• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.1321-1327
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• 2006

This paper presents the calculation of unbalanced magnetic pull (UMP) that causes rotor misalignment in induction motor. The excessive noise and vibration will be occurred by means of rotor misalignment. Angular misalignment of rotor will produce air-gap permeance wave which is function of axial and circumferential coordinate. In this paper, the UMP is calculated using permeance and magneto motive force (MMF) in the case of static and dynamic misalignment. Based on the percentage of misalignment, the result shows that the UMP and magnetic pressure are increased according to the increasing of misalignment. The UMP is occurred not only in It frequency component but also the others.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.1058-1062
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• 2003

This paper proposes a self-organizing fuzzy controller (SOFC) design technique applied to the vibration control of a dynamic system under irregular disturbance. In this controller, the fuzzy rules generate control signal continuously using the array of input and output pairs without using any special controller model. The generated rules are saved in the fuzzy rule matrix in real-time by self-organizing methods. This fuzzy logic control is demonstrated by simulation and shows the efficiency of the real-time self-organizing fuzzy controller in this system.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2013.10a
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• pp.92-93
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• 2013

In this study, Shock Absorption performance of Magneto-rheological elastomer(MRE) is identified through the drop impact test. Magneto-rheological materials are divided into two groups by MR fluid in fluid state and MR elastomer in solid state like rubber. The stiffness characteristics of Magneto-rheological material can be changed as magnetic field is applied. The impact loads in MR elastomer were measured under weight of impactor. Experiment results are shown through the experiments to confirm the effect of shock absorption of MR elastomer. Thus, the MR elastomer can be applied to shock absorber used in area that shock occurs.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11b
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• pp.780-785
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• 2001

A moving-magnet type pickup actuator is proposed, which has the back-yoke to improve th sensitivity. Through the magnetic path analysis, we can find that the flux density is increased i the air gap by the pole assignment of magnet and the adding of back-yoke can reduce the flu leakage and induce 40％ up of flux density. Experimental results show that the sensitivity i improved in the tracking direction, however, the improvement doesn't occur in the focusing direction. Finally, the compensation performance is tested in HD-DVD system. And it is verifie that the actuator can compensate the disc tilt of ${\pm}$0.7$^{\circ}$.

• 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.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.423-427
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• 2004

In this work, we propose a new ultrasonic damage inspection method in plate structures. The proposed method employs an OPMT (Orientation-adjustable Patch-type Magnetostrictive Transducer) in order to make the ultrasonic waves focused on the specific target point. For experiments, virtual grid points were set up at every 50 mm in an aluminum plate and two OPMTs were used for inspection. If there exists a crack in a plate, the reflected Lamb wave from the crack is measured in addition to the direct waves from the transmitting transducer to the receiving transducer.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.3
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• pp.229-234
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• 2010

This paper presents the analysis of pitch static attitude(PSA) in thermally assisted magnetic recording(TAMR) suspension. The TAMR suspension using an optical fiber has high stiffness such as vertical, pitch and roll. Therefore, P-torque is greatly increased by the optical fiber. Also, flying height(FH) of the slider with TAMR suspension can be largely changed by PSA. In this paper, we focus on the FH by PSA of TAMR suspension. The FH is investigated using various PSA and proper PSA is proposed.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.13 no.3
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• pp.172-179
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• 2003

Linear matrix Inequality based $H_\infty$ robust controller is designed to control the motion of a 4-axis unbalanced rigid asymmetric rotor supported and controlled by two active magnetic bearings in this paper. To this end, the equations of motion of the system are derived via Hamilton's variational principle and transformed to a state-space form for the standard $H_\infty$ control problem. LMI-based controller, which does not require additional assumptions beyond the usual stabilizability and detectability assumptions, is designed based upon the pole place weighting function and loopshaping technique. The obtained results are compared with those reported in the available literature and the efficiency of the proposed LMI-based $H_\infty$ control is revealed.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.21 no.9
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• pp.834-841
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• 2011

Obtaining the real exciting force is important for the analysis of structural vibration or sound radiation to represent the actual condition. But in most cases, it is so difficult to get the actual force signals by direct measurement using sensors due to complex geometry. This paper suggests advanced source identification method which can be applied to the prediction of radiated noise considering correlations between measured signals. This method was implemented to the identification of the fan force in the refrigerator. The analysis of structural vibration and radiated noise caused by the fan force was also performed. The comparison between predicted SPL and measured SPL of the radiated noise by the refrigerator fan showed good agreement.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.27 no.2
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• pp.175-181
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• 2017

In the present work, to achieve high braking performance with restricted size, characteristics of magneto-rheological (MR) fluid brake is numerically investigated considering different magnetic core shapes. As a first step, structural configuration of the MR brakes are proposed with four different magnetic core shapes, such as single flat, single inclined, dual flat and dual inclined. To estimate braking performance of the proposed MR brakes, electromagnetic analysis is carried out and the results of magnetic field intensity distribution are observed. Based on the electromagnetic analysis results, braking torque of the MR brake is estimated according to magnitude of current input and results are discussed. It is observed that enhanced braking torque can be achieved by adopting the modified magnetic core shape under limited small size of the MR brake.