• 조명전기설비학회논문지
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• 제29권9호
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• pp.14-22
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• 2015

TIn this paper, a centering method for an unfocused input character using the spherical domain system and the centering character to use the shift invariant feature for the recognition system is proposed. A system for recognition is implemented using the centroid method with coordinate average values, and the results of an above 78.14% average differential ratio for the character features were obtained. It is possible to extract the shift invariant feature using spherical transformation similar to the human eyeball. The proposed method, which is feature extraction using spherical coordinate transform and transformed extracted data, makes it possible to move the character to the center position of the input plane. Both digital and optical technologies are mixed using a spherical coordinate similar to the 3 dimensional human eyeball for the 2 dimensional plane format. In this paper, a centering character feature using the spherical domain is proposed for character recognition, and possibilities for the recognized possible character shape as well as calculating the differential ratio of the centered character using a centroid method are suggested.

• 대한기계학회논문집
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• 제17권10호
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• pp.2483-2490
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• 1993

This paper presents a systematic formulation for the kinematic and dynamic analysis of flexible multibody systems. The system equations of motion are derived in terms of relative and elastic coordinates using velocity transformation technique. The position transformation equations that relate the relative and elastic coordinates to the Cartesian coordinates for the two contiguous flexible bodies are derived. The velocity transformation matrix is derived systematically corresponding to the type of kinematic joints connecting the bodies and system path matrix. This matrix is employed to represent the equations of motion in relative coordinate space. Two examples are taken to test the method developed here.

• 한국측량학회지
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• 제27권5호
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• pp.555-563
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• 2009

모바일 매핑 시스템 또는 로봇이 GPS (Global Positioning System)와 다중 스테레오 카메라만 탑재 할 경우, V-SLAM(Vision based Simultaneous Localization And Mapping)에 의한 카메라 외부표정과 3차원 데이터를 GIS데이터와 연계 또는 카메라 외부표정의 누적에러를 제거하기 위해 극부 카메라 좌표계에서 GPS (Global Positioning System) 좌표계로 변환이 필요로 한다. 이 요구사항을 만족시키기 위해, 본 논문은 GPS와 V-SLAM에 의한 3쌍의 카메라의 위치를 이용하여 GPS좌표계에서 카메라 자세를 계산하는 새로운 방법을 제안하였다. 제안한 방법은 간단한 4단계로 구성되어 있다; 1)각 3개의 카메라 위치에 기반한 두 평면 법선벡터가 병렬이되도록 하는 사원수 (quaternion)를 계산한다, 2) 계산된 사원수를 통하여 V-SLAM에 의한 3개의 카메라 위치를 변환한다, 3) 변환된 위치에서 두번째 또는 세번째 점이 GPS에 의한 점과 일치하도록 하는 두번째 사원수를 계산한다, 4)두 사원수의 곱을 통하여 최종 사원수 결정한다. 최종 사원수는 극부 카메라 좌표계에서 GPS좌표계로 변환할 수 있다. 추가적으로, 촬영된 물체 위치에서 카메라를 보는 시야각을 기반으로 물체의 3차원좌표 갱신방법을 제안하였다. 본 논문은 제안한 방법을 시뮬레이션과 실험을 통하여 증명하였다.

• Interaction and multiscale mechanics
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• 제2권4호
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• pp.413-430
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• 2009

The stator tooth is a key component of the electromechanical integrated toroidal drive system. The stator tooth is spiral in shape and the calculation of its displacements is difficult. In this paper, using the coordinate transformation method, the displacements of the stator tooth in the local coordinate system are expressed as the function of the variable in the drive coordinate system. Using the minimum potential energy principle, the equations of the displacements of the stator tooth under the loads are deduced. The displacement distributions within the stator tooth are investigated and the changes of the displacement distributions along with the main parameters are analyzed. This research can offer the basis for the strength and stiffness design of the drive system.

• 한국자동차공학회논문집
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• 제5권4호
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• pp.152-159
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• 1997

This paper presents a vibration analysis method of crank shaft of six cylinder internal combustion engine. For simple analysis journal, pin and arm parts were assumed to have uniform section. Transfer Matrix Method was used, considering branched part and coordinate transformation part. Natural frequencies, modeshapes and transfer functions of crank shaft were investigated based upon the Euler beam theory: It was shown that the calculated natural frequencies, modeshapes agree well with the existing paper results.

• 대기
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• 제26권3호
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• pp.473-482
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• 2016

An accurate determination of turbulent fluxes over an urban area is a challenging task due to its morphological diversity and associated flow complexity. In this study, an eddy covariance (EC) method is applied over a highly heterogeneous urban area in a small city (Gongju), South Korea to investigate the quantitative influence of 'coordinate tilt' in determining the turbulent fluxes of sensible heat, latent heat, momentum, and carbon dioxide mass. Two widely-used coordinate transform methods are adopted and applied to eight directional sections centered on the site to analyze a 1-year period EC measurement obtained from the urban site: double rotation (DR) and planar fit (PF) transform. The results show that mean streamline planes determined by the PF method are distinguished from the sections, representing morphological heterogeneity of the site. The sectional pitch angles determined by the DR method also compare well with those in the PF method. Both the PF and DR methods show large variabilities in the determined streamline planes at each directional section, implying that flow patterns may form in a complicate way due to the surface heterogeneity. Resulting relative differences of the turbulent fluxes, defined by $(F_{DR}-F_{PF})/F_{DR}$, are found on average +13% in sensible heat flux, +21% in latent heat flux, +37% in momentum flux, and +26% in carbon dioxide mass flux, which are larger values than those reported previously for fairly homogeneous natural sites. The fractional differences depend significantly on wind direction, showing larger differences in northerly winds at the measurement site. It is also found that the relative fractional differences are negatively correlated with the mean wind speed at both stable/unstable atmospheric conditions. These results imply that EC turbulent fluxes determined over heterogeneous urban areas should be carefully interpreted with considering the uncertainty due to 'coordinate tilt' effect in their applications.

• 한국군사과학기술학회지
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• 제14권2호
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• pp.181-188
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• 2011

A simulation technique, which simulate dynamic motion and communication environments of ship in the lab, is needed in order to reduce the testing cost when we evaluate the transfer alignment performance of shipboard INS. Hardware-In-the-Loop Simulation(HILS) can be used as an effective test method for those system because it can provide flexible and realistic simulation environments, various test scenario, and repeated test environment in the lab without additional cost and person. This paper presents the methods for implementing the real time HILS environment for testing transfer alignment performance of shipboard INS. It includes real time executive for controlling realtime simulation and calculating the ship motion, communication method for interfacing between the systems, and coordinate transformation method for converting real ship coordinate attitude data to lab coordinate attitude data.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.658-663
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• 2003

A process of 3-D stereo particle image velocimetry(PIV)was developed for the measurement of an illuminated sliced section field of 3-D complex flows. The present method includes modeling of camera by a calibrator based on the homogeneous coordinate system, transformation of the oblique-angled image to the right-angled image, identification of 2-D velocity vectors by 2-D cross-correlation equation, stereo matching of 2-D velocity vectors of two cameras, accurate calculation of 3-D velocity vectors by homogeneous coordinate system, removal of error vectors by a statistical method followed by a continuity equation criteria, and finally 3-D display as the post processing. An experimental system was also used for the application of the proposed method. Two high speed digital CCD cameras and an Argon-Ion Laser for the illumination were adopted to clarify the time-dependent characteristics of the leading edge extension(LEX) in a highly swept shape applied to a delta wing found in modern air-fighters.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1998년도 Proceedings ICPE 98 1998 International Conference on Power Electronics
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• pp.615-619
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• 1998

Active power filter is a kind of device used for compensating instantaneous reactive and harmonic current in three-phase circuits. An essential technology that determines the behavior of an active power filter is the method of detecting the distorted current. Using three-dimensional space vectors, this paper describes a simple method for detecting the distorted current without any coordinate transformation. The effectiveness of the novel method is verified by the theoretical analysis and simulation.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2001년도 ICCAS
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• pp.61.2-61
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• 2001

The purpose of the initial alignment of a SDINS is to get a coordinate transformation matrix from the body frame to the navigation frame. The initial alignment is one of the most important processes in the navigation system since its error has a large influence on the navigation solution. In this paper, a real-time initial alignment algorithm for the SDINS is developed using the Kalman filter. The steady state error analysis is performed for the developed Kalman filter technique and the gyrocompass loop method. The performance of the developed alignment method is compared with the gyrocompass loop method through the real-time alignment experiments.