Abstract
Battery electric vehicles (BEVs) represent a possible sustainable solution for personal urban transportation. Presently, the most limiting characteristic of BEVs is their short range, mainly because of battery technology limitations. A proper design and control of the drivetrain, aimed at reducing the power losses and thus increasing BEV range, can contribute to make the electrification of urban transportation a convenient choice. This paper presents a simulation-based comparison of the energy efficiency performance of six drivetrain architectures for BEVs. Although many different drivetrain and transmission architectures have been proposed for BEVs, no literature was found regarding BEVs equipped with infinitely variable transmissions (IVTs). The analyzed drivetrain configurations are: single- (1G) and two-speed (2G) gear drives, half toroidal (HT) and full toroidal (FT) continuously variable transmissions (CVTs), and infinitely variable transmissions (IVTs) with two different types of internal power flow (IVT-I and IVT-II). An off-line procedure for determining the most efficient control action for each drivetrain configuration is proposed, which allows selecting the optimal speed ratio for each operating condition. The energy consumption of the BEVs is simulated along the UDC (Urban Driving Cycle) and Japanese 10-15 driving cycle, with a backward facing approach. In order to achieve the lowest energy consumption, a trade-off between high transmission efficiency and flexibility in terms of allowed speed ratios is required.
Highlights
Hybrid electric vehicles (HEVs) and battery electric vehicles (BEVs) are emerging as feasible solutions, especially for urban mobility, because of their environmental performance, including zero emission driving
The aim of this work is to compare the energy consumption of an urban battery electric vehicle equipped with different transmission layouts: single-speed (1G), two-speed (2G), half toroidal continuously variable transmissions (CVTs) (HT), full toroidal CVT (FT), series-infinitely variable transmissions (IVTs) with Type I power flow (IVT-I) [25], and parallel-IVT with Type II
For each of the analyzed variable speed transmissions, optimal gear selection maps were calculated by taking into account the efficiency of the electric motor and the transmission, and defining the optimal speed ratio for all the operating points of the drivetrain
Summary
Hybrid electric vehicles (HEVs) and battery electric vehicles (BEVs) are emerging as feasible solutions, especially for urban mobility, because of their environmental performance, including zero emission driving. HEVs and BEVs are characterized by different architectures according to the transmission system layout and number of propulsion units [1,2,3] Both HEVs and BEVs use electric motors (EMs) as primary or secondary sources of mechanical power. At the moment EMs for BEVs are usually coupled with single-speed transmissions even if this configuration constrains their performance, especially in case of electric motors characterized by a limited speed range. For this reason automotive research is moving towards transmission systems that can improve EM performance in HEVs and BEVs [5]
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