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Jeongwon Sohn,Seungwoo Hong,Myoungho Sunwoo IEEE 2013 IEEE Transactions on Vehicular Technology VT Vol.62 No.8
<P>This paper presents an alternator model suitable for electric power management research. The proposed model estimates the alternator driving torque under various driving conditions, such as engine speed, output current, and generation voltage. The base equations of the proposed model are derived from the equivalent circuit and the phasor diagram of the field-wound-type synchronous generator. Model parameters that affect power conversion efficiency were defined and identified through open and short load tests on a bench. Validation tests were also performed to evaluate model accuracy under several representative driving conditions. Through a case study, we show that the proposed model is the effective way to research power management.</P>
Jeongwon Sohn,선우명호,Kyunghan Min,Jaewook Shin,한만배 한국자동차공학회 2019 International journal of automotive technology Vol.20 No.1
To enhance the 48 V mild hybrid electric vehicle performance using a smaller capacity and lower voltage battery than the full hybrid electric vehicle, a novel power management strategy needs to be established that considers the characteristics and limitations of the components. This paper proposes a charge-sustaining control strategy as a ground principle of the 48 V hybrid electric vehicle control for managing the battery state-of-charge (SOC) to stay near the most efficient regime. The base efficiency characteristics of the component models including engine, motor/generator, and battery are determined in the form of efficiency maps using the powertrain analysis tool. Then the control strategy is formulated as a nonlinear optimal regulation problem that meets two conflicting control objectives, such as fuel efficiency improvement and state-of-charge maintenance. The optimal regulation problem implements a discrete-time Hamilton-Jacobi-Bellman approach. The proposed strategy is evaluated by comparing with the reference strategy applying the Dynamic Programming (DP), i.e. a global optimal result, under urban dynamometer driving schedule and worldwide harmonized light duty test cycle. Through the evaluation, the fuel efficiency of the proposed strategy with three different electrical loads is slightly deteriorated at most by 5.03 % from the DP results with staying within a desirable SOC. This suggests that the proposed strategy is operating very closely to global optimal performances.
동기 발전기 등가회로를 이용한 얼터네이터 토크 모델 설계
손정원(Jeongwon Sohn),홍승우(Seungwoo Hong),이현준(Hyunjun Lee),이주원(Joowon Lee),이민광(Minkwang Lee),선우명호(Myoungho Sunwoo) 한국자동차공학회 2012 한국자동차공학회 부문종합 학술대회 Vol.2012 No.5
This paper presents the alternator torque model derived from an equivalent circuit of synchronous generator. The model is designed to simulate the automotive alternator operated on various conditions. It reflects the torque variation mainly caused by dynamic characteristics such as engine speed, load current, and target voltage. The alternator torque works as the engine load directly, thus the model can be used for the establishment of energy management strategies. In this paper, a research case of the alternator generation control is introduced to validate a model application. The simulation result shows the model is applicable for the variety of energy management researches.
Graft Patency of No-Touch Saphenous Veins Used as Aortocoronary Bypass Grafts
Kim Jeongwon,Sohn Suk Ho,Choi Jae-Sung,Oh Se Jin,Hwang Ho Young 대한심장혈관흉부외과학회 2023 Journal of Chest Surgery (J Chest Surg) Vol.56 No.5
Background: This study evaluated the early, 1-year, and 3-year graft patency rates and mid-term clinical outcomes after no-touch saphenous veins (NT-SVs) were used as aortocoronary grafts in coronary artery bypass grafting (CABG). Methods: In total, 101 patients who underwent CABG using NT-SVs as aortocoronary grafts were included. The 2 most common indications for performing aortocoronary grafting with NT-SVs were unavailability of the left internal thoracic artery (n=36) and moderate lesions where flow competition was expected (n=27). Early (median, 1 day; interquartile range [IQR], 1–2 days), 1-year (median, 13 months; IQR, 11–16 months), and 3-year (median, 34 months; IQR, 27–41 months) graft angiography was performed in 98 (97.0%), 84 (83.2%), and 40 patients (39.6%), respectively. The median follow-up duration was 43 months (IQR, 13–76 months). Overall survival rates and the cumulative incidence of major adverse cardiac events were evaluated. Results: The operative mortality rate was 2% (2 of 101 patients). Early postoperative patency rates for overall and aortocoronary NT-SV grafts were 98.2% (223 of 227 distal anastomoses) and 98.2% (164 of 167), respectively. The 1- and 3-year patency rates for aortocoronary SV grafts were 94.9% (131 of 138) and 90.6% (58 of 64), respectively. The overall survival rates at 5 and 10 years were 81.7% and 59%, respectively. The cumulative incidence of major adverse cardiac events at 5 and 10 postoperative years was 20.7% and 39%, respectively. Conclusion: The feasibility of using NT-SVs as aortocoronary grafts in CABG was shown in this study, based on the graft patency rates up to 3 years and the mid-term clinical outcomes.
가스 조성이 저유전상수 a-C:F 층간절연막의 특성에 미치는 영향
박정원(Jeongwon Park),양성훈(Sung-Hoon Yang),이석형(Seoghyeong Lee),손세일(Seil Sohn),오경희(Kyunghui Oh),박종완(Jong-Wan Park) 한국진공학회(ASCT) 1998 Applied Science and Convergence Technology Vol.7 No.4
초고접적 회로의 미세화에 따라 다층배선에서 기생저항(parasitic resistance)과 정전용량의 증가는 RC 시정수(time constant)의 증가로 인하여 소자의 동작속도를 제한하고 있다. 이로 인하여 발생되는 배선지연의 문제를 해결하기 위하여 매우 낮은 유전상수를 갖는 층간 절연물질이 필요하다. 이러한 저유전상수 층간결연물질로서 현재 유기계 물질중의 하나인 a-C:F이 주목받고 있는 물질이다. 본 연구에서는 ECRCVD를 이용하여 a-C:F 박막과 Si기판사이의 밀착력을 향상시키기 위하여 a-C:H 박막을 500Å 증착한 후 a-C:F을 증착전력 500 W에서 원료가스의 유량비(C₂F_6/(C₂F_6+CH₄))를 0~1.0까지 변화시키면서 상온에서 증착하였다. a-C:F 박막의 특성은 SEM, FT-IR, XPS, C-V meter와 AFM등을 이용하여 두께, 결합상태, 유전상수, 표면형상 및 표면 거칠기를 관찰하였다. a-C:F 박막에서 불소함량은 가스 유량비가 1.0일 경우에는 최대 약 31 at.%정도 검출되었으며, 가스 유량비가 증가됨에 따라 증가하였다. 또한 유전상수는 a-C:H의 유전상수 ε=3.8에서 ε=2.35까지 감소하였다. 이는 영구 쌍극자 모멘트가 1.5인 C-H 결합은 감소하고 영구 쌍극자 모멘트가 0.6, 0.5인 CF, CF₂결합이 증가하였기 때문이다. 하지만 400℃에서 질소분위기로 1시간 동안 furnace 열처리 후에 가스유량비가 1.0인 a-C:F 박막에서 불소의 함량이 감소하여 C-F 결합이 줄어들었다. 이로 인하여 유전상수가 열처리전의 2.7에서 열처리후 3.2까지 상승하였다. As device dimensions approach submicrometer size in ULSI, the demand for interlayer dielectric materials with very low dielectric constant is increased to solve problems of RC delay caused by increase in parasitic resistance and capacitance in multilevel interconnections. Fluorinated amorphous carbon is one of the promising materials in ULSI for the interlayer dielectric films with low dielectric constant. However, poor thermal stability and adhesion with Si substrates have inhibited its use. Recently, amorphous hydrogenated carbon (a-C:H) film as a buffer layer between the Si substrate and a-C:F has been introduced because it improves the adhesion with Si substrate. In this study, therfore, a-C:F/a-C:H films were deposited on p-type Si(100) by ECRCVD from C₂F_6, CH₄ and H₂ gas source and investigated the effect of forward power and composition on the thickness, chemical bonding state, dielectric constant, surface morphology and roughness of a-C:F films as an interlayer dielectric for ULSI. SEM, FT-IR, XPS, C-V meter and AFM were used for determination of each properties. The dielectric constant in the a-C:F/a-C:H films were found to decrease with increasing fluorine content. However, the dielectric constant increased after furnace annealing in N₂ atmosphere at 400℃ for 1hour due to decreasing of fluorine concentration.
Seungwoo Hong,Inseok Park,Jeongwon Sohn,Yeongseop Park,Kangyoon Lee,Myoungho Sunwoo 한국자동차공학회 2010 한국자동차공학회 학술대회 및 전시회 Vol.2010 No.11
With the increasing demand for fuel efficient vehicles, an electric power generation strategy is required in order to generate electric energy efficiently in conventional internal combustion engine (ICE) vehicles. The electric power generation strategy is available with a voltage controlled alternator, and it determines the amount of the generated electric energy. In this paper, the power generation strategy for ICE vehicles is proposed with the model predictive control (MPC) method in order to improve fuel efficiency of vehicles. The proposed MPC based approach is composed of two parts: prediction of battery states and optimization of the electric power generation. In the first part, the battery state of charge (SOC) is predicted with the powertrain model. Based on this predicted information, the optimal trajectory of the alternator command input is obtained by using the quadratic programming (QP) optimization method. The proposed algorithm is validated through simulation and compared with other conventional strategies used in commercial software. It is proven that the MPC based electric power generation strategy can improve the fuel efficiency.
Lee, Hyunjun,Han, Manbae,Sohn, Jeongwon,Sunwoo, Myoungho American Society of Mechanical Engineers 2014 Journal of engineering for gas turbines and power Vol.136 No.11
<P>This paper presents a novel method to estimate an exhaust pressure at 357 different steady-state engine operating conditions using a diesel particulate filter (DPF) mass flow model to precisely control the air quantity for a light-duty diesel engine operated with dual-loop exhaust gas recirculation (EGR) and variable geometry turbocharger (VGT) systems. This model was implemented on a 32 bit real-time embedded system and evaluated through a processor-in-the-loop-simulation (PILS) at two transient engine operating conditions. And the proposed model was validated in a vehicle. By applying Darcy's law, the DPF mass flow model was developed and shows a root mean square error (RMSE) of 3.7 g/s in the wide range of the DPF mass flow and above 99% linear correlation with actual values. With such reasonable uncertainties of the DPF mass flow model, the exhaust pressure was estimated via the application of a nonlinear coordinate transformation to the VGT model. The DPF mass flow based exhaust pressure estimation exhibits below 6% error of the exhaust pressure under steady-state conditions. The method was also validated through the PILS and the vehicle test under transient conditions. The results show a reasonable accuracy within 10% error of the exhaust pressure.</P>