Active Shift Control for Hybrid Electric Vehicles

In this paper, we will cover shift control of the transmission mounted electric device (TMED) hybrid vehicle. The TMED hybrid vehicle has a configuration in which an auto-matic transmission and a traction motor are serially connected, but the shift control is still performed almost like a conventional internal combustion engine-based vehicle. That is, during the shift control the friction torque by hydraulic pressure inside the transmission synchronizes the input shaft speed and the output shaft speed while maintaining the transmission input torque constant. It is difficult to precisely control the hydraulic pressure due to variations on temperature change and amount of oil, and so on. The proposed method in this paper which is called as an active shift control (ASC) attempts to compensate for the uncertainty of hydraulic control by controlling the transmission input speed through the traction motor. The new method is composed of an inner-loop controller and an outer-loop controller such that the inner-loop controller using a disturbance observer is designed to eliminate model uncertainties, and disturbances, and the outer-loop controller is composed of a proportional controller and feed-forward controller to track the target speed. To the best of my knowledge, the ASC is the first shift control paradigm to replace the existing shift control concept. In order to show the effectiveness of the proposed method, the experimental results through actual vehicle will be shown.