• 대한전기학회논문지:시스템및제어부문D
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• 제50권8호
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• pp.367-375
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• 2001

In Underwater Flight Vehicle depth control system, the followings must be required. First, it needs robust performance which can get over modeling error, parameter variation and disturbance. Second, it needs accurate performance which have small overshoot phenomenon and steady state error to avoid colliding with ground surface or obstacles. Third, it needs continuous control input to reduce the acoustic noise and propulsion energy consumption. Finally, it needs interpolation method which can sole the speed dependency problem of controller parameters. To solve these problems, we propose a depth control method using Fuzzy Sliding Mode Controller with feedforward control-plane bias term and Neural Network Interpolator. Simulation results show the proposed method has robust and accurate control performance by the continuous control input and has no speed dependency problem.

• 대한의용생체공학회:의공학회지
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• 제13권2호
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• pp.125-132
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• 1992

Background EEG signals can be represented as the sum of a conventional AR process and an innovation process. It Is know that conventional estimation techniques, such as least square estimates (LSE) or Gaussian maximum likelihood estimates (MLE-G ) are optimal when the innovation process satisfies the Gaussian or presumed distribution. When the data are contaminated by outliers, however, these assumptions are not met and the power spectrum estimated by conventional estimation techniques may be fatally biased. EEG signal may be affected by artifacts, which are outliers in the statistical term. So the robust filtering estimation technique is used against those artifacts and it performs well for the contaminated EEG signal.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1990년도 하계학술대회 논문집
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• pp.77-80
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• 1990

This paper presents a continuous-time robust direct adaptive algorithm in the presence of bounded disturbances and / or unmodeled dynamics. In the new algorithm, Narendra's adaptation law is adapted. And a term, proportional to the product of tracking error and normalizing signal, is added to the conventional control law. It is shown that the performance of the adaptive schemes is improved if a proportional adaptation tera is added to the control law. The scalar case is only discussed in the stability analysis. Computer simulation is presented to complement the theoretical result.

• 제어로봇시스템학회논문지
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• 제4권2호
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• pp.170-177
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• 1998

In this paper, a unified solution of Hankel norm approximation problem is proposed by $\delta$-operator. To derive the main result, all-pass property is derived from the inner and co-inner property in the $\delta$-domain. The solution of all-pass becomes an optimal Hankel norm approximation problem in .delta.-domain through LLFT(Low Linear Fractional Transformation) inserting feedback term $\phi(\gamma)$, which is a free design parameter, to hold the error bound desired against the variance between the original model and the solution of Hankel norm approximation problem. The proposed solution does not only cover continuous and discrete ones depending on sampling interval but also plays a key role in robust control and model reduction problem. The verification of the proposed solution is exemplified via simulation for the zero-order Hankel norm approximation problem and the model reduction problem applied to a 16th order MIMO system.

• 대한전기학회논문지
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• 제39권3호
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• pp.291-300
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• 1990

This paper presents a robust discrete-time direct adaptive pole-placement with new discrete parameter adaptation algorithm (PAA), the standard RLS is suitably modified by adding a term which is exponentially proportional to the filtered tracking error and using a signal normalization. It is shown that it makes the overall adaptive system more robust in the presence of disturbances or unmodeled dynamics. In order to discuss the robustness improvement by using the input-output stability theory, the overall adaptive control system is reformulated and the sector theory is applied. In addition, computer simulation results are presented to complement the theoretical development.

• 대한수학회지
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• 제59권6호
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• pp.1153-1170
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• 2022

In this paper, we investigate the portfolio optimization problem under the SVCEV model, which is a hybrid model of constant elasticity of variance (CEV) and stochastic volatility, by taking into account of minimum-entropy robustness. The Hamilton-Jacobi-Bellman (HJB) equation is derived and the first two orders of optimal strategies are obtained by utilizing an asymptotic approximation approach. We also derive the first two orders of practical optimal strategies by knowing that the underlying Ornstein-Uhlenbeck process is not observable. Finally, we conduct numerical experiments and sensitivity analysis on the leading optimal strategy and the first correction term with respect to various values of the model parameters.

• 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.

• The Journal of Asian Finance, Economics and Business
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• 제6권2호
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• pp.75-82
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• 2019

The paper aims to investigate the impacts of long-term savings motives on fostering household participation and contribution to savings mechanisms in rural Vietnam. The paper is organized in five parts: introduction, data description, methodology, empirical results, and conclusion. The quantitative methodology is employed and three simultaneous estimation methods, including instrumental variable model, two-step model, and Heckman model are used to test these impacts as well as the robustness of results. In each model, the paper examines the impacts of independent factors on both household participation and household contribution to savings mechanisms. Two sets of independent variables: long-term savings motives (profit-making investment, accumulation for big expenditure, providing for old age, and cost of educations) and control variables (dependency rate, number of people in household, and household wealth) are in each model. A set of dataset of 2,314 households for analysis is obtained from household survey in rural Vietnam. Robust statistical findings indicate that profit-making investment emerged to be the strongest motive fostering household participation to savings mechanisms while other long-term savings motives have little or no impact on fostering household participation to savings mechanisms. In addition, education investment encourages household contribution to savings mechanisms in rural Vietnam.

• 한국정보과학회논문지:소프트웨어및응용
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• 제37권8호
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• pp.629-640
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• 2010

영상에서 일부분을 제거하거나 훼손된 영상에서 훼손된 부분을 복원하기위해 예제기반 인페인팅 방법이 주로 사용되고 있다. 예제 기반 인페인팅은 데이터 항 계산, 신뢰도 항 계산, 그리고 복사할 패치 선택 등 세가지 부분으로 구성되어 있는데 본 논문에서는 이들 각각 부분을 개선하여 기존의 예제기반 인페인팅 방법의 성능을 향상하는 방법을 제안한다. 기존에는 데이터 항을 계산하는데 편미방을 이용해서 국부적인 기울기를 구하기 때문에 잡음에 민감한 문제가 있어 이를 16개의 방향성 마스크를 사용하여 전역적 기울기를 구하도록 하여 잡음에 강건하도록 개선하였다. 신뢰도 항을 계산하는 과정에서 복원할 영역 내부에서 신뢰도 값이 매우 작아지는 문제를 개선하기 복원할 영역의 내부에서 신뢰도 항이 천천히 감소하도록 하는 방법을 제안하였다. 또한 복원할 영역에서 가까운 패치에 가중치를 주도록 패치 선택 방법을 개선하였다. 여러 가지 영상에 대한 실험한 결과 제안된 방법을 통한 인페인팅이 기존의 예제 기반 인페인팅보다 자연스럽게 복원함을 알 수 있었으며 훼손된 영상을 복원하는 경우에도 제안된 방법이 기존 방법보다 오차가 줄어듦을 알 수 있었다.

• 대한전기학회논문지
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• 제40권6호
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• pp.606-614
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• 1991

A robust direct adaptive controller with respect to additive and multiplicative unmodeled dynamics is designed. A new term, proportional to the product of the bounded tracking error and normalizing signal, is added to the conventional control input for improvement of robustness and performances of an adaptive system. It is shown by the mathematical analysis and simulation results that the stability of the closed loop system is guaranteed and the performance of the system is improved.