• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.1333-1334
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• 2007

Page-oriented angle multiplexing Holographic data storage system is the one of promising techniques for high capacity and data transfer rate, but its size and narrow tilt margin is pointed as a demerit. To overcome this weak point, in this paper, 2-axis deck mechanism for compensation of disc is employed to Compact size Holographic Data Storage (CHDS) which consists of minimized optical components and small 2-axis actuator moving linear & angle direction. Compensation of radial/tangential disc tilt with 2-axis deck mechanism is demonstrated.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.782-787
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• 2002

In optical disk drives (ODD), the demands of high data density and high speed have been increasing rapidly to achieve high data capacity and data transfer rate. The short wavelength laser, High NA objective lens, and high track following performance are needed to raise data density and data rate. For high-performance actuator, the improvement of linearity and acceleration become more important. Also, 3-axis actuator for active tilt compensation is introduced to overcome the decrease in disk tilt tolerance which is induced by short wavelength laser. In this paper, a hybrid type 3-axis actuator is presented and a new yoke structure, which can reduce the interaction between yoke and moving magnet, is designed to keep the efficiency of magnetic circuit. Experimental results show the validity of the yoke in the hybrid type actuator.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11a
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• pp.173-178
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• 2001

부분구조 합성법(substructuring or substructure synthesis)은 부분구조(substructure)의 주파수 응답함수(FRFs, frequency response functions)를 이용하여 합성된 전체 구조물의 동특성(dynamic behavior)을 파악하는 기술로서 이에 관한 이론은 명확하며 간단하다. 즉, 역행렬 계산과 같은 기본적인 행렬연산으로 부분구조 합성을 수행한다. 그러나, 여러 가지 요인으로 인하여 계산된 합성 결과는 실제로 결합된 전체 구조물의 동특성과는 차이를 보인다. 현실적인 이유로 고려하지 못하는 회전자유도와 실험에서 수반되는 여러 가지 측정오차는 주요한 요인이며 이에 대한 연구 또한 많이 진행되었다. 본 연구에서는 이러한 요인 중, 상대적으로 덜 중요하게 평가된 모드자름 오차(modal truncation error)의 영향을 고려한다. 단순한 구조물에 대하여 모의실험을 수행함으로써, 모드자름 오차로 인하여 완전히 잘못된 합성 결과가 나을 수 있다는 것을 보인다. 측정된 FRE를 이용하여 이러한 오차를 보정(compensation)하는 소개하고 이를 대상 구조물에 적용하여 모드자름 오차의 영향을 상당히 줄일 수 있다는 것을 보인다. 복잡한(complicated) 구조물에 대하여 모드자름 오차의 영향을 줄이기 위해서 모든 FRFs를 보정하는 것은 어려우므로 현실적인 대안을 모색한다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.346-350
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• 2004

In Blu-ray(BD) optical system, as a short laser wavelength of laser diode and thin cover layer thickness of' disc, the proper adjustment of spherical aberration should be performed. Considering thin cover layer' thickness and tolerance variation of disc in BD optical system, spherical aberration in BD format is mort: serious than CDㆍDVD format Especially, in dual-layer disc, to compensate the aberration at each layer, optical component should be moved finely in the way of optical path. In this study, 1 -axis moving actuator was introduced as the method of compensating the spherical aberration, and the mechanism of the system was described. Finally, its effect on optical system will be mentioned.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.520-524
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• 2002

Multi-reference, scan-based Acoustical Holography is a useful measurement technique when insufficient microphones are available to measure a complete hologram at once. When the sound sources are stationary, the whole hologram can be constructed by joining together sub-holograms captured using a relatively small scan array. Here that approach is extended by the development of a formulation that explicitly includes the acoustical transfer functions between the reference microphones and the scanning microphones. Based on those expressions, a compensation procedure of spectral variance due to source-non-stationarity is proposed. It has been verified both numerically and experimentally that this procedure can help suppress spatially distributed noise caused by the source level non-stationarity that is always present in a measurement.

• 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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• 2005.11a
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• pp.213-216
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• 2005

This paper presents force feedback control performance of a 3DOF haptic device that can be used for minimally invasive surgery (MIS). As a first step, a 3DOF electrorheological (ER) joint is designed using a spherical mechanism. And it is optimized based on the mathematical torque modeling. Subsequently, the master haptic device is manufactured by the spherical joint. In order to achieve desired force trajectories, model based compensation strategy is adopted for the ER master. Therefore, Preisach model fur the PMA-based ER fluid is identified using experimental first order descending (FOD) curves. A compensation strategy is then formulated through the model inversion to achieve desired force at the ER master. Tracking control performances for sinusoidal force trajectory are presented, and their tracking errors are evaluated.

• Journal of the Korean Society of Mechanical Technology
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• v.20 no.6
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• pp.790-795
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• 2018

In this study, we analyzed the structural safety and vibration characteristics of rotational drive in 3D CT scan equipment using finite element analysis. The analysis results showed a safety factor of 9.2 and a left and right vertical deflectional deviation of 0.24mm from the maximum equivalent stress. After applying weight compensation of 27.7kgf, the structural analysis reduced the safety factor to 7.6, but the deflectional deviation of the left and right structure was reduced to 0mm. Also, we presented the optimum design of rotational drive through the vibration analysis.

• Smart Structures and Systems
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• v.14 no.3
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• pp.327-345
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• 2014

This paper presents a composite control strategy for the active suppression of vibration due to the unknown disturbances, such as external excitation, harmonic effects and control spillover, as well as high-frequency accelerometer measurement noise in the all-clamped stiffened plate. The proposed composite control action based on the modal approach, consists of two contributions including feedback part and feedforward part. The feedback part is the well-known PID controller, which is widely used to increase the structure damping and improve its dynamic performance close to the resonance frequencies. In order to get better performance for vibration suppression, the weight matrixes is optimized by chaos sequence. Then an improved disturbance observer (IDOB) as the feedforward compensation part is developed to enhance the vibration suppression performance of PID under various disturbances and uncertainties. The proposed IDOB can simultaneously estimate the various disturbances dynamically as well as measurement noise acting on the system and suppress them by feedforward compensation design. A rigorous analysis is also given to show why the IDOB can effectively suppress the unknown disturbances and measurement noise. In order to verify the proposed composite control algorithm (IDOB-PID), the dSPACE real-time simulation platform is used and an experimental platform for the all-clamped stiffened plate active vibration control system is set up. The experimental results demonstrate the effectiveness, practicality and strong anti-disturbances ability of the proposed control strategy.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2010.10a
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• pp.201-207
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• 2010

In this study, the SIP (Soil-cement Injected precast Pile) method among the Low-vibration & Low-noise pile driving methods was decided into study compensation. Ground vibrations by the SIP methods step by step divide and were analyzed. Quantitative response values and ground vibration equations with reliability were presented from findings of this study. Also, vibration responses that are occurred by the SIP method of construction were compared as quantitative with vibration responses by general method of construction that are presented in existent study. Ground vibration values by the SIP method correspond to level of 17 ~ 57% of values that are assumed by the Attewell & Famer's equation, respectively, and these result compares in reliability 50% and separated distance 10 ~ 50 m. Also, those values were analyzed that correspond to level of 14 ~ 96% of ground vibration values by the Prof. Park's equation, respectively. Construction limit extents, separation distances from vibration occurs position, were presented that can satisfy domestic criteria for vibration control for the SIP methods. Those presented in this paper were divided newly according to reliability.