• Proceedings of the Korean Society of Precision Engineering Conference
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• 2012.05a
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• pp.489-490
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• 2012

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.11
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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.

• Proceedings of the Korean Magnestics Society Conference
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• 2002.12a
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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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• 1993.10a
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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.

• Electrical & Electronic Materials
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• v.8 no.5
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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.

• Proceedings of the Korean Magnestics Society Conference
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• 1998.05a
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• pp.92-93
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• 1998

• Journal of Magnetics
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• v.21 no.4
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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.

• Journal of the Korean Magnetics Society
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• v.4 no.2
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• pp.106-113
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• 1994

This paper deals with the magnetic forces of the combined levitation and guidance EDS(Electrodynamic Suspension) maglev system when the car bogie is tilted by the roll, pitch and yaw. The end effect on the magnetic forces are considered by calculating the air-gap flux without the assumptions for its pattern. Induced voltages and currents of the ground coils are given as results. The restoring torque due to roll, pitch and yaw of the bogie body are also examined. It has been shown that the end effect of the concentrically loaded vehicle are not negligible and the combined EDS is stable maglev system against disturbing forces.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2007.11a
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• pp.25-26
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• 2007

• Journal of Electrical Engineering and Technology
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• v.12 no.4
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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.