On the Comparison of 2- and 4-Wheel-Drive Electric Vehicle Layouts with Central Motors and Single- and 2-Speed Transmission Systems

Abstract

<jats:p>Electric vehicles (EVs) are characterized by a significant variety of possible powertrain configurations, ranging from one to four electric machines, which can have an on-board or in-wheel layout. Multiple models of production EVs have recently been introduced on the market, with 4-wheel-drive (4WD) architectures based on a central motor within each axle, connected to the wheels through a gearbox, a differential, and half-shafts. In parallel, an important body of research and industrial demonstrations have covered the topic of 2-speed transmission systems for EVs, with the target of enhancing longitudinal acceleration and gradeability performance, while increasing the operating efficiency of the electric powertrain. Although several recent studies compare different electric powertrain architectures, to the best of the authors’ knowledge the literature misses a comparison between 2-wheel-drive (2WD) and 4WD configurations for the same EV, from the viewpoint of drivability and energy consumption. This paper targets this gap, by assessing 2WD and 4WD powertrain layouts with central motors, for a case study light passenger car for urban mobility, including consideration of the effect of single- and 2-speed transmission systems. An optimization routine is used to calculate the energy-efficient gear state and/or torque distribution for each considered configuration. For the specific EV, the results highlight the favourable trade-off of the single-speed 4WD layout, capable of reducing the energy consumption during driving cycles by approximately 9% with respect to the conventional 2WD layout with single-speed transmission, while providing satisfactory drivability and good gradeability, especially in low tire–road friction conditions.</jats:p>

Assessment of the Energy Consumption and Drivability Performance of an IPMSM-Driven Electric Vehicle Using Different Buried Magnet Arrangements

“…The case study EV is a light four-wheel-drive electric car, with two identical on-board IPMSMs, one per axle. The four-wheel-drive powertrain layout with central motors is becoming rather common in recent electric vehicles, see [14,43,44], as it conjugates a simple configuration of the individual powertrains (see [45] for an example of powertrain optimization study) with the enhanced performance of a four-wheel-drive system. Each IP-MSM is connected to the two wheels of the axle through a single-speed mechanical transmission with open differential, half-shafts, and constant velocity joints, according to the schematic in Figure 9.…”

Comparison of Energy Consumption of Different Electric Vehicle Power Systems Using Fuzzy Logic-Based Regenerative Braking

“…All-wheel drive (AWD) configurations are quite better than front-wheel drive (FWD) and rear-wheel drive (RWD) configurations in energy-saving comparison because in AWD configurations braking force on both front, and rear axles can be recovered by regenerative braking. Furthermore, FWD configurations are relatively more effective in regenerative braking than RWD configurations because of the location of the vehicle's center of gravity, which is generally close to the front side, and the impact of the inertial force while braking [23,24,25].…”

Comparison on Energy Economy and Vibration Characteristics of Electric and Hydraulic in-Wheel Drive Vehicles

“…Various electric vehicle configurations have been proposed in academia and industry. At the moment, most of the electric vehicles on the market such as Tesla, Mercedez-Benz EQC, Nissan Leaf and BMW i3 are equipped with single gear transmissions owing to the large speed range and low-speed high-torque characteristics of electric motors [1,2]. Some electric vehicles use two motors on the front axle and rear axle respectively to further improve the vehicle dynamic performance [3].…”