• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 춘계학술대회논문집
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• pp.362-365
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• 2004

'Coil' occupies a much important position in delivering driving force of optical pick-up actuators. Up to now the main stream has been a winding coil type actuator, but actuators using FP-Coil(Fine Pattern Coil) have been considered for the more compacted and simple manufacturing process and have variously spreaded the application fields by product. We have tried to design actuators using PCB-Coil(Printed Circuit Board Coil) which has benefits in terms of price and manufacturing process. Especially this research has two main things those are to reduce the vibration of sub-resonance and to assure the do sensitivity in the performance of asymmetric optical pick-up actuator with PCB-Coil.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 춘계학술대회논문집
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• pp.1925-1932
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• 2000

Damage detection methods using vibration modes are investigated on ring structures and. modal behavior of the slightly asymmetric rings is examined. Mode shapes changes, MSER(modal strain energy ratio) and MCR(modal curvature ratio) are applied to identify the locations of faults or damages. Parameters are calculated and compared by finite element analysis on rings with designed local damages. Damages are modeled as reduced stiffness in the analysis. The results show MSER and MCR can be proper factors to detect local damages in ring structures.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2009년도 추계학술대회 논문집
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• pp.627-628
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• 2009

• 소음진동
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• 제8권2호
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• pp.346-352
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• 1998

This paper presents actuating characteristics of an asymmetric high-speed optical pick-up fine actuator that can be installed in a small area such as a notebook personal computer. In the asymmetric actuator four points (mass center, actuation center, supporting point of wire suspension on a bobbin, and optical axis) are not coincident so that the proposed actuator suspension reveals undesirable suspension resonance in the pitch and yaw direction. Lumped parameter dynamic model in each direction is used to investigate the driving characteristics with respect to relative location of the four points. Some of desired design directions toward reducing resonance peaks are suggested by using sensitivity information. In order to avoid undesirable resonance, at least supporting point on the obbin must be located in the middle of the mass and actuation center of the asymmetric pick-up actuator.

• Journal of Mechanical Science and Technology
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• 제15권7호
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• pp.866-875
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• 2001

The complex modal testing methods developed for asymmetric rotors are briefly discussed and their performances are experimentally evaluated. For the experiments, a laboratory test rotor is excited by using a newly developed, cost effective magnetic exciter equipped with Hall sensors, which measure the excitation forces. It is concluded that the exciter system is characterized by a wide bandwidth and a high resolution for both the excitation and force measurement, and that the one-exciter/two-sensor technique for complex modal testing of asymmetric rotors is superior to the standard two-exciter/two-sensor technique in terms of practicality and realization.

• Structural Engineering and Mechanics
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• 제33권3호
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• pp.339-355
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• 2009

The sealed, tuned liquid column gas damper (TLCGD) with gas-spring effect extends the frequency range of application up to about 5 Hz and efficiently increases the modal structural damping. In this paper the influence of several TLCGDs to reduce coupled translational and rotational vibrations of plan-asymmetric buildings under wind or seismic loads is investigated. The locations of the modal centers of velocity of rigidly assumed floors are crucial to select the design and the optimal position of the liquid absorbers. TLCGD's dynamics can be derived in detail using the extended non-stationary Bernoulli's equation for moving reference systems. Modal tuning of the TLCGD renders the optimal parameters by means of a geometrical transformation and in analogy to the classical tuned mass damper (TMD). Subsequently, fine-tuning is conveniently performed in the state space domain. Numerical simulations illustrate a significant reduction of the vibrations of plan-asymmetric buildings by the proposed TLCGDs.

• International Journal of Railway
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• 제3권3호
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• pp.83-89
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• 2010

This paper attempts to extract the fundamental dynamic properties, i.e. natural frequencies, damping ratios of the 48 m-long, $20^{\circ}$ skewed real bridge with PSC girders wrapped by a steel plate. The forced vibration test is achieved by mounting 12 Hz-capacity of artificial oscillator on the top of bridge deck. The acceleration histories at the 9 different locations of deck surface are recorded using accelerometors. From this full-scaled vibration test, the two possible resonance frequencies are detected at 2.38 Hz and 9.86 Hz of the skewed bridge deck by sweeping a beating frequency up to 12 Hz. The absolute acceleration/energy exhibits much higher in case of higher-order twist mode, 9.86 Hz due to the skewness of bridge deck which leads asymmetric situation of vibration. This implies the test bridge is under swinging vertically in fundamental flexure mode while the bridge is also flickered up and down laterally at 9.86 Hz. This is probably by asymmetric geometry of skewed deck. A detailed 3D beam-shell bridge models using finite elements are performed under a series of train loads for modal dynamic analyses. Thereby, the effect of skewness is examined to clarify the lateral flickering caused by asymmetrical geometry of bridge deck.

• Structural Engineering and Mechanics
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• 제29권5호
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• pp.505-530
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• 2008

This paper proposes the application of active multiple tuned mass dampers (AMTMD) for translational and torsional response control of a simplified two-degree-of-freedom (2DOF) structure, able to represent the dynamic characteristics of general asymmetric structures, under the ground acceleration. This 2DOF structure is a generalized 2DOF system of an asymmetric structure with predominant translational and torsional responses under earthquake excitations using the mode reduced-order method. Depending on the ratio of the torsional to the translational eigenfrequency, i.e. the torsional to translational frequency ratio (TTFR), of asymmetric structures, the following three cases can be distinguished: (1) torsionally flexible structures (TTFR < 1.0), (2) torsionally intermediate stiff structures (TTFR = 1.0), and (3) torsionally stiff structures (TTFR > 1.0). The even distribution of the AMTMD within the whole width and half width of the asymmetric structure, thus leading to three cases of installing the AMTMD (referred to as the AMTMD of case 1, AMTMD of case 2, AMTMD of case 3, respectively), is taken into account. In the present study, the criterion for searching the optimum parameters of the AMTMD is defined as the minimization of the minimum values of the maximum translational and torsional displacement dynamic magnification factors (DMF) of an asymmetric structure with the AMTMD. The criterion used for assessing the effectiveness of the AMTMD is selected as the ratio of the minimization of the minimum values of the maximum translational and torsional displacement DMF of the asymmetric structure with the AMTMD to the maximum translational and torsional displacement DMF of the asymmetric structure without the AMTMD. By resorting to these two criteria, a careful examination of the effects of the normalized eccentricity ratio (NER) on the effectiveness and robustness of the AMTMD are carried out in the mitigation of both the translational and torsional responses of the asymmetric structure. Likewise, the effectiveness of a single ATMD with the optimum positions is presented and compared with that of the AMTMD.

• 한국전산유체공학회지
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• 제16권1호
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• pp.7-13
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• 2011

The fluid-structure interaction of a towed body is simulated using a developed code, which is based on the flux-difference splitting scheme on the hybrid Cartesian/immersed boundary method. To improve the stability in the coupling between the fluid and structure domains, a scheme is used, in which the effects of structure deformation are treated implicitly. The developed code is validated for the fluid-structure interaction problem through comparisons with other results on the vortex-induced vibration of elastically mounted cylinders. To simulate behavior of a towed body, an asymmetric tension modelling for a towing cable is suggested. In the suggested model, the tension is proportional to the elongation of the cable, but the cable has no effect on the body motion whenever the distance between the endpoints of the cable is smaller than the original length of the cable. The fluid-structure interactions of a towed body are simulated on the basis of different parameters of the towing cables. It is observed that the suggested tension model predicts the snapping for a shorter towing cable, which is in accordance with the reported results.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 추계학술대회논문집
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• pp.504-514
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• 2003

We investigate global bifurcation in the subharmonic motion of a circular plate with one-to-one internal resonance. A system of autonomous equations are obtained from the partial differential equations governing the system by using Galerkin's procedure and the method of multiple scales. A perturbation method developed by Kovacic and Wiggins is used to find Silnikov type homoclinic orbits. The conditions under which the orbits occur are obtained.