• The Transactions of the Korean Institute of Electrical Engineers B
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• v.53 no.7
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• pp.444-451
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• 2004

Conventional magnetic levitation systems could show unsatisfactory performance under air-gap disturbance due to rail irregularities. In this paper, we propose a feedback control system with discrete Kalman filter for air-gap disturbance attenuation. It is shown that excellent system performance can be obtained with the use of discrete Kalman filter, and that results from experiments agree well with those of simulations.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.10
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• pp.165-171
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• 1998

An axial electromagnetic levitation system using attractive force is a highly nonlinear system due to the nonlinearity of materials, variable air gap and flux density. To control the levitating system with large air gap, a conventional PID control based on the linear model is not satisfactory to obtain the desired performance and the position tracking control of the sinusoidal motion by simulation results. Thus, sliding mode control(SMC) based on the input-output linearization is suggested and evaluated by simulation and experimental approaches. Usefulness of the SMC to this system is conformed experimentally. If the expected variation of added mass can be included in the gain conditions and the model, the position control performance of the electromagnetic levitation system with large air gap will be improved with robustness.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.9
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• pp.84-91
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• 2003

This paper concerns on one-DOF non-rotating active magnetic bearing (AMB) system subject to base motion. In such a system, it is desirable to retain the axis within the predetermined air-gap while the base motion forces the axis to deviate from the desired air-gap. Motivated from this, an optimal acceleration feedforward control is proposed to reduce the base motion response without deteriorating other feedback control performances. Experimental results demonstrate that the proposed optimal feedforward control reduces the standard deviation of the air-gap to 29％ that by feedback control alone.

• Journal of Power Electronics
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• v.12 no.2
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• pp.305-316
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• 2012

The paper presents an accurate loss model based controller of an induction motor to calculate the optimal air gap flux. The model includes copper losses, iron losses, harmonic losses, friction and windage losses, and stray losses. These losses are represented as a function of the air gap flux. By using the calculated optimal air gap flux compared with rated flux for speed sensorless indirect vector controlled induction motor, an improvement in motor efficiency is achieved. The motor speed performance is improved using a fuzzy logic speed controller instead of a PI controller. The fuzzy logic speed controller was simulated using the fuzzy control interface block of MATLAB/SIMULINK program. The control algorithm is experimentally tested within a PC under RTAI-Linux. The simulation and experimental results show the improvement in motor efficiency and speed performance.

• Transactions of the Society of Information Storage Systems
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• v.10 no.1
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• pp.1-6
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• 2014

Plasmonic lithography is the latest technique to overcome diffraction limit of previous optical lithography. In the plasmonic lithography, the nano gap between nano metal wave guide and photoresist should be in sub-wavelength region. SIL-based plasmonic lithography is the one of the solutions to maintain small air gap. However, the nano gap control is so sensitive that a little disturbance is able to have a large effect on the nano gap control. So, we analyzed the characteristics of disturbance, and then modified the previous controller to suppress the disturbance. We applied two peak filters which were fixed one and adaptively changeable one. We experimentally confirmed the improvement of the nano gap control, which reduced nano gap error by 30 %. The proposed control will improve the quality of lithography pattern.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.53.5-53
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• 2001

In continuous galvanizing process at steel making plant, coating weight on the surface of strip that pass through air knife is controlled by the pressure at the chamber of air knife and the gap between the nozzle of air knife and strip. The pressure can be easily measured and controlled. But it is difficult to measure the distance between Air knife nozzle and strip, and also difficult to decide how much distance air knife move. Because, the gap between nozzle and strip varies with the height of air knife, intermesh of stabilizing roll and welding of strips that have different thickness. In this research, we developed a gap sensor that can measure the relative distance between Air knife nozzle and strip. And several tests are performed to find optimal condition for application at real plant. We performed test in which the possibility of the sensor to apply ...

• Proceedings of the KSR Conference
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• 2011.05a
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• pp.824-829
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• 2011

EMS-type Maglev vehicle maintains constant levitation air-gap between electromagnet and guideway by using gap sensor. The other words, when Maglev vehicles levitating over the guideway, mass of the vehicle effects through 1st (electromagnetic air-gap control) and 2nd (air-spring) suspension to grider. Resonace between electromagnetic suspension and grider could be occurred, which causes instability and poor ridecomfort. This paper is to test the dymanic interaction between levitation air-gap and switching system grider that has less mass and high natural frequencies than other type of general girders.

• Journal of Magnetics
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• v.22 no.2
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• pp.315-325
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• 2017

Magnetically suspended sensitive gyroscopes (MSSGs) provide an interesting alternative for achieving precious attitude angular measurement. To effectively reduce the measurement error caused by the non-uniformity of the air-gap flux density in a MSSG, this paper proposes a novel compensation method based on measuring and modeling of the air-gap flux density. The angular velocity measurement principle and the structure of the MSSG are described, and then the characteristic of the air-gap flux density has been analyzed in detail. Next, to compensate the flux density distribution error and improve the measurement accuracy of the MSSG, a real-time compensation method based on the online measurement with hall probes is designed. The common issues caused by the non-uniformity of the air-gap flux density can be effectively resolved by the proposed method in high-precision magnetically suspended configurations. Comparative simulation results before and after compensation have verified the effectiveness and superiority of the proposed compensation method.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.11a
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• pp.195-198
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• 1999

A technique is investigated for achieving broadband properties by controlling the operation frequency of microstrip antennas. The control is achieved by applying DC bias to the microstrip antenna. Air gap antenna with PZT post is fabricated. by using in C-band. In the case of Air gap antenna, the variation of center frequency was about 16Mhz and the bandwidth was increased up to 123.3% at 15dB, 160.7% at 20dB than before applying DC bias respectively. The change property of frequency in air gap antenna is nearly the same the C-V property in PZT.

• Proceedings of the KIEE Conference
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• 2004.04a
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• pp.253-255
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• 2004

Conventional magnetic levitation systems could show unsatisfactory performance under air-gap disturbance due to rail irregularities. In this paper, we propose a feedback control system with discrete Kalman filter for air-gap disturbance attenuation. It is shown that excellent system performance can be obtained with the use of discrete Kalman filter, and that results from experiments agree well with those of simulations.