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Dynamic driveline torque estimation during whole gear shift for an automatic transmission
Choi, Hyunseok,Hwang, Jaewoong,Choi, Seibum Elsevier 2018 Mechanism and machine theory Vol.130 No.-
<P><B>Abstract</B></P> <P>This study proposes a novel method for estimation of driveline torque of wet type AT (Automatic transmission). The previous methods of torque estimation in the clutch-to-clutch shift mechanism is mainly applicable to the single gear shift. Thus, they require specific definitions of each gear shift and signal processing corresponding to the multi-gear shift. This study distinctly develops driveline torque estimator based on the whole transmission model, which is capable in applying on any conditional gear shift. This paper, also, incomparably investigates brake/clutch model including centrifugal force, describing physical behavior of real parts. In addition, the development of the method includes adaptive brake and clutch torque estimator in order to compensate variation factor during the shift. The estimation performance of the proposed estimator is evaluated both in simulations and experiments. The results demonstrate that the proposed methods can estimate the driveline torques effectively during the whole gear shift and well describes the typical clutch-to-clutch phenomena such as inter-locking.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A whole gear shift model without signal processing for a vehicle with an AT is developed with practical aspects. </LI> <LI> Wet typed brake and clutch are modeled describing physical behavior of real parts. </LI> <LI> A torque estimator with adaptation is designed to estimate torque through both brakes or clutches and the output shaft in an AT. </LI> <LI> The effectiveness of the developed torque estimator is demonstrated by simulations and experiments. </LI> <LI> The proposed methods well describe the typical clutch-to-clutch phenomena such as inter-locking. </LI> </UL> </P>
A Triple-Power-Mode Digital Polar CMOS RF Power Amplifier With LO Duty Cycle Control
Choi, Hyunseok,Lee, Dong-Ho,Hong, Songcheol IEEE 2016 IEEE microwave and wireless components letters Vol.26 No.9
<P>A triple-power-mode digital polar CMOS power amplifier (DPA) with a high dynamic range is presented. The triple-power-mode to enhance the efficiency when operating under back-off power is facilitated by the combination of a switched output transformer to change the load impedance and a reduced duty cycle of the LO input signal of the DPA for additional back-off power. This static power-mode method for the low-power region can be used with a DPA which has a high dynamic range in conjunction with a digitally controlled bias generator. An improvement in the PAE from 14.5% to 28.7% is achieved at a back-off power of 6.5 dB from a peak output power of 21.54 dBm at 1.7 GHz. A digital transmit power control (TPC) range of 68.2 dB for WCDMA is realized without any external components.</P>
Hyunseok Choi(최현석),Tao Jiang(강타오),Hong Seok Kim(김홍석) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.4
Titanium alloys are widely used in orthopedic devices because of their low density, high tensile strength, good corrosion resistance, and biocompatibility. However, since titanium and its alloys have inferior surface properties in terms of friction and wear resistance, there are still limitations in their application to the parts where sliding contact occurs. In this study, SiC nanoparticles were laser clad on the Ti-6Al-4V surface to simultaneously improve the friction and wear properties of the titanium alloys. Laser cladding was performed by changing the ambient conditions and laser parameters. The effect of process variables on the microstructure, hardness, and friction coefficient of the coating layer was analyzed. SiC nanoparticles reacted with the Ti element in the molten pool to create the reinforcement phases such as TiC and Ti<sub>5</sub>Si<sub>3</sub>. Oxygen supplied in the laser cladding process contributed to significantly reducing the coefficient of friction of the Ti-6Al-4V surface by creating the oxide phases such as TiO<SUB>2</SUB> and SiO<SUB>2</SUB>. Consequently, after the laser surface treatment of SiC nanoparticles in an oxygen environment, the hardness of Ti-6Al-4V improved by about three times and the coefficient of friction was reduced by more than 80%.
Hyunseok Choi,Yumi Lee,Songcheol Hong Professional Technical Group on Microwace Theory a 2014 IEEE Transactions on Microwave Theory and Techniqu Vol. No.
<P>A digitally modulated CMOS power amplifier (DPA) for a polar transmitter with a high dynamic range is presented. To improve local oscillator (LO) leakage, which limits the minimum output power of the DPA, the unit amplifier cell of the DPA employs a balanced mixer-type LO canceller at the power stage and a virtual ground is introduced in the layout of the output-power combining networks. A high dynamic range of the output power is simply achieved by adjusting gate-bias voltage of a cascode transistor in each power amplifier (PA) cell using a digitally controlled bias generator. This architecture allows a few-mA drain current at a low Tx power level without degrading the linearity. An array of unit PA cells is segmented to have a 10-bit amplitude resolution, and the bias generator is designed to have 8-bit control of the average output power. The peak output power is 24.4 dBm with an overall efficiency of 43% at 800 MHz. The total output dynamic range is 102.8 dB. A simple static pre-distortion helps the DPA achieve an average efficiency of 35% with a root mean square error vector magnitude of 3.59% while delivering linear output power of 22 dBm for WCDMA. The range of the digital transmit-power control for the WCDMA signal is 49.7 dB. This chip is fabricated in a 65-nm RF CMOS process.</P>
차량 네트워크에서 차량의 이동성 정보를 이용한 차량 클라우드 서비스 안정성 향상을 위한 차량 클라우드 관리 방안
최현석(Hyunseok Choi),남영주(Youngju Nam),신용제(Yongje Shin),Mugerwa Dick,이의신(Euisin Lee) 한국통신학회 2021 한국통신학회 학술대회논문집 Vol.2021 No.2
본 논문은 차량 네트워크에서 차량들의 이동 정보를 이용하여 차량 클라우드를 유지하는 방안을 제시한다. 최근 사용자가 요구하는 데이터의 급격한 증가로 인하여 기지국이 부담해야할 트래픽이 거대해지고 있다. 따라서, 주변에 있는 차량을 이용하여 클라우드를 생성하는 방안으로 기지국의 부담을 완화시키는 연구가 진행 중이다. 본 논문에서는 클라우드가 붕괴되는 상황을 예측하여 미리 재구성함으로서 클라우드를 유지하는 방안을 제시한다. 시뮬레이션은 NS-3로 진행되었으며 성능 결과에서 기지국이 감당하는 패킷 수가 현저히 감소하였다.
수조식 양식장의 태양광발전시스템 리모델링 교체 효과 : 시뮬레이션을 통한 에너지절감효과 분석
최현석(Hyunseok Choi),나종혁(Jonghyuk Na),이현영(Hyunyoung Lee),노재엽(Jayeop Noh) 한국태양광발전학회 2021 Current Photovoltaic Research Vol.9 No.1
In the past, marine pollution caused by radioactivity and wastewater discharge caused mass destruction. As an alternative, the land farming system became common and operational. In recent years, safety and environmental problems caused by declining population due to aging of fishermen and underdeveloped facilities have always been lurking, so improvement is urgently needed. As part of the new renewable energy 3020 plan announced by the government in 2017, a new model was proposed to improve the environment as well as save energy when the roof of a water tank farm was remodeled into a solar power system. Study, when the existing roof was remodeled and replaced with a water tank farm in Busan as an empirical model, the energy saving rate was analyzed by comparing the actual electricity consumption and power generation.