• 한국자기학회지
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• 제23권3호
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• pp.89-93
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• 2013

본 연구에서는 홀센서의 감도를 높이기 위해 사용되는 자속집속기의 두께, 홀소자와의 상대적 위치, 모서리 형상에 따르는 발생 자계를 유한요소법을 이용하여 계산하였다. 자속집속기의 두께가 얇을수록 발생 자계가 커지는 것을 알 수 있었고, 이 경향은 반자계를 고려한 겉보기 상대투자율의 두께의존성과 유사하다는 것을 알 수 있었다. 홀소자와의 상대적 위치에 따라 최대의 자계를 발생시키는 자속집속기의 최적의 두께가 변화하는 것을 알 수 있었다. 자속집속기와 홀소자의 간격이 가까울 경우, 자속집속기의 모서리 형상에 경사가 없는 것이 유리하지만, 자속집속기와 홀소자의 간격이 멀어질수록 자속집속기의 모서리를 경사지게 하는 것이 유리하다는 것을 알 수 있었다.

• Journal of Magnetics
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• 제18권4호
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• pp.454-459
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• 2013

This paper deals with an optimal angle error reduction method of magnetic position sensor using hall effect elements. The angle detection simulation for the magnetic position sensor is performed by 3 dimensional finite element method and Taguchi method, one of the design of experiments. The magnetic position sensor is required to generate ideal sine and cosine waveforms from its hall effect elements according to rotation angle for precise angle information. However, the output signals are easy to include harmonics due to uneven magnetic field distribution from permanent magnet in the air-gap in the vicinity of hall effect elements. For the Taguchi method, three design parameters related to position of hall effect elements and shape of back yoke are selected. The characteristics of optimal magnetic position sensor are compared with those of original one in terms of simulation as well as experiment. Finally, the performances of the motor adopting original model and optimal model are represented for the purpose of verification of motor performance due to signals from magnetic position sensor.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2004년도 제22회 춘계학술대회논문집
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• pp.262-270
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• 2004

Basic experiments were carried out using the THT-IV low-power Hall thruster to examine the influences of magnetic field shape and strength, and acceleration channel length on thruster performance and to establish guidelines for design of high-performance Hall thrusters. Thrusts were measured with varying magnetic field and channel structure. Exhaust plasma diagnostic measurement was also made to evaluate plume divergent angles and voltage utilization efficiencies. Ion current spatial profiles were measured with a Faraday cup, and ion energy distribution functions were estimated from data with a retarding potential analyzer. The thruster was stably operated with a highest performance under an optimum acceleration channel length of 20 mm and an optimum magnetic field with a maximum strength of about 150 Gauss near the channel exit and with some shape considering ion acceleration directions. Accordingly, an optimum magnetic field and channel structure is considered to exist under an operational condition, related to inner physical phenomena of plasma production, ion acceleration and exhaust plasma feature. A new Hall thruster was designed with basic research data of the THT-IV thruster. With the thruster with many considerations, long stable operations were achieved. In all experiments at 200-400 V with 1.5-3 mg/s, the thrust and the specific impulse ranged from 15 to 70 mN and from 1100 to 2300 see, respectively, in a low electric power range of 300~1300 W. The thrust efficiency reached 55 %. Hence, a large map of the thruster performance was successfully made. The thermal characteristics were also examined with data of both measured and calculated temperatures in the thruster body. Thermally safe conditions were achieved with all input powers.

• Journal of Information Display
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• 제3권4호
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• pp.19-22
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• 2002

In this paper, we introduce an efficient three-dimensional magnetic field mapping system for a Deflection Yoke (DY) in Cathode-Ray Tube (CRT). A three-axis Hall probe mounted in a small cylindrical bar and three-stepping motors placed in a non-magnetic frame were utilized for the mapping. Prior to the mapping starts, the inner contour of DY was measured by a laser sensor to make a look-up table for inner shape of DY. Three-axis magnetic fields are then digitized by a three-dimensional Hall probe. The results of the mapping can be transformed into various output formats such as multi pole harmonics of magnetic fields. Field shape in one, two and three- dimensional spaces can also be displayed. In this paper, we present the features of this mapping device and some analysis results.

• 한국산학기술학회논문지
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• 제14권5호
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• pp.2381-2387
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• 2013

본 논문에서는 전동기의 속도 센서로 사용되는 마그네틱 센서의 3차원 전자장 해석 기술 및 분석 방법에 대하여 논하였다. 마그네틱 센서는 레졸버 및 엔코더와 같은 속도센서에 비해 가격이 싸고 활용성이 높은 장점이 있는 반면, 정밀도가 낮으며 외부 자기장에 대하여 간섭을 많이 받는 단점이 존재한다. 마그네틱 센서는 전동기가 회전할 때 사인과 코사인 파형이 발생된다. 그러나 홀 소자 근처에서의 자기적 노이즈로 인하여 사인 및 코사인 신호가 왜곡이 발생하여 각도 오차로 나타난다. 본 논문에서는 마그네틱 센서의 홀 소자의 적절한 위치 선정과 주위에 적절한 요크를 다꾸찌 방법에 의해 최적 설계를 수행하여 이러한 왜곡을 방지하고자 하였다. 해석방법으로는 3차원 유한요소법을 이용하여 해석의 정밀도를 높였다.

• Journal of Power Electronics
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• 제18권3호
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• pp.714-722
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• 2018

This paper presents a wide-range speed control scheme of brushless DC (BLDC) motors based on a hall sensor with separated low- and normal-speed controllers. However, the use of the hall sensor signal is insufficient to detect motor speed in the low-speed region because of low sensor resolution and time delay. In the proposed method, a micro-stepping current control method according to the torque angle variation is presented. In this mode, the motor current frequency and rotating angle are determined by the reference speed without the actual speed fed by the hall sensor. The detected torque angle is used to adjust the current value in a limited band to control the current value in accordance with the load. The torque angle is detected exactly at the changing point of the hall sensor signal. The rotor can follow the rotating flux with the variable torque angle. In a normal speed range, the conventional vector control scheme is used to control the motor current with a PI speed controller using the hall sensor. The torque characteristics are analyzed on the basis of the back EMF and current shape. To adopt the vector control scheme, the continuous rotor position is estimated by the measured speed and hall sensor position. At the mode changing point between low and normal speed range, the proper initial current command and reference rotor position are calculated. The calculated current command can reduce the torque ripple during transient mode. The proposed method is simple but effective in extending the speed control range of a conventional BLDC motor with hall sensor without the need for a high-resolution encoder. The effectiveness of the proposed method is verified by various experiments on a practical BLDC motor.

• Journal of Magnetics
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• 제17권4호
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• pp.285-290
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• 2012

Electric Power Steering (EPS) system is superior to conventional Hydraulic Power Steering (HPS) system in aspect of fuel economy and environmental concerns. The EPS system consists of torque sensor, electric motor, ECU (Electric Control Unit), gears and etc. Among the elements, the torque sensor is one of the core technologies of which output signal is used for main input of EPS controller. Usually, the torque sensor has used torsion bar to transform torsion angle into torque and needs linear characteristic in terms of flux variation with respect to rotation angle of permanent magnet. The torsion angle of both ends of a torsion bar is measured by a contact variable resistor. In this paper, the sensor is accurately analyzed using 3D finite element method and its characteristics with respect to four different shapes of the stator teeth are compared. The four shapes are rectangular, triangular, trapezoidal and circular type.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2002년도 International Meeting on Information Display
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• pp.868-871
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• 2002

In this paper, we introduce an efficient three-dimensional magnetic field mapping system for a Deflection Yoke (DY) in Cathode-Ray Tube (CRT). A three-axis Hall probe mounted in a small cylindrical bar and three stepping motors placed in a nonmagnetic frame are utilized for the mapping. Prior to the mapping starts, the inner contour of DY is measured by a laser sensor to make a look-up table for inner shape of DY. Three-axis magnetic fields are then digitized by a three-dimensional Hall probe. The results of the mapping can be transformed to various output formats such as multipole harmonics of magnetic fields. Field shape in one, two and three-dimensional spaces can also be displayed. In this paper, we present the features of this mapping device and show some analysis results.

• 한국음향학회지
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• 제37권5호
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• pp.356-362
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• 2018

장방형 평면의 한쪽 끝에 자리잡아 벽체와 천장 등의 1차 혹은 2차반사음을 많이 확보할 수 있는 슈박스 콘서트홀의 무대와는 달리, 객석으로 둘러싸인 무대의 빈야드 콘서트홀은 무대 위의 연주자들이 자신이나 다른 연주자들의 연주음 크기나 화음을 모니터링 할 수 있는 초기반사음이 절대 부족하다. 무대 주변벽에서의 반사음을 기대할 수 있지만 무대라이저와 그 위의 연주자들에 의해 상당부분 가려지기 때문에 그 효과는 극히 제한적이다. 무대반사판(ensemble reflector)은 무대의 상부에 설치하여 연주자들의 모니터링을 가능하게 함으로써 연주음의 앙상블을 향상시키는 데 기여할 수 있는 효과적인 수단이다. 2,000여석 규모의 커다란, 따라서 높은 천장으로 인해 유효한 초기 천장반사음을 확보하기 힘든 대형 빈야드 콘서트홀에서 적절한 위치와 형태와 면적을 갖는 효율적인 무대반사판을 설계하고 무대서포트에 관한 정량적 지표를 토대로 그 효과를 검증하였다.

• 건축역사연구
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• 제31권6호
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• pp.59-68
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• 2022

This paper is an architectural historical study on Chimi of Hwangnyongsa Temple. In this research, the shape and cross-section of the chimi are reviewed. The results of the study are as follows. The chimi is a form in which the head part facing the maru is omitted, and the upper and lower body are separated. The upper and lower bonds are assembled into a two types of joint throughout the side of the torso, and then bound with an iron strap. Because of the absence of ridge line in the front, and the narrow curved surface which makes the side plate close to the plane, the entire cross-section is triangular, and the rear plate maintains the shape of the chimi. The naerimmaru connected to the side of the chimi has a slope, so it is clear that the chimi was used on the woojingak-jibung(hipped-roof), and the wing part and back of the chimi are erected on the side roof. The height of the yongmaru and chunyeomaru is about the same and the roofing tiles of those are in contact. The roofing tiles of chunyemaru should be cut to fit the angle of the contacting part. The maru is 30 stories high of roofing tiles as a result of the on-board survey. Based on reference on the shape and timing of the production of chimi, the height of chimi, and the maru is believed to have been built before the Unified Silla Period and used in buildings with at least seven-kan frontage. Buildings corresponding to these construction conditions can be seen as Central hall and East hall in Hwangnyongsa temple.