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Modal Parameter Estimation of Membrane for Standard Microphone Sensitivity Calibration (표준 마이크로폰 감도 교정을 위한 진동막의 모달 파라미터 측정)

  • 권휴상;서상준;서재갑;박준홍
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2002.05a
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    • pp.298-302
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    • 2002
  • Equivalent volume estimation of the coupler and two coupled microphones has a key role in standard microphone pressure calibration. The equivalent volume of the microphone is determined by the dynamic characteristics of the diaphragm system and front cavity. Therefore the modal parameters of diaphragm system - natural frequency and damping fatter - should be measured explicitly for the estimation of the equivalent volume. The diaphragm system is composed of the vibrating diaphragm, back slit behind diaphragm, pressure equalization vent, and front cavity which are acoustically coupled. In the measurement, the electrostatic actuator was used to excite the system with the swept sine, and the frequency response was obtained. The close actuator in front of the diaphragm must influence the radiation impedance of the system, and then the modal parameters. From the measured frequency response, the natural frequency and the damping factor could be estimated with the Complex exponential method based on the Prony model and the zero crossing real and imaginary plot.

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Dynamic Behavior Analysis for HDD Spindle Motors with Rotor Eccentricity (HDD 스핀들 구동용 BLDC 전동기의 편심을 고려한 동적 거동 해석)

  • 김태종;김경태;황상문
    • Journal of KSNVE
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    • v.10 no.6
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    • pp.977-984
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    • 2000
  • Vibration of disk drive spindle is one of the major limiting factors in achieving higher track densities in hard disk drives. Vibration of a BLDC motor is a coupled phenomenon between mechanical characteristics and magnetic origins through the motor air-gap. In this paper, radial magnetic forces for symmetric and asymmetric BLDC motor are calculated with respect to the various rotor eccentricity using analytic method. Based on the results of the radial magnetic forces, transient whirl responses of the spindle motor are analyzed using finite element and transfer matrices. Results show that an asymmetric motor has a worse effects on unbalanced magnetic forces and vibration when mechanical and magnetic coupling exists.

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Probe-based Storage Device(PSD)용 정전형 2축 MEMS 스테이지의 설계 및 제작

  • 백경록;전종업;박규열;박홍식;정주환;홍승범
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2004.05a
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    • pp.156-156
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    • 2004
  • 정보화 및 휴대화 시대에 있어서 폭증하는 정보량을 보다 작은 용기에, 보다 많이 그리고 보다 저렴하게 저장하기 위해서는, 기존 저장기기의 한계를 극복할 수 있는 새로운 개념의 차세대 정보 저장기기가 요구되어 진다. 나노미터 사이즈의 주사탐침이 기록매체표면에 근접하여 정보를 기록/재생하는 PSD는 상기한 저장기기의 대용량화, 소형화, 그리고 저가격화를 충족시킬 수 있는 신개념의 저장기기로, 그 기술적 근간을 SPM(Scanning Probe Microscope)기술과 MEMS(Micro Electro Mechanical Systems) 제작기술에 두고 있다.(중략)

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세라믹 노즐에 유도된 정전기력을 이용한 ZnO seed 미세패턴 연구

  • Byeon, Sang-Eon;Lee, Gyeong-Il;Kim, Seon-Min;Lee, Cheol-Seung;Kim, Seong-Hyeon;Lee, Hyeon-Ju;Lee, Jae-Hyeok;Im, Byeong-Jik;Jo, Jin-U;Seo, Dae-Sik
    • Proceedings of the Korean Vacuum Society Conference
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    • 2011.02a
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    • pp.481-481
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    • 2011
  • 이 논문은 세라믹 노즐(내경: 20 um)을 제작하여 새로운 프린팅 방식인 정전기수력학방식을 이용하여 유리기판위에 직경 30 um의 ZnO seed dot를 패턴하였다. 정전기수력학은 기존의 프린팅 방식과 달리 전기장으로 유도된 노즐을 이용하여 액적을 토출시키는 새로운 프린팅 방법이다. 패턴된 ZnO seed는 열처리후 수열합성법을 이용하여 성장시켰다. 같은 방법으로 잉크젯 프린팅을 이용하여 ZnO seed 패턴 후 열처리하여 수열합성을 이용하여 성장시켰다. 잉크젯 프린팅 방식을 이용하여 성장된 ZnO nanowire는 위성 액적이 떨어져 ZnO seed dot 주변에 ZnO nanowire가 성장하였다. 반면, 정전기수력학 프린팅 방식을 이용하여 성장된 ZnO nanowires는 ZnO seed 패턴 중앙에 집중되어 ZnO nanowire가 성장하였다.

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Fabrication and Characterization of Electrostatically Actuated Microcantilever Mass Sensors (정전기력으로 구동되는 마이크로 캔틸레버 질량 센서의 제작과 특성)

  • Lee, Jung-Chul;Choi, Bum-Kyoo
    • Journal of Sensor Science and Technology
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    • v.20 no.1
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    • pp.40-45
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    • 2011
  • Microcantilevers have been actively used in probe-based microscopy and gravimetric sensing for biological or chemical analytes. To integrate actuation or detection schemes in the structure, typical fabrication processes include several photolithographic steps along with conventional MEMS fabrication. In this paper, a simple and straightforward way to fabricate and operate silicon microcantilever mass sensors is presented. The fabricated microcantilever sensors which can be electrostatically actuated require only two photolithographic steps. Resonant characteristics of fabricated microcantilevers are measured with a custom optical-lever and results show size-dependent quality factors. Using a $40\;{\mu}m$ long, $7\;{\mu}m$ wide, and $3\;{\mu}m$ thick cantilever, we achieved subfemtogram mass resolution in a 1 Hz bandwidth.

A Study on the High Frequency Inductor for the Surface Shape Control of the Liquid Metal (I) (액체금속의 표면형상제어를 위한 고주파 유도코일 시스템에 대한 연구)

  • 오영주;강경하;정순효;심재동
    • Journal of the Korean Magnetics Society
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    • v.6 no.6
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    • pp.375-381
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    • 1996
  • This study is conducted to develop the high frequency inductor with ferro-yoke for the surface shape control. A 3- Dimensional simulation program based on the finite element method is developed for calculating electromagnetic field of the high frequency inductor. The validity of the program and the capability to control the liquid metal shape are confirmed by comparison between the results from calculation and those from measurement.

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A Study on Efficiency Improvement of Surface Preparation Process for Ship's Block - the Effect of Design and Operation Parameters for the Abrasive Recovery System (조선용 블록의 도장 전처리 효율 향상 연구 - 연마재 회수 효율 제어 인자별 특성 평가)

  • Baek Jea jin;Lee Byung Hun
    • Special Issue of the Society of Naval Architects of Korea
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    • 2005.06a
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    • pp.198-205
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    • 2005
  • Reduction of labor hour for cleaning up of the used abrasives after blasting. is attempted by improving the efficiency of abrasive recovery process in the protective coating of ship's block, For this purpose, the theoretical background for pneumatic transport technology in the abrasive recovery system as well as experimental evaluation on the effect of design parameters such as flow pattern, saltation velocity and pressure drop on the efficiency of the abrasive recovery system are employed . By optimizing the operating parameters such as the length and diameter of the suction hose, specification of recovery device and recovery mouth, a new method which can dramatically increase the efficiency of abrasive recovery system, is proposed.

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Investigation on Metal Transfer in GMA Welding through Dimensional Analysis (차원 해석을 통한 GMA 용접의 금속이행 현상에 관한 분석)

  • 최상균;유중돈
    • Journal of Welding and Joining
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    • v.17 no.1
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    • pp.62-70
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    • 1999
  • Since various parameters including the welding conditions and material properties are involved in metal transfer, it is difficult to figure out the effects of each parameter. In this study, dimensional analysis in performed to reduce the number of the parameters and to reveal the effect of each parameter on metal transfer. Dimensionless parameters are derived based on the inertia force and surface tension, and their contributions on metal transfer are estimated by analyzing the calculated results using the volume of fluid (VOF) method. Among several dimensionless parameters, $N_{SE}(=$\mu$_{0}I^{2}/d_{w}${\gamma}$)$ which represents the ratio of the electromagnetic force to surface tension, is found to be appropriate to describe metal transfer and estimate the transition current. Predicted results of transition current and drop size are in reasonably good agreements with available experimental date which show the validity of proposed dimensional analysis.

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환단면 선형유도편자펌프의 유로 내 MHD 동특성 해석

  • 김희령;김용균;이용범;최석기;남호윤
    • Proceedings of the Korean Nuclear Society Conference
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    • 1998.05a
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    • pp.672-677
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    • 1998
  • 액체금속로 순환 냉각재인 전기전도성 나트륨 유체를 전자기적으로 구동시키는 선형유도 전자펌프의 유로내 과기유체역학적(MHD) 특성 분포를 해석적으로 계산하였다. 유로 내 반지름 방향의 좌표에 따라 유속, 점성력 및 전자기 구동력 둥을 계산하여 하트만 수(H$_{a}$ )에 따른 유체 특성의 변화를 그래프로 도시하였다. 하트만 수(H$_{a}$ )가 증가할수록 도전성 나트륨 유체의 유속 분포는 점점 평탄해지고 점성력은 전자기력에 비해 무시할 정도로 작은 값을 가짐을 알 수 있었다. 따라서 적지 않은 자기장에 의해 구동되는 전자펌프에 있어서 금속 유체는 마치 일정 두께의 금속 고체로 취급될 수 있음을 예측할 수 있었다.

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A Study on Active Vibration Isolation Using Electro-Magnetic Actuator (전자기력을 이용한 능동제진에 관한 연구)

  • 손태규;김규용;박영필
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.18 no.5
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    • pp.1169-1181
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    • 1994
  • Vibration isolation of mechanical systems, in general, is achieved through passive or active vibration isolators. Passive vibration isolator has an inherenrt performance limitation. Whereas, active vibration isolator provides significantly superior vibration-isolation performance at the cost of energy sources and sensors. Recently, in many cases, such as suspension system, precision machinery ... etc, active isolation system outweighs its limitation. Therefore, many studies, researches, and applications are carried out in this field. In this study, vibration-isolation characteristics of an active vibration control system using electromagnetic force actuator are investigated. Several control algorithms including optimal, feedforward are used for active vibration isolation. From the experimental results of each algorithm, effective control algorithms for this active vibration-isolation system are proposed.