• 제어로봇시스템학회논문지
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• 제17권3호
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• pp.199-205
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• 2011

This paper presents an algorithm capable of detecting free space for the autonomous vehicle navigation. The algorithm consists of two main steps: 1) estimation of longitudinal profile of road, 2) detection of free space. The estimation of longitudinal profile of road is detection of v-line in v-disparity image which is corresponded to road slope, using v-disparity image and hough transform, Dijkstra algorithm. To detect free space, we detect u-line in u-disparity image which is a boundary line between free space and obstacle's region, using u-disparity image and dynamic programming. Free space is decided by detected v-line and u-line. The proposed algorithm is proven to be successful through experiments under various traffic scenarios.

• 한국군사과학기술학회지
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• 제27권3호
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• pp.329-337
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• 2024

Free-space optical communication technology enables the high-speed data transmission and excellent anti-jamming security. We conduct research on satellite-to-ground free-space optical communication links for high-speed transmission of large-capacity surveillance and reconnaissance data. Since the satellite continues to move along its orbit while the optical signal is transmitted between the satellite and the ground, the pointing angle of the beam from the ground terminal needs to be corrected by Point Ahead Angle(PAA) so that the transmitted light reaches the expected location of the satellite. In this paper, we present the algorithm for PAA estimation and control.

• Asia pacific journal of information systems
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• 제2권2호
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• pp.71-84
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• 1992

Analysis for the file with distributed free space such as a VSAM has been done. Birth and death process has been adopted to describe the status changes of control intervals in a VSAM file. File utilization is calculated as a function of the number of control intervals which contain different number of records in them. Effect of the control interval sizes and the loading factors are analyzed over the time horizon.

• Journal of information and communication convergence engineering
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• 제8권3호
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• pp.267-272
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• 2010

For the last decade, recurrent neural networks (RNNs) have been commonly applied to communications channel equalization. The major problems of gradient-based learning techniques, employed to train recurrent neural networks are slow convergence rates and long training sequences. In high-speed communications system, short training symbols and fast convergence speed are essentially required. In this paper, the derivative-free Kalman filter, so called the unscented Kalman filter (UKF), for training a fully connected RNN is presented in a state-space formulation of the system. The main features of the proposed recurrent neural equalizer are fast convergence speed and good performance using relatively short training symbols without the derivative computation. Through experiments of nonlinear channel equalization, the performance of the RNN with a derivative-free Kalman filter is evaluated.

• 대한전기학회논문지
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• 제38권12호
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• pp.971-982
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• 1989

An integrating position estimation algorithm has been developed for the navigation system of a free-ranging AGV system. The navigation system focused in this research work consists of redundant wheel encoders for the relative position measurement and a vision sensor for the absolute position measurement. A maximum likelihood method and an extended Kalman filter are implemented for enhancing the performance of the position estimator. The maximum likelihood estimator processes noisy, redundant wheel encoder measurements and yields efficient estimates for the AGV motion between each sampling interval. The extended Kalman filter fuses inharmonious positional data from the deadreckoner and the vision sensor and computes the optimal position estimate. The simulation results show that the proposed position estimator solves a generalized estimation problem for locating the vehicle accurately in space.

• Current Optics and Photonics
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• 제3권3호
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• pp.210-214
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• 2019

The allowable path-deviation time of aircraft in a free-space optical communication system has been estimated from various trajectories, using different values of aircraft speeds and turn rates. We assumed the existence of a link between the aircraft and a ground base station. First, the transmitter beam's divergence angle was calculated through two different approaches, one based on a simple optical-link equation, and the other based on an attenuation coefficient. From the calculations, the discrepancy between the two approaches was negligible when the link distance was approximately 110 km, and was under 5% when the link distance ranged from 80 to 140 km. Subsequently, the allowable path-deviation time of the aircraft within the tracking-error tolerance of the system was estimated, using different aircraft speeds, turn rates, and link distances. The results indicated that the allowable path-deviation time was primarily determined by the aircraft's speed and turn rate. For example, the allowable path-deviation time was estimated to be ~3.5 s for an aircraft speed of 166.68 km/h, a turn rate of $90^{\circ}/min$, and a link distance of 100 km. Furthermore, for a constant aircraft speed and turn rate, the path-deviation time was observed to be almost unchanged when the link distance ranged from 80 to 140 km.

• 천문학회보
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• 제43권2호
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• pp.58.2-58.2
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• 2018

Theoretically, the magnetic helicity transport flux through the solar surface into the upper atmosphere can be estimated indefinitely precisely by magnetic field footpoint tracking if the observational resolution is infinitely fine, even with magnetic flux emergence or submergence. In reality, the temporal and spatial resolutions of observations are limited. When magnetic flux emerging or submerging, the footpoint velocity goes to infinity and the normal magnetic field vanishes at the polarity inversion line. A finite observational resolution thus generates a blackout area in helicity flux estimation near the polarity inversion line. It is questioned how much magnetic helicity is underestimated with a footpoint tracking method due to the absence of information in the blackout area. We adopt the analytical models of Gold-Hoyle and Lundquist force-free flux ropes and let them emerging from below the solar surface. The observation and the helicity integration can start at different emerging stages of the flux rope, i.e., the photospheric plane initially cuts the flux rope at different levels. We calculate the magnetic helicity of the flux rope below the photospheric level, which is eventually to emerge, except the helicity hidden in the region to be swept by the blackout area with different widths. Our calculation suggests that the error in the integrated helicity flux estimate is about half of the real value or even larger when small scale magnetic structures emerge into the solar atmosphere.

• 한국항공우주학회지
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• 제45권5호
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• pp.376-385
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• 2017

본 연구는 변위를 추정하기 위한 가속도 시간 적분 방법의 단점을 완화하기 위해 구조물의 가속도와 모드 형상을 이용한 보 구조물 변위 추정 기법을 제안하였다. 기존의 가속도 시간 적분 방법은 구조물의 초기 조건을 알기 어렵고 잡음에 의한 오차가 누적되기 쉽다는 문제가 있었다. 이런 문제를 해결하기 위해 모드 중첩법에 기반을 두는 변위 추정기법을 도출하였고 기법의 타당성을 검증하기 위해 2가지의 외팔보 진동 실험을 수행하였다. 실험으로부터 측정된 가속도 데이터와 외팔보의 모드 형상을 이용하여 보 구조물 정적 변위와 동적 변위를 추정하였고 레이저 변위 센서를 이용하여 직접 측정된 변위와 비교하였다. 이를 통해 제안된 보 구조물 변위 추정 기법의 타당성 및 유용성을 검증하였으며 추정한 변위와 직접 측정한 변위가 잘 일치함을 확인하였다.

• 한국방송∙미디어공학회:학술대회논문집
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• 한국방송공학회 2009년도 IWAIT
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• pp.583-587
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• 2009

In this paper we propose a new method of Depth-Image-Based Rendering (DIBR) for Free-viewpoint TV (FTV). In the proposed method, virtual viewpoint images are rendered with 3D warping instead of estimating the view-dependent depth since depth estimation is usually costly and it is desirable to eliminate it from the rendering process. However, 3D warping causes some problems that do not occur in the method with view-dependent depth estimation; for example, the appearance of holes on the rendered image, and the occurrence of depth discontinuity on the surface of the object at virtual image plane. Depth discontinuity causes artifacts on the rendered image. In this paper, these problems are solved by reconstructing disparity information at virtual camera position from neighboring two real cameras. In the experiments, high quality arbitrary viewpoint images were obtained.

• 한국항공우주학회지
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• 제42권10호
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• pp.833-841
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• 2014

본 논문에서는 공중에 띄운 풍선을 카메라를 이용하여 촬영하고 이를 영상처리를 통하여 추적한 다음 그 움직임 정보를 이용해서 풍속을 추정하는 알고리즘을 제안한다. 여기서 사용되는 풍선은 아무런 장치가 장착되지 않은 것을 사용하므로 소모적이지만 저렴하며, 모든 지상 장비들은 반영구적으로 사용 가능하므로 효용성이 높다. 또한 다수의 카메라를 사용함으로써 정밀한 3차원 정보 획득이 가능하며, 일정 영역의 바람 속도장 추정이 가능하다. 본 논문에서 제안하는 시스템은 풍선의 공기 역학적 모델과 영상처리를 통한 추적 시스템 그리고 속도 추정 알고리즘으로 구성된다. 각각의 알고리즘을 단위 검증한 후에 설계한 검증 시스템과 가시화 프로그램을 통하여 통합 검증 및 시뮬레이션을 수행한다.