04CVT-31 CVT1 CVT 2004 Category: CVT-systems Title : Model Based Control for a Pressure Control Type CVT Wansik Ryu: Ph.D Student, School of Mechanical Engineering, Sungkyunkwan University, 300 Chunchun-dong, Suwon, 440-746, Korea, e-mail : firstname.lastname@example.org Juhyun Nam, Engineer, Jatco, Korea Yongjoon Lee, General Manager, Hyundai Motor Company Hyunsoo Kim*: Professor, School of Mechanical Engineering, Sungkyunkwan University, 300 Chunchun-dong, Suwon, 440-746, Korea, e-mail : email@example.com Abstract Hydraulic control for a metal belt CVT ratio control can be classified into two types : (1) flow control and (2) pressure control. In the flow control system, the CVT ratio control is carried out by controlling the oil flow to and from the primary actuator. On the other hand, in the pressure control system, the desired speed ratio is obtained by controlling the primary actuator pressure. It is known that the pressure control is easier than the flow control in maintaining the desired speed ratio. Furthermore, the pressure control system has an advantage of preventing the belt form slippage in active manner since it is possible to control the primary belt clamping force directly through the pressure control. In the flow control system, the belt-pulley slippage can be controlled in passive manner, for instance, by adopting the outlet orifice to restrict the exhaust oil flow, which provides the residual pressure. In this paper, a model based control algorithm for a pressure control type CVT has been developed. Firstly, the P-line is proposed to predict the shift performance using the steady state pressure characteristics. The P-line shows the pressure difference which can be used to evaluate the shift speed. Two types of ratio control valves : type(I) without line pressure area on the valve spool and type(II) with line pressure area are designed using the P-line. For the two types of the ratio control valves, shift speed is evaluated by the P-line. It is found from the experiments that the larger the pressure difference from the P-line, the faster * To whom all the correspondence concerning this paper should be addressed. 04CVT-31 CVT1 the shift speed. To design the model based control, steady state characteristics for the pressure control type CVT ratio valve are obtained by the simulation and experiments and the model based controller is designed. It is found from the experimental results that the linear controller such as PID control can be applied in the pressure control type CVT with satisfactory tracking performance and robustness meanwhile nonlinear control algorithm or adaptive control gains are required for the flow control type CVT. Moreover, the model based controller shows superior robustness to the PID controller especially for the overdrive range while having similar tracking performance with the PID control. Taking the advantage of the pressure control type CVT, a model based primary pressure control algorithm is proposed to prevent the belt-pulley slip. It is also found from the experiments that the model based control provides higher primary pressure to prevent the slip. However, the increased primary pressure causes slower downshift response, which requires compromise between the safety and the performance.
Pages to are hidden for
"Model Based Control for"Please download to view full document