• 한국시뮬레이션학회논문지
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• 제21권4호
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• pp.35-46
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• 2012

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.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1996년도 Proceedings of the Korea Automatic Control Conference, 11th (KACC); Pohang, Korea; 24-26 Oct. 1996
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• pp.157-160
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• 1996

Physical systems axe generally continuous-time in nature. However as the data measured from these systems is generally in the form of discrete samples, and most modern signal processing is performed in the discrete-time domain, discrete-time models are employed. This paper describes methods for estimating the coefficients of continuous-time system within a closed loop control system. The method employs a recursive estimation algorithm to identify the coefficients of a discrete-time bilinear-operator model. The coefficients of the discrete-time bilinear-operator model closely approximate those of the corresponding continuous-time Laplace transform transfer function.

• Journal of Communications and Networks
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• 제1권2호
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• pp.86-88
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• 1999

The Discrete Fourier Transform (DFT) and the Inverse Discrete Fourier Transform (IDFT) are commonly used in signal processing applications, in particular in digital communication sys-tems using the multi-carrier modulation principle. In such systems an IDFT is computed at the transmitter end, and a DFT at the re-ceiver end. This paper examines a technique of computations, for which only negligible differences appear between the DFT and the IDFT calculations while the number of arithmetic operations re-quired is substantially reduced. This offers significant advantages for the design of an IDFT/DFT processor for Discrete Multitone(DMT) systems.

• 대한전자공학회논문지
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• 제26권10호
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• pp.1507-1517
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• 1989

Singular values and their gradients have been used to analyze the stability and sensitivity of continuous multiloop systems. But this method has been limited to the discrete systems. This method is extended in this paper to analyze discrete systems directly in discrete domain. To do this, derived is the relationship in the disrete system between the stability margins and the minimum singular value of the return differene matrix, and also implemented is a method which computes singular value gradients. This method is applied to the lateralattitude control loop of a remotely piloted vehide both in continuous case and discrete case for verification of its utility.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1990년도 한국자동제어학술회의논문집(국내학술편); KOEX, Seoul; 26-27 Oct. 1990
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• pp.400-405
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• 1990

This paper deals with the design technique of the controller for the discrete system control using Extended Safe Petri Net which is deduced from Petri Net as its subclass with a specific constraint and which is introduced to develop the design and analysis for the discrete systems. First, we propose a construction matrix suitable for the discrete systems that represent the marking flows which are the dynamic behavior of the discrete systems. Next, we develop a method that can design the controller for the discrete system control by analyzing the proposed construction matrix into the incidence matrix of Extended Safe Petri Net. Finally, the validity of the proposed method is shown by using the incidence matrix and matrix equation of Extended Safe Petri Net model.

• 대한전기학회논문지:전력기술부문A
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• 제48권5호
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• pp.580-585
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• 1999

This paper deals with the stability of discrete time linear systems with time varying delays in state. In this paper, the magnitude of time-varying delays is assumed to be upper-bouded. The stability of discrete time linear systems with time-varying delays in state is related with the stability of discrete time linear systems with constant time delay in state. To show this, a new Lyapunov function is proposed. Using this Lyapunov function, a sufficient condition for the asymptotic stability is derived.

• 한국시뮬레이션학회논문지
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• 제10권3호
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• pp.1-14
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• 2001

A hybrid system is defined as a mixture of continuous systems and discrete event systems. This paper first proposes a framework for hybrid systems modeling, called Hybrid Discrete Event System Specification (HDEVS) formalism. It then presents a method for simulators interoperation in which a continuous system simulator and a discrete event simulator are executed together in a cooperative manner. The formalism can specify a hybrid system in a way that a continuos system and a discrete event system are separately modeled by their own specification formalisms with a support of well-defined interface. We call such interface an A/E converter for analog-to- event conversion and an E/A converter for event-to-analog conversion. Simulators interoperation is based on the concept of pre-simulation in which simulation time for a continuous simulator is advanced in accordance with a discrete event simulator.

• Transactions on Control, Automation and Systems Engineering
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• 제2권4호
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• pp.244-247
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• 2000

In this paper, a discrete-time sliding mode controller for linear time-varying systems with disturbances is proposed. The proposed method guarantees the systems state is globally uniformly ultimately bounded(G.U.U.B) under the existence of time-varying disturbances.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1997년도 한국자동제어학술회의논문집; 한국전력공사 서울연수원; 17-18 Oct. 1997
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• pp.411-413
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• 1997

This paper presents the problem of fault-tolerant robust supervisory control of timed discrete event systems (DESs). First the concept of faults is quantitatively defined in timed DESs and fault tolerable event sequences are presented as a desired legal language. Given a timed DES with model uncertainty, the conditions for the existence of a supervisor which always guarantees fault tolerable event sequences embedded in the system are derived.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.1414-1417
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• 2003

In this paper, sliding mode controller for discrete-time nonlinear systems with uncertainties and disturbances are proposed. The concept of time-delay control (TDC) which consists of estimating the uncertain dynamics of the system through past observations of the system response is used. The proposed controller guarantees that the closed-loop system states are globally uniformly ultimately bounded (GUUB). It is also shown that the closed-loop system states are globally uniformly asymptotically stable (GUAS) if uncertainties are constant.