• Proceedings of the KIEE Conference
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• 2001.10a
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• pp.161-164
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• 2001

This paper presents a digital speed sensorless control system for Reluctance Synchronous Motor (RSM) drives with direct torque control (DTC). The system consist of stator flux observer, rotor speed estimator, torque estimator two hysteresis band controllers, an optimal switching look-up table. IGBT voltage source inverter, and TMS320C31DSP controller by using fully integrated control software. The stator flux observer is based on the combined voltage and current model with stator flux feedback adaptive control that inputs are current and voltage sensing of motor terminal with estimated rotor angle for wide speed range. The rotor speed is estimated by the observed stator flux-linkage space vector. The estimated rotor speed can be determinated by differentiation of the rotor position used only in the current model part of the flux observer for a low speed operating area. In order to prove the suggested speed sensorless control algorithm. There are some simulation and testing at actual experimental system. The developed digitally high- performance speed sensorless control system are shown a good speed control response characteristic results and high Performance features using 1.0Kw RSM.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07a
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• pp.280-283
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• 2004

This paper discribes the design concept, fabrication process and measuring result of 2.5kV Gate Commutated Thyristor devices. Integrated gate commutated thyristors(IGCTs) is the new power semiconductor device used for high power inverter, converter, static var compensator(SVC) etc. Most of the ordinary GTOs(gate turn-off thyristors) are designed as non-punch-through(NPT) concept; i.e. the electric field is reduced to zero within the N-base region. In this paper, we propose transparent anode structure for fast turn-off characteristics. And also, to reach high breakdown voltage, we used 2-stage bevel structure. Bevel angle is very important for high power devices, such as thyristor structure devices. For cathode topology, we designed 430 cathode fingers. Each finger has designed $200{\mu}m$ width and $2600{\mu}m$ length. The breakdown voltage between cathode and anode contact of this fabricated GCT device is 2,715V.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.74-75
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• 2005

Organic Light Emitting Diodes are attractive as alternative display components because of their relative merits of being self-emitting, having large intrinsic viewing angle and fast switching speed. But because of their relatively short history of development, much remains to be studied in terms of their basic device physics and design, manufacturing techniques, stability and so on. We invested electrical properties of N, N-diphenyl-N, N bis (3-methyphenyl)-1, 1'-biphenyl-4, 4'-diamine and tris-8-hydroxyquinoline aluminum when their thickness were changed variedly from 3:7 to 7:3 of their thickness ratios. And we also studied their optimal thickness respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.461-462
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• 2006

A single-gap and single-gamma transflective liquid-crystal (LC) display using patterned vertical alignment (PVA) mode was designed. In the device, a vertical electric field drives a vertically aligned LC to tilt down to optimize polarization efficiency. Electrodes of transmissive and reflective area were patterned $22.5^{\circ}$ and $45^{\circ}$ with respect to the polarizer so that a tilt-down direction of the LC director was $22.5^{\circ}$ and $45^{\circ}$ in the reflective and transmissive regions, respectively. In the device, the cell gap was the same for both regions, and the gamma curve matched each other in both regions because tilt angle of LC director was the same according to the applied voltage. Moreover, the dark state was irrespective of the cell retardation value at normal direction, which was highly important in massive fabrications. The switching principle and electro-optic characteristics of the device are reported herein.

• Current Optics and Photonics
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• v.6 no.3
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• pp.252-259
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• 2022

In this paper, a dual-function dynamically tunable metamaterial absorber is proposed. At frequency points of 1.545 THz and 3.21 THz, two resonance peaks with absorption amplitude of 93.8% (peak I) and 99.4% (peak II) can be achieved. By regulating the conductivity of photosensitive silicon with a pump laser, the resonance frequency of peak I switches to 1.525 THz, and that of peak II switches to 2.79 THz. By adjusting the incident polarization angle by rotating the device, absorption amplitude tuning is obtained. By introducing two degrees of regulation freedom, the absorption amplitude modulation and resonant frequency switching are simultaneously realized. More importantly, dynamic and continuous adjustment of the absorption amplitude is obtained at a fixed resonant frequency, and the modulation depth reaches 100% for both peaks. In addition, the sensing property of the proposed MMA was studied while it was used as a refractive index sensor. Compared with other results reported, our device not only has a dual-function tunable characteristic and the highest modulation depth, but also simultaneously possesses fine sensing performance.

• Journal of the Korean Society for Precision Engineering
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• v.14 no.5
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• pp.118-127
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• 1997

In this study, We use microstep control to reduce vibration of step motor. Microstep control of step motor is usually thought of as an extension of conventional step motor control technology. The essence of micro stepping is that we divide the full step of a step motor into a number of substep called microstep and cause the stepmotor to move through a substep per input pulse. In ideal case, by controlling the individual phase currents of a two-phase step motor sinusoidally we can get uniform torque and step angle. But due to the nonlinear characteristics of the step motor, we need to compensate current waveform to improve the over-all smoothness of the conventional micro stepping system. We implement digital Pulse Width Modul- ation (PWM) driver to drive step motor and microphone was used for detecting vibration. Driver enables speed change automatically by increasing or decreasing micro stepping ratio which we call Automatic Switching on the Fly. To compensate the torque harmonics, neural network is applied to the system and we found compensated optimal input current waveform. Finally we can get smooth motion of step motor in a wide range of motor speed.

• Journal of Power Electronics
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• v.15 no.3
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• pp.621-633
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• 2015

This paper proposes the analysis and design of a DC-side symmetrical zero-current-switching (ZCS) Class-D current-source driven resonant rectifier to improve the low power-factor and high line current harmonic distortion of lighting applications. An analysis of the junction capacitance effect of Class-D ZCS rectifier diodes, which has a significant impact on line current harmonic distortion, is discussed in this paper. The design procedure is based on the principle of the symmetrical Class-D ZCS rectifier, which ensures more accurate results and provides a more systematic and feasible analysis methodology. Improvement in the power quality is achieved by using the output characteristics of the DC-side Class-D ZCS rectifier, which is inserted between the front-end bridge-rectifier and the bulk-filter capacitor. By using this symmetrical topology, the conduction angle of the bridge-rectifier diode current is increased and the low line harmonic distortion and power-factor near unity were naturally achieved. The peak and ripple values of the line current are also reduced, which allows for a reduced filter-inductor volume of the electromagnetic interference (EMI) filter. In addition, low-cost standard-recovery diodes can be employed as a bridge-rectifier. The validity of the theoretical analysis is confirmed by simulation and experimental results.

• Journal of Institute of Control, Robotics and Systems
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• v.20 no.12
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• pp.1284-1289
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• 2014

In this Paper, outdoor position estimation system was implemented using GPS (Global Positioning System) and INS (Inertial Navigation System). GPS position information has lots of errors by interference from obstacles and weather, the surrounding environment. To reduce these errors, multiple GPS system is used. Also, the Discrete Wavelet Transforms was applied to INS data for compensation of its error. In this paper, position estimation of the mobile robot in the straight line is conducted by EKF (Extended Kalman Filter). However, curve running position estimation is less accurate than straight line due to phase change in rotation. The curve is recognized through the rate of change in heading angle and the position estimation precision of the initial curve was improved by UPF (Unscented Particle Filter). In the case of UPF, if the number of particle is so many that big memory gets size is needed and processing speed becomes late. So, it only used the position estimation in the initial curve. Thereafter, the position of mobile robot in curve is estimated through switching from UPF to EKF again. Through the experiments, we verify the superiority of the system and make a conclusion.

• Journal of the Korean Society of Safety
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• v.19 no.4 s.68
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• pp.141-149
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• 2004

The automobile equipped with a gasoline engine uses the ignition coil, namely, a high voltage generator, to make the mixed fuel ignited and burned in the combustion chamber, which results in the power to drive the engine. The ignition coil functions to convert a low voltage of the primary into a hiか voltage of the secondary by switching method, which will be transmitted to the electrode. Here, if the ignition coil has a defect even a little, it cannot function well. In this study, it was chosen epoxy molding ignition coil in recently and epoxy resin which is insulation material as specimens, and it was measured the characteristics of the partial discharge occurring to the specimens when those were applied to a voltage, and thereby, it was researched and analyzed the distribution of phase angle, amount and count of discharge due to the changing voltage, And as the result is applying to the actual automobile ignition system, it can be expected the enhancement of the performance of the ignition coil and the reliability of the electrical equipment.

• Journal of the Korean Magnetics Society
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• v.4 no.3
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• pp.244-248
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• 1994

Magnetic and Magneto-optical characteristics of NdTbFeCo alloy films and NdTbFeCo/TbFeCo double-layered films have been investigated. It was observed that the Kerr rotation(${\theta}_{k}$) in the short wavelength region increased and the coercivity decreased as the substitutional amount of Nd for Tb in NdTbFeCo film at the constant FeCo content. In spite of the increased ${\theta}_{k}$, a small coercivity of NdTbFeCo film made this medium unsuitable for magneto-optical recording medium at short wavelength. An effort was made to improve coercivity by exchange coupling with TbFeCo film of high coercivity. In the exchange-coupled $Nd_{16.9}Tb_{15.2}Fe_{50.4}Co_{17.5}(150\;{\AA})/Tb_{21.1}Fe_{65.0}Co_{13.9}(300\;{\AA})$ double-layered film, the magnetization reversal switching field and the Kerr rotation angle were increased to about 6.0 KOe and $0.32^{\circ}$ at 500 nm, respectively. This result indicates that exchange-coupled NdTbFeCo/TbFeCo film can be a promising candidate for agneta-optical rerding medium short wavelenhth.