• 대한전기학회논문지:전력기술부문A
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• 제48권10호
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• pp.1287-1292
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• 1999

In large-scale systems, we frequently encounter the time-delay and the uncertainty, and these should be considered in the design of controller because these are the source of the degradation of the system performance and instability of system. In this paper, we consider the robust stability of the linear large scale systems with the uncertainties and the time-delays. The considered uncertainties are both structured uncertainty and the unstructured uncertainty. Also, the considered time-delays are time-varying having finite time derivative limits. Based on the Lyapunov theorem and the linear matrix inequality(LMI) technique, we present two sufficient conditions that guarantee the robust stability of the system. The conditions are expressed as the LMI forms which can be easily checked their feasibility by using the well-known LMI control toolbox. Finally, we show by two examples that our results are less conservative than the previous results.

• 한국항행학회논문지
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• 제26권6호
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• pp.504-509
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• 2022

본 논문에서는 시변 지연 시간이 있는 선형 이산 시변 구간 시스템에 비구조화된 불확실성이 존재하는 경우에 대하여 안정조건을 다룬다. 구간 시스템은 시스템 행렬들이 구간행렬의 형태로 주어지는 시스템으로 본 논문에서는 이러한 구간 시스템 행렬과 상태변수의 지연 시간이 시변인 특성을 갖는 시스템에 대하여, 비선형성을 포함하며 그 크기만을 알 수 있는 비구조화된 불확실성이 존재하는 경우에 대한 시스템의 안정조건을 제안한다. 안정조건의 유도는 리아프노프 방정식의 상한 해를 이용하는 기존 결과와는 다르게 리아프노프 안정 조건을 기반으로 이루어지며, 간단한 부등식의 형태로 표현되어 안정성 판단에 편리하게 적용될 수 있는 장점을 갖는다. 또한, 제안된 안정조건은 기존에 발표된 다양한 선형 이산 시스템에 대한 안정 조건을 포함할 수 있는 포괄적이고 강력한 것으로, 시변 지연시간 변동 크기, 불확실성의 크기와 구간행렬의 범위를 모두 조건식에 포함하게 된다. 새로운 조건의 우수함은 유도과정에서 증명되어지며 수치예제를 통하여 제안된 조건의 효용성과 우수성을 검증한다.

• 전자공학회논문지SC
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• 제40권3호
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• pp.99-108
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• 2003

본 논문에서는 시변 시간지연을 가지는 특이시스템에 대한 보장비용 상태제환 제어기 설계방법을 제시한다. 보장비용 제어기가 존재할 충분조건과 보장비용 제어기 설계방법 및 보장비용 함수의 상한치를 구하는 최적화 문제를 선형행렬부등식, 특이치 분해(singular value decomposition), 슈어 여수(Schur complements) 정리, 변수 치환 등에 의하여 제시한다. 구한 충분조건은 선형행렬부등식의 형태로 되기 때문에 보장비용 제어기의 이득과 보장비용 함수의 상한치를 포함하는 충분조건의 모든 해를 동시에 구할 수 있다, 또한, 제안한 알고리듬을 이용하면 변수 불확실성과 시변 시간지연을 동시에 가지는 특이시스템에 대한 강인 보장비용 제어기 설계문제에도 쉽게 확장됨을 보인다. 마지막으로, 제안한 알고리듬의 타당성을 수치예제를 통하여 확인한다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1998년도 제13차 학술회의논문집
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• pp.147-150
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• 1998

The report presents basic functions of Time-delay System Toolbox (for MATLAB) -the general-purpose software package for Computer Aided Design of control systems with delays. The Toolbox is a collection of algorithms, expressed mostly in m-files for simulating and analysis of MIMO linear and nonlinear systems with discrete and distributed (time-varying) delays.

• Journal of Electrical Engineering and Technology
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• 제8권6호
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• pp.1542-1550
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• 2013

This paper presents new results on delay-dependent global exponential stability for uncertain linear systems with interval time-varying delay. Based on Lyapunov-Krasovskii functional approach, some novel delay-dependent stability criteria are derived in terms of linear matrix inequalities (LMIs) involving the minimum and maximum delay bounds. By using delay-partitioning method and the lower bound lemma, less conservative results are obtained with fewer decision variables than the existing ones. Numerical examples are given to illustrate the usefulness and effectiveness of the proposed method.

• Transactions on Control, Automation and Systems Engineering
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• 제1권2호
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• pp.99-105
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• 1999

This paper presents a fuzzy H$\infty$ filtering problem for a class of uncertain nonlinear systems with time-varying delayed states and unknown inital state on the basis of Takagi-Sugeno(T-S) fuzzy model. The nonlinear systems are represented by T-S fuzzy models, and the fuzzy control systems utilize the concept of the so-called parallel distributed compensation. Using a single quadraic Lyapunov function, the stability and L2 gain performance from the noise signals to the estimation error are discussed. Sufficient conditions for the existence of fuzzy H$\infty$ filters are given in terms of linear matrix inequalities (LMIs). The filtering gains can also be directly obtained from the solutions of LMIs.

• 한국통신학회논문지
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• 제30권11A호
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• pp.1021-1026
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• 2005

본 논문에서는 시변 페이딩 채별에 적합한 멀터스텝 LS 선형예측기를 갖는 새로운 예측 CDMA 폐루프 전력 제어 방식을 제안한다. 제안된 방식은 다중 전력 제어 그룹 지연을 효과적으로 보상하여 주며 단일 스텝 예측기를 갖는 기존의 예측 CLPC 방식이나 비예측 CLPC 방식에 비하여 우수한 성능 이득을 갖는다.

• Journal of Communications and Networks
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• 제9권3호
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• pp.219-228
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• 2007

In this paper, we present a novel blind adaptive multiuser detector structure and three robust recursive filters to improve the performance in CDMA environments: Sigma point kalman filter (SPKF), particle filter (PF), and Gaussian mixture sigma point particle filter (GMSPPF). Our proposed robust recursive filters have superior performance over a conventional extended Kalman filter (EKF). The proposed multiuser detector algorithms initially use Kalman prediction form to estimated channel parameters, and unknown data symbol be predicted. Second, based on this predicted data symbol, the robust recursive filters (e.g., GMSPPF) is a refined estimation of joint multipaths and time delays. With these estimated multipaths and time delays, data symbol detection is carried out (Kalman correction form). Computer simulations show that the proposed algorithms outperform the conventional blind multiuser detector with the EKF. Also we can see it provides a more viable means for tracking time-varying amplitudes and time delays in CDMA communication systems, compared to that of the EKF for near-far ratio of 20 dB. For this reason, it is believed that the proposed channel estimators can replace well-known filter such as the EKF.

• 제어로봇시스템학회논문지
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• 제10권7호
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• pp.583-589
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• 2004

Modem control systems often use a communication network to send measurement and control signals between nodes. Communication delays can be time varying. The length of the time delays is often hard to predict and modeled as being random. This paper proposes a combined controller used to compensate network time delay by estimating the delay with the interacting multiple model (IMM). The network delay is modeled as a Markov chain and 3 modes representing heavy, medium, and low network loads are used in the IMM. The proposed method is applied to an optimal control system with double integrators and the results are compared with the existing control methods.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.915-920
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• 2003

Modern control systems often use a communication network to send measurement and control signals between nodes. Communication delays can be time varying. The length of the time delays is often hard to predict and are modeled as being random. This paper proposes a combined controller used to compensate network time delay by estimating the delay with the interacting multiple model (IMM). The network delay is modeled as a Markov chain and 3 modes representing heavy, medium, and low network loads are used in the IMM. The proposed method is applied to an optimal control system with double integrators and the results are compared with the existing control methods.