• 한국지능시스템학회논문지
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• 제27권2호
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• pp.106-112
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• 2017

본 논문에서는 자기부상 물류이송시스템의 부상 및 추진제어기 설계 방법을 제안하였다. 부상제어기는 롤과 피치 움직임을 최소화시키기 위해 전자석간의 상호영향을 고려하여 설계하였다. 자기부상이송시스템의 구조적인 단점을 해결하기 위하여 기준입력단에 지수형 필터를 적용하여 기존 제어기의 문제점을 개선하였다. DSP기반의 제어하드웨어를 개발하고, 정격 공극 부상 실험을 통해 부상제어기법이 설계 목표를 만족함을 검증하였다. 추진제어기는 공간벡터 전압변조기법을 사용하고, 레일의 전 구간에 부착된 바코드 정보로부터 절대위치를 감지하여 위치 및 속도 프로파일을 추종하도록 설계하였다. 추진제어 왕복 이동 실험을 통해 위치 제어 결과가 만족할만한 성능임을 확인하였다.

• Journal of Electrical Engineering and Technology
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• 제9권2호
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• pp.514-522
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• 2014

A new type of high precision electromagnetic suspension (EMS) which can support heavy tray along long stroke rail is proposed in this paper. Compared with the conventional EMS, the suggested moving-core typed EMS has the levitation electromagnets (EMs) on the fixed rail. This scheme has high load capability caused by iron-core and enables simple tray structure. Also it does not have precision degradation caused by heat generation from EMs, which is a drawback of conventional EMS. With these merits, the proposed EMS can be an optimal contactless linear bearing in next generation flat panel display (FPD) manufacturing process if the ability of long stroke movement is proved. So a special Section Switching Algorithm (SSA) is derived from the resultant force and moment equations of the levitated tray which enables long stroke movement of the tray. In order to verify the feasibility of the suggested SSA, a simple test-setup of the EMS with 2 Section-changes is made up and servo-controlled in the simulation and experiment. The simulation shows the perfect changeover the EMs, and the experiment shows overall control performance of under ${\pm}40{\mu}m$ gap deviations. These results reveal that the newly suggested contactless linear bearing can simultaneously achieve high load capability and precision gap control as well as long stroke.

• 대한기계학회논문집A
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• 제37권12호
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• pp.1559-1565
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• 2013

고가가이드웨이를 주행하는 상전도흡인식 자기부상열차(EMS-Type Maglev)는 가이드웨이의 유연성으로 인하여 전자석 현가시스템과 동적 상호작용을 일으켜 부상공극에 영향을 미친다. 특히, 전체 건설비를 줄이기 위하여 경량화 가이드웨이를 지향하면서 시스템 설계단계부터 차량과 가이드웨이 사이의 동적상호작용 해석에 의한 심도 있는 부상공극 분석이 더욱 필요하다. 본 논문에서는 보다 정교한 차량/가이드웨이 동적상호작용 해석모델이 제안된다. 제안된 모델은 가상시제 기반의 3 차원 전체차량, 모달합성법에 의한 유연 가이드웨이 및 피드백 제어기가 포함된 부상전자석의 동적 모델들이 하나로 통합된 것이다. 제안된 모델을 도시형 자기부상열차에 적용하여 차량의 속도와 레일조도가 부상공극 및 가이드웨이에 미치는 영향을 분석하였다.

• 한국구조물진단유지관리공학회 논문집
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• 제26권3호
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• pp.21-28
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• 2022

TMD는 다른 진동제어장치에 비해 구조가 단순하며, 구조물에 발생하는 정형화된 형태의 진동에 우수한 제어성능을 보인다. 그러나 다른 제어장치에 비하여 진동제어범위가 좁아 예상치 못한 외부하중으로 인하여 발생하는 진동주기에는 취약하다. 본 연구에서 개발된 ETMD는 Mass를 전자석으로 구성하여 전류를 공급할 때 자기장이 형성됨과 동시에 마찰판과의 마찰력을 상승시켜 Mass의 거동을 순간적으로 제어한다. 개발된 ETMD의 제어성능 평가를 위하여 모형 단순보 교량 중앙에 ETMD를 설치한 후 중앙부 최대 수직변위가 발생하는 3.02Hz 조건으로 강제 진동을 발생시켜 휨거동 제어실험을 수행하였다. 실험결과 ETMD는 중앙부 최대 수직변위가 발생하는 3.02Hz에서 변위 감쇠율이 57.51%로 우수한 제어성능을 발휘하며 그 외에 진동주기에도 안정적인 제어성능을 보이는 것을 확인하였다.

• 한국초등과학교육학회지:초등과학교육
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• 제26권4호
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• pp.440-448
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• 2007

The purpose of this study is to examine elementary students' conceptions of magnetic fields around various magnets by drawing tasks. A total of 105 elementary students from the 3rd and 6th grade levels were asked to draw how iron filings would arrange around magnets. We classified their drawings of magnetic field lines with some criteria to identify conceptions of magnetic forces and checked them through interviewing about their representative drawing. Through analyzing drawings, we discovered that 40% of elementary students drew the correct arrangement of iron filings around a bar magnet. In the case of two bar magnets in opposite directions, 33% of them drew correct patterns of iron dust and around two magnets in the same direction only 20% did well. Only 2.9% and 7.6% of students presented the correct drawings of magnetic fields near a disc and a horseshoe magnet. While 3rd grade students were supposed to be poor in drawings of magnetic fields around a loose and a dense coil which was not learned about, only 31% and 23% of 6th grade students who have just studied electromagnetism properly drew patterns of iron dust. This shows that only one quarter of students understood the magnetic filed lines even after instruction of electromagnetism. Many of 6th grade students learned a solenoid becomes just as a permanent magnet, but very few of them correctly drew a magnetic field line could distinguish between the iron dust around a loose and dense coil. After interviewing students, it is found that students consider magnetic forces to be existed only in parts of magnet because many of them drew magnetic field line of a specific areas around magnets. Students had misconceptions that magnetic forces exist only on the poles not in the middle around a horseshoe magnet. Also the disc-shape magnet made students to reveal various types of misconceptions: N- and S-poles are mixed in a whole magnet and right part of a disc-shape magnet is N-pole, left part is S-pole. Students who had not studied magnetic fields of around a magnet and electromagnets could not draw the correct patterns of iron dust suggest that it is indispensable for students to teach how patterns of iron filings would represent a visual image of magnetic fields in order to understand magnetic fields.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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• pp.260-260
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• 2013

Multiferroic materials have attracted much attention due to their fascinating fundamental physical properties and technological applications in magnetic/ferroelectric data-storage systems, quantum electromagnets, spintronics, and sensor devices. Among single-phase multiferroic materials, $BiFeO_3 $ is a typical multiferroic material with a room temperature magnetoelectric coupling in view of high magnetic-and ferroelectric-ordering temperatures (Neel temperature $T_N$~647 K and Curie temperature $T_C$~1,103 K). Rare-earth ion substitution at the Bi sties is very interesting, which induces suppressed volatility of Bi ion and improved ferroelectric properties. At the same time, Fe-site substitution with magnetic ions is also attracting, and the enhanced ferromagnetism was reported. In this study, $Bi_{1-x}Dy_xFe_{0.95}Co_{0.05}O_3$ (x=0, 0.05 and 0.1) bulk ceramic compounds were prepared by solid-state reaction and rapid sintering. High-purity $Bi_2O_3$, $Dy_2O_3$, $Fe_2O_3$ and $Co_3O_4$ powders with the stoichiometric proportions were mixed, and calcined at $500^{\circ}C$ or 24 h to produce $Bi_{1-x}Dy_xFe_{0.95}Co_{0.05}O_3$. The samples were immediately put into an oven, which was heated up to $800^{\circ}C$ nd sintered in air for 30 min. The crystalline structure of samples was investigated at room temperature by using a Rigaku Miniflex powder diffractometer. The field-dependent magnetization measurements were performed with a vibrating-sample magnetometer. The electric polarization was measured at room temperature by using a standard ferroelectric tester (RT66B, Radiant Technologies).

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
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• pp.250-250
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• 2012

Recently, multiferroic materials have attracted much attention due to their fascinating fundamental physical properties and potential technological applications in magnetic/ferroelectric data storage systems, quantum electromagnets, spintronics, and sensor devices. Among single-phase multiferroic materials, $BiFeO_3$, in particular, has received considerable attention because of its very interesting magnetoelectric properties for application to spintronics. Enhanced ferromagnetism was found by Fe-site ion substitution with magnetic ions. In this study, $BiFe_{1-x}Ni_xO_3$ (x=0 and 0.05) bulk ceramic compounds were prepared by solid-state reaction and rapid sintering. High-purity $Bi_2O_3$, $Fe_3O_4$ and NiO powders were mixed with the stoichiometric proportions, and calcined at $450^{\circ}C$ for 24 h to produce $BiFe_{1-x}Ni_xO_3$. Then, the samples were directly put into the oven, which was heated up to $800^{\circ}C$ and sintered in air for 20 min. The crystalline structure of samples was investigated at room temperature by using a Rigaku Miniflex powder diffractometer. The Raman measurements were carried out with a Raman spectrometer with 514.5-nm-excitation Ar+-laser source under air ambient condition on a focused area of $1-{\mu}m$ diameter. The field-dependent magnetization and the temperature-dependent magnetization measurements were performed with a vibrating-sample magnetometer. The x-ray diffraction study demonstrates the compressive stress due to Ni substitution at the Fe site. $BiFe_{0.95}Ni_{0.05}O_3$ exhibits the rhombohedral perovskite structure R3c, similar to $BiFeO_3$. The lattice constant of $BiFe_{0.95}Ni_{0.05}O_3$ is smaller than of $BiFeO_3$ because of the smaller ionic radius of Ni3+ than that of Fe3+. The field-dependent magnetization of $BiFe_{0.95}Ni_{0.05}O_3$ exhibits a clear hysteresis loop at 300 K. The magnetic properties of $BiFe_{0.95}Ni_{0.05}O_3$ were improved at room temperature because of the existence of structurally compressive stress.

• Smart Structures and Systems
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• 제29권4호
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• pp.625-640
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• 2022

Maglev rail joints are vital components serving as connections between the adjacent F-type rail sections in maglev guideway. Damage to maglev rail joints such as bolt looseness may result in rough suspension gap fluctuation, failure of suspension control, and even sudden clash between the electromagnets and F-type rail. The condition monitoring of maglev rail joints is therefore highly desirable to maintain safe operation of maglev. In this connection, an online damage detection approach based on three-dimensional (3D) convolutional neural network (CNN) and time-frequency characterization is developed for simultaneous detection of multiple damage of maglev rail joints in this paper. The training and testing data used for condition evaluation of maglev rail joints consist of two months of acceleration recordings, which were acquired in-situ from different rail joints by an integrated online monitoring system during a maglev train running on a test line. Short-time Fourier transform (STFT) method is applied to transform the raw monitoring data into time-frequency spectrograms (TFS). Three CNN architectures, i.e., small-sized CNN (S-CNN), middle-sized CNN (M-CNN), and large-sized CNN (L-CNN), are configured for trial calculation and the M-CNN model with excellent prediction accuracy and high computational efficiency is finally optioned for multiple damage detection of maglev rail joints. Results show that the rail joints in three different conditions (bolt-looseness-caused rail step, misalignment-caused lateral dislocation, and normal condition) are successfully identified by the proposed approach, even when using data collected from rail joints from which no data were used in the CNN training. The capability of the proposed method is further examined by using the data collected after the loosed bolts have been replaced. In addition, by comparison with the results of CNN using frequency spectrum and traditional neural network using TFS, the proposed TFS-CNN framework is proven more accurate and robust for multiple damage detection of maglev rail joints.