• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.5
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• pp.416-422
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• 2016

This paper presents preliminary performance analysis of a satellite formation flying testbed, which is under development by Astrodynamics and Control Laboratory, Department of Astronomy, Yonsei University. A model reference adaptive controller (MRAC) with a first-order reference model is chosen to enhance the response of reaction wheel system which is subject to uncertainties caused by unmodelled dynamics and measurement noise. In addition, an on-line parameter estimation (OPE) technique based on the least square is combined to eliminate the effect of angular measurement noise by estimating the moment of inertia. Both numerical simulations and hardware experiments with MRAC support the effectiveness and applicability of the adaptive control scheme, which maintains the tracking error below $0.25^{\circ}$ for the entire time span. However, the high frequency control input generated in hardware experiment strongly suggests design modifications to reduce the effect of deadzone.

• Proceedings of the Acoustical Society of Korea Conference
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• 1991.06a
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• pp.32-37
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• 1991

고해상도 신호처리의 기본적인 문제는, 관찰 데이터의 개수가 작고 신호 대 잡음비(SNR)가 낮아서, 푸리에 분석기법에 의해 주기신호가 분해되지 않는 경우에, 신호의 파라미터를 추정하는 것이라 할 수 있다. 주기신호의 주파수 추정 문제에서는 일반적으로 주기신호의 개수를 알고 있다고 가정하는데, 주기신호의 개수가 사전에 알려져 있지 않은 경우, 주파수 추정은 결국 주기신호의 개수결정문제가 되어, EVD나 SVD를 이용한 개수 결정방법이 활발히 연구되어 왔다. 고해상도 신호처리에서는 EVD나 SVD의 비선형 특성 상임게치 신호 대 잡음비가 존재하며 이 SNR보다 낮은 경우 심각한 왜곡현상을 보이게 되어, 주파수 추정 또는 주기신호의 개수결정에 큰 오차를 보이게 된다. 주기신호의 개수를 사전에 알고 있는 경우, 임게치 SNR를 낮추려는 노력으로는 overdetermined over-ranked structured correlation matrix의 rank reduction과 averaging을 이용한 신호 향상방법(signal enhancement)이 연구되어 왔다. 그러나 사전에 주기신호의 개수를 알아야만 하는 결점이 있고, 잡음이 백색이여야 하는 제약이 있었다. 일반적으로 환경 잡음은 유색이고, 주기신호의 개수를 사전에 모르는 경우이므로, 낮은 SNR에서의 주파수 추정문제는 유색잡음을 고려한 신호향상으로 임게치 SNR을 낮추고 주기신호의 개수를 결정한 후 주파수 추정이 이루어져야 한다. 본 논문에서는 이를 위해 광대협 유색잡음에서의 신호향상과 그 과정 중 중 주기신호의 개수를 결정하는 알고리즘ㅇ르 제시하고자 한다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.15 no.12
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• pp.1044-1052
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• 1990

We have investigated the digital bit synchronization problem in baseband communication receiver systems using the Gauss-Markov estimation technique which is equivalent to the weighted least square method. The realized bit synchronizer, including the data detector, processes the input signal two dimensionally into the transition phase and data level under the white Gaussian noise environment. We have confrmed the realiation of the bit synchronizer via computer simulation. In addition, we have compared and evaluated the estimation error performance of the proposed method with that of the conventional DTTL method and of the minimum likelihood method.

• The Transactions of the Korean Institute of Power Electronics
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• v.10 no.1
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• pp.13-20
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• 2005

This paper has proposed an algorithm for the initial pole position estimation of a permanent magnet linear synchronous motor(PMLSM). The algorithm finds the initial pole position observing the maximum values of a position generated by the new proposed two reference frames for the same force input. So, the proposed algorithm does not utilize the motor parameters and is insensitive to them. Moreover, the proposed algorithm is easily realized because the proposed method is just using PI controller

• The Journal of the Acoustical Society of Korea
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• v.26 no.8
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• pp.415-425
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• 2007

This paper proposes a method of underwater source localization using the wideband interference patterns matching. By matching two interference patterns in the spectrogram, it is estimated a ratio of the range from source to sensor5, and then this ratio is applied to the Apollonius circle. The Apollonius circle is defined as the locus of all points whose distances from two fixed points are in a constant value so that it is possible to represent the locus of potential source location. The Apollonius circle alone, however still keeps the ambiguity against the correct source location. Therefore another equation is necessary to estimate the unique locus of the source location. By estimating time differences of signal arrivals between source and sensors, the hyperbola equation is used to get the cross point of the two equations, where the point being assumed to be the source position. Simulations are performed to get performances of the proposed algorithm. Also, comparisons with real sea experiment data are made to prove applicability of the algorithm in real environment. The results show that the proposed algorithm successfully estimates the source position within an error bound of 10%.

• Journal of Broadcast Engineering
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• v.24 no.6
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• pp.919-927
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• 2019

In this paper, we propose an accurate camera calibration method for acquiring multiview stereoscopic images. Generally, camera calibration is performed by using checkerboard structured patterns. The checkerboard pattern simplifies feature point extraction process and utilizes previously recognized lattice structure, which results in the accurate estimation of relations between the point on 2-dimensional image and the point on 3-dimensional space. Since estimation accuracy of camera parameters is dependent on feature matching, accurate detection of checkerboard corner is crucial. Therefore, in this paper, we propose the method that performs accurate camera calibration method through accurate detection of checkerboard corners. Proposed method detects checkerboard corner candidates by utilizing 1-dimensional gaussian filters with succeeding corner refinement process to remove outliers from corner candidates and accurately detect checkerboard corners in sub-pixel unit. In order to verify the proposed method, we check reprojection errors and camera location estimation results to confirm camera intrinsic parameters and extrinsic parameters estimation accuracy.

• Journal of the Korean Institute of Telematics and Electronics T
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• v.36T no.4
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• pp.30-37
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• 1999

This study suggested the Fuzzy Lyapunov dimension. The Fuzzy Lyapunov dimension is to evaluate the quantitative variation of the attractor. In this paper the speaker recognition is evaluated by the Fuzzy Lyapunov dimension. It has been proved that the suggested Fuzzy Lyapunov dimension is superior in the discrimination characteristics between standard reference pattern attractors, and in reference to the test pattern attractor, it has been verified that it is the speaker recognition parameter which absorbs the pattern variation. In order to evaluate the Fuzzy Lyapunov dimension as speaker recognition parameter, the mistaken recognition according to discrimination error in each of speaker and standard reference pattern was estimated, and the validity of the speaker recognition parameter was experimental. As the result of the speaker recognition experiment, 97.0[%] of recognition ratio was obtained, and it was confirmed that the Fuzzy Lyapunov dimension was fit for the speaker recognition parameter.

• Journal of Broadcast Engineering
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• v.25 no.3
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• pp.439-448
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• 2020

In this paper, we propose a modified optimization algorithm for point cloud matching of multi-view RGB-D cameras. In general, in the computer vision field, it is very important to accurately estimate the position of the camera. The 3D model generation methods proposed in the previous research require a large number of cameras or expensive 3D cameras. Also, the methods of obtaining the external parameters of the camera through the 2D image have a large error. In this paper, we propose a matching technique for generating a 3D point cloud and mesh model that can provide omnidirectional free viewpoint using 8 low-cost RGB-D cameras. We propose a method that uses a depth map-based function optimization method with RGB images and obtains coordinate transformation parameters that can generate a high-quality 3D model without obtaining initial parameters.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.47 no.3
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• pp.59-66
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• 2010

This paper is proposed an adaptive fuzzy bilinear synchronization design for uncertain $L\ddot{u}$ chaos system. It is assumed that the $L\ddot{u}$ chaos system has unknown parameters. First, The $L\ddot{u}$ chaos system can be reconstructed via TS fuzzy bilinear modeling. We design an adaptive fuzzy bilinear synchronization control scheme based on TS fuzzy bilinear $L\ddot{u}$ chaos system with uncertain parameters. Lyapunov theory is employed to guarantee the stability of error dynamic system between TS fuzzy bilinear $L\ddot{u}$ chaos system and the proposed slave system and to derive the adaptive laws for estimating unknown parameters. Simulation results is given to demonstrate the validity of our proposed synchronization scheme.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2008.11a
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• pp.215-218
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• 2008

본 논문에서는 스테레오 카메라로부터 획득된 좌, 우 영상의 변이를 추정하여 3차원 공간 좌표(x, y, z)를 얻어내고, 거리측정과 가상공간 제어를 통해 사용자에게 현실감을 제공하는 실시간 3차원 공간 인식 시스템을 제안한다. 스테레오 카메라로 부터 획득된 좌, 우 영상은 시점의 차이 때문에 동일 물체에 대한 좌, 우 영상의 좌표 값의 차이를 발생시키는 데 이를 변이(disparity)라 정의한다. 관심 영역의 변이를 추정할 때 일반적으로 관심 영역의 모든 화소(pixel)의 변이를 추정하지만, 제안한 알고리즘에서는 관심 영역의 2차원 중심 좌표(x, y)의 변이만을 추정하여 계산량을 줄이고 실시간 처리가 가능하도록 하였다. 카메라 파라미터를 이용하여 획득된 변이로부터 깊이 정보(depth)를 얻어내고 3차원 공간 좌표를 획득한다. 손을 관심 영역으로 설정한 시스템에서 3차원 공간 좌표는 실시간으로 사용자의 손의 움직임에 의해 획득되고, 가상공간(virtual space)에 적용되어 사용자가 가상공간을 조작할 수 있는 듯한 느낌을 준다. 실험을 통해 제안한 알고리즘이 1.5m 거리 내에서의 깊이 측정시 평균 0.68cm의 오차를 가짐을 확인 할 수 있었다.