• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 하계학술대회 논문집
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• pp.393-397
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• 2001

A linear ultrasonic motor was designed by a combination of the first longitudinal and fourth bending mode, the motor consisted of a straight aluminum alloys bar bonded with a piezoelectric ceramics element as a driving element. That is, L$_1$-B$_4$ linear ultrasonic motor can be constructed using a multi-mode vibrator of longitudinal and bending modes. The simulation with variation of material characteristics of piezoceramic were performed as use of finite element analysis ANSYS 5.5, such as elastic compliance, piezoelectric constant, electro-mechanical coupling coefficient, poisson's ratio and density. The results of simulation, elastic compliance constant s$_{11}$ and piezoelectric constant d$_{31}$ had the most of influence on the elliptic-motion. This results consist with using transverse effect of material. The used motor were piezoceramics of 4 layers, and the dimensions were 65$\times$5$\times$3.5mm(LxWxt).).

• 한국전기전자재료학회논문지
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• 제15권7호
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• pp.602-608
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• 2002

In this study, microstructural and piezoelectric characteristics of PNW-PMN-PZT ceramics manufactured using attrition milling method were investigated. Sintering temperature of the ceramics was varied from $1080^{\circ}C$ to $1240^{\circ}C$. With increasing sintering temperature, dielectric constant increased. In the specimen sintered at $1120^{\circ}C$, electromechanical coupling factor(Kp) and density showed the maxinum values of 0.546 and 7.78[$g/\textrm{cm}^3$], respectively. In the specimen sintered at $1160^{\circ}C$, mechanical quality factor(Qm) also showed the maxinum value of 1,943. Contour vibration mode piezoelectric transformer with the size of $27.5{\times}27.5{\times}2.5mm$ using PNW-PMN-PZT ceramics was manufactured and its driving characteristics for T5 fluorescent lamp was investigated. Taking into consideration temperature rise of 6.8[$^{\circ}C$] and efficiency of 98.23%, it can be concluded that the transformer is suitable for driving the T5 fluorescent lamp.

• 대한기계학회논문집A
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• 제20권9호
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• pp.2812-2818
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• 1996

A cantilever beam with a mass and a spring at the end can be use to model a miniature flexible arm. It is necessary to know the natural frequencies and mode shapes to discuss its free vibration, especially when modal analysis is employed. A beam is clamped-free. In this paper we look at the lateral vibration of beams that have step changes in the properties of their cross sections. The frequency equation is derived by Bernoulli-Euler formulation and is sloved by the separation of variable. The parameters of the beam, 'mass and spring stiffness' are defined as nondimensionalized parameters for wide application of the results. According to the change of eigenvalues and mode shape are presented for this beam. The results presented are the eigenvalues and the natural frequencies for the first three modes of vibration. Results show that the parameters have a significant effect on the natural frequency.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 C
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• pp.1511-1514
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• 2002

This paper presents design and construct of flat type step-down piezoelectric transformer for the application to AC adaptor. This piezoelectric transformer operated in resonance vibration mode. In this paper, finite element method(FEM) was used for analysing piezoelectric transformers. Stress and electric field of the transformer were simulated at resonance frequency. Using this simulation results, we manufactured improved Rosen type piezoelecric transfomer and measured its output characteristics. As results, output power was linearly increased by increasing input power at resonance frequency and it was found that the transformer an invariable output power for input power. From these results, we expect that this piezoelecric transfomer can be applied to small size and low capacitive AC adaptor.

• 센서학회지
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• 제18권6호
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• pp.461-466
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• 2009

This paper represents a piezoelectric ultrasonic linear actuator with flexural vibration mode. The actuator is composed of two piezo ceramics, the elastic body, and the connecting tip. It is driven by the frictional force between the connecting tip and the linear motion guide. Unimorph actuators have flexural vibration. Its middle point is fixed so that suitable to the flexural vibration of $3/2\lambda$. These vibrations contribute to elliptical motion by mixed mode between longitudinal and transverse mode. It was generated when the ultrasonic electrical signals with 90 degree phase difference are applied to two ceramics. A linear movement can be easily obtained using the elliptical motion. The ATILA, FEM simulator has been used to design actuator and verify the kinetic and dynamic analysis. We used the ceramics of $20\times10\times1$ mm size and confirmed the flexural vibration of the $3/2\lambda$ at the 79 kHz through the scanning of 3D-vibrometer. The maximum velocity of actuator was 221 mm/sec and the thrust force of actuator was 2.7 N in 200Vp-p of additional voltage.

• 한국전기전자재료학회논문지
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• 제20권11호
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• pp.948-952
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• 2007

In this study, a low temperature sintering multilayer piezoelectric transformer for a DC-DC converter was manufactured using $(Pb,Ca,Sr,)(Ti,Mn,Sb)O_3$ ceramics. Its electrical properties were investigated according to the variation in frequency and load resistance. The voltage step-up ratio of the multilayer piezoelectric transformer showed a maximum value at a resonant frequency of input part and increased with an increase of load resistance. The efficiency of the multilayer piezoelectric transformer showed the highest value at a load resistance of 17 $\Omega$. The output power was increased with increasing input voltage. Temperature increase of the multilayer piezoelectric transformer was increased with the increase of output power. At the load resistance of 17 $\Omega$, the multilayer piezoelectric transformer showed the temperature rises of about $20^{\circ}C$ at the output power of 18 W, and stable driving characteristics.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 추계학술대회 논문집 Vol.16
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• pp.340-343
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• 2003

This paper presents characteristics of piezo transformer for AC-DC converter. This transformer uses transverse vibration mode and the origin of the structure was the ring dot type transformer. Because, the ring dot type transformers produce only step-up phenomenon, we made a multi-layered ring dot structure for a step-down output. The characteristics of the transformer were simulated by using the ANSYS. And frequency and voltage were measured by changing the load resistance and current. Frequencies that have the maximum output voltage and current were gradually increased, when the resistance were increased. Output voltage and current show a stable linearity according to the input voltage. The maximum output power was expected greater than 20 [W]. So, we expect that this type of multi-layered step-down ring dot transformer can be adopted for a small AC adapters.

• 한국항공운항학회지
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• 제9권1호
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• pp.59-69
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• 2001

복합재로 된 회전날개깃을 상자보로 모델링하고 수동/능동 감쇠를 주기 위해 ACL(Active Constrained Damping Layer)을 상하양면에 부착하고 복합변위이론에 기초한 유한요소방법을 이용하여 구조해석을 수행하였다. 이 이론은 ACL내의 복합재와 점탄성층 그리고 압전층의 전단변형효과를 정확하게 모델링하는데 효과적이다. Hankel 의 특이값을 이용해 축차모델을 유도하였으며 축차모델과 측정된 출력에 기초한 LQG 제어기를 설계하였다. 그러나 LQG 제어기는 공칭 운전속도에서는 좋은 성능을 보여주었으나 운전속도가 변하는 상황에 대해서는 강인안정성을 보여주지 못했다. 이 LQG제어기의 강인안정성을 개선하기 위하여 루프전달회복을 통한 강인한 제어기를 설계하였다. 수치 예를 통해 제시된 제어기가 회전날개깃의 공기역학적인 안정성을 개선하는데 효과적이며 동체모드와 연계된 리드-래그 모드감쇠를 증가시켜 회전날개깃의 진동을 효과적으로 억제하는 것을 보였다.

• 한국강구조학회 논문집
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• 제22권5호
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• pp.477-485
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• 2010

다양한 모니터링 센서는 구조물의 손상측정과 예측에 많이 사용되고 있다. 광섬유센서, 압전소자(PZT) 센서, MEMS(Micro Electro Mechanical System)센서 등의 스마트 센서는 기존 센서를 대체하여 많은 분야에서 사용되고 있다. 본 논문에서는 PZT센서를 실험체에 부착한 후 충격하중을 가하여 PZT센서의 출력 전압의 특성을 이용하여 실험체의 손상을 예측하고자 하였다. PZT센서를 이용한 보 이음부의 손상실험에서는 $H-400{\times}200{\times}8{\times}13$ 철골을 이용하여 단순보를 제작하고 중앙에 볼트 이음을 하였으며, PZT센서의 민감도 측정을 위해 기존 가속도계의 가속도값과 PZT센서의 전압값의 FFT 결과를 비교하였다. 또한 이음부의 볼트풀림을 이용하여 단순보의 손상을 가정하고 손상계측실험도 병행하였다. 철골 플레이트 보의 손상계측 실험에서는 $PL600{\times}65{\times}5.8$로 단순보 실험체를 제작하여 세 곳에 손상을 주어 충격하중 실험을 하였다. 손상의 정도는 쇠톱을 이용하여 보 단면의 양쪽에 6~42 mm로 절단하였다. FFT를 사용하여 손상의 유무에 따른 고유진동수의 비(${\omega}_c/{\omega}$)를 구하여 손상을 파악하였고 모드에 따른 손상의 위치와 정도를 파악하였다.

• 한국전기전자재료학회논문지
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• 제30권5호
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• pp.263-269
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• 2017

A piezoelectric cantilever energy harvester (PCEH) driven in longitudinal (3-3) vibration mode was fabricated, and its electrical properties were evaluated by varying the resistive load. A commercial PZT piezoelectric ceramic with a high piezoelectric charge constant ($d_{33}$) of 520 pC/N and the interdigitated (IDT) electrode pattern was used to fabricate the PCEH driven in longitudinal vibration. The IDT Ag electrode embedded piezoelectric laminates were co-fired at $850^{\circ}C$ for 2 h. The 3-3 mode PCEH was successfully fabricated by attaching the piezoelectric laminates to a SUS304 elastic substrate. The PCEH exhibited a high output power of 3.8 mW across the resistive load of $100k{\Omega}$ at 100 Hz and 1.5 G. This corresponds to a power density of $10.3mW/cm^3$ and a normalized global power factor of $4.56mW/g^2{\cdot}cm^3$. Given the other PCEH driven in transverse (3-1) vibration mode, the 3-3 mode PCEH could be better for vibration energy harvesting applications.