• Transactions on Control, Automation and Systems Engineering
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• 제4권4호
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• pp.253-263
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• 2002

This paper presents an adaptive feedback linearization control scheme for induction motors using stator fluxes. By using stator flukes as states, overparameterization is prevented and control inputs can be determined straightforwardly unlike in existing schemes. This approach leads to the decrease of the relative degree for the flux modulus and thus yields a simpler control algorithm than the prior results. In this paper. adaptation schemes are suggested to compensate for the variations of stator resistance. rotor resistance and load torque. In particular, the adaptation to the variation of stator resistance with a feedback linearization control is a new trial. In addition, to improve the convergence of rotor resistance estimation, the differences between stator currents and its estimates are used for the parameter adaptation. The simulations show that torque and flux are controlled independently and that the estimates of stator resistance, rotor resistance, and load torque converge to their true values. Actual experiments on a 3.7㎾ induction motor verify the effectiveness of the proposed method.

• 전력전자학회논문지
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• 제9권5호
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• pp.413-419
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• 2004

고피나스 모델 자속관측기를 사용한 유도전동기 직접벡터제어 시스템에서 회전자 시정수에 오차가 있을 경우 시스템의 동특성이 저하되는 현상을 살펴보았으며, 이를 해결하기 위한 방안으로 MRAC를 이용한 회전자 시정수 실시간 추정 알고리즘을 제안하였다. 제안한 방식의 타당성을 검증하기 위해서 자속관측기에 사용되는 전동기 상수들의 오차가 회전자 시정수 추정에 미치는 영향을 실험적으로 분석한 결과 전동기 상수에 다소 오차가 있더라도 회전자 시정수의 추정오차는 5% 이내로 수렴됨을 보였다. 따라서 본 연구에서 제안한 회전자 시정수 추정 알고리즘을 고피나스 모델 자속관측기에 적용하게 되면 전동기 상수 변동에 강인한 유도전동기 직접벡터제어 시스템을 구현할 수 있다.

• 대한수학회보
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• 제38권1호
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• pp.29-53
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• 2001

This note presents a an indirect adaptive control scheme for first-order continuous-time systems. The estimated plant model is controllable and then the adaptive scheme is free from singularities. The singularities are avoided through a modification of the estimated plant parameter vector so that its associated Sylvester matrix is guaranteed to be nonsingular. That properties is achieved by ensuring that the absolute value of its determinant does not lie below a positive threshold. A modification scheme based on the achievement of a modified diagonally dominant Sylvester matrix of the parameter estimates is also given as an alternative method. This diagonal dominance is achieved through estimates modification as a way to guarantee the controllability of the modified estimated model when a controllability measure of the ‘a priori’ estimated model fails. In both schemes, the use of a hysteresis switching function for the modification of the estimates is not required to ensure the nonsingularity of the Sylvester matrix of the estimates.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 하계학술대회 논문집 B
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• pp.1060-1062
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• 1996

This paper presents a discrete adaptive observer for MIMO system of an IM model in DQ reference model. The IM model in the stationary frame is discretized and it is transformed into the canonical observer form. The unknown parameter is choosen as rotor speed. The adaptive law for parameter adjustment is obtained as a set of recursive equations which are derived by utilizing an exponentially weighted normalized least-square method. The proposed adaptive observer converges rapidly and is also shown to track time-varying plant parameter quickly. Its effectiveness has been demonstrated by computer simulation.

• 한국정밀공학회지
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• 제11권6호
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• pp.143-157
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• 1994

This paper is concerned with the position control of electrohydraulic servo system under parameter variation. An adaptive sliding mode control which uses the direct parameter estimation scheme, is proposed to design a robust controller for fast and accurate control of the system. It is shown that the adaptive sliding mode control algorithm is robust and effective in attaining fast and accurate position control of system under time-dependent parameter variation. It is also shown experimentally that chattering phenomena in a sliding mode control can significantly be reduced by using boundary layer technique, and that new approach in sliding mode control introducing a term proportional to the distance between the current state and the sliding surface in the control law is effective to obtain fast response and to increase stability of the system. Computer simulation on the dynamic performance of the control system is also presented.

• 한국통신학회논문지
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• 제34권2C호
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• pp.200-208
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• 2009

H.264/AVC의 매크로블록 단위의 비트율 제어 방법은 부적당한 양자화 파라미터 할당으로 인해 한 프레임에 할당된 목표 비트가 일찍 고갈되곤 하는 문제가 있다. 이 경우 잔여 매크로블록들을 부호화 하기 위해 제한 범위내의 가장 큰 양자화 파라미터가 사용되고 화질 저하로 이어진다. 또한 양자화 파라미터의 할당을 위해 사용되는 헤더 비트량 예측도 이전 프레임과 현재프레임의 부호화된 매크로블록들의 헤더 비트량의 평균으로 구해진다. 따라서 실제 발생하는 헤더 비트량과 오차가 크다. 본 논문에서는 현재 프레임에서 부호화 도중 발생하는 조기 목표 비트 고갈을 막기 위해 이전 프레임들에서 음수 목표 비트를 갖는 매크로블록의 수를 이용한 적응적 양자화 파라미터 결정 방법과 정확한 양자화 파라미터 결정을 위해 향상된 헤더 비트량 예측 방법을 제시한다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 하계학술대회 논문집 B
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• pp.1037-1041
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• 1996

Input-output linearization technique in nonlinear control does not guarantee the robustness in the presence of parameter uncertainty or unmodeled dynamics, etc. However, it has been used as an important preliminary step in achieving additional control objectives, for instance, robustness to parameter uncertainty and disturbance attenuation. An indirect adaptive control scheme based on input-output linearization is proposed in this paper. The scheme consists of a Hopfield network for process parameter identification and an adaptive sliding mode controller based on input-output linearization, which steers the system response into a desired configuration. A numerical example is presented for the trajectory tracking of uncertain nonlinear dynamic systems with slowly time-varying parameters.

• 한국산학기술학회논문지
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• 제15권2호
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• pp.1044-1050
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• 2014

매입형 영구자석 동기전동기의 제어기법으로 많이 사용되는 단위전류 당 최대 토크제어기법이 제대로 적용되려면 전동기의 고정자 저항, 인덕턴스의 값, 그리고 영구자석에 의해 형성되는 쇄교 자속과 같은 전동기 상수들의 값을 정확히 알아야 한다. 이러한 상수들의 값은 내부 온도 및 전류 등의 변화에 따라 계속 변하기 때문에 정확하게 추정하기가 매우 어렵다. 본 논문에서는 적응제어기법을 이용하여 이러한 상수들의 값을 추정하는 알고리즘을 제시한다. 제시하는 알고리즘은 MRAS(Model Reference Adaptive System)기법으로 실제 전류의 값을 이용하여 상수들을 추정하게 된다. 제시하는 알고리즘의 우수성은 시뮬레이션을 통해 입증하도록 한다.

• ETRI Journal
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• 제45권3호
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• pp.379-393
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• 2023

Underwater communication (UWC) is widely used in coastal surveillance and early warning systems. Precise channel estimation is vital for efficient and reliable UWC. The sparse direct-adaptive filtering algorithms have become popular in UWC. Herein, we present an improved adaptive convex-combination method for the identification of sparse structures using a reweighted normalized leastmean-square (RNLMS) algorithm. Moreover, to make RNLMS algorithm independent of the reweighted l₁-norm parameter, a modified sparsity-aware adaptive zero-attracting RNLMS (AZA-RNLMS) algorithm is introduced to ensure accurate modeling. In addition, we present a quantitative analysis of this algorithm to evaluate the convergence speed and accuracy. Furthermore, we derive an excess mean-square-error expression that proves that the AZA-RNLMS algorithm performs better for the harsh underwater channel. The measured data from the experimental channel of SPACE08 is used for simulation, and results are presented to verify the performance of the proposed algorithm. The simulation results confirm that the proposed algorithm for underwater channel estimation performs better than the earlier schemes.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 학술대회 논문집 전문대학교육위원
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• pp.160-164
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• 2007

MRAS observer, which is based on adaptive control theory, estimates speed and position by using optimal observer gains on the basis of Lyapunov stability theory. However, in case of MRAS theory, position estimation error is in existence because of non-linearity for inductance variation and limit cycles for position estimation. The adaptive sliding observer based on the variable structure control theory estimates the speed and position for zero of estimation error by using the sliding surface equal to the error between speed and position estimation. The binary observer estimates the rotor speed and rotor flux with alleviation of the high-frequency chattering, and retains the benefits achieved in the conventional sliding observer, such as robustness to parameter and disturbance variations. The speed and position sensorless control of SRM under the load and inductance variation is verified by the experimental results.