Discrete Event System Simulation Research Articles

Maneuvering control simulation of underwater vehicle based on combined discrete-event and discrete-time modeling

When designing or acquiring underwater vehicles such as submarines and torpedoes, it is necessary to predict their performance precisely and perform tests repeatedly using modeling and simulation at both the engineering level and the tactical engagement level. For simulation performed for analysis purposes at the engineering level, which requires a considerable amount of computation power, a discrete-time system simulation that computes significant values at every single unit time using the established mathematical model or engineering model is mainly employed. To simulate a complex or complicated task such as a traffic analysis or tactical measure of effectiveness (MOE) analysis at the engagement level, it is appropriate to use a discrete-event system simulation that causes transition between model states through the triggering of events on the basis of the passing of messages between simplified mathematical models coupled in various ways. In this paper, we studied a maneuvering control of underwater vehicle from the perspective of a combined discrete-event and discrete-time system simulation; the simulation model is established on the basis of discrete-event system specification (DEVS) formalism, which is a representative modeling formalism of a discrete-event system simulation. In detail, the simulation includes DEVS modeling implementations of simulation execution time control and discrete-time step size control in real time at the time of performing a discrete-time system simulation for the purpose of three-dimensional visualization or carrying out a performance analysis using the DEVS model. This hybrid approach makes possible to build a simulation-based expert system which supports the decision making for the acquisition of an underwater vehicle.

Um modelo híbrido simulação-otimização para análise de capacidade de um sistema de transporte ferroviário de granéis agrícolas em ciclo fechado

Neste artigo é proposto um modelo híbrido simulação-otimização para a análise de políticas operacionais para o transporte ferroviário de grãos em um sistema fechado que possibilitem aumentar a sua capacidade global. O núcleo do modelo proposto é um sistema de simulação discreta por eventos desenvolvido em linguagem "Visual Basic for Applications" (VBA), o qual possibilita analisar regras mais flexíveis para decisões quanto ao tratamento de filas. Mais especificamente, dez decisões relacionadas às operações ferroviárias (alocação de ativos ferroviários e gestão de filas) são substituídas por regras de priorização que buscam refletir as decisões tomadas na prática. É também proposta uma heurística baseada no algoritmo de Hooke & Jeeves para determinar o melhor subconjunto de regras de priorização. O modelo foi aplicado a um problema real que corresponde ao sistema de transportes de grãos constituído pela Ferrovia Centro-Atlântica, Estrada de Ferro Vitória a Minas e pelo o Porto de Tubarão. Os resultados demonstram que essas regras de priorização proporcionam maior capacidade global do sistema quando comparadas as decisões mais simples próprias de um modelo de simulação discreta por eventos.

Automatic simulation model generation supported by data stored in low level controllers

One of the most widespread techniques to evaluate various aspects of a manufacturing system is discrete-event simulation (DES). However, building a simulation model of a manufacturing system is a difficult task and needs great resource expenditures. Automated data collection and model buildup can drastically reduce the time of the design phase as well as support model reusability. Since most of the manufacturing systems are controlled by low level controllers (e.g., PLCs, CNCs) they store structure and control logic of the system to be modeled by a DES system. The paper introduces an ongoing research of PLC program processing method for automatic simulation model generation of a conveyor system of a leading automotive factory. Results of the validation process and simulation experiments are also described through a case study.

Execution Data Connected Simulation for Production Operation Planning and Control

Abstract Due to the large number of the resources, the frequent reengineering of manufacturing processes and the often changing product types, the maintenance of the simulation model and the provision of up-to-date input data are almost always difficult. The paper introduces new quantitative analysis method including processing time and batch calculation algorithms applied in the automatic building of discrete-event simulation systems. The simulation model and the mentioned algorithms are both directly interfaced with real execution databases and the overall solution supports the shop-floor managers in making control decisions. The applicability of the elaborated approach is illustrated by the results of experiments relying on real historical data.

SiMA: a discrete event system specification-based modelling and simulation framework to support model composability

In this paper we briefly present our views on composability of models and interoperation of simulations; we introduce our simulation software framework, namely Simulation Modelling Architecture (SiMA), and we present our contributions to the underlying formal model (i.e. discrete event system specification). We also present our simulation construction environment, which supports composability of simulation models through a simulation construction tool chain. Finally, we provide a case study where a sample simulation scenario is used to demonstrate the features of our SiMA environment that facilitate composability of simulation models.

Supporting dynamic simulations with Simulation Modeling Architecture (SiMA): a Discrete Event System Specification-based modeling and simulation framework

In this paper, we present our approach to introduce dynamism support to simulation environments, which adopts a Discrete Event System Specification (DEVS)-based modeling and simulation approach and builds upon previous work on Simulation Modeling Architecture (SiMA), a DEVS-based simulation framework developed at TUBITAK UEKAE. In the relevant literature there are already proposed solutions to the dynamism support problem. One particular contribution offered in this study over previous approaches is the systematic framework support for post-structural-change state synchronization among models with related couplings, in a way that benefits from the strongly typed execution environment SiMA provides. In addition to introducing theoretical extensions to basic SiMA, we report the results of performance measurements to illustrate the added value of dynamism extensions over the basic version, using a sample wireless sensor network simulation.

Automatic Simulation Model Generation Based on PLC Codes and MES Stored Data

One of the most widespread techniques to evaluate various aspects of an existing manufacturing system is discrete-event simulation (DES). However, building a simulation model of a manufacturing system needs great resource expenditures. Automated data col-lection and model buildup can drastically reduce the time of the design phase as well as support model reusability. Since most of the manufacturing systems are controlled by low level controllers they store structure and control logic of the system to be modeled by a DES system. The paper introduces an ongoing research of PLC code processing method for automatic simulation model gen-eration of a conveyor system of a leading automotive factory.

Managing Distribution in Refined Products Pipelines Using Discrete-Event Simulation

The management of oil-product pipelines represents a critical task in the daily operation of petroleum supply chains. Efficient computational tools are needed to schedule pipeline operations in a reliable and cost-effective manner. This work presents a novel discrete event simulation system for the detailed scheduling of a multiproduct pipeline consisting of a sequence of pipes that connects a single input station to several receiving terminals. The pipeline is modeled as a non-traditional multi-server queuing system involving a number of servers at every pipe end that perform their tasks in a synchronized manner. By using alternative priority rules, the model decides which server should dispatch the entity waiting for service to the associated depot. Also, the model deals with the timely fulfillment of terminal demands and the system response to unexpected events. In combination with optimization tools, the proposed simulation technique permits to easily manage real-world pipelines operations with low computational effort.

Modelling and optimisation of assembly processes

The following article is a case study for scheduling of assembly processes. Two optimisation methods, mixed integer programming solver and heuristic simulation-based optimisation are compared to each other. It can be shown, up to which model complexity the solver methods have the advantage over the simulation-based methods concerning a possible online application. Both the mathematical formulation as well as the discrete event simulation system, bases on a meta-model – a special Petri net. It is shown that bipartite graphs, i.e. Petri nets, avoid ambiguities in the case of alternative assembly sequences and have advantages in comparison to the usual simple precedence graphs. The results of optimisation experiments are described by the example of assembling a numeric controlled milling table. The model is capable of reflecting multiple parallel assembly processes, alternative assembly steps and can predict characteristics like utilisation, stock or adherence to schedules.

A hybrid simulation framework for the evaluation of common radio resource management scenarios

We present a hybrid modeling framework with interacting simulative and analytic submodels for the efficient evaluation of common radio resource management (CRRM). It enables a cost–benefit investigation of different CRRM algorithms and architectures. Centralized as well as decentralized scenarios can be clearly defined by five standard components, namely the radio access system, the environment, the user equipment, the CRRM information manager, and the CRRM decider. The costs and time consumption of CRRM operations are taken into account via chargeable messages. The clarity of the model enables an efficient investigation of CRRM algorithms based on optimization theory, game theory, physical models, and other methods. The resulting framework has been implemented as a hybrid simulation model using the discrete event simulation system OMNeT++. A convenient and straightforward integration of different wireless network technologies and user service demands is also supported; models for the universal mobile telecommunications system (UMTS) and the global system for mobile communications/enhanced general packet radio service (GSM/EGPRS) are already integrated. The scope of the proposed framework is demonstrated by the evaluation of realistic scenarios.

Exploring airport traffic capability using Petri net based model

The first part of the paper introduces a novel tool for modeling and simulation of discrete event system. This tool called GPenSIM is a Petri net based simulator and offers significant benefits to model builders such as flexibility to include diverse libraries, ease of extending the models, and ease of programming. The second part of the paper presents a case study on modeling and optimization of airport traffic management; this study is to explore air traffic management capability of Evenes airport in Norway. The case study shows that with GPenSIM, modeling and simulation problems of large industrial discrete event systems can be done. Future research directions are discussed as well.

A Modified Statistical Process Control Approach for Warm-up Selection in Discrete-Event Simulation

HLA-based simulation systems are multivariate discrete-event simulation systems, and sometimes with small samples in essential, for which exists initial transient issue. Simulation models begin in fixed initial values, which are always different from the steady state values. A variety of selection methods have been developed these years, but no one method could be recommended above others. Among these methods, the familiar statistical process control method is a popular way to deal with the warm-up selection, with the deficiency for multivariate and small samples. Based on SPC, individuals and moving range, multivariate exponentially weighted moving average chart for Individuals and Hotelling T2 method, a modified SPC method is proposed. The case of military domain simulation scenario and some empirical experiments, illustrate the validity of the modified SPC method.

Studying performance of DEVS modeling and simulation environments using the DEVStone benchmark

The Discrete Event System Specification (DEVS) formal modeling and simulation (M&S) framework (which supports hierarchical and modular model composition) has been widely used to understand, analyze and develop a variety of systems. Numerous DEVS simulators have been developed; nevertheless, evaluating the performance of such simulators is a complex process and it has been usually done using ad hoc methods. DEVStone, instead, is a synthetic benchmark that can be used to automate the evaluation of the performance of DEVS-based simulators. DEVStone generates a suite of models with varied structure and behavior automatically. To do so, it uses a standardized mechanism that can be the basis for comparisons between simulation software tools. As a proof of the concept, we present various tests in which DEVStone was used to study the efficiency of five different simulation engines. In this case, we compared various versions of the CD++ simulator, and then compared its performance with the ‘A Discrete Event System Simulator’ (ADEVS) M&S tool. This is the first effort in which these simulation tools have been thoroughly compared with a very demanding set of experiments. The use of DEVStone allowed a standardized and exhaustive method to compare different features of the simulation software. We show how the basic ideas used for DEVStone facilitates performance analysis for upgrades and updates of a given simulation engine, while also providing a common metric to compare different M&S environments.

Optimisation approaches for batch scheduling in semiconductor manufacturing

In this research, several approaches for the optimisation of batch processes are investigated and compared. The motivation for this is the analysis of an oven work centre in a semiconductor wafer fab. Different objectives like keeping operational due dates as well as the minimisation of lot completion time will be optimised with regard to existing process constraints. First, the problem is modelled from two different viewpoints: as scheduling problem and with the help of a simulation system. For this, it used mixed integer programming (MIP) and a discrete event simulation system respectively. As a next step, a MIP time window decomposition approach combining simulation and mathematical programming is discussed. This reduces the complexity of the given problem by solving local sub-problems. Experiments on real manufacturing data determine the optimisation potential for the work centre using the different approaches. This allows, among others, a comparison to dispatching strategies as they are used in the manufacturing line.

Contributors

Contributors

The Design of Multi-Level Interrupt Virtual Experiment Based on Object-Oriented

The virtual reality technology is a three-dimensional virtual environment composed by computer hardware, software and various of sensors. It creates an unprecedented wealth of content and more fantastic teaching environment which reflects strong advantage in experiment and practice. In accordance with the needs of experiment teaching, multi-level interrupt virtual experiment environment is studied combining with the characteristics of its principle. The experiment environment is based on Tec-xp test box designed and developed by Tsinghua University computer factory. Microsoft Visual C++6.0 language is adopted for software platform development. Seen from the system needs analysis, object-oriented simulation method is adopted for modeling in this experiment environment. Meanwhile combining with computer system features and the characteristics of Computer Organization Principle teaching, the basic theory and methods of discrete event system simulation are used, which make the operation of virtual environment the same as on real device.

Modelling and simulation of complex manufacturing systems using statechart-based actors

This paper describes a multi-agent architecture based on the actors computational model, for the distributed simulation of discrete event systems whose entities have a complex dynamic behaviour. Complexity is dealt with by exploiting statechart-based actors which constitute the basic building blocks of a model. Actors are lightweight reactive autonomous agents that communicate to one another by asynchronous message passing. The thread-less character of actors saves memory space and fosters efficient execution. The behaviour of actors is specified through “distilled statecharts” that enable hierarchical and modular specifications. Distributed simulation is achieved by partitioning a system model among a set of logical processes (theatres). Timing management and inter-theatre communications rest in a case on the High Level Architecture services. The paper illustrates the practical application of the proposed modelling and simulation methodology by specifying and analysing a complex manufacturing system.

An efficient optimistic time management algorithm for discrete-event simulation system

Time Wrap algorithm is a well-known mechanism of optimistic synchronization in a parallel discrete-event simulation (PDES) system. It offers a run time recovery mechanism that deals with the causality errors. For an efficient use of rollback, the global virtual time (GVT) computation is performed to reclaim the memory, commit the output, detect the termination, and handle the errors. This paper presents a new unacknowledged message list (UML) scheme for an efficient and accurate GVT computation. The proposed UML scheme is based on the assumption that certain variables are accessible by all processors. In addition to GVT computation, the proposed UML scheme provides an effective solution for both simultaneous reporting and transient message problems in the context of synchronous algorithm. To support the proposed UML approach, two algorithms are presented in details, with a proof of its correctness. Empirical evidence from an experimental study of the proposed UML scheme on PHOLD benchmark fully confirms the theoretical outcomes of this paper. (Received in June 2009, accepted in April 2010. This paper was with the authors 5 months for 3 revisions.)

Bridge construction schedule generation with pattern-based construction methods and constraint-based simulation

This paper presents a novel methodology which assists in automating the generation of time schedules for bridge construction projects. The method is based on a simulation of construction works, taking into account the available resources and the interdependencies between individual tasks. The simulation is realized by means of a discrete-event simulation software originally created for plant layout in the manufacturing industry. Due to the fact that the fixed process chains provided are too rigid to model the spontaneous construction task sequences, a constraint module that dynamically selects the following task has been incorporated. Constraint module input data is formed by activity packages comprising of the affected building element, the required material, machine and manpower resources, as well as the technological pre-requisites of the activity to be performed. Since manual creation of the large set of activity packages is laborious and error-prone, a 3D model-based application has been developed which allows the interactive assignment of construction methods to individual building elements. To facilitate this process, a level-of-detail approach has been implemented which allows the user to successively refine both the process model and the corresponding product model. The discrete-event simulation system uses all the given information to create a proposal for the construction schedule automatically, which may then be refined using standard scheduling software.

Event Scheduling in Simulation of Discrete Event Systems with Application on Queuing Systems.

Queuing theory and other of discrete and continuous event systems have theory aesthetic but the more assumptions which indepent these theories are not accurate as compared with real situation, also the queue problem is one of the most scientific problems that require simulation to analysi it. Because of that the aim of this research is to design event scheduling for simulation of discrete event systems and according to simulation time with application on simple and multiple queuing using MATLAB program (V.7.0)