• Title/Summary/Keyword: Electro-mechanical analysis

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On the Energy Conversion Efficiency of Piezoelectric Vibration Energy Harvesting Devices (압전 진동 에너지 수확 장치의 에너지 변환 효율에 대한 고찰)

  • Kim, Jae Eun
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.39 no.5
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    • pp.499-505
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    • 2015
  • To properly design and assess a piezoelectric vibration energy harvester, it is necessary to consider the application of an efficiency measure of energy conversion. The energy conversion efficiency is defined in this work as the ratio of the electrical output power to the mechanical input power for a piezoelectric vibration energy harvester with an impedance-matched load resistor. While previous research works employed the electrical output power for approximate impedance-matched load resistance, this work derives an efficiency measure considering optimally matched resistance. The modified efficiency measure is validated by comparing it with finite element analysis results for piezoelectric vibration energy harvesters with three different values of the electro-mechanical coupling coefficient. New findings on the characteristics of energy conversion and conversion efficiency are also provided for the two different impedance matching methods.

Analysis on Actuation Mechanism of Micro Actuator by Bubble Formation (기포형성에 의한 마이크로 액추에이터의 구동기구 해석)

  • 오시덕;승삼선;곽호영
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.19 no.2
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    • pp.418-426
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    • 1995
  • A bubble-powered microactuator is designed conceptually. And the actuation mechanism due to bubble growth and collapse is studied numerically and analytically. In this analysis, it is estimated that the time lag for bubble formation on micro line heater, the duration of the bubble growth and collapse and the pressure change in actuator due to the bubble evolution. Based on these calculations, the actuator control scheme is visualized. This actuator may be applicable to the system which needs to pump liquid correctly and regularly.

A Review on Cooling Technologies for Micro and Miniature Devices and Systems

  • Yoon, Jae-Sung;Choi, Jong-Won;Kim, Min-Soo
    • International Journal of Air-Conditioning and Refrigeration
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    • v.15 no.2
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    • pp.70-77
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    • 2007
  • As electric and mechanical devices have been miniaturized and highly integrated, heat generation per unit volume has been greatly increased. Therefore, effective cooling methods for micro and miniature systems have emerged as critical issues nowadays and a lot of studies have been carried out to find an optimum cooling strategy. This paper reviews recent researches on the cooling technologies which are mainly based on micro-fabrication processes. Design, development, experiments and numerical analysis of various cooling devices are discussed and their characteristics, problems and advantages are compared.

The Development of Hybrid Vertical Grinding System (차세대 하이브리드 수직형 복합 연삭시스템의 개발)

  • Choi, Seung Geon;Kim, Seong Hyun;Choi, Woong Kirl;Lee, Eun Sang;Choi, Ji Hun;Lee, Seok Joo;Kim, Kyu Dong
    • Journal of the Korean Society for Precision Engineering
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    • v.30 no.11
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    • pp.1139-1145
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    • 2013
  • Machine tools are the cores of industrial development in recent period. It is difficult to develop a system which can do cutting and grinding process in the one system. Hybrid Vertical Grinding System is capable of processing in a single apparatus cutting or grinding. The modal analysis and structural analysis for the development of Hybrid Vertical Grinding System is the first time of domestic work. This paper describes the technologies of Hybrid Vertical grinding machine and intend to introduce the studies in the development of the Hybrid Vertical Grinding System.

Modeling and Dynamic Analysis of Electro-mechanical System in Machine Tools(2$^{nd}$ Report) - Modeling and Dynamic Analysis of Feed Drive System - (공작기계 시스템의 모델링과 동적특성 분석 (제2보) - 이송계의 모델링과 동적특성 분석 -)

  • Park, Yong-Hwan;Shin, Heung-Chul;Moon, Hee-Sung;Choe, Song-Yul
    • Journal of the Korean Society for Precision Engineering
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    • v.16 no.2 s.95
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    • pp.218-224
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    • 1999
  • In the feed drive systems of machine tools that consist of many mechanical components such as motor, coupling, ballscrew, nut or table, a torsional vibration is often generated because of its elastic elements in torque transmission. Generally, the accuracy of motion control system is strongly influenced by the dynamic behavior of coupled transmission components. Especially, a torsional vibration caused by the elasticity of mechanical elements might deteriorate the quick movement of system and lead to shorten the life time of the mechanical transmission elements. So, it is necessary to analyze the electromechanical system mathematically to optimize the dynamic characteristics of the feed system. In this paper, the mathematical model of a feed drive system was developed and its mechanical characteristics were analyzed on the basis of the proposed model. The design concepts of speed control loop to stabilize a feed drive system were also proposed.

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Development and Verification of Analytical Model of a Pilot Operated Flow Control Valve for 21-ton Electric Excavator (21톤급 전기 굴삭기용 파일럿 작동식 유량제어 밸브의 해석모델 개발 및 검증)

  • Kim, D.M.;Nam, Y.Y.;Seo, J.H.;Jang, J.S.
    • Journal of Drive and Control
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    • v.12 no.3
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    • pp.52-59
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    • 2015
  • An electro hydraulic poppet valve (EHPV) and a variable orifice poppet are assembled in a single block, which is referred to as a RHINO but is also generally called a pilot-operated flow control valve. In this study, we analyzed the structure and the operating principle for a RHINO applied in a 21-ton electric excavator system. The RHINO was experimentally tested to measure the dynamic responses and the pressure energy loss. In this test, we investigated the variation in the conductance coefficient according to the increase in the supply pressure under a constant current and a variation in the flow rate according to the increase in the current. Then, the geometrical shapes and the spring stiffness of the RHINO were considered to develop an analysis model. The characteristics (current-force and hysteresis) for the solenoid based on the experimental data were reflected in the analysis model that was developed, and the reliability of the analysis model was also verified by comparing the experimental and analytical results. The developed model is thus considered to be reliable for use in a wide range of applications, including optimum design, sensitivity analysis, parameter tuning, etc.

Spectral Element Analysis for the Electro-Mechanical Admittance of a Piezoelectric Wafer Bonded on a Plate (판구조물에 부착된 압전소자의 전기역학적 어드미턴스 스펙트럼 요소 해석)

  • Kim, Eun-Jin;Shon, Sohn;Park, Hyun-Woo
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 2009.04a
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    • pp.239-242
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    • 2009
  • 구조물의 표면에 부착된 압전소자(이하 PZT)의 전기역학적 어드미턴스(Electro-mechanical admittance)는 PZT와 구조물의 상호작용에 의해 발생하는 PZT의 압전효과와 유전성(dielectric)이 결합되어 발생되는 신호이다. 고주파수 대역에서 PZT의 전기역학적 어드미턴스는 구조물의 국부손상에 민감하게 반응하는 것으로 알려져 있다. 실험에서 측정된 PZT의 전기역학적 어드미턴스 분석에 널리 쓰이는 Liang 모델은 구조물을 단자유도계로 단순화하여 구조물의 동적특성이 전기역학적 어드미턴스에 미치는 영향을 정확하게 나타내기 어렵다. 유한요소법을 통해 PZT와 구조물의 상호작용을 해석하면 이러한 문제점을 해결할 수 있다. 그러나 고주파 대역에서 정확한 해석을 위해서는 유한요소망을 조밀하게 구성해야 하므로 많은 계산비용이 수반된다. 이 연구에서는 유한요소법과 비교하여 월등히 적은 계산비용으로 고주파 대역의 동적 응답을 매우 정확하게 모사할 수 있는 스펙트럼 요소법(Spectral Element Method ; 이하 SEM)을 통해 판구조물에 부착된 PZT의 전기-역학적 어드미턴스를 해석한다. 수치 예제 및 실험 예제를 통하여 내민보에 부착된 PZT에서 발생하는 전기-역학적 어드미턴스를 취득하고 이를 SEM해석 결과와 비교한다.

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A Microcatuator for High-Density Hard Disk Drive Using Skewed Electrode Arrays (경사 전극 배열을 이용한 고밀도 하드 디스크의 마이크로 구동부 제작)

  • Choi, Seok-Moon;Park, Sung-Jun
    • Journal of Institute of Convergence Technology
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    • v.1 no.2
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    • pp.6-15
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    • 2011
  • This paper reports the design and fabrication of a micro-electro-mechanical-system(MEMS)-based electrostatic angular microactuator for a dual-stage servo. The proposed actuator employs a novel electrode pattern named "skewed electrode array(SEA)" scheme. It is shown that SEA has better linearity than a parallel plate type actuator and stronger force than a comb-drive based actuator. The moving and the fixed electrodes are arranged to make the driving force perpendicular to the rotating moment of arm. By changing the electrode overlap length, the magnitude of electrostatic force and stable displacement will be changed. In order to optimize the design, an electrostatic FE analysis was carried out and an empirical force model was established for SEA. A new assembly method which will allow the active electrodes to be located beneath the slider was developed. The active electrodes are connected by inner and outer rings lifted on the base substrate, and the inner and outer rings are connected to platform on which the slider locates. Electrostatic force between active electrodes and platform can be used for exiting out of plane modes, so this provides the possibility of the flying height control. A microactuator that can position the pico-slider over ${\pm}0.5{\mu}m$ using under 20 volts for a 2 kHz fine-tracking servo was designed and fabricated using SoG process.

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Semi-active and Active Vibration Control to Improve Ride Comfort in Railway Vehicle (철도차량 승차감 향상을 위한 반능동/능동 진동제어)

  • You, Wonhee;Shin, Yujeong;Hur, Hyunmoo;Park, Junhyuk
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2013.04a
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    • pp.248-253
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    • 2013
  • The maximum speed is one of the most important performance in high speed railway vehicle. The higher the train speed is, the worse the ride comfort is, In order to solve this problem, a semi-active or active suspension can be applied to high speed railway vehicle. The variable damper with hydraulic solenoid valve is used in the semi-active suspension. But the variable damper with hydraulic solenoid valve requires tank for supplying fluid. The MR(Magneto Rheological) damper can be considered instead of hydraulic variable damper which needs additional device, i.e. reserver tank for fluid. In the case of active suspension, hydraulic actuator or electro-mechanical one is used to suppress the carbody vibration in railway vehicle. In this study the MR damper and electro-mechanical actuator was considered in secondary suspension system of high speed railway vehicle. The dynamic analysis was performed by using 10-DOF dynamic equations of railway vehicle. The performance of the semi-active suspension and active suspension system were reviewed by using MATLAB/Simulink S/W. The vibration suppression effect of semi-active and active suspension system were investigated experimentally by using 1/5-scaled railway vehicle model.

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Wave propagation analysis of smart strain gradient piezo-magneto-elastic nonlocal beams

  • Ebrahimi, Farzad;Barati, Mohammad Reza
    • Structural Engineering and Mechanics
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    • v.66 no.2
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    • pp.237-248
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    • 2018
  • This study presents the investigation of wave dispersion characteristics of a magneto-electro-elastic functionally graded (MEE-FG) nanosize beam utilizing nonlocal strain gradient theory (NSGT). In this theory, a material length scale parameter is propounded to show the influence of strain gradient stress field, and likewise, a nonlocal parameter is nominated to emphasize on the importance of elastic stress field effects. The material properties of heterogeneous nanobeam are supposed to vary smoothly through the thickness direction based on power-law form. Applying Hamilton's principle, the nonlocal governing equations of MEE-FG nanobeam are derived. Furthermore, to derive the wave frequency, phase velocity and escape frequency of MEE-FG nanobeam, an analytical solution is employed. The validation procedure is performed by comparing the results of present model with results exhibited by previous papers. Results are rendered in the framework of an exact parametric study by changing various parameters such as wave number, nonlocal parameter, length scale parameter, gradient index, magnetic potential and electric voltage to show their influence on the wave frequency, phase velocity and escape frequency of MEE-FG nanobeams.