A Smart Torque Control for a High Efficiency 4WD Electric Vehicle.

At the state-of-the-art, electric propulsion systems based on hub-motors allow mechanical components to be removed, increasing also the vehicle stability. However, since motors and wheels are directly coupled, when a high propulsion torque is delivered, in such a configuration the motors could work in low efficiency operative points, negatively affecting the vehicle consumptions. In this paper, a torque distribution strategy is defined to minimize these consumptions. The propulsion configuration under investigation is a four-wheel drive that adopts two different couples of Brushless DC (BLDC) hub motors. The proposed research highlights how the electric efficiency is improved when the propulsion torque required by the vehicle is delivered by the BLDCs in an asymmetric way, according to the motors operative conditions. Since this torque repartition dynamically changes while the vehicle is running, the effects on the vehicle stability are also evaluated. Such an analysis is performed considering, as reference, a Class A vehicle, principally designed for the urban mobility.