Development of a line pressure control algorithm for reducing the power loss in hybrid electric vehicle

In this paper, a line pressure control algorithm was developed to reduce the energy loss of the AT-based hybrid vehicle. A hybrid vehicle performance simulator was developed. Via the analysis of the power flow and lever, the torque exerted on the friction elements was calculated for each gear step of the HEV. From the calculated torque at each friction element, the optimal line pressure was determined for the given transmission at each transmission input torque and gear step. Using the HEV performance simulator, it was found that torque capacity of the friction element is capable of transmitting the torque by optimal line pressure. It was found from the simulation results that optimal line pressure control algorithm suggested in this study is able to reduce of the hydraulic control system energy loss approximately 36% compared with that of control algorithm which uses constant line pressure.