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장효환,전윤식,Chang, Hyo-Whan,Jun, Yoon-Sik 대한기계학회 1998 大韓機械學會論文集A Vol.22 No.3
Shift quality of an automatic transmission in a vehicle is mainly affected by transient pressures in the hydraulic system during shifting. In this study, dynamic modelings of the hydraulic system and the power train of an automatic transmission are made systematically by a bond-graph method. The dynamic characteristics of the line pressures and clutch/brake pressures during shiftings are investigated by simulations and verified by experiments. The effects of clutch/brake pressures on the shift torque are also investigated through driving simulation.
가스보조식 이중행정 유압브레이커의 민감도 해석에 의한 성능 향상
류택직(Taek Jik Ryoo),장효환(Hyo Whan Chang) 유공압건설기계학회 2009 유공압건설기계학회 학술대회논문집 Vol.2009 No.11
A gas-assisted hydraulic breaker uses both hydraulic and pneumatic energies and an appropriate balance between two energies mostly effects its performance. Mathematical modeling of the breaker is established and verified by experiment. Through sensitivity analysis using AMESim, the key design parameters are selected and nearly optimized to maximize the output power as well as the impact energy for long and short strokes. As the results, the impact energy and output power are increased significantly compared with the current design. The dynamic characteristic of the piston displacement is also improved by the design change.
전윤식,장효환,Jun, Yoon-Sik,Chang, Hyo-Whan 대한기계학회 1998 大韓機械學會論文集A Vol.22 No.3
Most of feedback shift controllers developed in the past have fixed control parameters tuned by experts using a trial and error method. Therefore, those controllers cannot satisfy the best control performance under various driving conditions. To improve the shift quality under various driving conditions, a new self-organizing controller(SOC) that has an optimal control performance through self-learning of driving conditions and driver's pattern is designed in this study. The proposed SOC algorithm for the shift controller uses simple descent method and has less calculation time than complex fuzzy relation, thus makes real-time control passible. PCSV (Pressure Control Solenoid Valve) control current is used as a control input, and turbine speed of the torque converter is used indirectly to monitor the transient torque as a feedback signal, which is more convenient to use and economic than the torque signal measured directoly by a torque sensor. The results of computer simulations show that an apparent reduction of shift-transient torque is obtained through the process of each run without initial fuzzy rules and a good control performance in the shift-transient torque is also obtained.