具有多项式时间复杂性的避免制造系统死锁控制策略

基于系统 Petri 网模型, 研究自动制造系统的避免死锁问题. 对不含中心资源的制造系统, 证明了它只包含安全和死锁两类可达状态. 通过一步向前看的方法, 给出了系统多项式时间复杂性的最佳避免死锁策略. 对一般系统定义了一种辅助 Petri 网. 利用辅助网的最佳避免死锁策略, 提出了综合一般制造系统多项式复杂性的避免死锁策略的方法.     

基于资源配置混杂Petri网的混杂系统生产过程建模

为了增强混杂Ｐｅｔｒｉ网解决资源共享和资源冲突的能力,定义一种新的混杂Ｐｅｔｒｉ网模型———资源配置混杂Ｐｅｔｒｉ网,提出了相应的使能和激发规则．将对连续变迁和离散变迁的控制作用引入混杂Ｐｅｔｒｉ网,同时,增加了资源配置变迁和资源释放变迁,用于有效分配可重复利用的资源．以典型的混杂生产过程为例,研究混杂系统生产过程建模．研究结果表明,所定义的模型描述能力强,模型语义正确合理,能够有效描述和分析混杂系统生产过程．     

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.     

基于扩展混成Petri网的CPS无人车系统建模与分析

信息物理融合系统(Cyber-Physical System,CPS)是一个集计算系统、通信系统、感知系统、控制系统和物理系统于一体的复杂系统,其行为是一种由离散计算过程与连续物理过程深度融合并紧密交互的混成行为。针对这种特性,采用混成Petri网对CPS建模,并在此基础上添加时间约束,即对离散变迁关联一个延迟时间,对连续变迁关联一个激发速率函数,同时引入抑止弧和测试弧的概念以提高Petri网的表达能力,由此提出一种新的模型——扩展混成Petri网模型。然后,对CPS应用中无人驾驶车辆系统的躲避障碍物场景进行建模,将建立的模型按照一定的规则转化为与之对应的Simulink模型,并通过Matlab仿真对系统行为及属性进行分析。     

化工间歇过程的时间Petri网模型和优化控制

针对化工间歇生产过程的特点及优化问题,本文提出用时间Ｐｅｔｒｉ网对过程建模,用动态规化方法对过程实行优化控制,并研究了该优化策略下的算法和控制设计问题。     

微分Petri网的稳定性分析

针对混合系统的特点,建立其微分Petri网（DPN）的模型．首先,给出一类DPN的稳定性概念和稳定性引理;然后通过引入两类函数,利用关联矩阵的信息对DPN的稳定性进行具体分析,进而构造新的复合能量函数,得到DPN的稳定性定理;最后通过仿真例子说明定理的有效性．     

A re-configurable multi-agent system architecture for error recovery in production systems

Multi-agent systems for manufacturing systems appear to provide adequate response to abrupt disturbances on the shop floor. To date, most of the work has been focused on planning and scheduling but very little work has been done on issues pertaining to monitoring, diagnostics and error recovery. Our approach addresses the issue of combining the discipline of hierarchical systems with the agility of multi-agent systems. Within the context of a hierarchy, the focus is on the workstation level and, in particular, the construction of a re-configurable system having production agents, error recovery agents, and a mediator agent structure connecting production and recovery agent hierarchies. In addition, the relationship to a multi-level, multi-layer hierarchy control is established. This latter hierarchy, based on Petri Net constructs, serves, in one sense, as a retrieval based resource for process planning and generation of recovery plans for production and recovery agents within the proposed multi-agent system. An objective of this effort is to provide a test-bed for comparison of hierarchical systems, heterarchical, and a hybrid combination which is the focus of the investigation presented here.     

Modal control of linear time invariant systems

A procedure is presented for the determination of a linear control law (for a system with one input) such that the resultant closed–loop System has specified eigenvalues. The design procedure is simpler than existing techniques.     

一种基于扩展Petri网的工作流建模方法

工作流技术是计算机应用领域的一个新的研究热点。将Petri网引入工作流模型是一种常见的建模方法。但是,传统的PN不能直接用于描述比较复杂的工作流模型。本文根据C．A．Ellis定义的信息控制网、W．M．P．vanderAalst定义的工作流网,结合工作流本身的特点,对Petri网进行扩展,提出了一种描述工作流模型的新方法--信息控制Pettri网,并给出其表示工作流模型的正确性定义和验证。     

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.     

基于Petri网的工作流层次模型及结构分析

在对工作流网络理论研究的前提下,结合企业业务流程建模的应用特点,提出了几种将工作流网络分层的思想,并着重介绍了将继承特性用于Petri网建模的方法。     

一种Petri网层次模型建模工具的设计与实现

为解决使用Petri网建模遇到的状态空间爆炸问题,提出使用层次模型,采用分层细化逐步求精的方法建立Petri网分层模型.设计并实现基于图形用户界面的普通边界为1的Petri网分层建模工具软件.用户在交互方式下建立Petri网层次模型,并可修改、删除、存储、分层平面化、简单功能模拟、导入和导出可复用Petri子网和将模型翻译为预定义的模型描述语言源程序.     

Sensitivity of optimal control systems with bang-bang control†

The effects of small parameter variations on the performance index of optimal control systems with initial and final target manifolds, free end time, and bang-bang control are analysed in this paper. A new approach to the sensitivity equation is presented. This approach takes into account the pulse-shaped variation produced by the parameter change on the bang-bang control. An expression, that relates the variations of the performance index, the trajoctory, the final time, and the parameter, is derived. This expression extends to the class of optimal systems with bang-bang control, a result previously obtained by Courtin and Rootenberg (1971).     

Firing rate optimization of cyclic timed event graphs by token allocations

In this paper, we deal with the problem of allocating a given number of tokens in a cyclic timed event graph (CTEG) so as to maximize the firing rate of the net. We propose three different approaches. The first one is a “greedy” incremental procedure that is computationally very efficient. The only drawback is that the convergence to the optimum is guaranteed only when the set of places where tokens can be allocated satisfies given constraints. The other two procedures involve the solution of a mixed integer linear programming problem. The first one needs the knowledge of the elementary circuits, thus it is convenient only for those classes of CTEG whose number of elementary circuits is roughly equal to the number of places, such as some kanban-systems. On the contrary, the second one enables one to overcome this difficulty, thus providing an efficient tool for the solution of allocation problems in complex manufacturing systems like job-shop systems.     

层次建模分析方法在C4ISR系统中的应用

C4ISR系统是一个规模庞大、层次分明的离散动态系统。文章提出了一种面向C4ISR系统的UML和Petri网结合的建模分析方法。该方法采用从上到下的层次分析方法。用扩展的UML模型对系统组织结构和系统的静态特征进行描述,用扩展的Petri网模型描述和分析系统动态特性,通过相应的规则将Petri网模型转化成状态图和序列图。新方法可以对系统要求进行验证,同时还可以编程实现。最后通过该方法,对一个C4ISR系统进行了建模分析。     

Structuring Acyclic Petri Nets for Reachability Analysis and Control

The incidence matrices—from places to transitions and vice versa—of an acyclic Petri net can obtain a block-triangular structure by reordering their rows and columns. This allows the efficient solution of some reachability problems for acyclic Petri nets. This result is further used in supervisory control of Petri nets; supervisors for Petri nets with uncontrollable transitions are constructed by extending the method of Yamalidou et al. (1996) to Petri nets where transitions can be executed simultaneously. A large class of Petri nets with uncontrollable transitions is given for which the maximally permissive supervisor can be realized by a Petri net. The original specification is algorithmically transformed—by using the results for acyclic Petri nets—into a new specification to take the presence of uncontrollable transitions into account. The supervisor is obtained by simple matrix multiplications and no linear integer programs need to be solved. Furthermore, a class of Petri nets is given for which the supervisor can be realized by extending the enabling rule with OR-logic.