• The Journal of the Korea institute of electronic communication sciences
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• v.13 no.1
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• pp.93-100
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• 2018

This study proposes a controller that compensates torque error for precise angular velocity tracking and a method to compensate the stability of controller in implementation. Also, it is proved that the designed controller can be asymptotically stable based on Lyapunov stability theory. The proposed controller is able to control the d-axis reference current to arbitrary values and easily achieve control performance with two gains. As a result of applying to IPMSM of about 750W class, the steady state error with reference speed 1200 [RPM] is within 0.1 [%]. And it can be seen that it is an asymptomatic stable controller overcoming disturbance within about 0.2 second in application of constant load of about 5 [Nm].

• Journal of the Institute of Convergence Signal Processing
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• v.5 no.1
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• pp.60-65
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• 2004

Induction heating system is time varying system around curie point. So, it has many troubles which are system shut down and change the load impedance. In this paper has been designed the parallel resonant inverter which controlling the constant power and tracking the load resonant frequency with PLL is possible, in order to minimize switching losses and solve it's many troubles. The current full-bridge type parallel resonant inverter of an induction heating system was composed of IGBT in switching device. For regulating the output power of an induction heating system, the Fuzzy logic controller is used. The Fuzzy controller makes the control signal for a stable power regulating control and when reference is changed, it is superior to adaptability. It has been evaluated a stable behavior for a noise with switching and a load disturbance.

• Journal of Power Electronics
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• v.13 no.2
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• pp.197-205
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• 2013

In energy injection resonant AC-AC converters, due to the low frequency effect of the AC input envelope and the low energy injection losses requirement, the constant and steady control of the high frequency AC output envelope is still a problem that has not been solved very well. With the aid of system modeling, this paper analyzes the mechanism of the envelope pit on the resonant AC current. The computing methods for the critical damping point, the falling time and the bottom value of the envelope pit are presented as well. Furthermore, this paper concludes the stability precondition of the system AC output. Accordingly, an optimal control method for the AC output envelope is put forward based on the envelope prediction model. This control method can predict system responses dynamically under different series of control decisions. In addition, this control method can select best series of control decisions to make the AC output envelope stable and constant. Simulation and experimental results for a contactless power transfer system verify the control method.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.16 no.1
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• pp.112-117
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• 2017

The arc, generated by Tungsten Inert Gas(TIG) welding, is stable and provides excellent quality of the weld. Since automation is difficult, a lot of work is performed by hand. In addition, to obtain the uniform weld quality is difficult when using a base metal having a nonuniform welding line, or when welding inside a pipe. Generally, TIG welding power has the characteristic of constant-current. The welding voltage is changed in proportion to the arc length. Hence, the automatic voltage control equipment should be applied at the TIG welding system. The automatic voltage control equipment has been designed using LabVIEW software. It consists of a manufactured voltage divider circuit, and jig for moving the torch. The voltage measurements and driving of the motor were performed through the algorithm implementation in LabVIEW. Welding was conducted while increasing the arc length. In this process, it was confirmed that the automatic voltage control equipment kept the arc length constant.

• Journal of IKEEE
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• v.24 no.4
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• pp.954-960
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• 2020

This paper proposes a speed variable proportional resonant current control method for a single-phase permanent magnet synchronous motor(PMSM). Due to the electromagnetic characteristics of a single-phase PMSM, negative and zero torques are generated in the part corresponding to the phase difference between the stator current and the back electromotive force. In addition, overcurrent limitation is required because of the low stator resistance and inductance in sensorless operation. When using the vector control for current control of single-phase PMSM under these conditions, processes of coordinate transformation, inverse coordinate transformation, and generation of virtual dq-axis components are required. However, the proposed variable speed proportional resonant current control method does not need the coordinate transformation used for AC motors. In this paper, we have confirmed stable maneuverability by using variable proportional resonant current control algorithm, and proposed sensorless control based on a mathematical model of a single-phase PMSM without a position sensor when reaching a constant speed. The usefulness of the current control method was verified through several experiments.

• Journal of the Microelectronics and Packaging Society
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• v.18 no.1
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• pp.29-33
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• 2011

The current density in copper electroplating is directly related with the productivity and then to increase the productivity, the increase in current density is required. To obtain the high mass flow rate, rotating disk electrode(RDE) was employed. High rotational speed in RDE can increase the mass flow rate and then high speed electroplating was possible using RDE to control mass flow. Two types of cathode were used. One is RDE and another is rotating cylindrical electrode(RCE). A constant-current, constant-voltage and linear sweep voltammetry were applied to investigate current and voltage relationship. The maximum current density without evolution of hydrogen gas was increased with rotational speed. Over 400 rpm, maximum current density was higher than 1000 A/$m^2$. The diffusion coefficients of copper calculated from the slope of the plots are $5.5{\times}10^6\;cm^2\;s^{-1}$ at $25^{\circ}C$ and $10.5{\times}10^6\;cm^2\;s^{-1}$ at $62^{\circ}C$. The stable voltage without evolution of hydrogen gas was -0.05 V(vs Ag/AgCl). Additives were added to prevent dendritic growth on cathode deposits. The surface roughness was analyzed with UV-Vis Spectrophotometer. The reflectance of the copper surface over 600 nm was measured and was related with the surface roughness. As the surface roughness improved, the reflectance was also increased.

• Journal of Pharmaceutical Investigation
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• v.40 no.1
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• pp.23-31
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• 2010

In our previous work on levodopa delivery at pH 2.5 using iontophoresis, we found that cathodal delivery showed higher permeation than anodal delivery and electroosmosis plays more dominant role than electrorepulsion. In this work, we studied the transdermal transport of levodopa at very low pH (pH=1.0) where all levodopa molecules are cations, and evaluated some factors which affect the transdermal transport. The transport study at pH 2.5 was also conducted for comparison. The contribution of electrorepulsion and electroosmosis on flux was also evaluated. Using stable aqueous solution, the effect of electrode polarity, current density, current type and drug concentration on transport through skin were studied and the results were compared. We also investigated the iontophoretic flux from hydroxypropyl cellulose (HPC) hydrogel containing levodopa. In vitro flux study was performed at $33^{\circ}C$, using side-by-side diffusion cell. Full thickness hairless mouse skin were used. Current densities applied were 0.2, 0.4 or $0.6\;mA/cm^2$. Contrary to the pH 2.5 result, anodal delivery showed higher flux, indicating that electrorepulsion is the dominant force for the transport, overcoming the electroosmotic flow which is acting against the direction of electrorepulsion. Cumulative amount of levodopa transported was increased as the current density or drug concentration was increased. When amount of current dose was constant, continuous current was more beneficial than pulsed current in promoting levodopa permeation. Similar transport results were obtained when hydrogel was used as the donor phase. These results indicate that iontophoretic delivery of zwitterion such as levodopa is much complicated than that can be expected from small ionic molecules. The results also indicate that, only at very low pH like pH 1.0, electrorepulsion can be the dominant force over the electroosmosis in the levodopa transport.

• Journal of information and communication convergence engineering
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• v.3 no.4
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• pp.179-183
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• 2005

A photodiode capable of obtaining a sufficient photo/ dark current ratio at both forward bias state and reverse bias state is proposed. The photodiode includes a glass substrate, an aluminum film formed as a lower electrode over the glass substrate, an alumina film formed as an insulator barrier over the aluminum film, a hydrogenated amorphous silicon film formed as a photo conduction layer over a portion of the alumina film, and a transparent conduction film formed as an upper electrode over the hydro-generated amorphous silicon film. A good quality alumina $(Al_2O_3)$ film is formed by oxidation of aluminum film using electrolyte solution of succinic acid. Alumina is used as a potential barrier between amorphous silicon and aluminum. It controls dark-current restriction. In case of photodiodes made by changing the formation condition of alumina, we can obtain a stable dark current $(\~10^{-12}A)$ in alumina thickness below $1000{\AA}$. At the reverse bias state of the negative voltage in ITO (Indium Tin Oxide), the photo current has substantially constant value of $5{\times}10^{-9}$ A at light scan of 100 1x. On the other hand, the photo/dark current ratios become higher at smaller thicknesses of the alumina film. Therefore, the alumina film is used as a thin insulator barrier, which is distinct from the conventional concept of forming the insulator barrier layer near the transparent conduction film. Also, the structure with the insulator thin barrier layer formed near the lower electrode, opposed to the ITO film, solves the interface problem of the ITO film because it provides an improved photo current/dark current ratio.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.10
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• pp.1065-1072
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• 2008

A HDD adopts a sensorless brushless DC (BLDC) motor as a spindle motor. Because there is no direct sensor measuring rotor position. open loop commutations with inductive sensing are used to increase the rotor speed up to a certain speed where the zero crossings of the back electromotive force (EMF) voltage are measurable. Therefore, successful open loop commutations are necessary for the stable start-up control of the spindle motors. In this paper, the time scale and the number of the open loop commutations are employed for design parameters to guarantee robustness to torque constant variation and initial rotor position. The design results are verified by experiments on a very low current start-up of the spindle motor with various environment. The experimental results show that the design results can decrease the start-up failure rate considerably.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.4
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• pp.699-704
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• 2003

This paper has been studied about the design of optical transmitter with stable output wavelength in WDM transmission system. The stabilized constant current circuit is designed with deviation less than 10$\mu$A. The temperature control circuit is constructed for the control of internal temperature of laser diode. Also, the wavelength locker is used in optical output. Finally, A/D, D/A converter and micro-processor are used for the control of these.