析具有一定的参考价值.     

Process vs resource‐oriented Petri net modeling of automated manufacturing systems

Since the 1980s, Petri nets (PN) have been widely used to model automated manufacturing systems (AMS) for analysis, performance evaluation, simulation, and control. They are mostly based on process‐oriented modeling methods and thus termed as process‐oriented PN (POPN) in this paper. The recent study of deadlock avoidance problems in AMS led to another type of PN called resource‐oriented PN (ROPN). This paper, for the first time, compares these two modeling methods and resultant models in terms of modeling power, model complexity for analysis and control, and some critical properties. POPN models the part production processes straightforwardly, while ROPN is more compact and effective for deadlock resolution. The relations between these two models are investigated. Several examples are used to illustrate them. Copyright © 2010 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society     

基于随机Petri网的机群系统可信赖性研究

随机Petri网(SPN)是一种灵活有力的建模工具,在可信赖性研究方面已形成较为成熟的理论体系.采用SPN网对机群系统前端分配器及后端服务器进行建模,通过在系统建模时对前端分配器给予必要的修复保证,给出整个机群系统的SPN模型,在模型分析的基础上给出了机群系统的可信赖性参数,并对模型进行了仿真分析.仿真结果表明,在对关键系统前端分配器给予修复保证后,系统模型的稳态可用性将大大提高.     

晶圆重入加工的组合设备终止暂态的调度与分析

晶圆重入是半导体组合设备加工中典型的复杂加工工艺,分析和优化暂态加工过程对于晶圆重入加工具有重要意义.为了满足加工需求和提高组合设备的加工性能,基于稳态重入加工的双臂组合设备Petri网模型和1-晶圆周期调度策略,采用虚拟晶圆的加工模式分析了系统的终止暂态过程,讨论了系统终止暂态的加工时间分布,并给出相应的解析式进行描述.利用eM-Plant仿真平台建立了重入加工的双臂组合设备终止暂态的仿真模型,并用例子验证了1-晶圆周期调度的可行性及解析式的有效性,为研究晶圆重入加工过程的优化提供了有效方法和手段.     

具有清洗工艺的单臂组合设备终止暂态调度

随着多品种小批量生产模式的普及,导致了组合设备频繁的暂态加工过程.为了提高组合设备的生产柔性,同时考虑晶圆驻留时间约束和腔室清洗时间约束,研究了单臂组合设备的终止暂态调度问题.首先,提出了 1-周期清洗工艺的暂态调度规则,并采用了面向资源的Petri网对单臂组合设备的终止暂态过程进行建模,引入避免死锁的变迁触发规则;其次,根据系统的终止暂态时间特性并考虑不同的调度情形,建立了终止暂态调度的线性规划模型;最后,通过实例验证了该方法的可行性.实验结果表明,与运用改进拉式策略的虚拟晶圆方案相比,该调度方案可有效地减少组合设备终止暂态的完工时间,并满足晶圆制造的工艺要求.     

应用离散事件系统控制理论求解生产调度的新方法

众所周知, 生产调度问题属组合优化问题, 一般来说不存在求得精确最优解的多项式算法. 因此, 对于大规 模调度问题, 人们应用启发式算法和元启发式算法以企求得满意解. 在实际的应用中, 许多工业过程需要满足严格 的工艺约束. 对于这类过程的调度问题, 很难应用启发式算法和元启发式算法, 因为这些方法难于保证所求得调度 的可行性. 为了解决这一问题, 本文以半导体芯片制造中组合设备的调度问题作为例子, 介绍了一种基于离散事件 系统控制理论的生产调度新方法. 利用Petri网建模, 任何违反约束的状态均被描述为非法状态, 而使非法状态出现 的调度则是不可行调度. 通过可行调度的存在性分析, 该方法获得可行解空间并将调度问题转化为连续优化问题, 从而可以有效求解. 并且指出, 该方法可以应用于其他应用领域.     

View Transformation in Visual Environments applied to Algebraic High-Level Nets

Graph transformation systems are a well-founded and adequate technique to describe the syntax of visual modeling languages and to formalize their semantics. Moreover, graph transformation tools support visual model specification, simulation and analysis on the basis of the rich underlying theory.Despite the benefits of model validation by simulation, sometimes it is preferable for users to see the model's behavior not in the abstract layout of the formal model, but as scenarios presented in the layout of the specific application domain. Hence, we propose the integration of a domain-oriented animation view with the model transformation system. An animation view allows to define scenario animations in a systematic way based on the formal model. The specification of the well-known Dining Philosophers system as algebraic high-level Petri net serves as running example for the extension of the model by an animation view and the derivation of animation rules from the model transformation system. A scenario animation then is obtained as transformation by applying the animation rules to model states. This visualizes the behavior of the model in the layout of philosophers sitting around a table and eating with chopsticks. A prototypical implementation of the concepts in GenGED, a visual language environment, is presented.     

Cycle time analysis for wafer revisiting process in scheduling of single-arm cluster tools

Some wafer fabrication processes performed by cluster tools require revisiting. With wafer revisiting, a cluster tool is very difficult to be scheduled due to a large number of possible schedules for the revisiting process. Atomic layer deposition (ALD) is a typical process with wafer revisiting that should be performed by cluster tools. This paper discusses the scheduling problem of single-arm cluster tools for the ALD process. In scheduling such a system, the most difficult part is to schedule the revisit...     

Autonomy-subnet based structural synthesis and liveness guarantying policy of Petri net model of flexible manufacturing system

In this paper, an autonomous subnet based structural methodology forbottom-up synthesis of Petri Nets for Flexible Manufacturing Systems is proposed.Furthermore, the theoretical analysis of the model constructed by the method is carried byintensively using model's structural information, such as invariants, siphons, etc.. As aresult, the analysis leads us to draw the general conclusion that the model obtained isconservativeness and thus bound, and characterize its liveness in terms of zero-markingminimal siphons. It is based on model's structural information that distinguishes ourmethod from others. in line of this thought, a liveness guarantying policy for the obtainedmodel is proposed. Some control subnets are merged into the original model according tothe proposed synthesis rules in this paper to ensure that no minimal siphons are emptiedin any state, therefore the liveness is guaranteed. As a result, a live, conservative andrevertible Petri Nets is obtained. A practical example is also presented to     

Synthesis of deadlock prevention policy using Petri nets reachability graph technique

This paper proposes a subclass of generalized stochastic Petri net (GSPN) model, called TS³PR, which is modified the systems of simple sequential processes with resources (S³PR) with timed information. Based on the subclass of GSPN, a new deadlock prevention policy is developed by using reachability graph technique. The foundation of the new control policy is to manipulate all the dead states of the system nets. This study is able to change dead states into vanishing ones by additional immediate transitions. A live TS³PR model can then be obtained. It is worthwhile to notice that this study is different from adding additional control place policies in previous literature. Experimental results, indicate that our new control policy is with maximally permissive markings than conventional place‐control ones. As a result, we can infer that our proposed control policy seems to be used in Petri nets deadlocked systems. To our knowledge, this is the first work that employs the additional transitions to obtain the deadlock prevention policy. Copyright © 2010 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society     

广义随机Petri网在制造系统中的应用

介绍广义随机Petri网,通过把其状态分为隐状态和显状态并消去隐状态,使得计算复杂 度降低,并将其应用在一个制造系统模型上,使用禁止弧来消除制造系统的冲突.     

基于精炼操作的Petri网建模及其分析方法

针对复杂系统的Petri网建模及其分析问题,定义了Petri网的精炼操作及其相关的Petri网模型.基于序列投影,建立精炼Petri网与原网、子网间的动态行为关联关系,并分析了该精炼操作的相关动态性质,得到一组性质保持判据.最后,基于该方法实现了一个顺序资源共享系统的应用案例的建模及其分析.所提出的方法不仅为复杂系统的Petri建模提供了新的思路,而且有助于复杂Petri网模型的分析和验证.     

A deadlock prevention approach for a class of timed Petri nets using elementary siphons

To solve the problem of deadlock prevention for timed Petri nets, an effective deadlock prevention policy based on elementary siphons is proposed in this paper. Without enumerating reachable markings, deadlock prevention is achieved by adding monitors for elementary siphons, increasing control depth variables when necessary, and removing implicit, liveness‐restricted and redundant control places. The final supervisor is live. First, a timed Petri net is stretched into a stretched Petri net (SPN). Unchanging the system performance, each transition in the SPN has a unit delay time. Then the siphon‐control‐based approach is applied. Monitors computed according to the marking constraints are added to the SPN model to ensure all strict minimal siphons in the net invariant‐controlled. A liveness‐enforcing supervisor with simple structure can be obtained by reverting the SPN into a TdPN. Copyright © 2010 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society     

Design of liveness‐enforcing supervisors via transforming plant petri net models of FMS

This paper focuses on the deadlock prevention problems in a class of Petri nets, systems of simple sequential process with resources, S³PR for short. By structure analysis, we propose an approach that can transform a plant net model into a weighted S³PR (WS³PR) that is behaviorally equivalent to the plant model. The WS³PR is made to be live by properly reconfiguring its weight distribution such that its all strict minimal siphons are self‐max'‐controlled. The resulting WS³PR can serve as a liveness‐enforcing Petri net supervisor for the plant model after removing some idle and operation places. A live controlled system can be accordingly obtained by synchronizing a plant model and the places whose weights are regulated. This research shows that a small number of monitors is obtained, leading to more permissive behavior of the controlled system. Examples are used to demonstrate the proposed concepts and methods. Copyright © 2010 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society     

Cycle time analysis of dual-arm cluster tools for wafer fabrication processes with multiple wafer revisiting times

For some wafer fabrication processes, the wafers need to visit some processing modules for a number of times, which is referred to as the revisiting process. With wafer revisiting, it is very complicated to analyze the cycle time of a dual-arm cluster tool. Due to the fact that atomic layer deposition (ALD) process is a typical revisiting process in the semiconductor industry, study is conducted on cycle time analysis of dual-arm cluster tools for the ALD process with multiple revisiting times. The system is modeled by a type of Petri net. With this model, it is revealed that the system may never reach a steady state. Based on this finding, a method is presented to analyze the cycle time and analytical expressions are derived to calculate the cycle time for different cases. Several illustrative examples are given to show the applications of the proposed approach.     

一种基于代数语义的软件体系结构求精方法

软件体系结构是引导需求到实现的桥梁,目前在软件体系结构建模方法中主要分为形式化和非形式化两种。针对大型分布式系统的体系结构采用Petri网进行建模,兼顾了可视化操作和形式化的准确性,同时利用细化求精操作建立体系结构的层次模型,有效解决了状态空间爆炸问题。此外,在求精过程中为了保证用于下层求精的子网能准确表达上层行为规约,引入了进程代数来刻画Petri网的行为语义。最后,给出了进程项构造子网的算法及案例研究,并通过开源工具验证上述内容的正确性。     

基于Petri网的非相似余度飞控计算机可靠性分析

应用混合Petri网建立故障诊断模型,应用广义随机Petri网建立Boe ing 777非相似余度飞控计算机故障行为模型.描述了非相似余度系统的结构以及故障的产生和传播的动态过程,分析了该系统的可靠度和容错度,并有效地消除了瞬态故障对分析系统可靠性的影响.     

信标基底的可选择性在制造系统死锁控制中的应用

本文基于Petri网模型,讨论柔性制造系统的死锁控制问题.为了建立结构简单的Petri网控制器,本文在以前的工作中提出了信标基底的概念.信标基底是一组满足特定条件的严格极小信标集合.本文证明基于不同的信标基底,建立的受控系统其容许性能也不同.而容许性是评价死锁控制策略优劣的重要标准之一.故如何选择信标基底,提高受控系统的容许性能是值得研究的问题.本文讨论了使受控系统容许性能大大提高的信标基底的选择条件.基于该条件,为柔性制造系统建立有效的死锁控制策略.最后,通过两个例子解释该条件和策略.