• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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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).).

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.7
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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.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.9
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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.

• Proceedings of the KIEE Conference
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• 2002.07c
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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.

• Journal of Sensor Science and Technology
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• v.18 no.6
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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.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.11
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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.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.11a
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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.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.9 no.1
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• pp.59-69
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• 2001

The rotor blade is modeled using a composite box beam with arbitrary wall. The active constrained damping layers are bonded to the upper and lower surfaces of the box beam to provide active and passive damping. A finite element model, based on a hybrid displacement theory, is used in the structural analysis. The theory is capable of accurately capturing the transverse shear effects in the composite primary structure, the viscoelastic and the piezoelectric layers within the ACLs. A reduced order model is derived based on the Hankel singular value. A linear quadratic Gaussian (LQG) controller is designed based on the reduced order model and the available measurement output. However, the LQG control system fails to stabilize the perturbed system although it shows good control performance at the nominal operating condition. To improve the robust stability of LQG controller, the loop transfer recovery (LTR) method is applied. Numerical results show that the proposed controller significantly improves rotor aeromechanical stability and suppresses rotor response over large variations in rotating speed by increasing lead-lag modal damping in the coupled rotor-body system.

• Journal of Korean Society of Steel Construction
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• v.22 no.5
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• pp.477-485
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• 2010

Various monitoring sensors are used to predict and detect structural damage. Smart sensors, such as glass-fiber sensors, PZT, and MEMS, among others, have replaced traditional sensors. They are now being used in many areas. This study aims to predict the damage by measuring the PZT voltage attached on the specimen by the applied impact load. In the experiment to detect damages in beam connection, simple $H-400{\times}200{\times}8{\times}13$ beams were spliced with bolts. The results of FFT between PZT sensor and accelrometer were compared to measure the sensitivity of the PZT sensor. The damage to the beam was presumed by loosening the bolt, and then the damage measurement was accompanied. Secondly, a steel $PL600{\times}65{\times}5.8$ plate beam was fabricated for the purpose of experimenting on damage measurement. Impact loading test on three different locations was carried out. Damage width varied between 6~42mm on both sides by cutting, using a steel saw. The ratio of frequencies before and after the damage was computed to quantify the damage level by using FFT, and the change in mode pattern with the increased damage was investigated to measure the damage.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.5
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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.