• 대한기계학회논문집
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• 제19권9호
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• pp.2142-2153
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• 1995

A digital preview controller using optimal LQ control theory is suggested for tandem cold mills to achieve a remarkable improvement of the thickness accuracy. Optimal preview control system is constructed for each rolling stand of tandem cold mills for which the blocked noninteracting control is carried out, and it is compared with the optimal LQ control system which has only feedback control. And in the cases that all/some of disturbance inputs are previewable, full and partial preview controllers are designed, and their performance effects are compared and discussed. The simulation results show that the performance of tandem cold mills can be improved largely through partial preview control.

• 대한조선학회논문집
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• 제45권5호
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• pp.469-476
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• 2008

In this paper, it is shown that an input-output (I/O) feedback linearized controller can be designed rationally by utilizing the time-scale properties of heave and pitch for an underwater vehicle. It is assumed that the dynamics of the vehicle is restricted to the vertical plane. An output-feedback control is designed, which stabilizes steady cruising paths. It is shown that the vehicle dynamics with acceleration as output becomes minimum phase. The dynamics can be transformed into a reduced system through a kind of partial linearization and singular perturbation technique. The reduced system is not only minimum phase but also exactly I/O linearizable via feedback. The I/O dynamic characteristics of the heave and pitch modes can be made linear and decoupled. Furthermore it becomes independent of cruising condition such as vehicle velocity. This study may help for designing autopilot systems for underwater vehicles.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 추계종합학술대회 논문집(1)
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• pp.141-144
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• 2000

PRML (partial response maximum-likelihood) 과 FDTS/DF (fixed-delay tree search with decision feedback)는 기록 저장 시스템에서 준최적의 성능을 보임이 잘 알려져 있다. 그러나, 위와 같은 정보열 검출 기법은 피할 수 없는 복잡도 문제를 가지고 있다. 본 논문은 최소 run 길이 제한조건 d=2를 가진 광기록 채널을 위한 다양한 저복잡도 검출 기법을 다룬다. 우선, 결정 궤환 기법을 이용한 이산 정합 여파기 (discrete matched filter with decision feedback：DMF/DF)가 기존의 PRML로부터 유도된다. 유도된 시스템은 PRML보다 결정 궤환에 의한 성능 이득을 갖는다. 또한, 메트릭 계산을 사용하지 않는 저복잡도 FDTS/DF가 유도된다. 모의실험 결과에 의하면, 유도된 저복잡도 검출 기법들은 기록 밀도 S>=5.5에서 P(D)=1+D+D/sup 2/+D/sup 3/의 target을 갖는 PRML보다 우수한 성능을 보인다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2005년도 추계종합학술대회
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• pp.85-88
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• 2005

Space-time code is a good solution to get transmit diversity. During the last years a number of space-time block codes have been proposed for use in multiple transmit antenna systems. This code, however, was presented only for the special case of the certain numbers of transmit antennas and the certain modulation schemes. and designed under the assumption that the transmitter has no knowledge about the channel. In this work, on the other hand, we consider the case when the transmitter has partial, but not perfect knowledge about the channel. This system can have full diversity for arbitrary number of the transmit antennas with a little bits of feedback.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1993년도 한국자동제어학술회의논문집(국제학술편); Seoul National University, Seoul; 20-22 Oct. 1993
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• pp.197-201
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• 1993

A method for the closedloop control of the torsional tip motion of a piezo-polymer actuator is presented. The application of Lyapunov's direct, method to the problem is explored. A feedback control of the torsional tip motion of tile piezopolymer actuator is derived by considering tile time rate of change of the total energy of the system. If the angular velocity of the tip of the actuator is known, all the modes of tile actuator can be controlled simultaneously. This approach has tile advantage over the conventional methods in the respect that it allows one to directly with tile system's partial differential equations without resorting to approximations.

• 제어로봇시스템학회논문지
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• 제5권5호
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• pp.630-639
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• 1999

To achieve fast loading and unloading of containers from a container ship, quick suppression of the remaining sway motion of the container at the end of each trolley stroke is crucial. Due to the pendulum motion of the container and disturbances like sind, residual sway always exists at the end of trolley movement. In this paper, the sway-control problem of a container crane is investigated. A two-stage control is proposed. The first stage is a time optimal controlfor the purpose of fast trolley traveling. The second stage is a nonlinear control for the quick suppression of residual sway, which starts right after the first stage while lowering the container. The nonlinear control is investigated in the perspective of controlling an underatuated mechanical system, which combines partial feedback linearization to account for the known nonlinearities as much as possible, and variable structure control to account for the unmodeled dynamics and disturbances. Simulation and experimental results are provided.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1994년도 하계학술대회 논문집 A
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• pp.310-312
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• 1994

A partial shunt regulator (PSR) which is the power regulator of KOREASAT is modeled. The modeling of the PSR consist of solar array, power circuit, controller. and load models. To realize simple structure. a voltage source of the PSR controller is used the output voltage of the PSR. The model of the PSR has very complex structure with two additional coupled feedback loops. The complex model is simplified to a simple meaningful model with only main feedback control loop. The proposed model is compared to a PSR model with DC voltage source at the PSR controller. The proposed PSR model is verified by comparing the model with SPICE simulation for small signal analysis.

• Journal of Electrical Engineering and information Science
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• 제1권1호
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• pp.29-38
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• 1996

To improve the reliability of control systems, certain robustness to plant uncertainties and disturbance inputs is required in terms of well founded mathematical basis. Robust control theory was set up and developed until now from this motivation. In this field, H$_2$or H\ulcorner norm performance measures are frequently used nowadays. Moreover a mixed H$_2$/H\ulcorner control problem is introduced to combine the merits of each measure since H$_2$control usually makes more sense for performance while H\ulcorner control is better for robustness to plant perturbations. However only some partial analytic solutions are developed to this problem under certain special cases at this time. In this paper, the mixed H$_2$/H\ulcorner control problem is considered. The analytic(or semi-analytic) solutions of (sub)optimal mixed H$_2$/H\ulcorner state-feedback controller are derived for the scalar plant case and the multivariable plant case, respectively. An illustrative example is given to compare the proposed analytic solution with the existing numerical one.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제7권12호
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• pp.3200-3219
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• 2013

This paper proposes an adaptive combined scalable video coding (CSVC) system for video transmission over MIMO-OFDM (Multiple-Input Multiple-Output-Orthogonal Frequency Division Multiplexing) broadband wireless communication systems. The scalable combination method of CSVC adaptively combines the medium grain scalable (MGS), the coarse grain scalable (CGS) and the scalable spatial modes with the limited feedback partially from channel state information (CSI) of MIMO-OFDM systems. The objective is to improve the average of peak signal-to-noise ratio (PSNR) and bit error rate (BER) of the received video stream by exploiting partial CSI of video sources and channel condition. Experimental results show that the delivered quality using the proposed adaptive CSVC over MIMO-OFDM system performs better than those proposed previously in the literature.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1988년도 전기.전자공학 학술대회 논문집
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• pp.410-413
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• 1988

In this paper, the real-time optical associative memory using multiple hologram which is generated with two angular multiplexed reference beams and Fourier transformed object beam in the $BaTiO_{3}$ crystal based on DFWM mechanism. When one image is recorded in the $BaTiO_{3}$ crystal, complete image can be recalled by 9 % partial input of the stored original image without any additional thresholding and optical feedback process. As an experimental result of multiple Fourier hologram which is recorded with two binary images, OHCHAS and PARKHK, we can obtain complete image recalled by 1/6 partial input of the stored image.