一类受控Petri网的控制器设计

通过挖掘Petri网的内在的结构特性, 获得了一种新的解决禁止状态避免问题的控制器设计方法. 这种设计方法适用于一类具有特殊结构的受控Petri网 (即所有前向路径子网是状态机 )的状态反馈控制器设计. 在非并发的假设条件下, 所综合的控制器是最大允许.     

离散事件系统的协调反馈控制

本文探讨以Ｐｅｔｒｉ网为模型的离散事件系统（ＤＥＳ）的某种禁止状态避免问题，提出了以Ｐｅｔｒｉ网Ｎ为基网，设计具有外部输入位置Ｐｅｔｒｉ网（ＰＮＩＰ），对Ｎ进行协调反馈控制的方法。由Ｎ现行状态反馈决定的ＰＮＩＰ的控制状态，既保证Ｎ避免禁止状态，又使Ｎ具有最大自由度。     

一类受控Petri网的反馈控制综合方法

讨论受控Ｐｅｔｒｉ网的一类禁止状态避免问题，该类禁止状态用广义互 约束的形式给出。     

自动化仓库输送调度问题的建模与控制研究

基于面向对象着色Petri网模型和时态逻辑方法,对自动化仓库输送系统运行过程的调度问题进行研究。建立了系统的面向对象着色Petri网模型,讨论了该过程的死锁分析问题,给出了系统行为的时态逻辑规范和死锁避免的最大允许反馈控制策略。     

柔性制造系统实时调度的有色Petri网和状态方程模型

柔性制造系统(FMS)的实时调度问题是一个典型的并发系统(CA),亦称为离散事件动态系统(DEDS).这是一类很复杂的动态系统,本文尝试用Petri网和有色Petri网对FMS的实时调度问题建立动态模型并同时给出了代数形式的状态方程模型.     

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。     

一类活性Petri网控制器的冗余检测及结构简化

S4R(systems of sequential systems with shared resources)网是分析和解决柔性制造系统死锁现象常用的一种重要的Petri网子类模型,现有的基于S4R网的死锁预防方法通常采用对部分或者全部严格极小信标添加控制库所来实现.此类方法的不足在于得到的活性S4R控制器中往往存在冗余控制库所.针对已为网中每一个严格极小信标都逐一添加了控制库所和相关连接弧的活性S4R控制器,本文提出并设计了一种基于整数规划技术的冗余检测及结构简化方法,由此得到结构更简单、行为允许度更高的活性S4R控制器.该方法的核心思想是:如果网中已经存在一个p-不变式使得某个严格极小信标满足最大受控条件,那么为该严格极小信标添加的控制库所就是冗余的.由于该方法无需进行Petri网的可达性分析,避免了状态组合爆炸问题,因此具有较高的可行性和计算效率.最后用实验验证了本文方法的正确性和有效性.     

基于变迁覆盖的制造系统死锁控制策略

基于系统Petri网模型,研究柔性制造系统的死锁控制问题.论文利用变迁覆盖为系统设计活性控制器.变迁覆盖是由一组极大完备资源变迁回路组成的集合,其变迁集覆盖了Petri网中所有极大完备资源变迁回路的变迁集.验证变迁覆盖的有效性,然后仅对有效变迁覆盖中的极大完备资源变迁回路添加控制位置,就得到系统的活性受控Petri网.这种受控Petri网包含的控制位置个数少,从而结构相对简单.最后通过一个例子说明了所提出的死锁控制策略的构成与特点.     

基于混合整数规划的非阻塞监督控制器设计

提出一种新的死锁控制策略, 保证含有并发执行装配过程的一类柔性制造系统(Flexible manufacturing system, FMS) G-system的非阻塞性, 即在控制下, 受控系统从任意可达状态都可到达理想状态. 首先对Petri网模型运用混合整数规划算法求取一个最大的死信标, 然后从最大的死信标中求取一个需要受控的极小信标, 并对其添加控制库所, 从而保证所有信标的最大可控. 和现有方法相比, 该策略避免了求取所有的信标, 且添加较少的控制库所即可获得结构简单、许可行为趋于最优的控制器.     

Petri网的一类禁止状态问题的混合型监控器算法设计

针对广义互斥约束下Petri网的不可控影响子网为状态机的一类禁止状态问题,给出了观测器的设计方法,并基于观测器得到了求解最大允许控制策略的算法.利用观测器将广义互斥约束简化为单禁止库所约束,并将存在不可控变迁的问题简化为相当于变迁全部可控的问题,这有效地解决了不可控变迁带来的计算复杂性问题.最后,利用一个地铁交通调度示例验证和说明该监控器设计方法.     

POC net,a subclass of Petri nets,and its application to timed Petri nets

Liveness is one of the most important properties of the Petri net analysis. This property is concerned with a capability for firing of transitions. On the other hand, place-liveness is another notion related to liveness, which is concerned with a capability for having tokens in places. Concerning these liveness and place-liveness problems, this paper suggests a new subclass of Petri net, ‘POC nets’, as a superclass of AC nets and DC nets. For this subclass, the equivalence between liveness and place-liveness is shown and a sufficient condition for liveness for this POC net is derived. Then the results are extended to liveness problem of timed Petri nets which have transitions with finite firing durations and the earliest firing rule. Although liveness of a (non-timed) Petri net is neither necessary nor sufficient condition for liveness of a timed Petri net, it is shown that liveness is preserved if the net has POC structure. Furthermore, it is pointed out that if a POC net satisfies some additional condition, Petri net liveness is equivalent to timed Petri net liveness. Finally, it is shown that liveness of timed POC nets with TC structure and the earliest firing rule is decidable with deterministic polynomial time complexity.     

基于时延Petri网的DEDS的代数模型

用一种新的算子建立了结构无竞争时延Petri网和资源分配型时延Petri网的动态方 程,为该类系统的分析和控制提供了研究工具.     

正规语言闭包运算的Petri网构造方法

Petri网语言与Chomsky文法体系之间的关系已有了一些结论,已经证明正规语言是Petri网语言的一个子类。相关文献中给出了一种Petri网子类——恰当终结的标准Petri网,并且已经证明恰当终结的标准Petri网语言与正规语言的等价性。在此基础上,研究了正规表达式中Kleene闭包运算“*”的Petri网构造方法,分别给出了Kleene闭包运算“*”的ε-空标注和无ε-空标注Petri网模型的构造方法。该构造方法可由产生正规语言L的网模型直接得到产生正规语言L*的网模型。证明了对于恰当终结的标准Petri网,正规语言闭包运算“*”的构造是封闭的。     

New NP-Complete Problems in Performance Evaluation of Concurrent Systems Using Petri Nets

Timed Petri nets are useful in performance evaluation of concurrent systems. The maximum computation rate is achieved for minimal cycle time of timed Petri net. It is known that minimal cycle time problem for P-invariant Petri nets is NP-complete. In this paper we prove that the minimal cycle time problem, for non-P-invariant Petri nets and for a small subclass of P-invariant Petri nets called free-choice nets having live and safe marking, is NP-complete.     

标识T-网中同步距离的计算

同步距离是刻画事件之间同步关系的一个重要的定量分析手段.由于同步距离的求解不仅和网的结构特征有关系,而且和网的初始标识也存在关系,因此到目前为止还没有一个很简洁易行的算法来求解一般Petri网的同步距离.然而,一些特殊的Petri网子类,如标识T-图、标识S-图的同步距离的计算已经有了较简洁的求解方法.对另一个Petri网子类--标识T-网给出了其同步距离的计算方法.标识T-网也可以直接通过网的结构和初始标识分布情况来得到变迁之间的同步距离,不需要考察网系统的运行,这就使得同步距离的求解简单易行.文中给出了相应的求解定理.     

Half a century after Carl Adam Petri’s Ph.D. thesis: A perspective on the field

It is certainly worth remarking on half a century of a work defining a landmark in Discrete Event Dynamic Systems (DEDS) theory. This invited contribution aims to combine some historical facts with elements of a conceptual view on concurrent DEDS, giving pointers about the development of the field. Simplifying the historical trajectory, it can be said that the seed sown by Carl Adam Petri in 1962 first grew in America (essentially until the mid 1970s), where an appropriate intellectual ambiance existed in computer science, business process management and switching systems design. Later, many other new lines of activity, including logic control and performance evaluation, flourished in Europe. Today Petri nets are widespread all over the world. The conceptual paradigm of Petri nets deals inter alia with modeling, logical analysis, performance evaluation, parametric optimization, dynamic control, diagnosis and implementation issues. In summary, multidisciplinary in themselves, formalisms belonging to the Petri nets paradigm may cover several phases of the life-cycle of complex DEDS.Given the hundreds of research and text monographs on Petri nets, together with the many thousands of theoretical and applied contributions on the subject, not to mention the ISO (International Organization for Standardization) or IEC (International Electrotechnical Commission) standards for the use of Petri nets in engineering, this work cannot hope to be a complete survey or a tutorial in the more classical sense. It is more of an impressionistic overview of the field.     

可分解非对称选择网的活性和有界性

活性和有界性是网系统的重要行为特性.从分解以及尽可能简单分解的角度得到了非对称选择网的一个子类,可分解非对称选择网(简称DAC网),证明了DAC网系统活性的充分必要条件,同时给出了DAC网系统活性有界性的充分必要条件,也进一步讨论了判定一个Petri网系统是否是活的有界的DAC网系统的多项式算法.     

基于Petri网的PLC系统设计分析与远程监控

Petri网在离散事件的动态仿真中有着广泛的应用,而如何将Petri网应用到离散制造系统中具有重大的价值.以离散制造业中最常见的搬运机械手模型为基础,提出了它的Petri网模型设计方法,并且利用科学的转换方法将Petri网转化为梯形图,应用到在制造业中广泛使用的PLC系统中.利用这种设计方法,不仅能够轻松地将Petri网应用到实践当中,还能够对模型的死锁、生产周期和不变量进行定量的分析,给制造系统进行管理控制、故障诊断和现场监控带来方便.     

Integration of Petri nets and moment generating function approaches for system performance evaluation

This article integrates arbitrary stochastic Petri nets (ASPN) and moment generating function approaches for performance evaluation of discrete event dynamic systems (DEDS). These systems include computer-integrated manufacturing systems, resource-shared distributed systems, and communication networks. ASPN can describe various DEDS in which the time duration for activities may be a random variable of arbitrary distributions. In ASPN models, transitions with firing delays of general distributions are used to model these activities. Using our proposed performance analysis methodology, we first represent a system as an ASPN model, then generate its reachability graph and convert it into a state machine Petri net, derive the transfer functions of interesting performance measures through stepwise reductions, and finally obtain the analysis results. This method makes it possible to obtain analytical solutions of important performance indices. We use a robotic assembly system to illustrate the method. We obtain several important performance measures of a closed-form. Finally, we discuss the limitations of this approach and future research.     

Modeling and analysis of timed Petri nets using heaps of pieces

The authors show that safe timed Petri nets can be represented by special automata over the (max, +) semiring, which compute the height of heaps of pieces. This extends to the timed case the classical representation a la Mazurkiewicz of the behavior of safe Petri nets by trace monoids and trace languages. For a subclass including all safe free-choice Petri nets, we obtain reduced heap realizations using structural properties of the net (covering by safe state machine components). The authors illustrate the heap-based modeling by the typical case of safe jobshops. For a periodic schedule, the authors obtain a heap-based throughput formula, which is simpler to compute than its traditional timed event graph version, particularly if one is interested in the successive evaluation of a large number of possible schedules