• 대한전기학회:학술대회논문집
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• 대한전기학회 2011년도 제42회 하계학술대회
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• pp.1916-1917
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• 2011

A development of a new moving obstacle avoidance algorithm using a delay-time Compensation for a network-based autonomous mobile robot is proposed in this paper. The moving obstacle avoidance algorithm is based on a Kalman filter through moving obstacle estimation and a Bezier curve for path generation. And, the network-based mobile robot, that is a unified system composed of distributed environmental sensors, mobile actuators, and controller, is compensated by a network delay compensation algorithm for degradation performance by network delay. The network delay compensation method by a sensor fusion using the Kalman filter is proposed for the localization of the robot to compensate both the delay of readings of an odometry and the delay of reading of environmental sensors. Through some simulation tests, the performance enhancement of the proposed algorithm in the viewpoint of efficient path generation and accurate goal point is shown here.

• 한국음향학회지
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• 제24권1호
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• pp.58-68
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• 2005

본 논문에서는 잡음 환경에서 강인한 음성 인식을 위하여 특징 보상 기법의 성능을 향상시킬 수 있는 방법을 제안한다. 기존의 음성 모델 기반의 특징 보상 기법에서 이용되는 오염 음성 모델 추정 방식은 입력 음성에 대한 변별력 있는 사후 확률 예측을 보장하지 못하며, 부정확하게 계산된 사후 확률은 복구된 음성에서 명료도 하락의 문제를 일으킨다. 제안하는 기법에서는 오염 음성 모델 추정 과정에 분별적 훈련 방식의 하나인 최소 분류 오류 (MCE) 훈련 기법을 도입한다. MCE 훈련 기법을 적용하기 위해 변별력 하락의 가능성을 가지는 '경쟁 요소' 를 결정하는 기법을 제안한다. 병렬결합된 혼합 모델 (PCMM) 기반의 특징 보상에 MCE 훈련 기법을 적용하는 과정을 제안하고 변별력 향상의 영향을 관찰한다. Aurora 2.0 데이터베이스와 실제 자동차 주행 환경에서 수집된 음성 데이터베이스에 대한 성능 평가를 실시한다. 실험 결과는 제안한 기법이 음성 인식 성능 향상에 도움이 되는 것을 입증한다.

• KDI Journal of Economic Policy
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• 제38권3호
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• pp.17-35
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• 2016

In many advanced countries, most outside directors are executives, active or retired, at other firms; in other words, executives from other companies make executive compensation decisions. This situation may hinder the board of directors (BOD) in their efforts to optimize executive compensation levels objectively. Using a panel data analysis of the S&P 1500 companies, we provide supplemental evidence of whether, and to what extent, the concurrent executive employment of outside directors distorts the executive pay decisions at a given company. An unbiased fixed-effect estimation confirms that a $1.00 increase in CEO pay at outside directors' primary companies results in an approximate increase of $0.22 in CEO pay at the given company. From a policy perspective, this added agency problem - caused by the BOD and not by management - is noted as difficult to control; although a firm may establish board independence, the inherent concurrent employment of directors on a board continues to exist.

• 전기학회논문지
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• 제68권3호
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• pp.430-438
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• 2019

For a pump or a compressor motor, a high periodic load torque variation is induced by the mechanical works, and it causes system vibration and noise. To minimize these problems, load torque compensation method, injecting periodic torque current, could be utilized. However, with the sensorless control method, which is usually utilized in the pump and compressor for low cost, the periodic torque current degrades the accuracy of the rotor position estimation owing to the inductance variation. This paper analyzes the rotor position and speed estimation error of sensorless control method with constant motor parameters under period loading. Assuming the constant speed by the accurate load torque compensation, the speed error equation is derived in frequency domain with inductance depending on the stator current. Further, it is also shown that the rotor position error could be minimized by compensating the inductance variation. The simulation and experimental results verify that the derived speed error model and the validity of the inductance compensation method.

• Journal of Electrical Engineering and Technology
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• 제11권6호
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• pp.1707-1713
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• 2016

This paper proposes a dc error compensation algorithm using dq-synchronous coordinate transform digital phase-locked-loop in single-phase grid-connected converters. The dc errors are caused by analog to digital conversion and grid voltage during measurement. If the dc offset error is included in the phase-locked-loop system, it can cause distortion in the grid angle estimation with phase-locked-loop. Accordingly, recent study has dealt with the integral technique using the synchronous reference frame phase-locked-loop method. However, dynamic response is slow because it requires to monitor one period of grid voltage. In this paper, the dc offset error compensation algorithm of the improved response characteristic is proposed by using the synchronous reference frame phase-locked-loop. The simulation and the experimental results are presented to demonstrate the effectiveness of the proposed dc offset error compensation algorithm.

• 전기학회논문지
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• 제60권5호
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• pp.1011-1016
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• 2011

This paper presents a robust current controller for a surface-mounted permanent magnet synchronous motor(SPMSM) by using a PI observer. The decoupling PI(proportional-integral) controller combined with an additional feed-forward compensation has been used for the current controller. The classical feed-forward compensation using velocity information and system parameters is not expected to achieve a robust performance against parameter uncertainties. This paper has adopted a PI observer for the feed-forward compensation to cope with parameter uncertainties without using velocity information. A simple PI observer has been designed to compensate the disturbances that represent velocity coupled terms and parameter uncertainties. Experimental results as well as computer simulations with 630W SPMSM confirm that the proposed approach can deal with the effects of the disturbance and improve the control performance.

• 한국방송∙미디어공학회:학술대회논문집
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• 한국방송공학회 2009년도 IWAIT
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• pp.408-412
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• 2009

In this paper, a new efficient algorithm for global motion estimation is proposed. This algorithm uses a previous 4-parameter model based global motion estimation algorithm and M-estimator for improving the accuracy and robustness of the estimate. The first algorithm uses the block based motion vector fields and which generates a coarse global motion parameters. And second algorithm is M-estimator technique for getting precise global motion parameters. This technique does not increase the computational complexity significantly, while providing good results in terms of estimation accuracy. In this work, an initial estimation for the global motion parameters is obtained using simple 4-parameter global motion estimation approach. The parameters are then refined using M-estimator technique. This combined algorithm shows significant reduction in mean compensation error and shows performance improvement over simple 4-parameter global motion estimation approach.

• 한국정보통신학회논문지
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• 제14권4호
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• pp.959-966
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• 2010

정량적 초음파 분석(Quantitative Ultrasound Analysis)은 반향된 초음파 신호의 짧은 시간 간격의 주파수 성분을 추출하여 개별 초음파 지수의 값을 예측한다. 따라서 반향 신호의 정확한 주파수 특성 추출은 분석의 정확도와 정밀도 향상에 기본이 된다. 본 논문에서는 초음파 지수의 정량적인 예측 및 분석에 이용할 수 있는, 짧은 시간 간격의 반향 신호의 주파수 특성 추출 방법을 제안한다. 제안된 알고리듬은 인접한 반향 초음파 신호간의 위상 차이를 보상하고, 동일 반향 깊이를 가지는 작은 영역의 신호를 가중치 평균함으로써 보다 정확한 주파수 특성을 추출한다. 컴퓨터 모의 실험을 통한 수치 분석 결과, 제안된 알고리듬은 일반적인 주파수 추출 알고리듬보다 정확한 예측 결과를 보였으며, 예측 결과의 정밀도도 10% 이상 향상되었다.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1998년도 추계학술대회
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• pp.177-178
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• 1998

This paper is a study on compensation for error in estimation of mean pressure according to the change of arterial pressure shape. Because arterial pressure shape affects the mean pressure and blood volume which are important factors for measurement of blood pressure(BP), change of arterial pressure shape cause BP measurement error. In order to solve this problem, we add the compensation function C($\alpha$), depending on arterial pressure shape, to mathematical oscillometric model. Consequently, we could accurately estimate the blood pressure by correcting of the error using compensation function.

• 대한전기학회논문지:시스템및제어부문D
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• 제54권2호
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• pp.97-103
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• 2005

Most car navigation systems(CNS) estimate the vehicle's location using global positioning system(GPS) or dead reckoning(DR) system. However, the estimated location has undesirable errors because of various noise sources such as unpredictable GPS noises. As a result, the measured position is not lying on the road, although the vehicle is known to be restricted on the road network. The purpose of map matching is to locate the vehicle's position on the road network where the vehicle is most likely to be positioned. In this paper, we analyze some general map matching algorithms first. Then, we propose a map matching method using compensation vectors to improve the performance of map matching. The proposed method calculates a compensation vector from the discrepancy between a measured position and an estimated position. The compensation vector and a newly measured position are to be used to determine the next estimation. To show the performance improvement of the map matching using compensation vectors, the real time map matching experiments are performed. The real road experiments demonstrate the effectiveness and applicability of the proposed map matching.