• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.8
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• pp.601-604
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• 2010

In this study, the piezoelectric energy harvester was investigated employing the pillar structure with the diameter size of 50~500 um. Usually, the aspect ratio between the height and diameter was related with the piezoelectric performance. High aspect ratio was showed the low electric noise and high piezoelectric properties than low aspect ratio. Therefore, we have selected the Su-8 photo-resist and modified lithography process to manufacture the pillar structure with height above the 250 ${\mu}m$. In this presentation, we will report the process and properties of micro pillar structure based on the PMN-PZT (Pb$(Mg_{1/3}Nb_{2/3})O_3$-PbZrTiO$_3$) materials.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.21 no.12
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• pp.1120-1131
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• 2011

Researches using time reversal acoustics(TRA) for impact localization have been paid attention to recently. Dispersion characteristics of Lamb waves, which restrict the utility of classical nondestructive evaluation based on time-of-flight information, can be compensated through the application of TRA to Lamb waves on a plate. This study investigates the spatial focusing performance of time reversal Lamb waves on a plate using finite element analysis. In particular, the virtual sensor effect caused by multiple wave reflections at the boundaries of a plate is shown to enable the spatial focusing of Lamb waves though a very small number of surface-bonded piezoelectric(PZT) sensors are available. The time window size of forward response signals, are normalized with respect to the number of virtual active sensors. Then their effects on the spatial focusing performance of Lamb waves are investigated.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.55 no.8
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• pp.417-422
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• 2006

This paper presents the effect of driving waveform for piezoelectric bend mode inkjet printhead with optimized mechanical design. Experimental and theoretical studies on the applied driving waveform versus jetting characteristics were performed. The inkjet head has been designed to maximize the droplet velocity, minimize voltage response of the actuator and optimize the firing frequency to eject ink droplet. The head design was carried out by using mechanical simulation. The printhead has been fabricated with Si(100) and SOI wafers by MEMS process and silicon direct bonding method. To investigate how performance of the piezoelectric ceramic actuator influences on droplet diameter and droplet velocity, the method of stroboscopy was used. Also we observed the movement characteristics of PZT actuator with LDV(Laser Doppler Vibrometer) system, oscilloscope and dynamic signal analyzer. Missing nozzles caused by bubbles in chamber were monitored by their resonance frequency. Using the water based ink of viscosity of 4.8 cps and surface tension of 0.025 N/m, it is possible to eject stable droplets up to 20 kHz, 4.4 m/s and above 8 pl at the different applied driving waveforms.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.22 no.3
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• pp.408-413
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• 2013

Micro-features such as grooves and lenses, which perform optical functions in flat displays, should be manufactured with a good form accuracy because this is directly related to their optical performance. As the size of the display increases, it is very difficult to maintain a high relative accuracy because of the inherent geometric errors such as the waviness of a large-area plate. In this paper, the optical effect of these geometric errors is investigated, and surface-referenced micro-grooving to measure and compensate for such geometric errors on line is proposed to improve the form accuracy of the micro-grooves. A PZT-based fast depth adjustment servo system is implemented in the tool holder to maintain a uniform groove depth in reference to the wavy surface. Through experiments, the proposed method is shown to be an efficient way to produce high-quality micro- grooves on a wavy die surface.

• Journal of the Institute of Convergence Signal Processing
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• v.12 no.3
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• pp.181-187
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• 2011

In this thesis, digital in-line holographic microscopy has been implemented with enhanced phase shifting technique. It was demonstrated that the zero-order diffraction noise and the twin image can be eliminated by phase-shifting interferometry very effectively. Also the experimental and numerical reconstruction has been incorporated into one set-up operating in real time. Experimental results and the analysis of the phase map indicate that the proposed system can be very useful for the measurement of microscopic objects and 3-D microscopy.

• The Journal of the Korea institute of electronic communication sciences
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• v.7 no.5
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• pp.1165-1171
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• 2012

Latest, it is dealt with seriously problems that an intruder kidnapping students in elementary school. Especially young students is more vulnerable in these risks. Elementary School has many limitations in controlling the intrusion of trespassers. A problem occurs that requires a lot of manpower through the deployment and management of security systems such as CCTV and control systems. In this paper, we is designed and implemented the outsider access management system using a sensor network and PZT camera called the USN's core technology to monitoring the access control for controlling the mobility of the trespassers.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.4
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• pp.1229-1232
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• 2010

In this study, in order to develop multilayer piezoelectric transformer for high electromechanical coupling factor and mechanical quality factor. and to show the general approach to the design of inverters utilizing PT as a circuit element. The description of the piezoelectric effect is not present here and can be easily found in numerous publications as well as complex equations and formulae. What is the most important to understand is that "they are different" -one cannot just change an electromagnetic transformer (EMT) for a piezoelectric one. Several examples of PT-based circuitry will help to start and use multilayer piezoelectric transformer advantages most effectively.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.5
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• pp.65-71
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• 1998

This paper presents in-process compensation methodology to eliminate cutter runout and improve machined surface quality. The cutter runout compensation system consists of the micro-positioning mechanism with the PZT (piezo-electric translator) which is embeded in the sliding table to manipulate the radial depth of cut in real time. For the implementation of cutter runout compensation methodology. cutting force adaptive control was proposed in the angle domain based upon PI (proportional-integral) control strategy to eliminate chip-load change in end milling process. Micro-positioning control due to adaptive acuation force response improves the machined surface quality by compensation or elimination of cutter runout induced cutting force variation. This results will provide lots of information to build-up the precision machining technology.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.1
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• pp.22-26
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• 2011

On this paper, a circular unimorph-type piezoelectric transducer was proposed and studied. The transducer was fabricated by attaching a circular-shaped PZT ceramic to a circular plate of brass and output characteristics of the fabricated transducer were then analyzed and measured by changing driving points where the mechanical vibrations were applied. Two conditions depending on the location of vibration were respectively defined as a center forced model and an edge forced model. The resonance frequency and output voltage of the models were simulated by using ANSYS, a FEM(finite element method) program. Based on the results of the analyses, the vibration experiment was conducted and the output characteristics then measured through measurement equipment. As a result, the maximum output characteristics of two models were respectively generated at each resonance frequency and the resonance frequency of the center forced model was lower than the edge forced model.

• Journal of the Korean Society for Precision Engineering
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• v.34 no.1
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• pp.53-58
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• 2017

A fine stage is developed for the 3-DOF error compensation of a linear axis in order to improve the positioning accuracy. This stage is designed as a planar parallel mechanism, and the joints are based on a flexure hinge to achieve ultra-precise positioning. Also, the effect of Abbe's offsets between the measuring and driving coordinate systems is minimized to ensure an exact error compensation. The mode shapes of the designed stage are analyzed to verify the desired 3-DOF motions, and the workspace and displacement of a piezoelectric actuator (PZT) for compensation are analyzed using forward and inverse kinematics. The 3-DOF error of a linear axis is measured and compensated by using the developed fine stage. A marked improvement is observed compared to the results obtained without error compensation. The peak-to-valley (PV) values of the positional and rotational errors are reduced by 92.6% and 91.3%, respectively.