• Journal of Power Electronics
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• v.15 no.1
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• pp.268-277
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• 2015

In this paper, a dual-converter three-phase pulse width modulation (PWM) rectifier based on unbalanced one-cycle control (OCC) strategy is proposed. The proposed rectifier is used to eliminate the second harmonic waves of DC voltage and distortion of line currents under unbalanced input grid voltage conditions. The dual-converter PWM rectifier employs two converters, which are called positive-sequence converter and negative-sequence converter. The unbalanced OCC system compensates feedback currents of positive-sequence converter via grid negative-sequence voltages, as well as compensates feedback currents of negative-sequence converter via grid positive-sequence voltages. The AC currents of positive- and negative-sequence converter are controlled to be symmetrical. Thus, the workload of every switching device of converter is balanced. Only one conventional PI controller is adopted to achieve invariant power control. Then, the parameter tuning is simplified, and the extraction for positive- and negative-sequence currents is not needed anymore. The effectiveness and the viability of the control strategy are demonstrated through detailed experimental verification.

• Journal of Power Electronics
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• v.15 no.2
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• pp.399-410
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• 2015

A 6.5 V/50 kA high-frequency switching power supply (HSPS) system composed of 10 power modules is developed to meet the requirements of copper-foil electrolysis. The power module is composed of a two-leg pulse width modulation (PWM) rectifier and a DC/DC converter. The DC/DC converter adopts two full-wave rectifiers in parallel to enhance the output. For the two-leg PWM rectifier, the ripple of the DC-link voltage is derived. A composite control method with a ripple filter is then proposed to effectively improve the performance of the rectifier. To meet the process demand of copper-foil electrolysis, the virtual impedance-based current-sharing control method with load current full feedforward is proposed for n-parallel DC/DC converters. The roles of load current feedforward and virtual impedance are analyzed, and the current-sharing control model of the HSPS system is derived. Virtual impedance is used to adjust the current-sharing impedance without changing the equivalent output impedance, which can effectively reduce current-sharing errors. Finally, simulation and experimental results verify the structure and control method.

• Transactions of The Korea Fluid Power Systems Society
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• v.3 no.4
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• pp.21-28
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• 2006

The proportional control solenoid valves as well as the PWM solenoid valves operated by electric signal play an important role in the hydraulic system for automatic transmissions to improve the shift quality. However it is not generally available for the performance data because most of the automotive parts manufacturer don't release the specific test results, especially dynamic performance that is essential to design a shift control algorithm. In this research, a performance test equipment that can be applied to various types of pressure control solenoid valve was developed. It was implemented by 8-bit micro-controller with many useful functions such as adjustable PWM carrier frequency, embedded function generator, current controller, data monitoring and acquisitions, etc. for the test of dynamic performance of solenoid valve as well as the steady-state pressure characteristics. The performance test results for the direct type proportional control solenoid valve show not only the validity of overall functions but also its usefulness as a hydraulic valve tester.

• 제어로봇시스템학회:학술대회논문집
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• 1997.10a
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• pp.52-55
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• 1997

This paper discusses an automatic visual-servoing system, in which a laser and a CCD camera are used for imaging the pattern of joint groove. The algorithm used here is simple and robust to find out the gap width and gap center. As a consequence, the speed of algorithm is very fast and optimized. A feature of this system is that it processes only by summing the vertical line and horizontal line of screen without any image preprocessing in order to get the energy information of lines alternatively. It is practical and useful for the system requiring a fast process time of vision.

• 제어로봇시스템학회:학술대회논문집
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• 1997.10a
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• pp.1880-1883
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• 1997

An Parallax-Barrier type autostereoscopic display system is implemented to overcome the handicap of current glass-typed stereo imaging system which gives operators unnatural feeling and reluctance. This system is composed of image mixing part of two input images, A/D transformation part, scan conversion part to eliminate the rainbow interference phenomenon, and pin-hole type barrier lens. For the fine display the accurate slit width of barrier is calculated in consideration of retina size, and the samsung 10.4" TFT-LCO was used as flat display monitor.itor.

• 한국정보디스플레이학회:학술대회논문집
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• 2004.08a
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• pp.412-414
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• 2004

We have developed nucleation control methods applicable to a zone-melting recrystallization excimer laser annealing process for poly-Si films. Ribbon-shaped Si grains of 2 ${\mu}m$-width were successfully aligned side by side by means of a comb-shaped beam, and we have successfully fabricated TFTs with channels formed in those grains. Electron mobility in the TFTs is as high as 677-$cm^2$/Vs.

• Proceedings of the KIPE Conference
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• 1997.07a
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• pp.101-110
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• 1997

The circuit effects due to the transformer primary side series equivalent inductance in the Zero Voltage Switching Pulse Width Modulated Half Bridge DC/DC Converter and its impact on the effective duty are analyzed. The steady state equations and the small signal model of the converter are derived incorporating the effects of the complementary control and the utilization of transformer primary side series equivalent inductance. The open plant dynamics are analyzed on the basis of the model derived. The model predictions are confirmed by experimental measurements.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1996.04a
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• pp.95-99
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• 1996

In this paper, we proposed a method to measure the gap between the magnetic pole and the levitated object applying the inductance characteristic which vary according to gap. We made a driving circuit which supply the control input PWM(Pulse Width Modulation) signal and the carrier PWM signal to estimate the gap. Because the inductance is a function of gap, and the current of the carrier signal is a function of the inductance. We investigated the validity of the proposed method through the experimental results.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.363-368
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• 2001

Abutments in Kumdang bridge are massive concrete structures of which total height is l0m, length is 30m, and width is 7m. Therefore, there is every probability that early age thermal cracking such as hydration heat occur. We measure heat of hydration, strains of rebar, and stresses of concrete abutment during construction. Using analysis of measuring data, we examine thermal stresses, and make use of results as method which control thermal cracking. Finally, we develope thermal stress analysis program which have pre/post processor to be easy of accessing and the usefulness of that is estimated through comparison of results.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.05a
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• pp.23-28
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• 2002

This paper reports the performance results of hydration heat control of mass concrete walls with pipe cooling system. The thickness of walls ranged from 0.9 to 2.2m. In order to investigate the effect of pipe cooling on the thermal and thermal crack characteristics, the pipe cooling was conducted for 42 walls, and the investigation of thermal cracks was conducted for 14 walls. Based on the investigation, the pipe cooling method decreased the peak temperature of about 13-2$0^{\circ}C$ and the thermal crack width of about 30% for mass concrete walls.