High-Performance 4WD Electric Powertrain With Flywheel Kinetic Energy Recovery

Four-wheel-drive (4WD) full-electric powertrains offer great potential for vehicle performance and efficiency improvements. This study introduces a novel 4WD electric powertrain that significantly increases the overall powertrain performance and battery lifespan. The proposed powertrain benefits from a new compact and highly efficient flywheel-based kinetic energy recovery system (KERS) that enables us to overcome most of the shortcomings of the conventional battery-based KERS. The utilized KERS is capable of capturing or providing much higher mechanical power than its electrical power ratings. Meaning that, without overloading, the powertrain can capture more mechanical power than traction motors' nominal values. Moreover, since a significant part of the energy exchange takes place in mechanical form, only a portion of the initial kinetic energy (slip energy) needs to be converted into electrical form and be processed electrically. In the proposed powertrain, there is no energy exchange necessary between the battery and the powertrain during each accelerations or braking event, thus also reducing the battery power rating. Mathematical modeling and simulations were performed using space vector modeling method for the proposed powertrain. The results prove the functionality of the proposed 4WD powertrain. Experimental results are also presented for the proof of the concept.