• Journal of the Korean Institute of Intelligent Systems
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• v.24 no.2
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• pp.193-200
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• 2014

Piezoelectric actuators have been widely used in various applications because they have many advantages such as fast response time, repeatable nanometer motion, and high resolution. However Piezoelectric actuators have the strong hysteresis effect. The hysteresis effect can degrade the performance of the system using piezoelectric actuators. In past study, the parameters of the inverse hysteresis model are computed from the identified parameters using the Generalized Prandtl-Ishlinskii(GPI) model to cancel the hysteresis effect, however according to the identified parameters there exist the cases that can't form the inverse hysteresis loop. Thus in this paper the inverse hysteresis modeling mothod is proposed using the Inverse Generalized Prandtl-Ishlinskii(IGPI) model to handle that problem. The modeling results are verified by experimental results using various input signals.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.283.1-283.1
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• 2014

최근 주위 환경에 존재하는 다양한 에너지를 전기에너지로 회수 또는 수확하는 에너지 하베스팅 기술(energy harvesting technology)이 크게 주목을 받고 있으며, 이와 더불어 압전 나노발전소자(piezoelectric nanogenerator)의 연구가 활발해 진행되고 있다. 한편, 수열합성법 또는 전기화학증착법을 이용하여 비교적 간단하게 수직으로 성장된 산화아연 나노로드(ZnO nanorod)는 광대역 에너지 밴드갭(wide bandgap energy)과 압전(piezoelectric)특성을 갖게 된다. 이렇게 수직 정렬된 나노로드의 기하학적 구조는 외부 물리적인 힘에 의해 구부러짐(bending) 변형이 일어나 압전특성이 효과적으로 일어나며, 이런 현상을 이용하여 압전 나노발전소자에 응용할 수 있다. 본 연구에서는 상부의 전극의 표면 거칠기(surface roughness)를 증가시켜 외부 힘에 의해 산화아연 나노로드가 효과적으로 변형을 일으켜 압전 특성을 향상시켰다. 실험을 위해, 산화아연 마이크로로드 어레이 (microrod arrays)와 실리카 마이크로스피어(silica microsphere)를 각각 템플릿으로 이용하여 그 위에 금(Au)를 증착하여 상부전극을 제작하였다. 산화아연 나노로드와 마이크로로드는 전기화학증착법을 이용해서 저온공정($75^{\circ}C$)으로 ITO가 코팅된 PET 기판위에 성장하였으며, 인가된 전압의 세기를 변화시켜 산하아연 구조물의 크기를 조절하였다. 또한 화합합성법으로 실리카 마이크로 스피어를 준비하였다. 이러게 제작된 상부전극을 통해 기존의 사용되었던 전극과 비교하여 성능이 향상됨을 확인하였으며, 이와 함께 이론적인 분석을 진행하였다.

• The Journal of the Acoustical Society of Korea
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• v.21 no.2
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• pp.150-159
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• 2002

The possibility of a broadband noise reduction of piezoelectric smart panels is experimentally studied. Piezoelectric smart panel is basically a plate structure on which piezoelectric patch with shunt circuits is mounted and sound absorbing material is bonded on the surface of the structure. Sound absorbing materials can absorb the sound transmitted at mid frequency region effectively while the use of piezoelectric shunt damping can reduce the transmission at resonance frequencies of the panel structure. To be able to tune the piezoelectric shunt circuit, the measured electrical impedance model is adopted. Resonant shunt circuit composed of register and inductor in stories is considered and the circuit parameters are determined based on maximizing the dissipated energy through the circuit. The transmitted noise reduction performance of smart panels is investigated using an acoustic tunnel. The tunnel is a square crosses sectional tunnel and a loud speaker is mounted at one side of the tunnel as a sound source. Panels are mounted in the middle of the tunnel and the transmitted sound pressure across the panels is measured. Noise reduction performance of a double smart panel possessing absorbing material and air gap shows a good result at mid frequency region except the first resonance frequency. By enabling the piezoelectric shunt damping, noise reduction is achieved at the resonance frequency as well. Piezoelectric smart panels incorporating passive method and piezoelectric shunt damping are a promising technology for noise reduction in a broadband frequency.

• The Journal of the Acoustical Society of Korea
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• v.13 no.2
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• pp.60-67
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• 1994

This is the first of two companion papers which suggests the algorithm of the combined Finite Element Method and Infinite Element Method for the analysis of the axi-symmetric acoustic transducer in the open boundary. Using the algorithm, the numerical analysis for the transducer radiation impedance, directivity, and coupling effect between transducer elements are also conducted. In the second paper, the wideband array transducer is designed and its acoustic characteristics are examined on the basis of the results of the first paper.

• Journal of Advanced Marine Engineering and Technology
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• v.30 no.3
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• pp.351-358
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• 2006

The capability of high pressure injection with small fuel quantify at all engine operating conditions is one of the main feature in common rail fuel injection system, which is used in small and light-duty Diesel engine. The key parameter for the better atomized fuel sprays and multiple injections of this common rail fuel injection control, that can be freely selected irrespective of the engine speed and load is the mechanism controlling the needle energizing and movement in high pressure Diesel injector. In the electro-hydraulic injector, the injection nozzle is being opened and closed by movement of the injector's needle which is balanced by pressure between the nozzle seat and the needle control chamber. This study describes the macroscopic spray structure characteristics of the common rail Diesel injectors with different electric driving method i.e. the solenoid-driven and piezo-driven type. The macroscopic spray characteristics such as spray tip speed. spray tip penetration and spray cone angle were investigated by the high speed spray, which is measured by the back diffusion light illumination method with optical system for the high speed temporal photography in a constant volume chamber pressurized by nitrogen gas. As the results, the prototype piezo-driven injector system was designed and fabricated for the first time in domestic case and the effect of injector's needle response driven by different drive type was compared between the solenoid and piezo-driven injector It was found therefore. that the piezo-driven injector showed faster needle response and had better needle control capability by altering the electric input value than the solenoid-driven injector.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.2076-2081
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• 2004

Future exhaust gas limits for diesel-driven passenger cars will force the automotive industry to significantly improve the performance of engine. Since modern common-rail injection systems deliver more degrees of freedom referring to the injection process, again the optimization of the injection process could offer a possibility to meet the exhaust gas limits. This study describes the characteristic the pilot spray structure of piezo-driven injector for a passenger car common-rail system to be applicable multiple injection caused by fast response rather than solenoid-driven injector. The piezo-driven injector is prototype injector with same needle chamber of solenoid injector and the solenoid-driven one is commercial injector. The pilot spray characteristic such as spray tip penetration, spray speed, spray angle were obtained by spray images, which is measured by the Mie scattering method with optical system for high-speed temporal photography. It was found that piezo-driven injector effected electric change as important factor and showed faster response than solenoid-driven injector.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.3
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• pp.513-519
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• 2019

Typically, contaminated sediments cause clogging of the drain pipe, which increases the residual water pressure in the drain pipe; this study constructed a system for improving drainage efficiency of tunnels by reducing physical and chemical obstructions through ultrasonic energy generated by a PVDF film. The developed hybrid drainage system utilized a PVDF material film fused with an existing drainage tunnel and maintenance system resulting in the ability to initialize the reverse piezoelectric effect, which was evaluated through an on site application. In order to investigate the maintenance performance of the tunnel drainage system, contaminated sediments were simulated in a drainage pipe to test the effect of ultrasonic conditions on drainage efficiency in the laboratory. As a result of applying the developed portable equipment, the ultrasonic energy was generated for about 20 minutes resulting in a reduction of 74.62% of the contaminated sediments and improving drainage efficiency. From the tunnel, acoustic pressure measurements were taken to calculate the response rate while taking into account the laboratory results. In addition, PVDF film was attached to the transverse and longitudinal side of the drainage pipes where contaminated sediments occur most often in the field tunnel. these calculations show contaminant removal was 90% effective.