Gear-Shift Strategy for a Clutchless Automated Manual Transmission in Battery Electric Vehicles

The battery electric vehicles (BEVs) equipped with automated manual transmission (AMT) can realize gear-shift automatically and show many advantages in terms of reduction of fuel consumption and improvement of driving comfort and shifting quality. This paper focuses on the gear-shift control strategy for a clutchless AMT in a battery electric bus. Compared with the traditional ICE vehicles, the studied battery electric bus has the different powertrain structure, which consequently requires a different gear-shift strategy. First, the so-called clutchless AMT means that the clutch usually used in the conventional AMT vehicles is removed. Second, the synchronizer within the transmission is omitted and that means only the sleeves are employed to accomplish engagement of gears. In order to find the key factors that affect gear-shift operation of AMT in battery electric bus, the several gear-shift phases including “Gear Release”, “Synchronization”, and “Gear Engagement” are modeled. The analyses show that the gear-shift operation of clutchless AMT requires the motor with the capabilities of fast mode-switching (between torque output, speed control and free mode) and high-precise speed regulation. The corresponding gear-shift control strategy based on the previous modeling and analyzing is designed in this paper. Finally, the on-road test results are investigated and the conclusion is drawn.