• Journal of Industrial Technology
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• v.3
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• pp.3-8
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• 1983

미분방정식(微分方程式)으로 주어지는 높은 차수(次數)의 동특성(動特性) 시스템의 안정도(安定度)를 Lyapunov 이론(理論)을 이용(利用)하여 해석(解析)하였다. 대규모(大規模) 시스템 자체(自體)를 직접(直接) 해석(解析)함에 있어서는 그의 복잡성(複雜性)과 차수문제(次數問題)가 대두(擡頭)되어 매우 곤란하다. 따라서 가능(可能)한(限) 보다 작은 차수(次數)의 시스템으로 분할(分割)하여 해석(解析)하고 이를 다시 합성(合成)하여 종합(綜合) 해석(解析)하였으며 분할(分割)된 작은 차수(次數)의 시스템에 대해서는 수학행렬(數學行列)의 안정특성(安定特性)을 이용(利用)한 새로운 형태(形態)의 Lyapunov 함수(函數)를 사용(使用)하였다. 응용(應用)의 한 예(例)로써, 3개(個)의 동기발전기(同期發電機)를 가진 전력계통(電力系統)에 적용(適用)하여 기존(旣存)의 방법(方法)보다 용역(容易)하게 이 시스템의 안정도(安定度)를 판별(判別)할 수 있었다.

• Proceedings of the KIEE Conference
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• 1993.07a
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• pp.106-108
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• 1993

This paper gives derivations of voltage collapse conditions by using the Lyapunov function, which yields the exactly same results with the sensitivity analysis approach. On the other hand, the voltage collapse phenomenon is interpreted in the physical sense, and causes of the static voltage unstability and the dynamic voltage unstability are analyzed with the use of proposed Lyapunov function. In addition a new method is developed to calculate the power capacity limit of transmission lines with respect to voltage stability. This paper shows that it is able to analyze the voltage collapse with the Lyapunov direct method in the simple 2-bus system and proposes that the method works well by observing the variation of Lyapunov function as the load is increased in the system.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.61 no.4
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• pp.161-167
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• 2012

Energy conversion systems such as power inverters and converters are basically significant in establishing photovoltaic power systems to enhance power effectiveness. This paper proposes a new converter control method by using the Lyapunov redesign approach. We construct the proposed control mechanism linearly composed of nominal control and auxiliary control laws. The former is generally designed through a well-known power electronic technology and the latter is implemented to compensate real-time control error due to uncertain natures of converter systems in practice. For realizing adaptive control capability in the proposed control mechanism, a control parameter vector is estimated by utilizing a steepest descent based optimization method. We carry out numerical simulation with Matlab(c) software to demonstrate reliability of the proposed converter control system and conduct a comparative study to prove its superiority by comparing with a generic converter control methodology.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.1
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• pp.171-179
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• 2001

The purpose of this paper is the derivation and development of the new definitions and methods for the new estimation of robustness for the systems having structured uncertainties. This proposition adopts the theoretical analysis of the Lyapunov direct methods, that is, the sign properties of the Lyapunov function derivative integrated along finite intervals of time, in place of the original method of the sign properties of the time derivative of the Lyapunov function itself. This is the new sufficient criteria to relax the stability condition and is used to generate techniques for the robust design of control systems with structured perturbations. The systems considered are assumed to be nominally linear, with time-variant, nonlinear bounded perturbations. This new techniques demonstrate the improvement of robustness bounds from the numerical results.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.16 no.2 s.107
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• pp.207-213
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• 2006

In our previous research, we proposed a robust saturation controller which involves both control input saturation and structured real parameter uncertainties. This controller can analytically prescribed the upper and lower bounds of parameter uncertainties, and guarantee the closed-loop robust stability of the system in the presence of actuator's saturation. And the availability and the effectiveness of the proposed robust saturation controller were verified through numerical simulations. In this paper, we verify the robust stability of this controller through experimental tests. Expecially, we show unstable cases of other controllers in comparison with this controller. Experimental tests are carried out in the laboratory using a two-story test structure with a hydraulic-type active mass damper.

• Journal of the Korean Institute of Intelligent Systems
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• v.11 no.3
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• pp.208-214
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• 2001

본 논문은 시변 입력 지연을 포함한 Takagi-Sugeno (TS) 퍼지 시스템으로 표현 가능한 비선형 시스템을 위한 체계적인 제어기의 설계 기법을 제안한다. 입력 지연은 화학 공정 시스템, 인터넷 기반 가상 실험실, 자율 이동 로봇의 원격 제어등, 실제의 산업 현장에서 매우 빈번히 발생하는 현상이며 제어 시스템의 성능을 감소시키며, 안정성을 저해하는 요소로 알려져 있다. 따라서 본 논문에서 다루고자 하는 문제는 매우 실제적인 문제이며 반드시 해결하여야 할 문제이다. 본 논문은 Lyapunov-Razumikhin 안정 이론에 기반하여 TS 퍼지 모델 기반 제어기의 설계 조건을 제시한다. 최종적인 제어기의 설계 조건은 선형 행렬 부등식의 형태로 주어진다. TS 퍼지모델 기반 제어기가 안정화시킬 수 있는 입력지연의 상한 값을 최대화하기 위하여 이중 최적화 기법을 도입한다. 제안된 제어기 설계 기법의 우수성과 타당성을 입증하기 위하여 모의 실험을 수행하였다. 컴퓨터 시뮬레이션 결과, 본 논문에서 제안한 타당성을 입증할 수 있다.

• Journal of the Earthquake Engineering Society of Korea
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• v.5 no.3
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• pp.73-78
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• 2001

This paper presents sliding mode control(SMC) method using target variation rate of Lyapunov Function. SMC keeps the response of structure in sliding surface where structure is stable. It can design both linear controller and bang-bang controller. Linear control of previous research, however, can not make most of the performance of controller, because it is designed to satisfy the condition that the variation rate of Lyapunov function is minus. Also, in case of bang-bang controller, unnecessary large control force is generated. Presented method can utilize the capacity of controller efficiently by prescribing the target variation rate of Lyapunov function. Numerical simulation results indicate that the presented control methods can reduce the peak response larger than linear control, and it has control performance equivalent to bang-bang control.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2008.04a
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• pp.373-376
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• 2008

본 논문은 퍼지 펄스 폭 변조 (Pulse-width-modulation: PWM) 시스템의 안정도에 대해 다루게 된다. 복잡성을 가진 비선형 시스템은 Takagi-Sugeno (T-S) 퍼지 모델에 의해 효율적으로 논의될 수 있다. 본 논문에서는 기존의 LTI 시스템에서 논의 되었던 PWM 제어기 설계 문제를 퍼지 시스템으로 확장시킴으로써 PWM 제어기에 대한 논의의 저변을 확대시키고자 한다. 또한, 리아푸노프 (Lyapunov) 안정도에 기반 한 안정도 증명을 통해 퍼지 PWM 시스템의 안정도를 분석하고자 한다.

• Journal of the Korean Institute of Intelligent Systems
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• v.25 no.4
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• pp.349-354
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• 2015

This paper presents the stability conditions of the Takagi-Sugeno (T-S) fuzzy sampled-data filter. The error system between the T-S fuzzy system and fuzzy filter is presented. In the sense of the Lyapunov stability analysis, the stability conditions are given, which can be represented in terms of linear matrix inequalities (LMIs). The proposed stability conditions utilize the different approach from the conventional methods, and have better performance than that of the conventional ones. The simulation example is given to show the effectiveness of the proposed method.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.44 no.2 s.314
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• pp.1-9
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• 2007

In this paper, new results for perturbation bounds for unified decentralized systems by a unified approach using $\delta$ (defined as a shift operator at unified approach) are presented. Robust stability analysis of unified decentralized system is investigated by new robust stability bound under system uncertainties. New unified stability bounds are developed based on the unified Lyapunov matrix equation. It is shown that the system maintains its stability when new unified bounds are applied. Numerical example is presented to illustrate the proposed analysis.