• Proceedings of the KIEE Conference
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• summer
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• pp.989-991
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• 2004

There are many elements that affect the average torque of the single phase SRM. It is related with the stator and rotor pole arcs, the dwell angle of the exciting current, the turn on/off angle, etc., Most of all, the turn on/off angle is affect the design procedure of the driving and control circuit. So, in this study, it is intend to analyze the effect that the variations of the turn on/off angle affects the average torque. and then this analyses will be used to design the control driver of the single phase SRM.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.48 no.9
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• pp.461-466
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• 1999

The switched reluctance motor (SRM) would have torque ripple if not operated with an MMF waveform specified for switching angle and phase voltage. This paper describes the robustic control scheme that permits the phase torque to be flat by PLL(Phase Locked Loop) controller. In this control scheme, the locked phase signal of PLL controls the switching dwell angle and it's loop filter signal controls the switching voltage adaptively. Experimental results show that stable dynamic performance is obtained for torque and speed together with low torque ripple on the operation of variable loads.

• The Transactions of the Korean Institute of Power Electronics
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• v.5 no.3
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• pp.215-220
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• 2000

본 논문에서는 SRM운전에서 맥동토오크와 부하토오크의 변화로 인한 속도변경을 줄이기 위해 동적 도통각 제어 원리를 이용한 PLL(Phase Locked Loop) 속도제어 방식을 채택하였다. SRM은 많은 장점을 가지고 있으나 토오크리플에 따른 속도변동으로 정밀한 속도제어에 어려움이 있다. SRM 구동 시스템에 PLL을 적용한 결과 전동기는 강인한 정속도 운전을 할 수 있으며, 또한 운전속도에 따라 선행각을 조정함으로서 고효율 구동을 할 수 있었다. 구성된 시스템은 운전속도와 부하의 변화에 따라 선행각이 증가함으로써 뛰어난 동적 속도제어 특성을 갖고 있으며, 인버터 인가전압을 제어하는 선행각을 조정함으로서 일정부하 영역에서 높은 효율특성을 가진다. SRM 구동 시스템의 PLL 속도제어와 고효율 구동을 위한 도통각제어를 위해 TMS320F240 DSP를 사용함으로서 디지털 제어기의 유연성과 소형화를 꾀하였다.

• Proceedings of the KIPE Conference
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• 2014.07a
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• pp.207-208
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• 2014

본 논문에서는 복잡한 계산 없이 간단한 방법을 통하여 어느 레벨에서도 적용이 가능한 일반적인 N-레벨 식을 제안한다. 이 방법은 각 ${\alpha}$ 축과 ${\beta}$ 축을 움직여 N-레벨 인버터를 2-레벨 인버터로 단순화 한다. 이 과정으로 타입을 구분하지 않고 하나의 식으로 N-레벨 인버터의 dwell-time을 나타낼 수 있다. 시뮬레이션 결과를 통하여 본 논문의 타당성을 검증 하였다.

• Proceedings of the KIPE Conference
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• 2015.11a
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• pp.209-210
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• 2015

This paper presents a new model predictive control method without the effect of a weighting factor in order to reduce common-mode voltage (CMV) for a three-phase voltage source inverter (VSI). By utilizing two active states with same dwell time during a sampling period instead of one state used in conventional method, the proposed method can reduce the CMV of VSI without the weighting factor. Simulation is carried out to verify the effectiveness of the proposed predictive control method with the aid of PSIM software.

• Proceedings of the Korea Information Processing Society Conference
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• 2023.11a
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• pp.530-533
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• 2023

대중교통은 현대 사회에서 필수적인 요소이며 특히 출퇴근 시간대에는 도로 교통 상황에 영향을 덜 받는 지하철의 수요가 높은 편이다. 그러나 제한된 물리적 자원으로 인해 열차 내 혼잡도 증가와 열차 운행 지연은 불가피한 상황이다. 본 논문에서는 이를 해결하기 위한 한 가지 방법으로 강화학습기반 DQN 알고리즘을 이용한 열차 정차 시간 최적화 기법을 제안했다. 열차 정차 시간과 승차 인원 모두 고려하면서 최적화를 진행했을 때와 그렇지 않았을 때를 비교하면서 실험을 진행하여 성능을 분석했다.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.42 no.8 s.338
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• pp.33-40
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• 2005

This paper presents a structure of the searcher using a diversity in array antenna systems operating in the cdma2000 1x signal environments. The new technique exploits the fact that the In-phase and quadrature components of interferers can respectively be viewed as an independent gaussian noise at each antnna element in most practical cdma signal environments. The proposed PN acquisition scheme is a singles-dwell PN acquisition system consisting of two stages, that is, the searching stage and the verification stage. The searching stage independently correlates the receiver multiple signals with PN generator of each antenna element for obtaining the synchronous energy at the entire region. Then, the searching results of each antenna element are non-coherently combinind. The verification stage compares the searching energy with the optimal threshold, which is predesigned in the lock detector, and decides whether the acquisition is successful or fail. In this paper, we analyzed the effect of tile diversity order to determine the mean acquisition time. In general, it is known that the mean acquisition time significantly decrease as the number of antenna elements increases. But, as the diversity order goes up, the enhancement of the performance is saturated. Therefore, to decrease the mean acquisition time of the searcher, we must design the optimal array antenna systems by considering the operating SNR range of the receiver, the probability of detection $P_D$ and that of false alarm $P_{FA}$ . The Performance of the proposed PN acquisition scheme is analyzed in frequency selective Rayleigh fading channels. In this paper, the effect of the number of antenna elements on PN acquisition scheme is shown according to the probability of detection $P_D$ and that of false alarm $P_{FA}$.

• Progress in Medical Physics
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• v.8 no.1
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• pp.25-29
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• 1997

Ir-192 source activity for high dose rate brachytherapy is measured using Farmertype ionization chamber. The source-to-chamber distance is 10 cm and the measured charge unit is converted to activity unit. The measured values are compared to the values provided from vendor. Because of time dependency of Ir-192 source activity, the activities are regularly checked and compared to calculated values. As the accuracy of Ir-192 source activity is depend on the mechanical measurement setup, we estimated the precision of remote controlled source dwell position using home-made device and film scanner. The difference between measured and predicted dwell position is within 1 mm. As a result, the errors of source activity are 0.7${\pm}$1.5 ％ for measured and vendor-provided values and 0.l${\pm}$1.2％ for measured and time-dependent calculated vlaues. In conclusion, our measured activity has been comparable to the values provided from vendor and our brachytherapy unit has been very accurate until now. Regular quality control of brachytherapy is essential for successful treatment which depends on the accuracy of source position and activity.

• Journal of radiological science and technology
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• v.30 no.2
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• pp.147-151
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• 2007

AAPM TG43 report has recommended to measure air kerma strength with the strength of source. Main purpose of this study is to verify the accuracy of air kerma strength provided by manufacturer. Materials for this study were MAX-4001 Electrometer, HDR 1000 Plus of the corporation of standard imaging, and 6 french bronchial Applicator with 1000 mm. we measured ionization current in 10-90 mm range from the bottom of the central axis of chamber. The reference point of calibration displayed by the maximum ionization current in the ionization current curve was measured, and air kerma strength was computed from the maximum ionization current. we acquired 50 mm distance to correspond with the maximum ionization current in the ionization current curve. Its distance has perfectly fitted to the source reference point of calibration certificate of UW-ADCL. Air kerma strength computed value has measured about 0.5% more than calibration value provided by manufacturer. Air kerma strength of calibration certificate provided by manufacturer has acquired reliable results. This study shows that considering the move error of dwell position of source and the dead space length in well-type chamber is a good way to get an accurate result.

• Radiation Oncology Journal
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• v.21 no.2
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• pp.158-166
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• 2003

Purpose: To propose a conceptual design of a novel source for intensity modulated brachytherapy. Materials and Methods: The source design incorporates both radioactive and shielding materials (stainless steel or tungsten), to provide an asymmetric dose intensity in the azimuthal direction. The intensity modulated intravascular brachytherapy was performed by combining a series of dwell positions and times, distributed along the azimuthal coordinates. Two simple designs for the beta-emitting sources, with similar physical dimensions to a $^{90}Sr/Y$ Novoste Beat-Cath source, were considered in the dosimetric feasibility study. In the first design, the radioactive and materials each occupy half of the cylinder and in the second, the radioactive material occupies only a quater of the cylinder. The radial and azimuthal dose distributions around each source were calculated using the MCNP Monte Carlo code. Results: The preliminary hypothetical simulation and optimization results demonstrated the 87$\%$ difference between the maximum and minimum doses to the lumen wall, due to off-centering of the radiation source, could be reduced to less than 7$\%$ by optimizing the azimuthal dwell positions and times of the partially shielded intravascular brachytherapy sources. Conclusion: The novel brachytherapy source design, and conceptual source delivery system, proposed in this study show promising dosimetric characteristics for the realization of intensity modulated brachytherapy in intravascular treatment. Further development of this concept will center on building a delivery system that can precisely control the angular motion of a radiation source in a small-diameter catheter.