Efficient Power-Split Powertrain for Full Electric Vehicles

Abstract

Electric vehicles are typically employed in highly-variable operating conditions, especially during city drive. The variability in speed and torque results in suboptimal efficiency of the drive motor. However, recent technological advances in new embedded processing units and power electronics open the way to the adoption of novel efficient control strategies of the electric powertrain. This paper proposes an architecture that in contrast to the use of a single drive electric motor employs two drive motors of smaller size combined through a planetary gear. This power-split full-electric architecture ensures both drive motors to operate in their optimal working range resulting in a higher overall efficiency. A parametric optimization is performed showing an increase in the average efficiency of about 7% with respect to a single motor for the Artemis urban cycle.

Power-Flow and Mechanical Efficiency Computation in Two-Degrees-of-Freedom Planetary Gear Units: New Compact Formulas

“…Its capability of managing power flows from different sources is of paramount importance for energy saving. For these reasons, the mechanical efficiency of planetary multi degrees-offreedom planetary gear trains is a topic that received many contributions in recent times (e.g., [1][2][3][4][5][6][7][8][9][10][11][12][13][14]).…”

Dual-Motor Planetary Transmission to Improve Efficiency in Electric Vehicles

“…The main contributions of this research are: (i) evaluation of the increase in the energy efficiency of the proposed powertrain over different standard drive cycles; (ii) definition of the optimal nominal requirements of the planetary gear and electric motors; (iii) a control strategy to set the operating condition of the two electric motors in order to maximize the efficiency of the powertrain. While the idea of a dual-motor multispeed powertrain was preliminarily introduced in [21], this paper represents a substantial extension that introduces a discussion on: (a) system operations during regeneration stages; (b) the adoption of two different configurations of planetary gear that use a single-planet and a double-planet set; (c) the mechanical efficiency of the planetary gear that is explicitly modeled; (d) the performance evaluation of the powertrain for different standard driving cycles; (e) the optimal control strategy for the dual-motor planetary coupling based on a genetic algorithm. As a final remark, it should be noted that today many hybrid vehicles use a planetary gear transmission.…”