• Journal of Power Electronics
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• v.17 no.3
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• pp.821-834
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• 2017

This paper reports on a single-inductor multiple-output step-up converter with digital control. A systematic analog-to-digital-controller design is explained. The number of digital blocks in the feedback path of the proposed converter has been decreased. The simpler digital pulse-width modulation (DPWM) architecture is then utilized to reduce the power consumption. This architecture has several advantages because counters and a complex digital design are not required. An initially designed unit-delay cell is adopted recursively for the construction of coarse, intermediate, and fine delay blocks. A digital limiter is then designed to allow only useful code for the DPWM. The input voltage is 1.8 V, whereas output voltages are 2 V and 2.2 V. A co-simulation was also conducted utilizing PowerSim and Matlab/Simulink, whereby the 55 nm process was employed in the experimental results to evaluate the performance of the architecture.

• The Transactions of the Korean Institute of Power Electronics
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• v.25 no.2
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• pp.73-78
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• 2020

In this study, a novel reactive power control scheme is proposed to supply stable reactive power to the distribution line by compensating a ripple voltage of DC link. In a single-phase system, a magnitude of second harmonic is inevitably generated in the DC link voltage, and this phenomenon is further increased when the capacity of DC link capacitor decreases. Reactive power control was performed by controlling the d-axis current in the virtual synchronous reference frame, and the voltage control for maintaining the DC link voltage was implemented through the q-axis current control. The proposed method for compensating the ripple voltage was classified into three parts, which consist of the extraction unit of DC link voltage, high pass filter (HPF), and time delay unit. HPF removes an offset component of DC link voltage extracted from integral, and a time delay unit compensates the phase leading effect due to the HPF. The compensated DC voltage is used as feedback component of voltage control loop to supply stable reactive power. The performance of the proposed algorithm was verified through simulation and experiments. At DC link capacitance of 375 uF, the magnitude of ripple voltage decreased to 8 Vpp from 74 Vpp in the voltage control loop, and the total harmonic distortion of the current was improved.

• Journal of the Korean Institute of Intelligent Systems
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• v.17 no.5
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• pp.640-647
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• 2007

This paper presents a joint controller for a humanoid robot based on genetic algorithm. h humanoid robot has basically instability during walking because it isn't fixed on the ground. Moreover nonlinearities of the joints increase its instability. If one of them isn't satisfied, the robot may fall down at the ground during walking. To attack one of those problems, joint controller is proposed. It can perform tracking control preciously and reduce the effect of nonlinearities by gear, limitation of the input voltage, coulomb friction and so on. This controller is based on fuzzy-sliding mode controller (FSMC) and compensator and control gains are searched by a proposed genetic algorithm. It can reduce the effect by nonlinearities. Also, to improve the tracking performance, the proposed controller has motion controller. From the given controller, a humanoid robot can moved more preciously. Here, all the processes are investigated through simulations and it is verified experimentally in a real joint system for a humanoid robot.

• Proceedings of the KIPE Conference
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• 2018.11a
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• pp.95-97
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• 2018

The power quality of Single Phase Grid-Connected Inverters (GCIs) has received much attention with the increasing number of Distributed Generation (DG) systems. However, the performance of single phase GCIs get degraded due to several factors such as the grid voltage harmonics, the dead time effect, and the turn ON/OFF of the switches, which causes the harmonics at the output of GCIs. Therefore, it is not easy to satisfy the harmonic standards such as IEEE 519 and P1547 without the help of harmonic compensator. To meet the harmonic standards a certain kind of harmonic controller needs to be added to the current control loop to effectively mitigate the low order harmonics. In this paper, the harmonic compensation is performed using a novel robust harmonic compensation method based on Digital Lock-in Amplifier (DLA). In the proposed technique, DLAs are used to extract the amplitude and phase information of the harmonics from the output current and compensate it by using a simple PI controller in the feedforward manner. In order to show the superior performance of the proposed harmonic compensation technique, it is compared with those of conventional harmonic compensation methods in terms of the effectiveness of harmonic elimination, complexity, and implementation. The validity of the proposed harmonic compensation techniques for the single phase GCIs is verified through the experimental results with a 5kW single phase GCI. Index Terms -Single Phase Grid Connected Inverter (SPGCI), Harmonic Compensation Method, Total Harmonic Distortion (THD) and Harmonic Standard.

• Journal of Korea Society of Industrial Information Systems
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• v.24 no.2
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• pp.41-46
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• 2019

The application of series compensator in a power system affects other devices such as circuit breakers transient recovery voltage (TRV) problem. In this paper, we analyze the TRV effect on a line circuit breaker in the cases with and without thyristor-controlled series capacitor (TCSC) via simulation, and suggest an effective method to overcome the increase of TRV due to the TCSC installation. It also discusses the impact of proposed protection on metal oxide varistor (MOV). A 345 kV transmission line in Korea was selected as a study case. Grid system was modelled using PSCAD (Power Systems Computer Aided Design) / EMTDC(Electro Magnetic Transient Direct Current). The TRV was analyzed by implementing a short circuit fault along the transmission line and at the breaker terminal. The proposed protection scheme, the TRV satisfies the standard. However, the MOV energy capacity increased as the delay time increased. This result can solve the TRV problem caused by the expected transmission line fault in a practical power system.

• Korean Journal of Optics and Photonics
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• v.33 no.6
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• pp.287-294
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• 2022

This study presents a method for designing an athermal middle wavelength infrared (MWIR) zoom lens with the iterative selection of material compositions on an athermal glass map. The optical properties of glass for MWIR are generally very sensitive to temperature, compared with visible glass. To compensate for focus error due to temperature change, the non-athermalized zoom system requires a large amount of movement of a compensator, which results in an unstable zoom system. To solve this problem, the material compositions for an athermal zoom lens have effectively been obtained using the thermal aberration correction process analytically on an athermal glass map. An expander lens is used to enlarge the focal lengths of an original main zoom lens two times. Finally, while this expander is attached to an original athermal zoom system, the final zoom system equipped with this expander doubles the focal length ranges and has stable performance over a specified temperature range.

• Korean Journal of Metals and Materials
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• v.49 no.4
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• pp.348-354
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• 2011

Long-lasting brightness $Sr_{4}Al_{14}O_{25}$ : $Eu^{2+}$, $Dy^{3+}$, $Ag^{+}$ phosphor was synthesized by modified solid state reaction and its photoluminescence was investigated. $Sr(NO_3)_{2}$ and $Al(NO_3)_3{\cdot}9H_{2}O$ as starting materials, and $B_{2}O_{3}$ as a flux were mixed with $Eu_{2}O_{3}$ as an activator, $Dy_{2}O_{3}$ as a coactivator, and $AgNO_{3}$ as a charge compensator. The crystalline of target powder showed a single-phase $Sr_{4}Al_{14}O_{25}$ by the XRD characterization and the average particle size was about 20-30 ${\mu}m$ from the FE-SEM observation. $Ag^{+}$ ion doping effects (0-0.06 mol) on $Sr_{4}Al_{14}O_{25}:Eu^{2+},\;Dy^{3+},\;Ag^{+}$ phosphor were measured by photoluminescence spectrometer and luminescence meter. The of photoluminescence intensity of the $Sr_{3.64}Al_{14}O_{25}:Eu_{0.11},\;Dy_{0.22},\;Ag_{0.03}$ phosphor was higher than other compositions and afterglow brightness was 0.186 $cd/m^{2}$.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.36 no.5
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• pp.423-432
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• 2023

With the increasing demand for mobile devices featuring multi-touch operation, extensive research is being conducted on touch screen panel (TSP) Readout ICs (ROICs) that should possess low power consumption, compact chip size, and immunity to external noise. Therefore, this paper discusses capacitive touch sensors and their readout circuits, and it introduces research trends in various circuit designs that are robust against external noise sources. The recent state-of-the-art TSP ROICs have primarily focused on minimizing the impact of parasitic capacitance (Cp) caused by thin panel thickness. The large Cp can be effectively compensated using an area-efficient current compensator and Current Conveyor (CC), while a display noise reduction scheme utilizing a noise-antenna (NA) electrode significantly improves the signal-to-noise ratio (SNR). Based on these achievements, it is expected that future TSP ROICs will be capable of stable operation with thinner and flexible Touch Screen Panels (TSPs).

• Journal of Aerospace System Engineering
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• v.18 no.4
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• pp.1-9
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• 2024

In this study, we researched control compensation techniques to enhance control robustness against external forces and responsiveness to output dead zones in direct-actuated voice coil actuators for small guided missiles. An aircraft's wings must optimally control the command angle while managing various nonlinear external forces such as drag, lift, and thrust during flight. The small direct -drive voice coil actuator, when applied, benefits from small current requirements in no-load situations but suffers from diminished control robustness due to rapid increases in control current during external force applications. To address this issue, we designed and implemented a system that compensates for errors by accumulating additional output, thus improving the actuator's responsiveness in control scenarios with external forces. This was verified through experimental results.

• The Journal of Korean Society for Radiation Therapy
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• v.23 no.1
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• pp.41-49
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• 2011

Purpose: This study is designed to investigate radiotherapic valuation of Paraffin Wax, which is newly formed for this study and generally utilized in dentistry, and Mouth Piece and Putty impression, which are commonly used in radiotherapy, for oral cavity as a compensator. Materials and Methods: Each compensator was formed by $10{\times}10{\times}1cm$ and measured radiation dose attenuation ratio with reference of water phantom which is made of tissue-equivalent materials. Two patients with oral cancer underwent DRR (Digitally Reconstructed Radiogrph) of Offline Review Program of Aria System and Portal vision for 5 times for each material to evaluate reproducibility by each filling materials. Moreover, MU (monitor unit) changes by dose absorption were considered in the case of inevitable implication of an filling materials in the range for radiotherapy. Results: Radiation dose attenuation ratios were shown -0.7~+3.7% for Mouth Piece, +0.21~+0.39% for Paraffin Wax and -2.71~-1.76% for Putty impression. Error ranges of reproducibility of positions were measured ${\pm}3mm$ for Mouth Piece, ${\pm}2mm$ for Paraffin Wax and ${\pm}2mm$ mm for Putty impression. Difference of prescription MU from dose absorption with an filling material increased +7.8% (250 MU) in Putty impression and -0.9% (230 MU) in Paraffin Wax as converted into a percentage from the standard phantom, Water 232 MU. Conclusion: Dose reduction of boundary between cavity and tissue was observed for Mouth Piece. Mouth Piece also had low reproducibility of positions as it had no reflection of anatomy of oral cavity even though it was a proper material to separate Maxilla and Mandible during therapy. On the other hand, Putty impression was a suitable material to correctly re-position oral cavity as before. However, it risked normal tissues getting unnecessary over irradiation and it caused radiation dose decrease by -2.5% for 1cm volume in comparison of it of water phantom. Dose reduction in Paraffin Wax, Fat Tissue-Equivalent Material, was smaller than other impressions and position reproducibility of it was remarkable as it was possible to make an anatomy reflected impression. It was also well fitted to oral cavity to transfer radiation dose planned in radiotherapy. Thus, Paraffin Wax will be an ideal material in radiotherapy for patients with oral cancer.