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신창우(Shin, Chang-Woo),선종천(Sun, Jong-Choen),강연준(Kang, Yeon-June),백순권(Paik, Soon-Kwon) 한국소음진동공학회 2008 한국소음진동공학회 논문집 Vol.18 No.6
An improved beamforming method is proposed to measure the surface impedance of absorbing materials in a free field. It is possible to estimate the surface impedance by decomposing measured signals into incident and reflected signals by using the spatial filter matrix of the beamforming method. Wavelet do-noising techniques which reduce the white Gaussian noise are applied to improve the results. Phase calibration method is also used to improve the results of the measured surface impedance in a low frequency range. The results of the normal incidence experiments that are performed in a semi-anechoic chamber are verified by comparing with those of the standard test method that is presented in ASTM E1050. The proposed method is found to be reliable to measure the surface impedance for frequencies higher than 400 Hz.
신창우(Chang Woo Shin),최종대(Jongdae Choi),김범수(Beomsoo Kim),임원식(Wonsik Lim),차석원(Sukwon Cha) 한국자동차공학회 2012 한국자동차공학회 학술대회 및 전시회 Vol.2012 No.11
Drivers have come to expect better gear shifting since vehicle control systems have been improved. This paper proposes the shifting strategy based on a driver power demand. Dynamic Programming (DP) is used to obtain the optimal gear shift while maximizing fuel economy. The DP problem with fuel economy as the cost function is developed to solve within the power level, which is from 90% to 100% of demanded power. The optimal results at different power levels are combined to generate the shifting map based on the power demand. The driver’s power demand is interpreted as an engine power by the relationship between the accelerator pedal position and the vehicle speed. In order to apply the proposed gear shifting strategy, the vehicle simulation model is implemented on co-simulation. Simulation results show that the proposed shifting strategy improves fuel economy compared with the conventional gear shift map on driving cycles.
신창우(Chang Woo Shin),정종렬(Jong Ryeol Jeong),임원식(Won Sik Lim),차석원(Suk Won Cha) 한국자동차공학회 2010 한국자동차공학회 학술대회 및 전시회 Vol.2010 No.11
There is a big difference between electric vehicles(EVs) and conventional vehicles in the construction and power flow of the powertrain. Therefore, whenever someone develops an EV, they should take into consideration improvement of dynamic performance in EVs. In this paper, we conducted a research on a design method to determine the traction motor characteristics and the final reduction gear ratio in the electric bus, which consists of a motor, a battery system and a final reduction gear. We analyzed the required motor power of the electric bus based upon the maximum vehicle speed needed and the grading performance of the vehicle. This paper proposed a design method for the optimal final reduction gear ratio to satisfy vehicle acceleration performance by using a motor efficiency according to the driving cycles. By using the determined motor performance and the optimal gear ratio, backward simulation was conducted to confirm a variation of SOC(state of charge) for city bus driving cycles.