• 전력전자학회논문지
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• 제18권6호
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• pp.587-592
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• 2013

In this paper, the performance improvement of the sensorless control of IPMSM employing the active flux concept by the improved current estimator is presented. The accuracy of the current estimator used in a previous report is degraded when the motor parameters are not known exactly. A simple current estimator derived from estimated flux is proposed to improve the position estimation performance. In order to show the usefulness of the proposed estimation method, the simulation results using Matlab/Simulink and the experiment results are presented.

• The Journal of the Acoustical Society of Korea
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• 제19권2E호
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• pp.14-19
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• 2000

The forward propagated ultrasonic fields resulting from a circular plane or a concave transducer in layered fluid media as well as in homogeneous water are theoretically estimated by the angular spectrum method(ASMJ) combined with Rayleigh-Sommerfeld diffraction theory(RSDT), and measured by a precision 3-D scanning system with a needle-point hydrophone. To make the aliasing error negligible on the 2-D FFT in the theoretical estimation, the spatial discretization in the ASM are carefully considered for optimal selection of spatial sampling intervals and the size of discretization area. It is shown that the estimated fields agree reasonably with the measured ones.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 추계학술대회 논문집 학회본부
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• pp.113-115
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• 1997

This paper presents an efficient method which can estimate the system with unmodeled dynamics using D-L networks. The proposed method is to estimate system with unmodeled dynamics recursively from only input-output information, which can exclude additional procedure for system description and thus reduce the required computational burden for real-time estimation. Higher convergence speed is achieved with our manner when compared with widely-used conventional methods.

• 대한전기학회논문지:시스템및제어부문D
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• 제55권1호
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• pp.31-34
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• 2006

A simple robust fundamental frequency estimator on the time-frequency domain is proposed. Combined with the appropriately designed low-pass filter, the instantaneous frequency estimator based on the Teager-Kaiser energy function can detect the fundamental frequency of speech signal. The Teager-Kaiser function can be obtained through real computation and show the change of frequency as time goes. And when a speech block with N samples is processed with a lowpass fille. with length of L, it requires $O(N{\cdot}(L+5))operations,$ compared to $O(N{\cdot}2log_2N+L))operations$ in the recently introduced wavelet and conventional instantaneous frequency method. The computer simulation confirms the usefulness of the proposed fundamental frequency estimation method.

• 대한기계학회논문집A
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• 제40권8호
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• pp.703-710
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• 2016

로보틱스 연구에서, 모바일 로봇의 모션 제어를 위해서는 로봇의 실제 위치를 정확히 추정하는 것이 중요하다. 이를 위해 본 연구에서는, 두 개의 서로 다른 센서 데이터를 칼만필터로 융합하여 로봇의 위치인식을 개선하는 연구를 진행한다. 칼만필터로 융합한 두 개의 센서 측정값은 카메라 영상으로부터 측정된 모바일 로봇의 전역(global) 위치 좌표(x, y)값과 모바일 로봇 바퀴에 부착된 엔코더로부터 측정된 로봇의 직선 및 각속도 값이다. 다음으로 칼만필터로부터 계산된 모바일 로봇의 위치값을 모바일 로봇의 자세 안정화에 피드백하여 모션 제어의 퍼포먼스를 향상시켰다. 최종적으로 논문에서 제안한 센서융합 위치인식 기술과 모션제어기를 실제 로봇에 적용하여 실험적으로 검증하였다. 또한 모션제어에 단일 센서를 피드백으로 사용한 경우와 칼만필터로 융합한 위치 값을 사용한 경우를 비교하므로 칼만필터 기반 센서 융합 기술을 사용한 경우의 퍼포먼스 향상을 확인하였다.

• 대한원격탐사학회지
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• 제39권6_1호
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• pp.1185-1193
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• 2023

위성 영상을 활용하여 정확한 토양 수분도를 산정하는 연구는 원격탐사 응용 분야에 포함되는 중요한 기본 연구 주제 중 하나이다. 이 연구의 목적은 KOMPSAT-3/3A 영상과 KOMPSAT-5 SAR 영상을 적용하여 시험 지역에 대하여 토양수분도를 제작하고 산정된 결과를 정확도 검증 차원에서 미국 NASA에서 제공하는 Soil Moisture Active Passive (SMAP)의 토양수분 자료와 정량 비교하는 것이다. 한편 농림 식생 지대를 중심으로 토양수분도를 산정하기 위하여 환경공간정보서비스에서 제공하는 토지피복지도를 연구에 적용하였다. 시험 연구 지역은 이 연구에 적용한 수분 구름 모델(Water Cloud Model)에 기반한 토양수분 산정 알고리즘 적용에 필요한 입력 자료가 모두 가용한 제주 서부 지역을 선정하였다. 토양수분도 제작에 사용한 Synthetic Aperture Radar (SAR) 영상은 KOMPSAT-5 HV와 Sentinel-1 VV 영상이며, 식생지수는 KOMPSAT-3 영상의 지표반사도를 사용하였다. 이 연구에서 산출한 토양수분도 산정 결과와 SMAP (L-3) 자료를 차분 연산으로 비교하면 차이 값이 평균 4.13±3.60p%의 높은 일치도를 보이는 것으로 나타났고, SMAP (L-4) 자료와의 차분 연산 결과는 평균 14.24±2.10p% 수준의 일치도를 보였다. 이 연구를 통하여 향후 우리나라 위성영상과 공공 제공자료를 이용하여 정확도가 높은 정밀 토양수분도를 제작할 수 있는 가능성을 제시하였다.

• Communications for Statistical Applications and Methods
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• 제25권1호
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• pp.15-27
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• 2018

Parametric method of flood frequency analysis involves fitting of a probability distribution to observed flood data. When record length at a given site is relatively shorter and hard to apply the asymptotic theory, an alternative distribution to the generalized extreme value (GEV) distribution is often used. In this study, we consider the beta-P distribution (BPD) as an alternative to the GEV and other well-known distributions for modeling extreme events of small or moderate samples as well as highly skewed or heavy tailed data. The L-moments ratio diagram shows that special cases of the BPD include the generalized logistic, three-parameter log-normal, and GEV distributions. To estimate the parameters in the distribution, the method of moments, L-moments, and maximum likelihood estimation methods are considered. A Monte-Carlo study is then conducted to compare these three estimation methods. Our result suggests that the L-moments estimator works better than the other estimators for this model of small or moderate samples. Two applications to the annual maximum stream flow of Colorado and the rainfall data from cloud seeding experiments in Southern Florida are reported to show the usefulness of the BPD for modeling hydrologic events. In these examples, BPD turns out to work better than $beta-{\kappa}$, Gumbel, and GEV distributions.

• 한국소음진동공학회논문집
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• 제23권11호
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• pp.943-950
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• 2013

This paper discusses a harmonic response estimation method on the L$\acute{e}$vy plate with two opposite edges simply supported and the other two edges having free boundary conditions. Since the equation of motion of the plate is not self-adjoint, the modes are not orthogonal to each other on the domain. Noting that the L$\acute{e}$vy plate can be expressed using one term sinusoidal function that is orthogonal to other sinusoidal functions, this paper suggested the calculation method that is equivalent to finding a least square error minimization solution of the finite number of algebraic equations. Example problems subjected to a distributed area loading and a distributed line loading are defined and their solutions are provided. The solutions are compared to those of the commercial code, ANSYS. According to the verification results, it is expected that the suggested method will be useful to predict the forced response on the L$\acute{e}$vy plate with the distributed area or line loading conditions.

• Structural Engineering and Mechanics
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• 제14권4호
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• pp.381-400
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• 2002

This paper presents several applications of an improved estimator of the constitutive relation error (CRE) for plasticity problems. The cumulative aspect of the CRE estimator with respect to time is analyzed and we propose a first analysis of the local effectivity indexes of the CRE estimator in plasticity.

• Communications for Statistical Applications and Methods
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• 제2권2호
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• pp.347-349
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• 1995

In this paper a central limit theorem on $L^P(R)$ for $1{\leq}p<{\infty}$ is obtained with an example when ${X_n}$ is a sequence of independent, identically distributed random variables on $L^P(R)$.