• 제어로봇시스템학회:학술대회논문집
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• 1997.10a
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• pp.276-279
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• 1997

When a magnetostrictive material is exposed to a magnetic field, its geometry changes due to a magnetostrictive effect. The magnetostriction is analogous to the piezoeletricity. The displacement of the magnetostrictive material is proportional to the applied current while that of the piezoelectric material is proportional to the voltage. A magnetostrictive material generates large displacement and higher compressive force compared with a piezoeletric material. These advantages provide a good performance of a vibration isolation of a platform. In this work, it is applied to a driving actuator for vibration isolation of a platform. The properties of a magnetostrictive material are investigated in terms of hysteresis and displacement vs. applied current for a various preload. Modeling of the displacement of the vibration isolating actuator is performed as it behaves as a flow source. A sliding mode controller is designed to demonstrate the ability of the magnetostrictive actuator to reduce the vibration at the platform. The effectiveness of the proposed scheme is demonstrated through experimental works. The experimental results of the vibration of the platform axe presented in terms of time response and frequency response.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2008.04a
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• pp.331-336
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• 2008

An self-centering energy-dissipative (SCED) bracing system has recently been developed as a new seismic force resistant bracing system. The advantage of the SCED brace system is that, unlike other comparable advanced bracing systems that dissipate energy, such as the buckling restrained brace system, it has a self-centering capability that reduces or eliminates residual building deformations after major seismic events. In this study seismic performance of SCED braced frames is evaluated for a set of 20 design level earthquake records. According to analysis results the SCED systems showed more uniform interstory drift demand for buildings with 8 story or fewer. The residual deformation in SCED buildings turned out to be much less than that of moment-resisting frames.

• Journal of Electrical Engineering and Technology
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• v.12 no.2
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• pp.674-682
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• 2017

This paper presents an optimal initial firing angle control based on the energy consumption and regenerative energy of a parallel multi-pulse thyristor dual converter for urban railway power substations. To prevent short circuiting the thyristor dual converter, a hysteresis band for maintaining a zero-current discontinuous section (ZCDS) is essential during mode changes. During conversion from the ZCDS to forward or reverse mode, the DC trolley voltage can be stabilized by selecting the optimal initial firing angle without an overshoot and slow response. However, the optimal initial firing angle is different depending on the line impedance of each converter. Therefore, the control algorithm for tracking the optimal initial firing angle is proposed to eliminate the overshoot and slow response of DC trolley voltage. Simulations and experiments show that the proposed algorithm yields the fastest DC voltage control performance in the transient state by tracking the optimal firing angle.

• Proceedings of the KIEE Conference
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• 2008.04c
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• pp.86-88
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• 2008

The rotational loss is one of the most important problems for the practical use of the high power Flywheel Energy Storage System (FESS). This rotational loss is divided as the mechanical loss by windage and bearing and iron loss by hysteresis loop and eddy current in the part of the magnetic field. So, In this paper, a double-sided PMSM/G without the iron loss is designed by analytical method of the magnetic field and estimation of the back-EMF constant represented as the design parameter. This design model consists of the double-sided PM rotor with Halbach magnetized any and coreless 3-phase winding stator. The results show that the double-sided PMSM/G without iron loss can be applicable to the high power FESS.

• Proceedings of the KIPE Conference
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• 1997.07a
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• pp.352-356
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• 1997

This paper present the design of a novel neural-network (NN) based pulse-width modulation (PWM) techniques for a three-level power converter of electric trains along with nonlinear mapping of essential switching patterns and fault tolerance, which are inherent characteristics of NNs. Considering the importance of safety, power factor and harmonics of electric train power converters, two-level type and three-level type of power converters using NNs are precisely investigated and compared in computer simulation. A computer simulation shows that a new current control scheme provides an improved performance over a fixed-band hysteresis current control in many aspects.

• Journal of Mechanical Science and Technology
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• v.20 no.12
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• pp.2087-2093
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• 2006

In this paper, auto focus actuator, which is used to move a lens module in the mobile phone having a camera module, is developed. Camera module containing auto focus actuator requires to minimize total size because of characteristics of the application area such as mobile phone, digital camera, and personal digital assistant. There are stepping motor, voice coil motor, and piezoelectric motor as auto focus actuator. In this paper, voice coil motor having new electromagnetic configuration is proposed. And actuator using proposed voice coil motor is developed by optimal design method using magnetic circuit analysis. The sectional area of the developed actuator is reduced to 32.4% compared with actuator using general electromagnetic configuration. From the performance test, the developed actuator has moving stroke of 0.64 mm for 2.1 volt, hysteresis of 40 $\mu$m, full stroke current of 54 mA, and unit step motion of 3 $\mu$m.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.951-955
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• 2004

Piezoelectric(PZT) actuator can substitute for solenoid which is used in fluid control field because it has faster response times and no possibility of explosion. Besides, it is available in a high temperature and it has low energy consumption. In this study, pneumatic micro valve, bimorph type PZT actuator using the softner type PZT, carbon plate as a shim and its controller circuit were suggested and investigated. Performance tests and characteristics analysis, such as displacement, force, hysteresis and frequency properties, were carried out. The displacement of the actuator measured at the end point was 63 ${\mu}m$., force of the actuator was 0.052 N and maximum operating frequency was 15Hz. Also, characteristics of the micro valve with PZT actuator were evaluated in a testing system. The results show that the suggested PZT actuator is suitable for micro valve.

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.3
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• pp.166-175
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• 2002

Tank track rubbers, which undergo dynamic stresses and strains under various road conditions, leads to a result of considerable internal temperature rise due to the heat generation. Since rubber materials are not fully elastic, a part of the mechanical energy is converted into heat because of the hysteresis loss. Heat generation without adequate heat dissipation leads to heat build-up, i.e. internal temperature rise which, if excessive, exerts a bad influence upon the performance and the life of the tank track rubbers. The purpose of this paper is to predict temperature distributions of the rubber components off tank track subjected to complex dynamic loads under various read conditions. In steady state analysis temperature fields are displayed in contour shapes, and in unsteady analysis the temperature variations of some important nodes are represented graphically with respect to the running time of the tank.

• Journal of Electrical Engineering and Technology
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• v.8 no.6
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• pp.1337-1344
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• 2013

This paper presents a simplified modulation strategy for the three-leg VSI fed two-winding induction motor. The strategy provides independent unbalanced voltage control for the main and auxiliary windings. This make the motor can be reversed rotation through the range of motor speed operation without limitation of voltage boost of the auxiliary winding. To study the advantages of the proposed drive, the experimental results such as voltage stresses, hysteresis band of the currents in locus, and also acoustic noise levels of the three-leg VSI are compared with those of the conventional two-leg topology. The results obviously show that the proposed technique achieves superior performance compared with the traditional scheme in case of dramatic increase of DC bus utilization, effective reduction of harmonic voltages content, and also significant enhancement of motor efficiency.

• Journal of Advanced Marine Engineering and Technology
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• v.19 no.3
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• pp.91-98
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• 1995

To control speed or torque of induction motors, scalar control method that regulates the value of stator current had been used conventionally. But, vector control method which contrls the direction and the value of stator current at the same time has been introduced lately and employed widely. This paper describes comparative analyses of above two methods by computer simulation. As a result of the simulation, both methods showed good responses for high speed, but, vector control method characterized much better performance for low speed and sinusoidal input.