• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2000.02a
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• pp.170-172
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• 2000

This paper deals with the characteristic analysis of the flux damper with respect to the load, and the stability of Ag/Bi-2223 tapes in a high-Tc superconducting (HTS) synchronous motor. To find out the magnetic field distribution in a detailed model of the actual motor, the experimentally measured currents of the armature and the field windings are used as input parameters. The simulation results show that the flux damper shields the time varying field up to 10%, reduces armature reactance during the motor operation and during load changes, improving the stable motor operation. And it was observed that the flux damper generates loss by means of leakage flux, but this is not significant and it doesn't degrade the performance of the TS synchronous motor.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.227-230
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• 2005

The paper presents the identification of dynamic property of a rotor system with a squeeze film damper (SFD) using magnetic fluid. An electromagnet is installed in the inner damper of the SFD. The magnetic fluid is well known as a functional fluid. Its rheological property can be changed by controlling the applied current to the fluid and the fluid can be used as lubricant. Basically, the proposed SFD has the characteristics of a conventional SFD without an applied current, while the damping and stiffness properties change according to the variation of the applied electric current. Therefore, when the applied current is changed, the whirling vibration of the rotor system can be effectively reduced. The clustering-based hybrid evolutionary algorithm (CHEA) is used to identify linear stiffness and damping coefficients of the SFD based on measured unbalance responses.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.15 no.11 s.104
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• pp.1262-1267
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• 2005

The paper presents the identification of dynamic property of a rotor system with a squeeze film damper (SFD) using magnetic fluid. An electromagnet Is installed in the inner damper of the SFD. The magnetic fluid is well known as a functional fluid. Its rheological property can be changed by controlling the applied current to the fluid and the fluid can be used as lubricant. Basically, the proposed SFD has the characteristics of a conventional SFD without an applied current, while the damping and stiffness Properties change according to the variation of the applied electric current. Therefore, when the applied current is changed, the whirling vibration of the rotor system can be effectively reduced. The clustering-based hybrid evolutionary algorithm (CHEA) is used to identify linear stiffness and damping coefficients of the SFD based on measured unbalance responses.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.3
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• pp.1305-1310
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• 2014

MR(Magneto-Rheological) damper generates the magnetic shear force due to the cohesiveness of MR fluid influenced by a magnetic field. MR fluid consists of magnetic particles and a base liquid. In the present study, the damping forces of MR damper were investigated for density 1.3, 1.5 and $1.7g/cm^3$, and viscosity 1000 and 10000cp, and for the change of orifice shapes. It was found that the increase in the density and viscosity of MR fluid could change the damping force of MR damper due to the magnetic effects. Also, the damping forces on orifice shapes increased as the orifice gap and length decreased. These results showed that the properties of MR fluid and orifice shapes were important for the optimum design of MR damper.

• The KSFM Journal of Fluid Machinery
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• v.7 no.4 s.25
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• pp.24-31
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• 2004

The aim of this study is to provide fundamental information for the development of Semi-Active Damper Using Magnetic fluid. To achieve the aim, the damping effect of magnetic fluid is investigated by experiments that the diameter of inner circular bar and the input amplitude were varied in the magnetic field generated by the permanent magnet and the electromagnet coil. From the study, the following conclusive remarks can be made. As the diameter of inner circular bar and input amplitude increase, the damping effect is improved. This is explained by the fact that as the contact area between inner circular bar and magnetic fluid increases, the increase of friction lowers kinematic energy. If the magnetic field is generated, the damping effect is improved. This is explained the assumption that as the intensity of magnetic fluid particle increases, there is virtual mass phenomenon.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.4
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• pp.346-351
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• 2008

In this paper, the semi-active control of a helicopter landing gear using magneto -rheological(MR) damper is studied. A dynamic model of the MR damper is formulated by incorporating magnetic field-dependent Bingham properties of the MR fluid. The electromagnet of the MR damper is designed and its magnetic field is analyzed using a commercial finite element code. The damping characteristics of MR damper by changing the intensity of the magnetic field are investigated and the dynamic responses of the helicopter landing gear with MR damper are simulated. The semi-active control of the helicopter landing gear is simulated by implementing a sky-kook control algorithm and its performance is evaluated comparing to the passive control.

• Progress in Superconductivity and Cryogenics
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• v.1 no.2
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• pp.25-29
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• 1999

The purpose of this paper is to find the magnetic filed distribution inside the motor in order to find out if the high-Tc superconducting tapes operate stably in actual motor operation in a detailed model of the actual motor was analyzed through F.E.M.(finite Element Method). As a result, it has been proved that the high-Tc superconducting tapes can with-stand 4 A of current with staility. 4 A was the amount of current with stability. 4 A was the amount of current needed to achieve 600 A·turns which is required by the previous simulation aimed at developing this the flux damper reduces armature reactance during the motor operation. But it was observed that the flux damper generates loss by means of leakage flux and this decreases the output of the motor by about 5%.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11b
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• pp.739-744
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• 2001

In order to investigate the stability of magneto-rheological fluid based squeeze film damper (MR-SFD), its negative stiffness effect, which arises from magnetization of MR-SFD, is identified theoretically and experimentally. The analytical model of MR-SFD includes the magnetic circuit as well as the displacement stiffness associated with the squeeze mode of MRF. Extensive experiments are carried out to measure the magnetic attraction forces generated in the MR-SFD, with the excitation frequency and the eccentricity of the journal varied, which are controlled by an active magnetic bearing. The simulation and experimental results are found to be in good agreement. It is concluded that the negative stiffness effect dominates only in the low frequency region because its effect diminishes in the high frequency region due to the eddy-current loss.

• 제어로봇시스템학회:학술대회논문집
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• 2002.10a
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• pp.118.4-118
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• 2002

$\textbullet$ Magnetic floor hinge $\textbullet$ Recovering torque $\textbullet$ Eddy Currents $\textbullet$ Magnetic damper $\textbullet$ Optimal design $\textbullet$ Cost optimization

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.14 no.6
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• pp.470-477
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• 2004

This study shows the design process of a MR damper for semi-active suspension systems. Damping force characteristics of the designed damper was predicted through the flow analysis and magnetic analysis. The predicted results were compared with the experimental results and the initial design specification was modified according to the results.