On Hybrid Petri Nets

Petrinets (PNs) are widely used to model discrete event dynamic systems(computer systems, manufacturing systems, communication systems,etc). Continuous Petri nets (in which the markings are real numbersand the transition firings are continuous) were defined morerecently; such a PN may model a continuous system or approximatea discrete system. A hybrid Petri net can be obtained if onepart is discrete and another part is continuous. This paper isbasically a survey of the work of the authors' team on hybridPNs (definition, properties, modeling). In addition, it containsnew material such as the definition of extended hybrid PNs andseveral applications, explanations and comments about the timingsin Petri nets, more on the conflict resolution in hybrid PNs,and connection between hybrid PNs and hybrid automata. The paperis illustrated by many examples.     

半张量积理论在网络遥操作系统中的应用

研究了网络遥操作系统的半张量积建模问题.网络遥操作系统中存在人机交互以及大时延事件,这使得系统中既有离散事件动态又有连续动态,当系统的离散事件动态与底层连续动态相互作用耦合强烈时,系统的性能、行为分析变得更为复杂.本文通过引入半张量积给出了一种新的半张量积混杂建模方法,它把一类特定事件系统建模为布尔系统,通过半张量积方法得到类似于离散动态系统的方程.它将系统中离散事件和连续动态相互耦合的地方表达为半张量积的形式,最后经过扩张简化得到完整统一的系统数学模型,它将有利于进一步分析、计算.本文给出的半张量积建模方法和步骤具有一定的通用性和一般性.此外本文还对基于半张量积的混杂网络遥操作系统模型进行了基于事件控制和时间控制的仿真.仿真结果表明,半张量积建模方法完全可信、可行,基于事件控制的方法在网络遥操作控制中明显优于基于时间控制的方法.     

神光III控制系统的故障建模与分析

应用混合随机Petri网对神光III控制系统的故障进行了建模,并应用Visobj Net对建立的故障模型进行了仿真分析。网络化控制系统是一个离散和连续相结合的混合动态系统,具有动态、并发及同步等特征;神光III控制系统就是网络化控制技术在武器装备上的一个典型应用;对于复杂系统的建模和分析,Petri网是一个非常有效的工具。Petri网已经被证明是离散事件或异步系统很好的建模和分析工具,混合随机Petri网是Petri网的一个扩展,具有强大的建模功能。仿真结果表明,所建立的模型是正确的。     

混合系统在matlab环境下的建模和仿真

混合系统是集连续动态系统和离散事件为一体的复杂动态系统,是近年来控制理论研究领域的热门课题.由于混合系统既含连续变量义含离散事件,给处理这类系统带来了复杂性.一般混合系统建立模方法有:混合自动机,混合petri,时段演算及其扩展等模型.在概述混合系统概念与特点的基础上,介绍了混合系统研究中的建模与仿真问题.结合超市冰柜系统用混合自动机建模,并用MATLAB中的SIMULINK和STATEFLOW进行仿真.仿真结果表明效果很好,为系统分析和设计提供了有力的工具.     

Hybrid dynamical systems: robust control synthesis problems

The paper presents a new approach to robust control synthesis problems for hybrid dynamical systems. The hybrid system under consideration is a composite of a continuous plant and a discrete event controller. State and output feedback problems are considered. The main results are given in terms of the existence of suitable solutions to a dynamic programming equation and a Riccati differential equation of the H^∞ filtering type. These results show a connection between the theories of hybrid dynamical systems and robust and nonlinear control.     

混成系统研究综述

混成系统是一类既包含连续动态行为又包含离散动态行为的系统,这类系统在实际应用中显得越来越重要,对这类系统需要探索新的模型和研究方法。从建模、分析与验证三个方面综述了混成系统的研究现状和需要进一步研究的课题。     

一类不确定脉冲型混杂系统的保代价控制

针对混合代价函数,研究了参数不确定脉冲型混杂系统的保代价控制问题,给出了混杂状态反馈保代价控制律的设计方法,由此得到的控制律既能使系统闭环鲁棒渐近稳定,又可使系统的闭环混合代价指标在对象参数摄动的范围内不超过确定的上界.本文提出的控制律不仅包含连续时间动态,也包含离散事件动态,而且其离散事件动态行为不需要与被控系统的离散事件动态行为一致,因此设计时不要求被控系统的每个连续时间子系统都具有可控性.仿真结果表明所提设计方法是可行有效的.     

控制模态转移型系统的稳定切换

离散事件决策子系统和数值反馈子系统合成的混合控制系统呈现出复杂的稳定动态 特性.研究了在达到模态切换周期的控制规则下,相应的系统连续状态轨迹的平稳性.给出了具 有较少约束的李雅谱诺夫型判据,不要求全局一致的李雅谱诺夫函数,不要求每个模态下的能 量函数单调递减.     

冷连轧混合系统中离散事件仿真的建模及关键技术

本文以冷连轧过程仿真为例，分析了混合系统中离散事件的特点以及与连续部分的关 系，对系统进行了层次化分解，讨论了在混合系统仿真过程中对于离散事件部分的建模需要 注意的问题，同时给出了用有限状态机方法实现仿真建模的过程，以及实际应用中的关键技 术．     

面向原油库存管理过程的Petri网建模

石油化工工业属于典型的连续型生产工业,但在连续生产过程中又包含有离散变量, 具有明显的混杂动态系统特征.对于这样的混杂动态系统,混合Petri网是一种有效的建模方法.文章在已有的混合Petri网结构基础上,在离散变迁激发规则中加入了逻辑控制条件,并对原油库存管理过程这一兼有连续时间特性和离散事件特性的混合动态系统进行建模,并通过建模实例验证了其有效性和灵活性,从而为解决原油库存问题提供了具有参考价值的方法.     

Using a Discrete-Event System Specifications (DEVS) for designing a Modelica compiler

We introduce a new architecture for the design of a tool for modeling and simulation of continuous and hybrid systems. The environment includes a compiler based on Modelica, a modular and a causal standard specification language for physical systems modeling (the tool supports models composed using certain component classes defined in the Modelica Standard Library, and the instantiation, parameterization and connection of these MSL components are described using a subset of Modelica). Models are defined in Modelica and are translated into DEVS models. DEVS theory (originally defined for modeling and simulation of discrete event systems) was extended in order to permit defining these of models. The different steps in the compiling process are show, including how to model these dynamic systems under the discrete event abstraction, including examples of model simulation with their execution results.     

Discrete event representation of qualitative models using Petrinets

The paper discusses how Petri nets may be used for the qualitative modeling of physical systems. The qualitative state of a system is represented by the marking of the net. The crossing of a landmark value corresponds to the firing of a transition. We give a formal procedure to construct a Petri net model corresponding to a given set of qualitative equations. The approach can be used to study both autonomous systems and systems with forcing inputs. The dynamic behavior of the system can be studied as sequences of reachable markings of the net and can be computed with standard Petri net execution techniques. This approach also leads to a simple framework for the study of hybrid systems, i.e., systems whose behavior is described by both continuous and discrete event dynamics. Several examples, with applications to diagnosis and control, are fully discussed.     

基于OSG的混合系统三维仿真技术的研究与实现

在连续／离散混合系统的物流生产过程中,利用OSG（Open Scene Graph）开源软件包实现虚拟车间物流生产过程的三维仿真。为了开发一个性能良好的虚拟仿真系统,建立了合理的虚拟对象体系,解决了场景建模时的模型对象和三维仿真时的仿真对象的关系,使得整个运行过程效率更高。最后将离散事件与连续系统有效结合,在仿真时钟推进机制和基于消息的事件调度的控制下,实现了新的混合系统的三维仿真。     

基于混杂系统理论的制造系统仿真

根据制造系统连续事件与离散事件并存的特点,提出一种制造系统半实物仿真方法,设计连续事件和离散事件并存时仿真系统的时间推进机制。在Arena环境中实现对离散事件系统的建模,在Labview环境中实现特定连续变量事件的半实物仿真。设计并实现离散事件系统与连续事件的接口连接。仿真实验结果表明,该系统能较好地反映出整个制造系统的混杂特性,为混杂制造系统的仿真提供一种新的思路。     

炼油生产调度的混合Petri网建模

文章首先分析了炼油生产调度问题,指出炼油生产调度是一个既具有连续时间特性,又具有离散事件特性的混合动态系统,针对这种特性,该文在研究了连续Petri网和混合Petri网之后,将混合Petri网用于炼油生产调度系统的建模,为解决炼油生产调度的实时性问题提供了有力工具。     

一类混合系统仿真时钟无误差同步方法及性能分析

通过对一类混合系统仿真中的连续系统、离攻事件系统及推理决策系统各自储地钟的分析,得出了推理决策系统的仿真依赖于其他两个系统的结果,继而提出了用其中的连续系统仿真时钟去同步离散事件系统仿真时钟的无误差方法,并给出了相应的软件实现性能分析。     

AN APPROACH TO REASONING ABOUT HYBRID SYSTEMS

A formal approach is presented for proving temporal properties of dynamic systems. Its main advantage is that it can be used to prove properties of hybrid systems, i.e. those whose state contains both discrete and continuous parameters. In contrast, most current temporal reasoning techniques are restricted either to purely discrete systems or to purely continuous systems. Our approach is based upon a new modeling technique called DMOD. A DMOD model of a system defines the causality relation between events in the system, using definite clauses, i.e. logic programs. Thereby, the problem of reasoning about hybrid systems is reduced to one of reasoning about the behavior of definite clauses. As these possess a simple proof theory, reasoning is substantially simplified.     

Diagnosability analysis of hybrid systems cast in a discrete-event framework

This paper addresses the problem of assessing the diagnosability of hybrid systems modeled by a hybrid automaton coupling methods from the continuous and the discrete event model-based diagnosis fields. The discrete states of the hybrid automaton represent the modes of operation of the system for which the continuous dynamics are specified. The diagnosability of the continuously-valued part of the model is first analyzed and the new concept of mode signature is shown to characterize mode diagnosability from continuous measurements. Continuous dynamics are then abstracted by defining a set of signature-events associated to mode signature changes, preserving this way mode diagnosability. The behavior of the abstract hybrid system is then modeled by a prefix-closed language over the original event alphabet enriched by these additional events. Based on this language, diagnosability analysis of the hybrid system is cast into a discrete-event framework and hybrid diagnosability conditions are provided. A case study based on the Attitude and Orbit Control System of a spacecraft illustrates the method.     

混合系统剖析,描述与建模

混合系统是一种离散和连续构件交织的系统。通常以微分方程为连续模型，以离散事件系统或自动机为离散模型。通过分析混合系统的微观结构，文中提出了面向系统设计的描述语言ＤＤＬ。它能直观、精确刻画混合现象，方便设计决策描述，而且通过控制器符号与系统指称约束的延迟，为系统设计带来很大的灵活性。由ＤＤＬ描述的混合系统，经内部通信隐藏和系统单步协调积，可转换为混合变迁系统。