Double-Layer Energy Management for Multi-Motor Electric Vehicles

This paper proposes a double-layer energy management system (EMS) for electric vehicles driven by multiple permanent magnet synchronous motors. The system minimizes energy consumption and ensures safe longitudinal motion. The inner-layer distributes torques and flux currents by minimizing the motor input power. The outer-layer generates the total torque command by controlling the aggregated motor speed via a disturbance observer-based controller. A design condition that sufficiently guarantees the system's L-2 stability is presented. The condition is independent of the torque distribution ratios and can be checked conveniently via passivity notation without linearizing the total system. Various validation tests were performed using a three-wheel recreational electric vehicle (EV) platform. The advantage of the double-layer EMS has been compared with several EMSs proposed recently in the literature. Critical testing scenarios were employed, including sharp change in road friction during high acceleration. Test results reveal that, regardless of such condition, the double-layer EMS can prevent the wheel slip, thereby significantly reducing energy consumption. The New European Driving Cycle test was also conducted to demonstrate the merit of simultaneously optimizing torque distribution ratios and motor flux-currents.