• 대한기계학회논문집A
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• 제39권5호
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• pp.499-505
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• 2015

압전 진동 에너지 수확 장치의 설계 및 성능 평가 시 에너지 변환 효율을 고려하는 것은 매우 당연하다. 본 연구에서 고려하는 에너지 변환 효율은 부하 저항이 부착된 압전 진동 에너지 수확 장치에 입력되는 가진 진동 파워 대비 전기 출력 값으로 정의된다. 기존의 연구에서는 근사적으로 임피던스 정합된 부하 저항에서의 전기 출력을 고려한 반면, 본 연구에서는 최적의 임피던스 정합 값을 사용하여 새롭게 에너지 변환 효율 식을 유도하였다. 유도된 식의 타당성을 검증하기 위해 3 개의 서로 다른 전기-역학 연성 계수 값을 갖는 진동 에너지 수확 장치에 대한 유한 요소 해석 결과를 이용하였다. 또한, 부하 저항의 임피던스 정합 방법의 차이에 따른 에너지 변환 및 변환 효율 특성을 살펴보았다.

• 대한기계학회논문집
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• 제19권2호
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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.

• International Journal of Air-Conditioning and Refrigeration
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• 제15권2호
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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.

• 한국정밀공학회지
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• 제30권11호
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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.

• 한국정밀공학회지
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• 제16권2호통권95호
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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.

• 드라이브 ㆍ 컨트롤
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• 제12권3호
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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.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2009년도 정기 학술대회
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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.

• 융복합기술연구소 논문집
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• 제1권2호
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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.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2013년도 춘계학술대회 논문집
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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.

• Structural Engineering and Mechanics
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• 제66권2호
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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.