离散事件系统规范DEVS研究

离散事件系统是一类常见的系统，如何对这类系统进行描述与建模是离散事件系统仿真研究的核心内容。离散事件系统规范DEVS是一种离散事件系统形式化描述方法，它具有层次化和模块化的特点，利用该方法可对复杂的离散事件系统进行建模、设计、分析和仿真。该文详细介绍了DEVS基本模型和耦合模型，给出了DEVS在耦合运算下的封闭性构造证明，并提出了一种具有嵌套层次结构的DEVS耦合模型实现算法，该算法对基于DEVS描述的离散事件系统的仿真实现具有一定参考价值。     

一种DEVS原子模型向UML状态图映射方法研究

离散事件仿真规范DEVS形式化的一个重要不足在于它缺乏一种标准的、图形化的描述形式。该文研究提出了一种将DEVS的原子模型与复合模型分别映射到UML的状态图和组件图的方法,并用形式化的数学方法对DEVS原子模型向UML状态图的映射过程进行了描述与构造。这种映射将DEVS规范融入到了UML的描述形式当中,将DEVS的抽象化描述与UML的表示能力、计算机处理能力结合起来,为两种建模形式的统一提供了一个可行的思路。该文研究的成果在C^4ISR系统总体方案规范化建模中得到了逐步的应用。     

DEVS在IDEF0模型验证中的应用

IDEF0方法是结构化系统分析的重要方法,但IDEF0模型是静态的功能模型,不包含运行机制,不便于进行动态分析,导致对模型的验证较为困难.本文建立了IDEF0模型的形式化描述,并对IDEF0模型进行了扩展,提出IDEF0模型到离散事件系统规范(DEVS)模型的转化方法,通过DEVS的仿真运行来对IDEF0模型进行分析和验证.该方法实现了IDEF0方法中系统分析与模型验证的有效衔接,具有扩展性和灵活性,为IDEF0模型的验证提供了支持.     

重叠交替更新过程的DTSS仿真校验的两个问题

以常用重叠交替更新过程为对象模型, 讨论了离散时间仿真(Discrete time system specification, DTSS)校验的两个理论问题. 首先, 给出了基于仿真关键系统变量方差的输入/输出级仿真精度的定量度量. 其次, 针对精度度量难以求解的问题, 在Zeigler的仿真理论框架下给出了离散时间仿真和离散事件仿真(Discrete event system specification, DEVS)的等价性证明, 并根据这个结果给出了仿真误差度量的一种近似表达式.     

UML-BD在C3I系统中的应用

DEVS是对离散事件系统的一种形式化描述,它提供了一种层次的模块化的系统说明方法。该文中的UML-BD（UML Based on DEVS）方法就是在UML中结合DEVS这一特点,对UML进行一定的扩展;同时还在UML中还增加了时间的约束．满足系统的实时性的要求。基于C3I系统的层次性、实时性的特点,该文采用UML-BD方法对系统进行建模,构建出系统模型能够充分地展现系统特点。     

DEVS的面向对象可视化建模

DEVS是对离散事件系统的一种形式化描述,该文在DEVS中引入面向对象的方法,并采用UML（Unified Modeling Language)对它进行可视化建模。文中提出了基于DEVS的面向对象的一种建模规则和基于UML的可视化建模思想和方法,该方法是对DEVS和UML的扩充和改进。     

某航空兵场站机载弹药保障仿真研究

航空兵场站机载弹药保障的要素和环节众多,且相互影响、相互制约,通常采用计算机仿真对这类系统效能进行定量评估。本文对某航空兵场站机载弹药保障的力量构成、保障过程和特点进行了分析,并将其抽象为一个离散事件系统,建立了涵盖任务下达与执行、保障对象、保障资源以及保障过程等要素的建制单位离散事件仿真模型,并在此基础上开发了仿真系统。应用表明,该仿真模型运行正确、可靠,为某航空兵场站机载弹药保障效能评估提供了有力的分析工具。     

一种基于Modelica语言的混合系统DEVS模型架构

Modelica语言采用微分方程描述系统,此外它还具备面向对象编程语言的特性,因此它不仅适用于连续系统的建模,还支持离散系统的模型架构。因此,可以将Modelica作为一种混合系统的建模语言。提出了一个Modelica语言描述的DEVS（Discrete E Vent System specification离散事件系统规范）模型架构,并通过对模型的编译过程产生C＋＋代码,获取了同时描述连续系统和离散系统建模的能力。最后给出了用Modelica语言描述的一个飞机导航控制连续一离散仿真系统的例子。     

基于逻辑模型的自动化制造系统建模方法

系统调适是自动化制造系统在实际应用前的重要阶段，但是传统的系统调适存在周期长、成本高等问题。虚拟调适可以有效解决这些问题，在本次研究中提出采用离散事件系统规范(Discrete Event System Specification, DEVS)来构建虚拟调适系统中的逻辑模型，并对其进行了扩展和改进。同时利用DEVS++进行二次开发和仿真分析，重复验证建立的逻辑模型并进行修改。在结果的实例分析中，以自动化制造系统为例，对逻辑模型的建立进行了展示。同时该模型的召回率为91%,准确率为86%,F值为79%;其准确率相较于灰狼算法和文献方法分别提高了6.25%和14.86%。结果证实了实验中提出的基于逻辑模型的系统建模方法具有可行性和优越性，对于自动化制造系统的模型构建具有较好的技术参考价值。     

计算机离散事件仿真的原理

在介绍有关系统、模型和系统仿真的基本概念的基础上,本文详细说明了计算机离散仿真,其中包括离散事件系统的基本要素、离散事件系统模型及离散事件系统仿真策略.     

A transformation model from DEVS to SMP2 based on MDA

Simulation Model Portability standard 2 (SMP2) is a successful simulation model reuse standard in European Space Agency. Discrete Event System Specification (DEVS) is one of most common and powerful simulation model formalisms. Transforming a simulation model from DEVS representation to SMP2 representation is of great significance for model reuse. A Model Driven Architecture (MDA) based transformation methodology is presented first. According to this methodology, a MOF based DEVS metamodel is created and the mappings from DEVS metamodel to SMP2 metamodel are established. A transformation model from DEVS to SMP2 is described based on Query/View/Transformation (QVT) language. An illustrative example is detailed to demonstrate the application of the transformation model. The transformation model’s further application strategy and our next work are discussed in the final part.     

支持模型集成和重用的仿真语言研究

SRML是一种基于XML和脚本语言，用于表示仿真模型的参考标记语言。它试图确定一个灵活的表示仿真模型的参考标准，以加快模型的开发速度，支持模型的集成和重用，但是其草案大纲存在很多不足，需要进行扩展完善。总结了仿真模型集成和重用的关键因素，并提出结合DEVS、DEVS定义语言，研究扩展SRML的途径。重点介绍了DEVS和SRML之间的映射关系，以及SRML用于描述仿真模型的能力，如数据交互格式、继承关系、原子模型、组合模型、交互关系、仿真想定的描述等。扩展的SRML实现了仿真模型与仿真执行的分离，并继承了DEVS的所有特性，是一种平台无关的仿真语言，可以有效地支持仿真模型的集成和重用。     

Ordering of simultaneous events in distributed DEVS simulation

Simultaneous events are the events scheduled to occur at the same simulation time. This paper proposes a new event ordering mechanism for handling simultaneous events of DEVS models in distributed simulation. The DEVS formalism provides a formal framework for specifying discrete event models in a modular, hierarchical form. Thus, the formalism can ease the model verification and validation problems of distributed simulation. Also, the formalism separates models from underlying simulation algorithms. Hence, DEVS models can be simulated in both sequential and distributed environments without any modification. One important issue for such framework is to obtain the same results in both simulation environments. However, in distributed simulation of DEVS models, the processing order of simultaneous events may affect the simulation results. Thus, some ordering mechanism of events is required for well-defined simulation results. The proposed mechanism orders simultaneous events correctly with respect to their causal relationships in distributed DEVS simulation. Also, the mechanism guarantees the same ordering of simultaneous events in both sequential and distributed simulation environments.     

A family of simulation criteria to guide DEVS models validation rigorously,systematically and semi-automatically

The most common method to validate a DEVS model against the requirements is to simulate it several times under different conditions, with some simulation tool. The behavior of the model is compared with what the system is supposed to do. The number of different scenarios to simulate is usually infinite, therefore, selecting them becomes a crucial task. This selection, actually, is made following the experience or intuition of an engineer. Here we present a family of criteria to conduct DEVS model simulations in a disciplined way and covering the most significant simulations to increase the confidence on the model. This is achieved by analyzing the mathematical representation of the DEVS model and, thus, part of the validation process can be automatized.     

Activity-based DEVS modeling

Use of model-driven approaches has been increasing to significantly benefit the process of building complex systems. Recently, an approach for specifying model behavior using UML activities has been devised to support the creation of DEVS models in a disciplined manner based on the model driven architecture and the UML concepts. In this paper, we further this work by grounding Activity-based DEVS modeling and developing a fully-fledged modeling engine to demonstrate applicability. We also detail the relevant aspects of the created metamodel in terms of modeling and simulation. A significant number of the artifacts of the UML 2.5 activities and actions, from the vantage point of DEVS behavioral modeling, is covered in details. Their semantics are discussed to the extent of time-accurate requirements for simulation. We characterize them in correspondence with the specification of the atomic model behavior. We demonstrate the approach with simple, yet expressive DEVS models.     

一种基于DEVS的网络设备仿真模型

在分析目前网络设备仿真建模所面临的主要问题的基础上,简要介绍了 DEVS 规范及其基本构成要素;以以太网交换机为实例,对基于 DEVS 的网络设备仿真建模技术进行了研究,并实现了仿真建模。对该网络设备建模方法的优点做了总结,并就此建模方法在网络设备建模中的应用前景进行了展望。     

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.