Discrete Event System Specification Research Articles

C-DEVS형식론을 이용한 실시간 이산사건 제어시스템의 논리 해석 기법

실시간 시스템의 복잡도가 증가함에 따라 임시방편적 시스템 해석 방법은 시스템 동작 영역 전체를 완전하게 분석하는 데는 한계가 있다. 모델링을 기반으로 한 정형 기법은 그러한 한계점을 극복 할 수 있다. 본 논문은 모델 기반 정형 기법을 이용하여 실시간 시스템의 안전성 및 필연성 등과 같은 논리적 타당성을 이산 사건 모델 수준에서 분석하는 방법을 제안한다. 먼저, 분석 대상 실시간 시스템은 이산사건 수준에서 계층적으로 모듈화하여 모델을 명세하는 수학적 형식론인 DEVS (Discrete Event Systems Specification) 형식론으로 기술된다. 다음으로, 기술된 DEVS 모델은 시간 명세가 포함된 전역 상태 공간을 표현하는 C-DEVS (Communicating DEVS) 형식론으로 표현한 후 C-DEVS 형식론의 해석 알고리즘을 통해 시스템 동작을 분석된다. 제안된 C-DEVS 형식론 및 해석 알고리즘은 주어진 시스템의 동작 특성을 분석하는 과정에서 시스템의 상태 공간을 완전하게 빠짐없이 탐색하는 것을 보장한다. 간단한 건널목 제어 시스템의 안전성 분석 사례 연구를 통하여 제안된 모델 기반 해석 기법의 효율성을 예시 하였다. As complexity of real-time systems is being increased ad hoc approaches to analysis of such systems would have limitations in completeness and coverability for states space search. Formal means using a model-based approach would solve such limitations. This paper proposes a model-based formal method for logical analysis, such as safety and liveness, of real-time systems at a discrete event system level. A discrete event model for real-time systems to be analyzed is specified by DEVS(Discrete Event Systems Specification) formalism, which specifies a discrete event system in hierarchical, modular manner. Analysis of such DEVS models is performed by Communicating DEVS (C-DEVS) formalism of a timed global state transition specification and an associated analysis algorithm. The C-DEVS formalism and an associated analysis algorithm guarantees that all possible states for a given system are visited in an analysis phase. A case study of a safety analysis for a rail road crossing system illustrates the effectiveness of the proposed method of the model-based approach.

Parameter optimization of simulation models for material supply in an emergent disaster based on support vector machine

Modeling material supply in emergent disasters has become an effective means to foster emergency relief, for which Agent-DEVS (discrete event system specification) model parameter optimization is important. Based on fundamental support vector machine (SVM) principles, a parameter optimization flow for an Agent-DEVS model is put forward, and a parameter optimization model for the supply task parameter in simulation models for material supply in an emergent disaster is established. Some key techniques, including data extraction and preprocessing, kernel function selection and SVM model parameter preferences, are analyzed, and the comparison with the back-propagation neural network is examined. A simulation test shows that SVM has strong learning and fitting capabilities and weak dependence on samples. It enhances the dynamics of Agent-DEVS models. The self-learning ability significantly improves model intelligence and the optimized parameters provide models with more elaborate descriptive abilities.

Micro-Macro Modeling for Systems Biology with MR-DEVS

System-level understanding, which provides specific views on the system of interest focusing both on a macro and on a micro view, has been a recurrent theme in systems biology modeling. However only little work has been done to directly support the micro-macro linking explicitly in a modeling formalism. Multi-resolution discrete event systems specification (MR-DEVS) was introduced to model biology at system-level. MR-DEVS can model upward and downward causation and adapt to represent those systems with emergence and controlling relationship between the micro level and macro level in a biological system. Moreover, MR-DEVS is closed under coupling. And so, it can also model biological process at multiply level hierarchically and modularly.

Graphical modeling and simulation of discrete-event systems with CD++Builder

We introduce CD++Builder, an open-source environment that aims at providing easy-to-use graphical modeling tools to simplify the construction of models and the execution of simulations of complex Discrete Event System Specification (DEVS) models. The architecture and implementation of CD++Builder focuses on providing simple definition and reuse of components, offering easy extensibility to support new features. CD++Builder includes graphical editors for DEVS-coupled models, DEVS-Graphs and C++ atomic models; it provides code templates that are synchronized with their graphical versions, and it greatly simplifies the software installation and update procedures. We show how this environment can be used to build and simulate DEVS models, and we compare the process with previous versions and other simulation tools, showing that CD++Builder can improve model development by creating DEVS models in a completely assisted manner, including advanced graphical interfaces.

DEVS 형식론을 이용한 공항 PAR 관제 시스템 자동화 방안 검증

ABSTRACTThis paper proposes automatic precision approach radar (PAR) control system using digital signal to increase the safety of aircraft, and discrete event systems specification (DEVS) methodology is utilized to verify the proposed system. Traditionally, a landing aircraft is controlled by the human voice of a final approach controller. However, the voice information can be missed during transmission, and pilots may also act improperly because of incorrectness of auditory signals. The proposed system enables the stable operation of the aircraft, regardless of the pilot’s capability. Communicating DEVS (C-DEVS) is used to analyze and verify the behavior of the proposed system. A composed C-DEVS atomic model has overall composed discrete state sets of models, and the state sequence acquired through full state search is utilized to verify the safeness and the liveness of a system behavior. The C-DEVS model of the proposed system shows the same behavior with the traditional PAR control system.

NCW 통신 체계의 전투 효과도 분석을 위한 NetSPIN 통신 모델과 워게임 모델의 시뮬레이션 연동

ABSTRACTDue to the development of communication system in the warfare, the future warfare is changing to network-centric warfare (NCW). In the NCW, the communication effect has a significant influence on the combat power. There is growing importance for analysis of communication effect in the combat power. There are many researches about this issue, but there is no study on analysis using relationship between communication system and combat power. In this paper, we illustrates interoperation environment consisting of NetSPIN communication model and wargame model to analyze influence of parameters of communication model on combat effectiveness of wargame model. The wargame model is a corps-scaled model based on Discrete Event System Specification (DEVS) formalism. The communication model is a corps-scaled SPIDER network model of NetSPIN based on OPNET. Especially, we uses OAI matrix to identify parameters in communication simulator influencing on combat power, and analyze relationship between parameters and combat power through design of experiment and simulation by using them. For the future work, we expect that requirement analysis of communication equipment in NCW by using meta-modeling method

A novel parallelization technique for DEVS simulation of continuous and hybrid systems

In this paper, we introduce a novel parallelization technique for Discrete Event System Specification (DEVS) simulation of continuous and hybrid systems. Here, like in most parallel discrete event simulation methodologies, the models are first split into several sub-models which are then concurrently simulated on different processors. In order to avoid the cost of the global synchronization of all processes, the simulation time of each sub-model is locally synchronized in a real-time fashion with a scaled version of physical time, which implicitly synchronizes all sub-models. The new methodology, coined Scaled Real-Time Synchronization (SRTS), does not ensure a perfect synchronization in its implementation. However, under certain conditions, the synchronization error introduced only provokes bounded numerical errors in the simulation results. SRTS uses the same physical time-scaling parameter throughout the entire simulation. We also developed an adaptive version of the methodology (Adaptive-SRTS) where this parameter automatically evolves during the simulation according to the workload. We implemented the SRTS and Adaptive-SRTS techniques in PowerDEVS, a DEVS simulation tool, under a real-time operating system called the Real-Time Application Interface. We tested their performance by simulating three large-scale models, obtaining in all cases a considerable speedup.

Collaborative Modeling Process for Development of Domain-Specific Discrete Event Simulation Systems

The discrete event systems specification (DEVS) formalism supports the object-oriented (OO) specification of discrete event models in a hierarchical, modular manner. If a system that is to be modeled is domain-specific, the development of models with the use of the DEVS formalism would require domain knowledge about the system as well as to understand DEVS semantics. This paper proposes a collaborative modeling process to compensate for the lack of professional engineers. To compensate, this modeling process utilizes three types of engineers: domain engineer, modeling and simulation (M&S) engineer, and platform engineer. The process consists of four steps: conceptual modeling, model partition, model implementation, and model integration/simulation. The system requirements are used to specify domain models in the conceptual modeling step, and the models are partitioned into two types: discrete event-level model (DEM) and behavioral-level model (BM). The DEM is specified as the DEVS formalism, and the BM is defined as algorithms and equations. Each model is implemented separately, and the implemented models are integrated and simulated flexibly by using a dynamic linking library. The modeling process is then applied to develop a war game simulator. The advantage of this modeling process is that the collaborative work is related to the whole series of steps. This collaboration maximally utilizes the capabilities of the professional engineers by seamlessly separating yet correlating their works.

무기체계 교전 시뮬레이션을 위한 매트랩 기반 이산사건시뮬레이션 프레임워크의 개발

시뮬레이션 프레임워크는 시뮬레이션 응용 프로그램의 개발을 지원하는 기반 소프트웨어이다. 본 논문은 공학용 프로그래밍 언어로 광범위하게 사용되는 매트랩을 이용하여 개발된 이산사건시뮬레이션 프레임워크의 개발 과정을 기술하고 있다. 매트랩 객체지향프로그래밍을 토대로 새롭게 개발된 프레임워크는 매트랩 언어의 편리성과 이산사건시뮬레이션 형식론(DEVS: Discrete EVent System Specification Formalism)이 가지는 뛰어난 개발 방법론을 결합시킴으로써 무기체계 교전 시뮬레이션 프로그램 개발에서 요구되는 생산성, 유연성, 확장성을 제공한다. 더불어 매트랩의 병렬컴퓨팅 기술을 적용한 배치(Batch) 시뮬레이션 기능을 제공함으로써 몬테카를로 시뮬레이션 수행시 컴퓨터 환경에서 지원되는 CPU 코어의 수에 비례하여 응용 프로그램의 연산성능을 향상시킨다. Simulation Framework is a basic software tool used to develop simulation applications. This paper describes the development of a discrete event simulation framework based on DEVS(Discrete EVent System Specification) formalism, using MATLAB language which is widely used in technical computing and engineering disciplines. The newly developed framework utilizing MATLAB object oriented programming combines the convenience of MATLAB language and the sophisticated architecture of the DEVS formalism. Hence, it supports the productivity, flexibility, extensibility that are required for the simulation application software development of the weapon systems engagement. Moreover, it promises a simulation application the increased the computation speed proportional to the number of CPU of a multi-core processor, providing the batch simulation functionality based on MATLAB parallel computing technology.

Structured DEVS Formalism: 이산사건 시스템의 구조적 모델링 기법

최근 몇 십년간 이산사건시스템명세(DEVS) 형식론은 이산사건시스템을 모듈러하고 계층적으로 모델링할 수 있는 잘 정의된 의미론을 제공하여 왔다. 그럼에도 불구하고 실용 엔지니어들은 실세계의 시스템을 모델링에 적용하는데 어려움을 겪기도 하는데 이는 DEVS가 많은 상태와 사건들을 구조화되지 않은 형태로 명세해야 하는 것 때문이다. 본 논문은 집합 이론을 바탕으로 그러한 사건 및 상태집합들을 구조화된 형태로 표현하는 Structured DEVS 형식론과 이와 연관된 DEVS 다이어그램을 제안하고자 한다. 위상, 변수, 포트 등의 개념을 사용하여 집합들을 명세한 구조적 DEVS 형식론은 원래의 DEVS 형식론과 동등함을 증명하였다. DEVS 다이어그램을 이용하여 구조적 DEVS 형식론으로 표현된 예시 모델이 쉽게 객체지향 시뮬레이션 환경에서 구현될 수 있음을 보임으로써 제안된 형식론이 효과적임을 보였다. In recent decades, it has been known that the Discrete Event System Specification, or DEVS, formalism provides sound semantics to design a modular and hierarchical model of a discrete event system. In spite of this benefit, practitioners have difficulties in applying the semantics to real-world systems modeling because DEVS needs to specify a large size of sets of events and/or states in an unstructured form. To resolve the difficulties, this paper proposes an extension of the DEVS formalism, called the Structured DEVS formalism, with an associated graphical representation, called the DEVS diagram, by means of structural representation of such sets based on closure property of set theory. The proposed formalism is proved to be equivalent to the original DEVS formalism in their model specification, yet the new formalism specifies sets in a structured form with a concept of phases, variables and ports. A simplified example of the structured DEVS with the DEVS diagram shows the effectiveness of the proposed formalism which can be easily implemented in an objected-oriented simulation environment.

System theoretic foundations of modeling and simulation: a historic perspective and the legacy of A Wayne Wymore

AW Wymore, the founder of the world’s first systems engineering department at the University of Arizona, has been at the origin of the system theoretic foundations of modeling and simulation. Wymore’s intellectual family tree, which goes back to Gauss and Weierstrass, is given. How the authors met, cooperated, and advocated system theory for the advancement of modeling and simulation are explained. The concept of model-based simulation was also one of the outcomes of this cooperation. This article reviews the emergence of systems-theory-based modeling and simulation languages and environments, such as the General System Theory implementor and Discrete Event System Specification, and their relation to Wymore’s concepts. We also discuss the application of powerful software development frameworks to support user-friendly access to systems concepts and to increase the power to support systems design and engineering.

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.

A simulation approach for optimal design of RFID sensor tag-based cold chain systems

This study introduced a systematic approach for assessing alternative operational models and to determine optimal values for some of the core design parameters in an RFID sensor tag-based cold chain system. First of all, we defined an RFID and sensor data collection and storage model. Next, we developed an RFID sensor tag-based cold chain simulation model and a simulator based on Discrete Event System Specification (DEVS) formalism. Finally, based on a case study, we demonstrated a procedure for determining the optimal sensing interval value with the proposed simulator. The results from the case study have shown that the proposed approach presents important advantages to analyze the Key Performance Indicator (KPI) of cold chain systems according to changes of RFID sensor tag-based cold chain system’s operation models and parameter values.

A Qualitative Comparison of Two Hybrid DEVS Approaches

A hybrid system is defined as a system with mixed discrete event and continuous parts. Two ap- proaches for modeling and simulation of hybrid systems in the context of the Discrete EVent System Specification (DEVS) formalism are compared. Since the system theoret- ic DEVS approach has been introduced during the 1970ies, it has been completed by different extensions. The hybrid extensions checked against each other here, are the Quan- tized State Systems (QSS) method and a wrapper concept based on traditional ODE solvers. For a comparison from engineering practice point of view, these two hybrid DEVS approaches are analyzed within the scientific and technical computing environment MATLAB.

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.

군수지원시스템을 위한 에이전트 기반의 객체 지향 시뮬레이션 모델 아키텍처 설계 방법론

본 논문의 목적은 복잡한 군수지원시스템의 모델링과 시뮬레이션을 위한 방법론을 제안하는 것이다. 제안하는 군수지원시스템 시뮬레이션 모델을 구성하는 요소들은 세 가지가 있다 : Logistics force agent(static model), Military supplies transport manager(function model), Military supplies state manager(dynamic model). Logistics force agent는 main function agent와function agent로 구성된다. Function agent가 다른 Logistics force agent에도 적용할 수 있도록 설계되었으며, 이는 에이전트의 높은 조합성과 재사용성을 가진다. Military supplies transport manager는 보급로에 대한 정보를 가지며 military supplies state manager로부터 받은 결정변수를 기반으로 보급로를 결정하고 군수품을 수송하는 역할을 하는 에이전트이다. Military supplies state manager는 군수품 보급을 요청받고 보급량, 우선순위 따위의 결정 변수를 military supplies transport manager에게 알려주는 역할을 한다. 본 논문에서는 군수 시뮬레이션 모델의 설계를 위해 Discrete Event Systems Specification(DEVS) formalism을 이용하였다. Proposed in the paper is an agent based and object-oriented methodology to create a virtual logistics support system model. The proposed virtual logistics support system model consists of three types of objects: the logistics force agent model(static model), the military supplies transport manager model(function model), the military supplies state manager model(dynamic model). A logistic force agent model consists of two agent: main function agent and function agent. To improve the reusability and composability of a logistics force agent model, the function agent is designed to adapt to different logistics force agent configuration. A military supplies transport manager is agent that get information about supply route, make decisions based on decision variables, which are maintained by the military supplies state manager, and transport military supplies. A military supplies state manager is requested military supplies from logistics force agent, provide decision variables such as the capacity, order of priority. For the implementation of the proposed virtual logistics force agent model, this paper employs Discrete Event Systems Specification(DEVS) formalism.

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.

Torpedo evasion simulation of underwater vehicle using fuzzy-logic-based tactical decision making in script tactics manager

An underwater vehicle such as a submarine or a torpedo is a complex and complicated weapon system composed of various systems and subsystems. Usually, it takes around 10years, a substantial amount of money, and many research and development resources to complete the development of an underwater vehicle, right from the concept design to the mass production. Recently, in order to reduce the number of trial-and-error instances required for verifying the operation of an underwater vehicle, modeling and simulation (M&S) has been investigated and applied to an engineering-level simulation to analyze the performance of a system and a subsystem and to an engagement-level simulation to analyze the tactical and operational effectiveness. In this paper, we introduce a method for applying fuzzy logic to the tactical decision making of an underwater vehicle in an engagement-level simulation. In the scenario of an engagement between a light torpedo pursuing a submarine and the submarine attempting to evade the attack, the evasion methods for the submarine are modeled in fuzzy logic after tacticalization. For the simulation, we modeled a light torpedo and a submarine on the basis of DEVS (Discrete Event System Specification). Further, when a tactical decision had to be taken, the submarine model calls the tactics manager implemented outside of the model and passes its own state variables, which are necessary for tactical decision making, to the tactics manager. The tactics manager used in the tactical decision making process supports Lua and the Python scripting languages and is self-implemented. The tactics description of the submarine was implemented using Python scripting grammar and stored as a Python file (∗.py) to be inputted to the tactics manager. As the simulation results, we present the implemented fuzzy Python tactic description file of the submarine evasion tactics and the possibilities of submarine survival according to the tactics as a comparison. Finally, as the fundamental research on the application of artificial intelligence to the tactical decision making method of the model used in the engagement-level simulation, this work suggests the fuzzy-based tactics description method and presents the detailed procedures for the various actions, and their adopting effectiveness.

Automatic generation of equations of motion for multibody system in discrete event simulation framework

In this paper, the development of a simulation program that can automatically generate equations of motion for mutibody systems in the discrete event simulation framework is presented. The need to analyze the dynamic response of mechanical systems that are under event triggered conditions is increasing. General mechanical systems can be defined as multibody systems that are collections of interconnected rigid bodies, consistent with various types of joints that limit the relative motion of pairs of bodies. For complex multibody systems, a systematic approach is required to efficiently set up the mathematical models. Therefore, a dynamics kernel was developed to automatically generate the equations of motion for multibody systems based on multibody dynamics. The developed dynamics kernel also provides the numerical solver for the dynamic analysis of multibody systems. The general multibody dynamics kernel cannot deal with discontinuous state variables, event triggered conditions, and state triggered conditions, though. To enable it to deal with multibody systems in discontinuous environments, the multibody dynamics kernel was integrated into a discrete event simulation framework, which was developed based on the discrete event system specification (DEVS) formalism. DEVS formalism is a modular and hierarchical formalism for modeling and analyzing systems under event triggered conditions, which are described by discontinuous state variables. To verify the developed program, it was applied to an block-lifting and transport simulation, and dynamic analysis of the system is carried out.

Simulation of wind farm operations and maintenance using discrete event system specification

Wind farms provide a source of clean and renewable energy. However, unlike many industries where machines are operated under more or less static conditions, wind turbines suffer from stochastic loading due to the hourly or seasonal variation of wind speed and direction. The stochastic loading of wind turbines makes their degradation or failure prediction rather complex. This in turn makes the decision-making process of when and what type of maintenance action to undertake very challenging. This paper uses the discrete event system specification (DEVS) to develop a simulation model for wind farm operations and maintenance. The DEVS methodology1 provides a formal modeling and simulation framework based on dynamical systems theory and allows for hierarchical and modular model construction. We report on implementation results based on historical data that provide useful insights into wind farm operations under two different maintenance strategies, scheduled maintenance and condition-based maintenance. The results show that condition-based maintenance enables more wind power generation by reducing wind turbine failure rates and thus increasing wind turbine available.