• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.10a
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• pp.484-487
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• 2015

This paper describes a dual-input battery charger with MPPT control using photovoltaic and piezoelectric energy. Each energy is harvested from photovoltaic cells and piezoelectric cells and is stored to each capacitor. The battery voltage is boosted by charger block and two energy sources are used as input to charge battery capacitor. A DC-DC boost converter is designed to boost the battery voltage, and inductor sharing technique is employed such that only one inductor is required. The time division ratio for piezoelectric cell and photovoltaic cell is set to 8:1. The proposed circuit is designed in a 0.35um CMOS process technology. The condition of battery capacitor is managed by battery management block and the battery voltage can be boosted up to 3V. The maximum efficiency of the designed entire system is 88.56%, and the chip area including pads is $1230um{\times}1330um$.

• Smart Structures and Systems
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• v.26 no.3
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• pp.391-401
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• 2020

The present article reports the feasibility of the electrical energy generation from ambient low-frequency vibration using a piezoelectric material mounted on a bimorph cantilever beam actuator. A corresponding higher-order analytical model is developed using MATLAB in conjunction with finite element method under low-frequency with both damped and undamped conditions. An alternate model is also developed to check the material and dimensional viability of both piezoelectric materials (mainly focussed to PVDF and PZT) and the base material. Also, Genetic Algorithm is implemented to find the optimum dimensions which can produce the higher values of voltage at low-frequency frequencies (≤ 100 Hz). The delamination constraints are employed to avoid inter-laminar stresses and to increase the fracture toughness. The delamination has been done using a Teflon sheet sandwiched in between base plates and the piezo material is stuck to the base plate using adhesives. The analytical model is tested for both homogenous and isotropic material characteristics of the base material and extended to investigate the effect of the different geometrical parameters (base plate dimensions, piezo layer dimensions and placement, delamination thickness and placement, excitation frequency) on the model responses of the bimorph cantilever beam. It has been observed that when the base material characteristics are homogenous, the efficiency of the model remains higher when compared to the condition when it is of isotropic material. The necessary convergence behaviour of the current numerical model has been established and checked for the accuracy by comparing with available published results. Finally, using the results obtained from the model, a prototype is fabricated for the experimental validation via a suitable circuit considering Glass fibre and Aluminium as the bimorph material.

• Steel and Composite Structures
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• v.38 no.3
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• pp.337-353
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• 2021

Micro-electro-mechanical systems (MEMS) are widely employed in sensors, biomedical devices, optic sectors, and micro-accelerometers. New reinforcement materials such as carbon nanotubes as well as graphene platelets provide stiffer structures with controllable mechanical specifications by changing the graphene platelet features. This paper deals with buckling analyses of functionally graded graphene platelets micro plates with two piezoelectric layers subjected to external applied voltage. Governing equations are based on Kirchhoff plate theory assumptions beside the modified couple stress theory to incorporate the micro scale influences. A uniform temperature change and external electric field are regarded along the micro plate thickness. Moreover, an external in-plane mechanical load is uniformly distributed along the micro plate edges. The Hamilton's principle is employed to extract the governing equations. The material properties of each composite layer reinforced with graphene platelets of the considered micro plate are evaluated by the Halpin-Tsai micromechanical model. The governing equations are solved by the Navier's approach for the case of simply-supported boundary condition. The effects of the external applied voltage, the material length scale parameter, the thickness of the piezoelectric layers, the side, the length and the weight fraction of the graphene platelets as well as the graphene platelets distribution pattern on the critical buckling temperature change and on the critical buckling in-plane load are investigated. The outcomes illustrate the reduction of the thermal buckling strength independent of the graphene platelets distribution pattern while meanwhile the mechanical buckling strength is promoted. Furthermore, a negative voltage, -50 Volt, strengthens the micro plate stability against the thermal buckling occurrence about 9% while a positive voltage, 50 Volt, decreases the critical buckling load about 9% independent of the graphene platelet distribution pattern.

• The Transactions of the Korean Institute of Power Electronics
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• v.8 no.1
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• pp.70-79
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• 2003

In this paper, T5 28-watt fluorescent lamp ballast using a piezoelectric transformer is fabricated and its characteristic is investigated. Developed electronic ballast is composed of basic circuits and blocks, such as rectifier part, active power factor corrector part, frequency oscillation part using microcontroller and feedback control, piezoelectric transformer and resonant half bridge inverters. The fabricated ballast uses to variable frequency methode in external so exciting that the frequency of piezoelectric transformer could be generated by voltage control oscillator using microcontroller(AT90S4433). The current of fluorescent lamp is detected by feedback control circuit. The signal of inverter output is received using Piezoelectric transformer, and then its output transmitted to fluorescent lamp. Traditional electromagnetic ballasts operated at 50-60Hz have been suffered from noticeable flicker, high loss, large crest factor and heavy weight. A new electronic ballast is operated at high frequency about 75kHz, and then Input power factor, distortion of total harmonic and lamp current crest factor are measured about 0.9!35, 12H and 1.5, respectively Accordingly, the traditional ballast is by fabricated electronic ballast using piezoelectric transformer and voltage control oscillator because of its lighter weight, high efficiency, economic merit and saving energy.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.10a
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• pp.477-480
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• 2015

In this paper a low-voltage vibration energy harvesting circuit with MPPT(Maximum Power Point Tracking) control is proposed. By employing bulk-driven technique, the minimum operating voltage of the proposed circuit is as low as 0.8V. The designed MPPT control circuit traces the maximum power point by periodically sampling the open circuit voltage of a full-wave rectifier circuit connected to the piezoelectric device output and delivers the maximum available power to load. The proposed circuit is designed using a $0.35{\mu}m\;CMOS$ process, and the chip area including pads is $1.33mm{\times}1.31mm$. Simulation results show that the maximum power efficiency of the designed circuit is 85.49%.

• Journal of the Korean Society for Precision Engineering
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• v.33 no.7
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• pp.601-606
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• 2016

In this paper, an energy harvester is developed that has advantages regarding piezoelectric noise minimization, mass production, and an easily available environmental energy source, electromagnetic induction, as well as low-frequency bandwidth and high amplitude. A process for fabricating a three-dimensional multilayered planar coil using micro-electro-mechanical systems (MEMS) on a flexible printed circuit board FPCB is introduced. Optimal shape and size were calculated via internal resistance and inductance, and a prototype was fabricated through the MEMS procedure while considering the possibility of mass production. Although the internal resistance matched the designed value, the electromotive force generated did not reach the intended amount. The main reason for the decrease in efficiency was the low area of coil outskirt exposed to the magnetic field while there was relative motion between the magnet and the coil.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.29 no.4
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• pp.77-84
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• 2015

PZT ceramics, usually used pyroelectric materials exhibited a relatively highly Curie temperture(Tc) of $250-450^{\circ}C$ and permittivity constant of 500-1600. In this paper, the pyroelectric infrared detectors are applied two different types of pyroelectric materials, that is tetragonal crystal of ferroelectric $PbTiO_3$ and rhombohedral crystal of $Pb(Zr,Ti)O_3$. PZT ceramics shows not only highly Curie temperture but also excellent pyro and piezoelectric properties at the Zr/Ti(=52/48) ratio. Therefor in this paper, the pyroelectric infrared detectors are applied PZT ceramics, and obtained sensitive sensing characteristics by expriment case studies.

• Journal of Mechanical Science and Technology
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• v.20 no.12
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• pp.2087-2093
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• 2006

In this paper, auto focus actuator, which is used to move a lens module in the mobile phone having a camera module, is developed. Camera module containing auto focus actuator requires to minimize total size because of characteristics of the application area such as mobile phone, digital camera, and personal digital assistant. There are stepping motor, voice coil motor, and piezoelectric motor as auto focus actuator. In this paper, voice coil motor having new electromagnetic configuration is proposed. And actuator using proposed voice coil motor is developed by optimal design method using magnetic circuit analysis. The sectional area of the developed actuator is reduced to 32.4% compared with actuator using general electromagnetic configuration. From the performance test, the developed actuator has moving stroke of 0.64 mm for 2.1 volt, hysteresis of 40 $\mu$m, full stroke current of 54 mA, and unit step motion of 3 $\mu$m.

• Proceedings of the KIEE Conference
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• 1994.07a
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• pp.462-464
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• 1994

In this paper, noble electrical equivalent circuit ultrasonic motor is applied by model of parallel one from mechanical equation of piezoelectric device and characteristics estimation is done by equivalent converter. Uitrasonic motor is driven by oscillation circuit of two-phase high frequency inverter. Operating frequency of inverter is described by tracking control method of resonance frequency, according to change of load, temperature etc.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.284-287
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• 2001

This paper presents the robust control simulation of a composite beam using self-sensing actuators(SSA). The self-sensing actuator is a new concept for intelligent material, where a single piezoelectric element simultaneously functions as both a sensor and an actuator. In a practical implementation of the self-sensing actuator an electrical bridge circuit is used to measure strain. The circuit could provide significant information about strain in the element if it were well-balanced. Our aim is design a robust controller which guarantees that the performance of a self-sensing actuator is robust against perturbation of the bridge balance and to confirm the advantages of this technique. Simulation results show that the self-sensing actuator driven by the designed controller exhibits excellent performance in suppressing the vibration of a composite beam.