• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1997년도 한국자동제어학술회의논문집; 한국전력공사 서울연수원; 17-18 Oct. 1997
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• pp.371-374
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• 1997

Recently, the development of computer achieves a system which is similar to the mechanics of human visual system. The 3-dimensional measurement using monocular vision system must be achieved a camera calibration. So far, the camera calibration technique required reference target in a scene. But, these methods are inefficient because they have many calculation procedures and difficulties in analysis. Therefore, this paper proposes a native method that without reference target in a scene. We use the grid type frame with different line widths. This method uses vanishing point concept that possess a rotation parameter of the camera and perspective ration that perspect each line widths into a image. We confirmed accuracy of calibration parameter estimation through experiment on the algorithm with a grid paper with different line widths.

• 지질공학
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• 제5권3호
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• pp.331-337
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• 1995

3성분 단일 지진 관측의 방위각 결정에서 때때로 결과는 파형에 의존하고, 자동 관측은 불편하게 만든다. 본 연구에서는 시간-방향 스태킹 기술에 의해서 방위각이 아주 긴 파열(wave train) 관측으로부터 더 정확한게 결정되는 대안을 제안한다. 한반도 지진관측으로 취득한 디지털 파형을 가지고 시험한 결과 단순한 알고리즘은 광역거리에서 지진 진원의 방위각을 더 정확하게 결정하여 주는 것을 보여준다.

• 전자공학회논문지B
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• 제33B권3호
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• pp.142-150
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• 1996

Monopulse technique has been widely used for a bearing estimation of a desired signal. This method can estimate the bearing of the signal with only one pulse, so computational load and complexity are low and its processes are simple. But if the desired signal incidents with interferences or multiple signals exist in the beams, the method fails to estimate correct signal angle. To solve this problem, the method to use adaptive array was proposed. In conventional adaptive array methods, sum beam was formed with fixed weights and ifference beam was formed with adaptive weights determined to minimize beamformer output power with one or more linear constraints, or an algorithm to minimize each sum beam and difference beams simultaneously using adaptively formed one basic beam. Theroretical analyses and simulation results show that the performance of the proposed method is superior to that of conventional algorithms.

• 전산구조공학
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• 제3권3호
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• pp.125-131
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• 1990

본 논문에서는 시간 종속 하중을 받는 대형 전산구조응력 해석 문제를 위한 유한요소 모델링 기법이 소개된다. 유한요소모델링의 분할기준은 문제에 대한 해석 결과에 대한 오차선정에 근거를 둔다. 이 오차산정은 해석결과치에 의한 잔유 에너지의 크기를 유한요소별로 산정한다. 이의 시간존장 구조물에 대한 응용은, 구조연속체의 Ritz 고유진동 모드를 계산하고 이들 진동 모드 중에서 저주파에 상응하는 진동모드에 대해 잔유 에너지의 크기가 구조체 전체영역에서 평형을 유지하도록 유한요소 모델링을 수행한다. 마지막으로, 여기서 제안된 알고리즘이 몇 예제들을 통해서 검증된다.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2005년도 춘계학술대회논문집
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• pp.449-454
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• 2005

Brushless DC Motor(PM BLDCM) is widely used in industrial applications due to its high efficiency and power density. In order to increase reliability and reduce system cost, this paper studies particularly applicable method for sensorless PM BLDCM drive system. The resulting third harmonic signal keeps a constant phase relationship with the rotor flux for any motor speed and load condition, and is practically free of noise that can be introduced by the inverter switching, making this a robust sensing method. As a result, the method described here is not sensitive to filtering delays, allowing the motor to achieve a good performance over a wide speed range. In addition, a simple starting method and a speed estimation approach are also proposed.

• 대한수학회지
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• 제37권1호
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• pp.31-44
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• 2000

We study a free boundary problem satisfying Bernoulli type boundary condition along which the gradient of a piecewise harmonic solution jumps zero to a given constant value. In such problem, the free boundary splits the domain into two regions, the zero set and the harmonic region. Our main interest is to identify the global shape and the location of the zero set. In this paper, we find the lower and the upper bound of the zero set. In a convex domain, easier estimation of the upper bound and faster disk test technique are given to find a rough shape of the zero set. Also a simple proof on the convexity of zero set is given for a connected zero set in a convex domain.

• Journal of Communications and Networks
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• 제7권3호
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• pp.235-242
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• 2005

Multimedia applications and especially encoded video services, are expected to playa major role in the 3rd generation (3G) and beyond mobile communication systems. Given that future service providers are expected to provide video applications at various price and quality levels, quick and economically affordable methods for preparing/encoding the offering media at various qualities are necessary to be developed. This paper presents a method for objective evaluation of the perceived quality of MPEG­4 video content, based on a quantification of subjective assessments. Showing that subjectively derived perceived quality of service (PQoS) vs. bit rate curves can be successfully approximated by a group of exponential functions, the proposed method exploits a simple objective metric, which is obtained from the mean frame rate vs. bit rate curves of an encoded clip. The validity of this metric is assessed by comparing subjectively derived PQoS results to the corresponding ones, which come from the proposed objective method, showing that the proposed technique provides satisfactory PQoS estimation.

• Journal of Mechanical Science and Technology
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• 제16권3호
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• pp.302-309
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• 2002

This paper presents a technique for localization of a mobile robot using sonar sensors. Localization is the continual provision of knowledges of position that are deduced from its a priori position estimation. The environment of a robot is modeled by a two-dimensional grid map. We define a physically based sonar sensor model and employ an extended Kalman filter to estimate positions of the robot. Since the approach does not rely on an exact geometric model of an object, it is very simple and offers sufficient generality such that integration with concurrent mapping and localizing can be achieved without major modifications. The performance and simplicity of the approach are demonstrated with the results produced by sets of experiments using a mobile robot equipped with sonar sensors.

• 조명전기설비학회논문지
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• 제26권1호
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• pp.29-37
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• 2012

A simple and effective dead time compensation scheme for a PWM inverter-fed permanent magnet synchronous motor (PMSM) drive using the model reference adaptive control (MRAC) and coordinate transformation is presented. The basic concept is to first transform a time-varying disturbance caused by the dead time and inverter nonlinearity into unknown constant or slowly-varying one by the coordinate transformation, and then use the MRAC design technique to estimate this parameter in the stationary reference frame. Since the MRAC scheme is a suitable way of estimating such a parameter, the control performance can be significantly improved as compared with the conventional observer-based method tracking time-varying parameters. In the proposed scheme, the disturbance voltage caused by the dead time is effectively estimated and compensated by on-line basis without any additional circuits nor existing disadvantages as in the conventional methods. The asymptotic stability is proved and the effectiveness of the proposed scheme is verified.

• 대한전기학회논문지
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• 제38권10호
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• pp.795-804
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• 1989

A parallel analog-to digital converter with neuron-like elements is designed and optically implemented. Its operation principle is based on the simultaneous estimation of bit values for a given analog input. The architecture of the proposed analog-to-digital converter is simpler than that of an earlier one designed by the energy minimization technique, and its digital output is independent of the initial state. Mixed binary-to-full binary converters are also designed by using out analog-to-digital converters as basic computing elements. These converters have simple structures and fast conversion times compared with earlier ones.