Design, Control, and Validation of Two-Speed Clutchless Automatic Transmission for Electric Vehicle

Two-speed or multiple-speed automatic transmissions can obviously improve the overall manipulating performance in terms of shifting quality and energy efficiency when equipped in electric vehicles (EVs). This study details the design of a two-speed clutchless automatic transmission (2AT) for EVs and the motor-controlled shifting mechanism. First, a novel two-speed clutch automatic transmission is devised with a motor-controlled shifting mechanism, which enables the shift motions and the speed control of the driving motor for synchronization during shifts. Second, a coordinated control strategy of the driving motor and controlling the motor for shifting is detailed during different shifting processes to achieve fast and smooth shifting. The torque trajectory optimization during the synchronizing process is attained by applying Pontryagin's minimum principle. The simulation and experimental results verify the shifting mechanism design and the shift control algorithm in terms of shift response and smoothness for the designed 2AT.