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류완식(Wansik Ryu),김현수(Hyunsoo Kim) 한국자동차공학회 2005 한국자동차공학회 춘 추계 학술대회 논문집 Vol.2005 No.11_2
A modified ratio control algorithm is proposed for the improvement of the fuel economy for a metal belt CVT. In the modified ratio control algorithm, the CVT ratio is controlled to operate the engine on the optimal operation region which provides the best efficiency from the view point of the overall efficiency of the engine-CVT system. In order to construct the modified ratio map, the CVT system loss model is used by assuming that the all the loss is attributed to the torque loss. It is found from the simulation results that the fuel economy by the modified ratio control algorithm is improved by 5.5 percents compared with the existing ratio control.
류완식(Wansik Ryu),김현수(Hyunsoo Kim) 한국자동차공학회 2004 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
In this paper, CVT belt-pulley loss model is proposed. Experiments are performed to measure input and output power of the CVT belt-pulley. It is found from the experiments that the input and output power loss at a steady state depend on the speed and line pressure. In addition, transient loss model is introduced, which depends on the rotational speed, shift speed and inertia torque. Using the CVT belt-pulley loss model, simulation results are compared with the experiments for various speed and line pressure. It is found that the CVT belt-pulley loss model describes closely the actual power loss behavior.
류완식(Wansik Ryu),남주현(Juhyun Nam),이희라(Heera Lee),김현석(Hyunsuk Kim),이진희(Jinhee Lee),이용준(Yongjun Lee),김현수(Hyunsoo Kim) 한국자동차공학회 2002 한국자동차공학회 Symposium Vol.2002 No.11
CVT ratio control can be achieved by either flow control or pressure control. Since the pressure control method is able to control the pulley thrust. it has many advantages such as keeping the belt from slippage. In developing the ratio control valve. steady state and dynamic characteristics of metal belt CVT should be considered. In this paper. 2 types of ratio control valves are developed: type(l) with line pressure area on the ratio control valve spool and type(lI) without line pressure area. In addition. Kpsi line concept is introduced. which can be used to predict shift performance by the pressure margin to the boundary point. Simulation results show that the type(I) gives faster shifting response in downshift compared to that of the type(II), which is due to the residual pressure in the primary actuator. It is found from the simulation and experimental results that the ratio control valve(l) and (II) have advantages and disadvantages in shift speed while satisfying the design specification for the steady state and the dynamic characteristics.
류완식(Wansik Ryu),김현수(Hyunsoo Kim) 한국자동차공학회 2003 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
In this paper, shin performance for an independent control CYT is investigated. To realize the independent control, pressure control type ratio control valve and secondary valve are proposed. Using the dynamic models of the control valves and CYT dynamic model, shift performances are evaluated and compared with those by the conventional control CYT. It is found from the simulation that independent control CYT shows faster shift speed for the upshift. To improve the downshift shift speed, appropriate selection of the actuator area ratio is required.<br/>
류완식(Wansik Ryu),김현수(Hyunsoo Kim) 한국자동차공학회 2006 한국 자동차공학회논문집 Vol.14 No.4
A modified ratio control algorithm is proposed for the improvement of the fuel economy for a metal belt CVT. In the modified ratio control algorithm, the CVT ratio is controlled to operate the engine on the optimal operation region which provides the best efficiency from the view point of the overall efficiency of the engine-CVT system. In order to construct the modified ratio map, the CVT system loss model is used by assuming that the all the loss is attributed to the torque loss. It is found from the simulation results that the fuel economy by the modified ratio control algorithm is improved by 5.5 percents compared with the existing ratio control.
김필구(Pilgu Kim),류완식(Wansik Ryu),김현석(Hyunsuk Kim),김현수(Hyunsoo Kim) 한국자동차공학회 2005 한국자동차공학회 춘 추계 학술대회 논문집 Vol.2005 No.11_2
In this paper, pressure characteristics for an independent pressure control type CVT are investigated, and (j solution to reduce the pressure fluctuation at steady state is proposed. From the experiments, a pressure fluctuation is observed at some secondary pressure range. In order to analyze the pressure characteristics, dynamic models of the hydraulic control system including the CVT variator are obtained. Using the dynamic models, the parameters that affect the pressure fluctuation are investigated. From the simulations, it is found that the change of the hydraulic stiffness is the main reason for the pressure fluctuation. Modification of the notch area of the SCV supply p0l1 is proposed to decrease the hydraulic stiffness gradient of the supply line from the SCV to the CVT variator. From the simulation and the experiment, it is found that the pressure fluctuation can be reduced effectively by the hydraulic stiffness control.
박상준(Sangjoon Park),류완식(Wansik Ryu),송준걸(Juingeol Song),황성호(Sungho Hwang),김현수(Hyunsoo Kim) 한국자동차공학회 2004 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
This paper presents shift characteristics for DCT. To obtain the shift force, dynamic models of the DCT are constructed using MATLAB Simulink by considering the rotational inertia of every component. Based on the dynamic model of the DCT synchronizer, control actuator and vehicle model, a DCT simulator is developed. Using the simulator, the shift force and speed of the relevant shafts are obtained. In addition, the torque and acceleration are calculated during the shift process by considering the engaging and disengaging time of the two clutches. It is found from the simulator that non-interrupted torque transmission can be obtained by proper control of the two clutches.