• Journal of the Korean Society for Nondestructive Testing
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• v.23 no.4
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• pp.356-363
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• 2003

An eddy current testing system was developed for detection of flaws in the ferromagnetic steel tubes. Because the eddy current signals from the ferromagnetic steel tubes could be distorted easily due to an irregularity of magnetic permeability, magnetic saturation is required to suppress this variation of magnetic fields. A magnetic saturation probe with the Hemholtz coil was designed for the inspection of the steel tubes. The bandwidth pass filters were adapted to minimize the noise from the DC magnetization. When using the designed test probe, the flaw signals could be discriminated from the noise. The system was tested at the production line and showed a capability of detecting flaws, like a drilled hole of the diameter of 2.0mm at the moving speed of 1m/sec.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.2 no.2
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• pp.69-78
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• 1991

전자파장해 측정에 사용되는 대표적인 측정시설에는 접지면(ground plane)을 갖춘 야외시험장 (open area test site), 전자파반무향실(semianechoic chamber), TEM(transverse Electromagnetic) cell, 평행판선로(parallel plate line), 헬름홀츠코일(Helmholtz coil), 전자파잔향실(reverberating chamber) 등이 있으며, 이러한 시설은 시험대상기기의 크기, 주파수대역, 적용규격의 규제치, 측정하고자 하는 전자기장의 형태 및 편파면, 그리고 시험신호의 전기적 특성(주파수영역 또는 시간영역) 등을 고려하여 선택되고 구성되 어야 한다. 실제로 시험장소를 건설하는데 막대한 비용이 소요되고, 큰 측정오차를 유발시킬 수 있기 때문에 매우 신중 하게 설계, 구성하여야 한다.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.2
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• pp.98-104
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• 2001

전자장(EMF)에 의한 생체영향에 관한 연구에 있어서 사람에게 직접 실험하는 것은 윤리적으로나 객관적으로 제한점이 많다. 따라서 생체에 대한 유무해성을 파악하기 위해 in vitro 나 인강과 유사한 동물실험을 통해 그 영향을 조사하고 그 결과를 생체와 연관지어 예측하는 것은 기본 단계이다. 본 연구에서는 세포 및 동물실험을 위한 직류 및 교류(ELF) 자기장 발생장치를 헬름홀츠 코일과 솔레노이드 코일을 이용하여 구성하였으며, 실험시 중요한 자계의 균일도를 각각 비교하였다. 또한 발생자계의 패턴을 DC, 정현파, 구형파, 삼각파, 펄스 형태로 변화 시 킬수 있도록 컨드롤러를 내장시켰다. 발생 자계의 크기는 직류에서 최대 100 Gauss(10mT), 60Hz 정현파에 대해서는 최대 Gauss(2mT)의 출력이 가능하도록 설계하였다.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.39 no.3
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• pp.181-188
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• 2003

The objects of this study were to discuss the performance of its using magnetic compass and to do a trial manufacture of the apparatus generating artificial magnetic field of 3-axis type to assess the performance of compass using terrestrial magnetism in the various magnetic field. The results obtained were summarized as follows: The magnetic field of each axis showed the linearly increase in accordance with the increase of electrical current. Average range difference between measured and calculated values was 0.33∼1.93μT and there were no big difference. The magnitude and direction of magnetic field showed some change in the edge of Helmholtz coil, but it appeared to stabilize in the center. In the horizontal magnetic force of 0.30gauss and 0.40gauss, the measured and calculated values of the damping characteristic of magnetic compass showed a good agreement. However, the confidence level was low at the horizontal magnetic force of 0.50gauss.

• Journal of the Korean Magnetics Society
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• v.11 no.1
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• pp.38-44
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• 2001

The magnetic field standard below 1 mT with the resolution of 0.26 nT has been established. Earth magnetic field (EMF) is compensated automatically down to 0.1 nT/10 min. by a closed feedback system with Cs optical pumping magnetometer and 3-axis Helmholtz coils in nonmagnetic facilities. A multi-layer precision solenoid with the optimized single-current method generates the uniform magnetic field better than 1.0$\times$10$\^$-7/ within $\pm$ 1 cm region at its center. The coil constant of solenoid determined from Helium optical pumping magnetometer is 1.231 058 9 mT/A, and temperature coefficient is 0.38 nT/$\^{C}$. This standard system is used for calibration of low field magnetometers and testing relates to low field.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.11
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• pp.1300-1305
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• 2009

The various electromagnetic based actuation(EMA) methods have been proposed for actuating microrobot. The advantage of EMA is that it can provide wireless driving to microrobot. In this reason a lot of researchers have been focusing on the EMA driven microrobot. This paper proposed a swimming microrobot driven by external alternating magnet field which is generated by two pairs of Helmholtz coils. The microrobot has a fish-like shape and consists of a buoyant robot body, a permanent magnet, and a fin. The fin is directly linked to the permanent magnet and the magnet is swung by the alternating magnet field, which makes the propulsion and steering power of the robot. In this paper, firstly, we designed the locomotive mechanism of the microrobot boy EMA. Secondly, we set up the control system. Finally, we demonstrated the swimming robot and evaluated the performance of the microrobot by the experiments.