• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2012년도 춘계학술대회 논문집
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• pp.489-490
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• 2012

• 한국소음진동공학회논문집
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• 제19권11호
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• pp.1184-1191
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• 2009

A bearingless linear motor(BLLM) which consists of two stators and a common mover is able to levitate and move its mover without any linear bearing or even additive windings. In the previous study, BLLM was actively controlled on the translation and pitch motion, while the roll motion is passively stable. In order to control the roll motion, this paper suggests adding active magnetic bearings(AMBs) at bottom of the mover in BLLM. The AMBs control the roll motion and also partially supports the weight of the mover. In this paper, magnetic forces generated by the AMBs are estimated by using an FEM model. Based on the analysis results, the bias current of the AMBs is determined and a PD controller is designed. Through an experimental levitation test, it was verified that roll motion is well controlled by AMB during levitation.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2002년도 동계연구발표회 논문개요집
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• pp.122-123
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• 2002

현재 제철소 냉연공장에서는 수지처리 강판을 생산하기 위하여 수지 coater를 사용하고 있다. 그런데 강판의 이면 피복 시, applicator roll에 대한 back-up roll의 균일 하중 부하로 수지의 균일한 피복이 실현되나, 전면을 피복할 때 하중 부하를 위한 별도의 tool이 없는 상태로 강판의 hunting에 대응 불가능한 현장 layout으로 되어 전면 수지부착량 편차가 크게 발생되었다. (중략)

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1993년도 한국자동제어학술회의논문집(국내학술편); Seoul National University, Seoul; 20-22 Oct. 1993
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• pp.793-798
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• 1993

In this study the attitude control of the KOREASAT is investigated. The KOREASAT is a geostationary satellite and its 3 attitude angles, namely, roll, pitch and yaw angles, are stabilized by using the 3-axis stabilization technique. In the pitch control loop, the pitch attitude angle received from the earth sensor is processed in the attitude processing electronics by using PI type control logic, and the control command is sent to the momentum wheel assembly to generate the control torque by varying the wheel rate. The roll/yaw attitude control is performed by activating a magnetic torquer or by firing appropriate thrusters. The magnetic torquer interacts with the earth magnetic field to produce the control torque, and the thrusters are used to control the larger roll attitude errors. In this study dynamic modelling of the satellite is performed. And the earth sensor, the momentum wheel, and the magnetic torquer are mathematically modelled. The 3-axis attitude control logic is implemented to make the closed-loop system and simulations are carried out to verify the implemented control laws.

• E2M - 전기 전자와 첨단 소재
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• 제8권5호
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• pp.633-639
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• 1995

Dropouts in magnetic media are a primary quality deficiency which is detrimental to magnetic signal quality and thus the major impediment to error-free recording, especially in high density digital recorders. The specific form of defects and causes found to be responsible for signal dropouts occurring in magnetic tape were studied. Dropout occurred when the RF signal falls to low level due to the various types of surface defects. However, the fall in the level of the RF signal in gravure roll coated tapes was most often caused by foreign particles adhering to the magnetic tape. It was also shown from the present study that scattered particles trapped under the tape surface or put on the top can lift it as it crosses the head, creating a spherical tent shaped defect and causing a temporary signal drop. Dropout producing substances were identified through optical and microchemical analyses. The results were correlated with measured electrical signal losses combined with analytical microscopy to clarify source identification of defects.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 1998년도 춘계연구발표회 논문개요집
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• pp.92-93
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• 1998

• Journal of Magnetics
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• 제21권4호
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• pp.503-508
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• 2016

The roll- and pitch-induced eddy currents create a magnetic field that contributes to the total magnetic signature of naval vessels. The magnetic signature is of concern, as it exposes the ship to the threat of modern influence mines. It is estimated that the eddy current is the second most important source contributing to a ship's underwater magnetic field following the ferromagnetic effect. In the present paper, the finite element (FE) method is used to predict the eddy current signature of a real ship. The FE model is validated using the measurements of the Canadian research vessel CFAV QUEST at the Earth's Field Simulator (EFS) in Schirnau, Germany. Modeling and validation of the eddy current magnetic signature for a real ship represents a novelty in the field. It is shown that the characteristics of this signature depend on frequency. Based on these results, a ship's degaussing system could be improved to cancel both the ferromagnetic and the eddy current contribution to the magnetic signature simultaneously, reducing the susceptibility to sea mines.

• 한국자기학회지
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• 제4권2호
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• pp.106-113
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• 1994

초전도 반발식 자기부상열차의 동특성을 해석하기 위하여 외력에 의하여 대차가 기울어진 경우에 차량에 가해지는 전자력을 계산하였다. 집중부하방식의 열차에 있어서 크게 나타나는 단부효과 를 고려하기 위하여 공극자속의 형태에 대한 가정없이 자속분포를 계산하였으며, 대차의 옆질(roll), 뒷질(pitch) 및 편주(yaw)시의 전자력특성과 복원토오크를 검토하였다. 6개의 초전도자석이 탑재된 대 차가 차량의 양쪽에 설치된 열차에 대해서 계산한 결과, 토오크의 방향은 차량을 안정하게 하는 방향 으로 나타나서 본 자기부상시스템은 기본적으로 안정한 시스템임을 보여주고 있다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2007년도 추계학술대회 논문집
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• pp.25-26
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• 2007

• Journal of Electrical Engineering and Technology
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• 제12권4호
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• pp.1675-1682
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• 2017

This paper deals with three dimensional orientation estimation algorithm for an attitude and heading reference system (AHRS) based on nine-axis inertial/magnetic sensor signals. In terms of the orientation estimation based on the use of a Kalman filter (KF), the quaternion is arguably the most popular orientation representation. However, one critical drawback in the quaternion representation is that undesirable magnetic disturbances affect not only yaw estimation but also roll and pitch estimations. In this paper, a sequential direction cosine matrix-based orientation KF for AHRS has been presented. The proposed algorithm uses two linear KFs, consisting of an attitude KF followed by a heading KF. In the latter, the direction of the local magnetic field vector is projected onto the heading axis of the inertial frame by considering the dip angle, which can be determined after the attitude KF. Owing to the sequential KF structure, the effects of even extreme magnetic disturbances are limited to the roll and pitch estimations, without any additional decoupling process. This overcomes an inherent issue in quaternion-based estimation algorithms. Validation test results show that the proposed method outperforms other comparison methods in terms of the yaw estimation accuracy during perturbations and in terms of the recovery speed.