Modelica模型的序列化方法

Modelica是一种基于方程的陈述式建模语言,它具有面向对象、数组化表示、连续离散混合和可重用等多种特征,基于Modelica构建的模型和模型库通常规模庞大且结构复杂。编译Modelica模型的时间开销较大。本文从Modelica模型编译的角度出发,结合现有的序列化方法,提出以模型序列化来取代模型编译的部分工作,从而达到提升Modelica模型编译效率的目的。文中实现的Modelica模型序列化技术已在多领域物理系统建模与仿真平台MWorks中进行了验证与应用。     

Hybrid system modeling using the SIMANLib and ARENALib Modelica libraries

The ARENALib and SIMANLib Modelica libraries replicate the basic functionality of the Arena simulation environment and the SIMAN language. These libraries facilitate describing discrete-event models using the Arena modeling methodology. ARENALib and SIMANLib models can be combined with other Modelica models in order to describe complex hybrid systems (i.e., combined continuous-time and discrete-event systems). The implementation and design of SIMANLib and ARENALib is discussed. The ARENALib components have been built in a modular fashion using SIMANLib. The SIMANLib components have been described as Parallel DEVS models and implemented using DEVSLib, a Modelica library previously developed by the authors to support the Parallel DEVS formalism. The use of Parallel DEVS as underlying mathematical formalism has facilitated the development and maintenance of SIMANLib. The modeling of two hybrid systems is discussed to illustrate the features and use of SIMANLib and ARENALib: firstly, a soaking-pit furnace; secondly, the malaria spread and an emergency hospital. DEVSLib, SIMANLib and ARENALib can be freely downloaded from http://www.euclides.dia.uned.es/.     

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.     

一个通信系统的面向对象建模

OORAM是挪威工业研究中心和奥斯陆大学提出的一种新一代面向对象软件工程方法,而UseCase是目前在学术界和工业界已普遍接受的概念,通过结合UseCase和OORAM方法,对一个通信系统的面向对象建模进行了阐述。     

A hybrid model for real time simulation of urban traffic

In this paper a hybrid model is presented to predict the behavior of traffic in urban area. Intersections and on/off-ramps are modeled by Colored Timed Petri Nets while road links are modeled by a stochastic discrete time model. It is assumed that vehicle routings at each intersection are stochastic. A Particle Filter algorithm based on the hybrid model is developed to estimate the system state. The validation of the model by using real data is discussed. The limited computational effort required makes the model suitable to be used in simulation-based control schemes for urban traffic.     

面向对象的离散事件系统仿真软件的多线程实现

对象交互是近年来离散事件系统仿真中采用的一种比较先进的仿真建模方法。面向对象技术的采用,使它比传统的三种建模策略都更接近人的思维方式和实际系统的特征,因而建模能力较强。文章提出的多线程的实现方案,通过线程来模拟实际系统中各个独立地、并发地运行的实体,线程间通过消息传递相互影响,推进仿真进程,不仅提高了仿真效率,易于处理并发等复杂情况,也大大简化了软件的实现。     

面向对象离散事件仿真平台的设计

在对一般的离散事件系统仿真的共性进行抽象分析和建模基础上,采用面向对象思想设计开发了一个较通用的离散事件仿真平台类库,平台库采用C 编写,内嵌离散仿真计算引擎,封装了离散仿真程序设计的大部分通用底层功能,并且预定义了一些用户建模的常用类模块,具备使用简单有效,通用性好,代码重用性和扩展性强等特点.通过平台,仿真建模人员可以将主要精力集中于仿真系统的分析建模和逻辑描述方面,能大大减少建模时间,提高工作效率.     

异形螺杆加工过程动态仿真系统研究与实现

该文以面向对象分析和设计为基础，利用C 和OpenGL，使用三角形图元造型来研究数控机床加工异形螺旋杆的仿真过程。对工件和刀具求交问题进行了研究，提出了加工过程的三维仿真算法，得到了较实用的软件仿真系统，使整个复杂螺杆的加工过程从参数输入、刀具设计选择、干涉判定、插补计算、三维仿真到数控程序生成和控制加工完善地结合起来。     

Automated synthesis of hybrid Petri net models for robotic cells in the aircraft industry

The use of robots in the aircraft structural assembly is a challenge. The presence of human operators, auxiliary systems and industrial robots makes hybrid the dynamic behavior of a robotic cell in this context. Here, the focus is on the automated synthesis of a model for the sequencing of the activities of a robotic cell in the aircraft industry. The cell model is obtained from a simple specification of resources and tasks, considered the main cell components, running the algorithm presented in this paper. The effectiveness of the model is shown using a case study defined by the ongoing European project LOCOMACHS (LOw COst Manufacturing and Assembly of Composite and Hybrid Structures, http://www.locomachs.eu/).     

State observability and condition observability for a class of interacting discrete event systems

This paper introduces the concepts of state observability and condition observability for condition systems, a class of systems composed of discrete state components which interact via discrete binary signals called conditions. Given a set of externally observed conditions, state observability implies that the state of the system can be determined from the observations, and condition observability implies that all unobserved input and output conditions of the system can be determined from the observations. In this paper, we present a class of systems which is state observable and condition observable. We present a method to synthesize an observer system to provide state and condition signal estimates for a single component subsystem.     

A high performance framework for modeling and simulation of large-scale complex systems

Due to the quick advances in the scale of problem domain of complex systems under investigation, the complexity of multi-input component models used to construct logical processes (LP) has significantly increased. High-performance computing technologies have therefore been extensively used to enable parallel simulation execution. However, the traditional multi-process parallel method (MPM) executes LPs in parallel on multi-core platforms, which ignores the intrinsic parallel capabilities of multi-input component models. In this study, a vectorized component model (VCM) framework has been proposed. The design aims to better utilize the parallelism of multi-input component models. A two-level composite parallel method (CPM) has then been constructed within the framework, which can sustain complex system simulation applications consisting of multi-input component models. CPM first employs MPM to dispatch LPs onto a multi-core computing platform. It then maps VCMs to the multiple-core platform for parallel execution. Experimental results indicate that (1) the proposed VCM framework can better utilize the parallelism of multi-input component models, and (2) CPM can significantly improve the performance comparing to the traditional MPM. The results also show that CPM can effectively cope with the size and complexity of complex simulation applications with multi-input component models.     

卫星军用系统的联邦成员辅助开发工具研究

高层体系结构HLA是建模仿真领域的通用技术框架，以实现不同仿真系统之间的互操作。在面向卫星军事应用系统的HLA应用开发过程中，FOM／SOM的开发是一个重要步骤。该文对HLA联邦成员辅助开发工具进行了研究，论述了它的总体结构、功能模块和实现中的一些关键技术。同时文章还阐明了其在HLA联邦设计与开发过程中的重要作用。     

极小-极大-加系统(F,G,H)的能达能观性

在数字电路中,两个时间信号通过逻辑电路的"与"门相当于极大运算,"或"门相当于极小运算.因此,极小-极大-加系统可用于数字电路的时间分析.对于非线性极强的极小-极大-加系统(F,G,H),引入了分别能达和上限能观的概念.利用图论的方法给出了极小-极大-加系统(F,G,H)的状态变量xt为分别能达分量的充要条件,同时,还得到了xt为上限能观分量的充要条件.     

有线电视收费管理系统的分析、设计与开发

该文围绕ＣＡＴＶＭＩＳ收费管理系统的开发全过程,详细阐述了面向对象建模技术（ＯＭＴ）在ＣＡＴＶＭＩＳ开发过程中的应用;论述了通过ＲＤＢ和ＰＢ来实现ＯＭＴ分析、设计模型的全过程。     

Implementing a hybrid simulation model for a Kanban-based material handling system

Plant floor material handling is a loose loop in most assembly plants. Simulation offers a quick, controllable and tunable approach for prototyping complex material handling processes in manufacturing environments. This paper proposes a hybrid simulation approach, using both discrete event and agent-based technologies, to model complex material handling processes in an assembly line. A prototype system is implemented using a commercial multi-paradigm modeling tool. In this prototype, JIT principles are applied to both the production and the material handling processes. The system performance is evaluated and system optimization directions are suggested. The proposed hybrid modeling approach facilitates the implementation of a responsive and adaptive environment in that various “what-if” scenarios can be simulated under different simulation configurations and real-time situations.     

Partial Order Techniques for Distributed Discrete Event Systems: Why You Cannot Avoid Using Them

Monitoring or diagnosis of large scale distributed Discrete Event Systems with asynchronous communication is a demanding task. Ensuring that the methods developed for Discrete Event Systems properly scale up to such systems is a challenge. In this paper we explain why the use of partial orders cannot be avoided in order to achieve this objective. To support this claim, we try to push classical techniques (parallel composition of automata and languages) to their limits and we eventually discover that partial order models arise at some point. We focus on on-line techniques, where a key difficulty is the choice of proper data structures to represent the set of all runs of a distributed system, in a modular way. We discuss the use of previously known structures such as execution trees and unfoldings. We propose a novel and more compact data structure called “trellis.” Then, we show how all the above data structures can be used in performing distributed monitoring and diagnosis. The techniques reported here were used in an industrial context for fault management and alarm correlation in telecommunications networks. This paper is an extended and improved version of the plenary address that was given by the second author at WODES’ 2006.

Government preparedness: Using simulation to prepare for a terrorist attack

The heightened threat of terrorism has caused governments worldwide to plan for responding to large-scale catastrophic incidents. In England the New Dimension Programme supplies equipment, procedures and training to the Fire and Rescue Service to ensure the country's preparedness to respond to a range of major critical incidents. The Fire and Rescue Service is involved partly by virtue of being able to very quickly mobilize a large skilled workforce and specialist equipment. This paper discusses the use of discrete event simulation modeling to understand how a fire and rescue service might position its resources before an incident takes place, to best respond to a combination of different incidents at different locations if they happen. Two models are built for this purpose. The first model deals with mass decontamination of a population following a release of a hazardous substance—aiming to study resource requirements (vehicles, equipment and manpower) necessary to meet performance targets. The second model deals with the allocation of resources across regions—aiming to study cover level and response times, analyzing different allocations of resources, both centralized and decentralized. Contributions to theory and practice in other contexts (e.g. the aftermath of natural disasters such as earthquakes) are outlined.     

Using TRIO for designing a CORBA‐based application

We report on our experience in the Esprit OpenDREAMS project that targets the domain of Supervision and Control Systems (SCS). During this project we studied how a CORBA‐based application can be designed starting from a typical SCS requirement document by integrating a formal approach with some CORBA concepts. We present a case study that shows how an existing object‐oriented methodology based on the formal specification language TRIO can be tailored towards supporting CORBA‐based applications. The application taken into account is in the field of the Energy Management Systems, namely a diagnostic system for the steam condenser of a thermoelectric power plant. The paper describes how to obtain the architectural design of a CORBA‐based application starting from the formal specification of its requirements expressed in TRIO by means of a sequence of transformation steps. At the end of such sequence of steps a complete structure of the application classes, with their mutual relations and their IDL interfaces, is built. Finally, the paper discusses how TRIO can be used to validate the architectural choices made with respect to the application critical requirements. Copyright © 2000 John Wiley & Sons, Ltd.     

The synthesis and PLC implementation of hybrid modular supervisors for real time control of an experimental manufacturing system

In this paper, synthesis and PLC based implementation of hybrid modular supervisors for real time supervisory control of an experimental manufacturing system are proposed. The hybrid approach couples Ramadge–Wonham (RW) supervisors in the form of automata to uncontrolled PN models through inhibitor arcs. The RW supervisors can be obtained in monolithic or modular forms. In the monolithic case, there is only a single supervisor that has complex structure and huge number of states and events. The modularity of supervisors provides simple and small control structures compared to monolithic ones. Modular hybrid approach offers fewer states for the PLC implementation of the hybrid controller with less memory requirements. The applicability and effectiveness of the modular hybrid approach are demonstrated by the PLC based real-time control of an experimental manufacturing system for different cases. The obtained results show that modular supervisors require less memory space compared to monolithic counterparts.     

Hybrid optimization and simulation to design a logistics network for distributing perishable products

Dynamics in product quality complicate the design of logistics networks for perishable products, like flowers and other agricultural products. Complications especially arise when multiple products from different origins have to come together for processes like bundling. This paper presents a new MILP model and a hybrid optimization–simulation (HOS) approach to identify a cost-optimal network design (i.e. facility location with flow and process allocation) under product quality requirements. The MILP model includes constraints on approximated product quality. A discrete event simulation checks the feasibility of the design that results from the MILP assuming uncertainties in supply, processing and transport. Feedback on product quality from the simulation is used to iteratively update the product quality constraints in the MILP. The HOS approach combines the strengths of strategic optimization via MILP and operational product quality evaluation via simulation. Results, for various network structures and varying degrees of dynamics and uncertainty, show that if quality decay is not taken into account in the optimization, low quality products are delivered to the final customer, which results in not meeting service levels and excess waste. Furthermore, case results show the effectiveness of the HOS approach, especially when the change from one iteration to the next is in the choice of locations rather than in the number of location. It is shown that the convergence of the HOS approach depends on the gap between the product quality requirements and the quality that can be delivered according to the simulation.