• Journal of the Institute of Electronics Engineers of Korea SC
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• v.46 no.2
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• pp.7-14
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• 2009

In this paper we consider the problem of global finite-time stabilization for a class of uncertain nonlinear systems which include uncertainties. The uncertainties are time-varying disturbances or parameters belong to a known compact set. The proposed design method is based on backstepping and dynamic exponent scaling using an augmented dynamics, from which, a dynamic smooth feedback controller is derived. The finite-time stability of the closed-loop system and boundedness of the controller are preyed by the finite-time Lyapunov stability theory and a new notion 'degree indicator'.

• Journal of the Korean Institute of Intelligent Systems
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• v.20 no.2
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• pp.159-164
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• 2010

This paper focuses on the stability analysis and stabilization for networked control system with neutral type of time-delay. By utilizing the delay partitioning idea, new stability criteria are proposed in terms of linear matrix inequalities(LMIs). These conditions are developed based on the Lyapunov-Krasovskii functionals. Based on the derived criteria, a sufficient condition for te solvability of this problem is obtained in terms of linear matrix inequality without decomposing the original system matrices. Also, it is shown that the proposed controller design method is general for networked control systems. Finally, illustrative examples are presented to show the applicability of the proposed method.

• Journal of the Korean Institute of Intelligent Systems
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• v.10 no.4
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• pp.357-367
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• 2000

A new robust load-frequency control methodology is proposed for nonlinear power systems with valve position limits of the governor in the presence of parametric uncertaines. The TSK fuzzy model is adopted and formulated for fuzzy modeling of the nonlinear power system. A sufficient condition of the robust stabilitry is presented in the sense of lyapunov for the TSK model with parametric uncertainties. The intekkigent digital redesign technique for the uncertain power systems is also studied. The effectiveness of the robust digital fuzzy controller disign mothod is demonstrated through a numerical simulation.

• Journal of the Korean Institute of Intelligent Systems
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• v.18 no.2
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• pp.151-156
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• 2008

This paper presents the stability analysis and design for a sampled-data fuzzy control system with neutral type of time delay, which is formed by a nonlinear plant and a sampled-data fuzzy controller connected in a closed loop. The sampling activity and neutral type of time delay will complicate the system dynamics and make the stability analysis much more difficult than that for a pure continuous-time fuzzy control system. Based on the fuzzy-model-based control approach, LMI(linear matrix inequality)-based stability conditions are derived to guarantee the nonlinear networked system stability. An application example will be given to show the merits and design a procedure of the proposed approach.

• Journal of the Institute of Convergence Signal Processing
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• v.9 no.1
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• pp.89-97
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• 2008

Chaotic behavior in motor systems is undesired dynamics in real-time implementation since the speed is oscillated in a wide range and the torque is changed by a random manner. We present an adaptive control approach for time-varying permanent-magnet synchronous motors (PMSM) with chaotic phenomenon. We consider that its parameters are changed randomly within certain bounds. First, a nonlinear system model of a PMSM is transformed to derive a nominal linear control strategy. Then, an auxiliary control for compensating real-time control error occurred by system perturbation due to parameter change is designed by using Lyapunov stability theory. Numerical simulation is accomplished for evaluating its efficiency and reliability comparing with the traditional control method. Additionally, we test our control method in real-time motor experiment including a PSoC based drive system to demonstrate its practical applicability.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.42 no.1
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• pp.13-21
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• 2005

This paper presents a fuzzy model-based approach for synchronization of time-delay chaotic system with input saturation. Time-delay chaotic drive and response system is respectively represented by Takagi-Sugeno (T-S) fuzzy model. Specially, the response system contains input saturation. Using the unidirectional linear error feedback and the parallel distributed compensation (PDC) scheme, we design fuzzy chaotic synchronization system and analyze local stability for synchronization error dynamics. Since time-delay in the transmission channel always exists, we also take it into consideration. The sufficient condition for the local stability of the fuzzy synchronization system with input saturation and time-delay is derived by applying Lyapunov-Krasovskii theory and solving linear matrix inequalities (LMI's) problem. A numerical example is given to demonstrate the validity of the proposed approach.

• Journal of Advanced Navigation Technology
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• v.19 no.6
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• pp.574-580
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• 2015

The stability condition of linear discrete interval systems with a time-varying delay time is considered. The considered system has interval system matrices for both non-delayed and delayed states with time-varying delay time within given interval values. The proposed condition is derived by using Lyapunov stability theory and expressed by very simple inequality. Compared to previous results, the stability issue on the interval systems is expanded to time-varying delay. Furthermore, the new condition can imply the existing results on the time-invariant case and show the relation between interval time-varying delay time and stability of the system. The proposed condition can be applied to find the stability bound of the discrete interval system. Some numerical examples are given to show the effectiveness of the new condition and comparisons with the previously reported results are also presented.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2002.03a
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• pp.417-423
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• 2002

Magnetorheological(MR) 댐퍼는 적은 용량의 전력을 사용하고 반응속도가 빠른 장점 때문에 구조물의 내진제어에 적당하여, 근래에 주목받고 있는 새로운 장치이다. MR 댐퍼는 반능동 제어 장치로써, 능동 질량감쇠기와는 다른 특성을 갖는다. 즉 필요한 제어력을 제어신호로 직접 생성해 낼 수 없는 대신에 MR 댐퍼의 입력전원을 제어하여 간접적으로 제어한다. 따라서 MR 댐퍼의 반능동 제어장치로써의 특성을 고려하는 효과적인 제어기법이 요구된다. 그러므로 본 연구에서는 지진에 대한 구조물의 응답을 줄이기 위해서, MR댐퍼를 제어할 수 있는 반능동 제어기법을 Lyapunov 안정성 이론을 바탕으로 제안하고자 한다. 제안방법을 검증하기 위해, 전단형 MR 댐퍼를 1층과 2층에 설치한 수치예제를 수행하였다.

• Proceedings of the KIEE Conference
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• 2004.07d
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• pp.2248-2250
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• 2004

본 논문에서는 유연한 단일링크 매니퓰레이터의 끝단 위치 추적제어를 위해 웨이블렛 신경망을 이용한 강인 적응제어기를 제안한다. 전체 제어기는 웨이블렛 신경망에 의해 추정된 피드백 선형화 제어기와 그 추정오차를 보상하기 위한 보상제어기로 구성된다. 시스템의 출력값은 최소위상을 보장하기 위하여 재정의하여 사용된다. 구성된 웨이블렛 신경망의 연결 가중치는 Lyapunov 안정도 이론에 기초해서 조절된다. 제안된 제어기의 성능 향상은 PD 제어기와 비교함으로써 입증된다.

• Journal of the Korean Institute of Intelligent Systems
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• v.11 no.2
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• pp.109-114
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• 2001

본 논문에서는 비선형 제어시스템의 성능 개선을 위한 새로운 신경망 직접 적응제어 알고리즘을 제시하였다. 제어칙은 Gaussian RBF 신경망을 이용한 제어입력과 근사화 오차 및 외란의 영향을 제거하기 위한 보조제어 입력으로 구성하였다. 또한 신경망에 사용된 가중치와 보조입력의 파라미터를 조정하기 위한 적응칙은 Lyapunov 안정도 이론에 의하여 구하였다. 이렇게 함으로써 외란이나 근사화 오차에 관계없이 플랜트와 기준모델 사이의 오차가 0이 되도록 하는 알고리즘을 구할 수 있었다. 또한 제시된 알고리즘의 효용성을 알아보기 위하여 Duffing forced oscillation 시스템에 대하여 시뮬레이션 하여본 결과 만족할만한 성능을 얻을 수 있었다.