Abstract
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 clutch-less automatic transmission (2AT) for EVs and the motor controlled shifting mechanism. Firstly, 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. Secondly, a coordinated control strategy of the driving motor and controlling motor for shifting is detailed during different shifting processes to achieve fast and smooth shifting. The torque trajectory optimization during synchronizing process is attained by applying the 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.
Highlights
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)
In [16], the performance comparison of EVs when equipped with different transmissions is discussed, and the results reveal that the two-speed automatic transmission (AT) can lead to a preferable energy consumption economy
A parallel coordination control strategy for the control motor and driving motor is developed for the shifting processes
Summary
Respect to the varied and fixed ratio transmission over a standard driving cycle and highlights that the overall energy efficiency can be improved by 5 to 12% when equipped with a multi ratio gearbox. Dual clutch transmissions (DCT) for EVs have been widely investigated in [10,11,12], where the driving motor, clutch, hydraulic clutch actuator and multi-body dynamics of powertrain are modeled. To improve the driving performance and powertrain efficiency, the multi-speed transmissions are introduced for EVs [5]. This study designs a novel two-speed clutch-less automatic transmission (2AT) for EVs, and it only needs to control a single motor to rotate the camshaft unidirectionally through the worm gear mechanism, so as to facilitate fast and smooth shifting operation. The coordinated control strategies of the driving and control motors are designed with the target of fast and smooth shifting by dividing the shifting process into three stages, i.e., before-gear-disengagement, geardisengagement and gear-engagement.
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