• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.4
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• pp.397-404
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• 2010

The use of equivalent circuit models of piezoelectric energy harvesters is inevitable when power circuitry including rectifying and smoothing circuit elements is connected to them for evaluating DC electrical outputs. This is because it is difficult to incorporate the electro-mechanical coupling resulting from the additional circuitry into the conventional finite element analysis. Motivated by this observation, we propose a method to accurately extract the equivalent circuit parameters by using commercially available FEM software such as ANSYS which provides three-dimensional AC piezoelectric analysis. Then the equivalent circuit can be analyzed by circuit simulators such as $SimPowerSystems^{TM}$ of MATLAB. While the previous works have estimated the circuit parameters by experimental measurements or by analytical solutions developed only for limited geometries and boundary conditions, the proposed method has no such limitation because piezoelectric energy harvesters of any shapes and boundary conditions can be treated in FEM software. For the verification of the proposed method, multi-modal AC electrical power output by using a corresponding equivalent circuit is compared with that by ANSYS. The proposed method is then shown to be very useful in the subsequent evaluation of DC electrical output which is obtained by attaching a bridge diode and a storage capacitor to a piezoelectric energy harvester.

• Korean Journal of Optics and Photonics
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• v.17 no.2
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• pp.159-164
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• 2006

We demonstrate a compact optical coherence tomography(OCT) system based on the optical fiber delay line controlled by a cylindrical piezo-electric transducer(PZT). An 18-m length of single mode fiber is wrapped under constant tension around a PZT. Approximately 134 windings are used. Wraps of the long length of fiber allow the small expansion of the PZT to be magnified to an optical path length delay of 0.78 m. The OCT system shows characteristics for 2-dimensional imaging, exhibiting 96.9dB of signal-to-noise ratio(SNR), $18.6{\pm}0.5\;{\mu}m$ of axial resolution, and $5\;{\mu}m$ of lateral resolution with samples.

• 전기의세계
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• v.25 no.4
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• pp.17-23
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• 1976

세계제2차대전이후, 급속도로 발전해온 전기 및 전자공학으로 말미암아 현재의 시대를 electronic시대라고 불러도 과언이 아니다. 이러한 전자공학의 발전으로 수많은 전자장치소자가 새로이 개발되었다. 그중에서 전기 및 전자회로에서 없어서는 안될 싸이리스터라는 반도체소자가 있다. 싸이리스터의 특성을 응용하여 정지스위치로서 과전압보호회로, 지연회로, 온도조절기, 전자충전용, 조정기, 변압기탭전환, 용접기의 제어회로등에 이용되며 위상제어용으로 조광회로, 전기로의 온도제어, 전동기의 속도제어, 직류전동기의 주전류제어회로에 이용되고 전류기로서 정전압전원, 정정류전원으로 이용하며 쵸퍼, 인버어터로서 직류를 단속시키며 다시 교류로 변환하여 전압을 변화시킬 수 있다. 이밖에 정류자나 부러쉬가 없는 모터를 제조할 수 있다.

• Proceedings of the Optical Society of Korea Conference
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• 1988.06a
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• pp.112-116
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• 1988

Homodyne 방식으로 동작하는 광섬유 간섭계 센서는 주위 온도의 변화나 진동등에 의하여 시노의 크기가 불규칙하게 변화된다. 따라서 광섬유 간섭계가 직작조건에서 동작하도록 하여 감도를 최대로 유지시켜야 한다. 본연구에서는 원통형 압전자소자에 단일모드 광섬유룰 감아서 변환율 K=1.07$\pi$/V의 위상변조기를 만들고, 이를 이용하여 능동위상추적(active phase tracking)방식의 신호안정화 장치를 제작하고 광섬유 간섭계 센서의 공기중 읍압반응을 조사하였다.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.6 s.183
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• pp.64-71
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• 2006

A target of this paper is to study on the usefulness of the adaptive piezoelectric energy harvesting device as a wireless electrical power supply when it is driven by mechanical vibrations of low frequency. For this purpose, an adaptive control technique and a step-down converter are used. A THUNDER series a piezoelectric material (TH7-R), which has been developed by a NASA engineer is selected for this study. In order to provide a mechanical energy to the piezoelectric material, a mechanical motion vibrator is designed. The adaptive controller is implemented using a dSPACE DS1104 controller board. The do-dc converter with an adaptive control technique harvests energy at over five times the rate of direct charging without a converter.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.228-233
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• 2002

General modeling of a resonant shunting damper has been made from piezoelectric sensor/actuator equation. It is found that an additional damping, which is augmented to a system, is generated by the shunt damping effect. The transfer function of the tuned electrical absorber is derived for both series and parallel shunt circuit. The governing equations and associated boundary conditions are derived using Hamilton's Principle. The shunt voltage equation is also derived from the charge generated in PZT due to beam vibration. The frequency response function of the obtained mathematical model is compared with that of the tuned electrical absorber and experimental work. The vibration amplitude is reduced about 15 dB at targeted second mode frequency.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.04a
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• pp.374-378
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• 2014

The piezoelectric materials convert from mechanical energy to electrical energy. The piezoelectric materials are used in various engineering applications such as piezoelectric ultrasonic actuators. Since the piezoelectric coupling characteristics of the actuator systems should be considered at the initial design stage, it is essential to analyze the piezoelectric coupling characteristics of the ultrasonic actuators. In this study, we analyzed the electromechanical characteristics of piezoelectric stacked actuator using the equivalent circuit model with modal mass stiffness parameters. It was compared the admittance of piezoelectric stack actuators with the analytical circuit model and the finite element model. Also, the coupling coefficient of piezoelectric stack actuator was discussed according to the number of stacks of actuators.

• Electrical & Electronic Materials
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• v.9 no.8
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• pp.825-830
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• 1996

In this study, Characteristics of Ultrasonic Transducer fabricated with porous piezoelectric resonator, 3-D underwater object restoration using the self made ultrasonic transducer and modified SCL(Simple Competitive Learning) neural network are investigated. The self-made transducer was satisfied the required condition of ultrasonic transducer in water, and the modified SCL neural network using the acquired object data 16*16 low resolution image was used for object restoration of $32{\times}32$ high resolution image. The experimental results have shown that the ultrasonic transducer fabricated with porous piezoelectric resonator could be applied for SONAR system.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.108-108
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• 2010

휴대용 전자장비에 대한 수요증가와 합께 전자제품의 소형화, 박형화에 대한 요구가 점점 증대되고 있는데 전원 공급부가 대부분의 휴대용 전자장비에 있어서 가장 큰 부피를 차지하고 있다. 이러한 문제점올 해결하기 위한 방법으로 기존 마그네틱 권선 변압기를 압전 변압기로 대체하는 것을 고려할 수 있다. 그러나 ZVS 조건을 만족하기 위해서 입력 매칭 회로를 추가적으로 병렬 혹은 직렬로 인덕터를 추가적으로 사용해야 된다. 따라서 본 논문에서는 입력 매칭 회로의 인덕터 사이즈 팩터의 최적화에 대한 모델링을 분석 하고, 최적의 매칭 회로의 설계를 위한 가이드라인을 제시하였다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11a
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• pp.328.2-328
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• 2002

General modeling of a resonant shunting damper has been made Iron piezoelectric sensor/actuator equation. It is found that an additional damping, which is augmented to a system, is generated by the shunt damping effect The transfer function of the tuned electrical absorber is derived for both series and parallel shunt circuit. The governing equations and associated boundary conditions are derived using Hamilton's Principle. The shunt voltage equation is also derived from the charge generated in PZT due to beam vibration. The frequency response function of the obtained mathematical model is compared with that of the tuned eledtrical absorber and experimental work. The vibration amplitude is reduced about 15 dB at targeted second mode frequency.