The Torque Distribution Analysis for Dual Motor - Single Shaft Electric Drive

Abstract

The application of multispeed gearbox in pure electric drive gives a significant benefit in electric energy consumption saving. It is visible, especially in the case of city exploitation conditions of the electric vehicle. Independent on the kind of use multispeed transmission its application in pure electric drive required its automated operation, both for vehicle acceleration and deceleration. In the case of Automated Manual Transmission the disadvantage is interrupted driving torque during gear shifting. This negative feature can be removed thanks to the proper drive train structure. One of them is proposed dual motor - single shaft drive structure. It consists of two electric motors. One of them is connected to the multispeed transmission input while the second is connected to the multispeed transmission output shaft and then to the final drive. This way of electric motor arrangement in electric drive structure puts together the benefits of multi speed gearbox application as well as the possibility of vehicles propelling during gear shifting. Additionally, compared to the classic electric drive structure with multispeed transmission, each motor rated power can be limited because the total drive power is the sum of both the motor powers. It is resulting in motors current limitation thus the same the losses are also limited and the drive efficiency increase. It seems that the effect on energy saving can be greater when both motors cooperate together in the proper way. This cooperation depends on both motor torque distribution. The motor torque distribution must be done under best efficiency motor operation condition. In the paper the analyses of the torque distribution influence on efficiency and battery power for the proposed structure of electric drive was done. There was proposed the definition of torque distribution based on the required output torque demand. The factors allowing the evaluation of quality torque distribution have been proposed.