自控网系统建模工具的研究与开发

自控网系统是一类具有非线性关系和强大建模能力的Petri网。应用可视化编程平台Visual Studio.NET开发了自控网系统建模工具CyberNetTool。用户可在交互方式下建立自控网系统模型,并采用PNML格式文件来存储模型。构造了软件核心类,以实现界面控件管理和模型分析,详细描述了自控网系统各性质分析模块和动态仿真模块的实现算法。最后通过具体应用实例表明了该工具的正确性和实用性。     

线性定常系统的Petri网解耦控制

将Petri网与现代控制理论相结合,应用于连续系统的性能分析如可控性、可观性和稳定性等已日益普遍,但Petri网应用于系统的解耦控制研究很少.提出了广义连续自控网系统的形式化定义,描述了线性定常系统的广义连续自控网系统模型并分析了广义连续自控网系统模型与状态空间描述的等效性.基于状态反馈动态解耦的基本原理,探讨了利用Petri网模型结构实现线性定常系统解耦控制的新方法.该方法采用图的遍历算法,可有效的判断系统的可解耦性以及实现解耦控制律,避免了传统解耦控制方法中计算所需的大量矩阵运算.最后给出了两个具体的应用实例.     

自控网的S-不变的研究

自控网是一种自修正系统，主要用于并发系统中的程序规范以及工业控制中的数学建模等领域。自控纲的S-不变、T-不变的非线性，使得它无法直接套用Petri网中一些已有的分析方法。有关不变的讨论一般在具体系统中作具体分析，从而给出具体的解释。对于一般网中S-不变呈现的特性在自控网上是否有条件的成立却鲜有文献涉及，本文给出了一个相应的定理。     

自控网系统的仿真分析与硬件实现的研究

自控网系统是Petri网的一个子类,与P/T系统相比,有更强的描述能力和更复杂的性质。由于它的非线性关系,无法直接套用其它网系统的分析技术,影响了对它的研究。文章提出了用硬件描述语言对自控网系统进行描述,通过EDA工具进行仿真分析,揭示系统的性质。文章针对计算Fibonacci数列的自控网系统模型,详细介绍了这一方法,给出了ABEL语言源代码和仿真波形,源代码经编译、优化、适配并下载到在系统可编程逻辑器件中,得到了计算Fibonacci数列的专用芯片,这为自控网系统的分析和应用研究开辟了新的途径。     

基于Petri网的非线性多变量系统解耦控制

广义自控网系统是一类弧权值受库所控制的高级Petri网,能够简单有效地建模PID控制规律.借鉴单神经元PID控制原理,在广义自控网系统的基础上加入神经元网络的学习规则,设计基于广义自控网系统的PID控制器,并用于非线性多变量系统解耦控制.所提方法充分利用了自控网系统的特点,所设计的控制器模型能实现系统控制与参数学习的统一.结合双容水箱控制系统实例进行仿真分析,分析结果验证了所提方法的有效性.     

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.     

Pi+演算及其对Petri网的表达

为了研究Pi演算模型的表达能力,作者用它来表达Petri网系统,证明了Petri网的某些子类,如自由选择网等,可以直接用Pi演算表达.然而对于一般的Petri网,表达却遇到了困难.文中提出了一种对Pi演算的扩展,称为Pi+演算,在原有Pi演算的通信机制中增加了多原语同步通信机制.证明了所有一般Petri网系统均可以用P...     

基于自控网系统的混杂控制

混杂控制系统通常是复杂的非线性控制系统,难以用统一的模型进行建模. David和Alla提出的混杂Petri网,虽然可以解决一般混杂系统的建模问题,并得到了广泛的应用,但对于传统的如PID这类控制器,缺乏统一建模的能力.探讨了基于广义自控网系统的混杂控制方法,实现了对混杂控制器中监控器和数字控制器进行统一的Petri网建模.仿真实例设计了基于广义同步自控网系统的电加热炉控制系统,给出了可根据不同温度状态实施多种控制策略的变结构数字控制器模型,并详细分析了控制器的性能,证明了广义自控网系统具有十分强大的建模能力和广泛的应用前景.     

k-选择网和Pi演算的表达能力

文中定义了Petri网的一子类系列:k-选择网,它形成一个后类包含前类的Petri网子类的无穷序列,证明了此无穷序列的并集等于Petri网类,自由选择网是k=1的k-选择网,即1-选择网.在证明自由选择网系统可以用Pi演算表达的基础上,文中进一步证明了所有2-选择网系统可以用Pi演算表达.     

无冲突Petri网的结构活性判定研究

结构活性作为Petri网的重要结构性质,在Petri网活性判定领域具有较高的研究价值。从Petri网有向回路对结构活性的影响入手,分析与判定无冲突Petri网的结构活性,讨论库所元素及其后置变迁之间是否存在有向回路对Petri网结构活性的影响,研究该类Petri网结构活性判定方法的相关条件与结论,得到无冲突Petri网是满足结构活性的充分必要条件。分析结果表明,该判定方法可在多项式时间内判定无冲突Petri网的结构活性。     

Notes on Liveness and Boundedness of Extended Strong Asymmetric Choice Nets Ⅱ

In this paper,the Extended Strong,Asymmetric Choice NetsⅡ（ESACNⅡ),a subclass of Asymmetric Choice Nets(ACN) including Extended Free Choice Nets(EFCN) and Strong Asymmetric Choice Nets Ⅱ(SACNⅡ),is presented.A necessary and sufficient condition for liveress of ESACNⅡis proposed.Moreover,a criterion is introduced,which is necessary and sufficient for judgement of liveness and boundedness of ESACNⅡ,Meanwhile a polynomial time algoirithm is given to decide liveness and boundedness for ESACNⅡ.     

Some observations on supervisory policies that enforce liveness in partially controlled Free-Choice Petri nets

Every arc from a place to a transition in a Free-Choice Petri net (FCPN) is either the unique output arc of the place, or, the unique input arc to the transition [M.H.T. Hack, Analysis of production schemata by Petri nets, Master’s thesis, Massachusetts Institute of Technology, February 1972; W. Reisig, Petri Nets, Springer-Verlag, Berlin, 1985; T. Murata, Petri nets: properties, analysis and applications, Proc. IEEE 77 (4) (1989) 541–580]. We consider FCPNs that are not live [J.L. Peterson, Petri Net Theory and the Modeling of Systems, Prentice-Hall, Englewood Cliffs, NJ, 1981; W. Reisig, Petri Nets, Springer-Verlag, Berlin, 1985; T. Murata, Petri nets: properties, analysis and applications, Proc. IEEE 77 (4) (1989) 541–580], and we investigate the existence of supervisory policies that can enforce liveness in partially controlled FCPNs. The external agent, or supervisor, can only prevent the firing of some (i.e. not all) transitions in a partially controlled FCPN.

We first present an observation on supervisory policies that enforce liveness in partially-controlled FCPNs. Using this observation, we solve the supervisory synthesis problem for the family of c hoice-controlled FCPNs, defined in this paper. We then identify a new, sub-class of partially-controlled FCPNs that posses an easily-characterized (and easily-enforced) supervisory policy that enforces liveness.     

Extended Petri net-based modeling,analysis and simulation of an intelligent materials handling system

This paper describes, models, analyzes and simulates an intelligent materials handling system with diagnostic intelligence capabilities using Extended Petri Nets (EPNs). The important modeled system properties of safeness, liveness and reversibility, which guarantee that the system operates in a stable, deadlock free and cyclic manner are verified and illustrated through the simulation results, obtained through an EPN based software package. A real system, the USL CIM system, modified to function as an intelligent materials handling system with on-line adaptation capabilities is used as a case study.This work has been partially supported by the LEQSF Research Grant LEQSF (91–93) — RD-A-40. A short version of this paper has been presented at the 31st IEEE CDC, Tucson, Arizona, December 1992.     

共享合成Petri网的性质分析

组合Petri网的性质不变性对大型合成系统分析有着重要意义,从分析共享合成Petri 网的结构性质入手,分析了它的活性性质,给出了它的一个较为简单的活性判定的充要条件. 在此基础上,研究了共享合成Petri网的活性与行为不变性和状态不变性的关系,为系统合 成的活性和一致性的关系提供了分析依据.     

非确定Petri网

根据描述工作流模型的实际应用背景，提出了非确定变迁，非确定Petri网等概念，并定义了Petri网的等价关系，证明了在这种等价关系的意义下，非确定Petri网与传统的确定Perti网的等价性。     

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     

关于ESAC网活性和有界性的一个多项式算法

寻找实际可行的多项式算法一直是Petri网应用的重要方面.给出了关于扩展强化非对称选择网(extended strong asymmetric choice nets,简称ESAC网)结构活和结构有界的一个判定算法.该算法可简单、有效地测试结构活结构有界的ESAC网的初始标识是否是活标识.ESAC网覆盖了自由选择网,因此,该算法应用范围较为广泛.     

An Application of Independent, Increasing, Free-Choice Petri Nets to the Synthesis of Policies that Enforce Liveness in Arbitrary Petri Nets

The class of Independent, Increasing, Free-Choice Petri nets (II-FCPNs) was introduced in (Sreenivas, 1997c), where it is shown that any II-FCPN can be made live via supervision using a readily available policy. In a live Petri net (PN). Petri Net Theory and Modeling of systems. Prentice-Hall, Englewood Cliffs, NJ, Reisig (1985). Petri Nets. Springer, Berlin), it is possible to fire any transition from every reachable marking, although not necessarily immediately. In this paper we identify a class of PNs, where every transition is controllable, that are not necessarily II-FCPNs, that can be made live via supervision using a readily available policy constructed from the policy that enforces liveness in an II-FCPN.     

Modeling the Exogenous Coordination of Mobile Channel-based Systems with Petri Nets

In this paper, we discuss how to model systems that communicate through and are coordinated by mobile channels. Mainly, we focus on modeling the exogenous coordination behavior imposed by these channels. We use Petri Nets as our modeling language, for they provide a graphically and mathematically founded modeling formalism. We give Petri Nets for a set of mobile channel types. This allows us to construct models of applications, by taking the Petri Net of each component and each mobile channel, and composing them together. For this purpose, we define a special Petri Net composition function. We also discuss analysis and simulation of these models and their exogenous coordination behavior.     

基于Stateflow的Petri网仿真方法

Stateflow是matlab环境下与simulink整合在一起的专门用来对复杂响应系统和事件驱动系统进行仿真的工具箱。应用其对Petri网模型进行仿真，提出了一种对Petri中资源的分类方法，根据petri网中资源的流通方式将资源分为循环资源、非循环资源．及隐性资源。并结合变迁的个数和激活方式给出了从一个已知的Petri网构造其相应的Stateflow的具体规则．及详细步骤，最后结合某汽车冲压单元的建模进行举例说明。构造过程显示出文中提出的仿真方法具有使用简单、通用性强、扩展性好的特点。