An Energy Saving Strategy of Torque and Battery Distribution for an Electric Vehicle Driven by Multiple Traction Motors

This paper proposes an energy saving strategy of torque and battery distribution (TBD) for an electric vehicle (EV). This EV is driven by three traction motors: one 15 kW motor drives front wheels indirectly through reduction gears, and two 7 kW in-wheel motors are directly installed inside both rear wheels. Each traction motor has independent motor drive and battery pack. Once the driver accelerates the vehicle, the best torque distribution among the three motors is determined by Particle Swarm Optimization (PSO) theory for minimizing energy consumption according to the torque-speed-efficiency (TNE) maps of the three traction motors. At the same time, the States of Charge (SOC) of the three battery packs are kept in balance to avoid unexpected battery depletion and to improve the driving range of the EV. Compared with the energy saving strategy by PSO without charge balancing in simulations, the proposed TBD strategy improved the driving range by 27.9% for the straight-line New European Driving Cycle (NEDC) and 7.67% for the cornering NEDC along a circle of 100-m radius, while the batteries' SOC gaps were maintained within a prescribed limit. At this, all the battery energy can be effectively used for extending driving range with an energy consumption efficiency of 99.5%. The proposed TBD is promising for energy economy of the EVs with multiple traction motors and batteries. © 2019 IEEE.