Optimized Torque Path Control for Energy Efficiency in Electric Vehicles

This paper presents a comparative analysis of three torque distribution strategies for a dual-motor all-wheel drive (AWD) battery electric vehicle: 50/50 axle torque split between the front and rear axle, front-wheel drive only with rear axle disengaged, and a proposed minimizing-losses torque optimization strategy with active Rear Axle Disconnect (RAD). Developed as part of the EcoCAR EV Challenge, this study aims to maximize energy efficiency without compromising performance. A cost-function-based control strategy was designed to minimize combined electric machine (EM) and drivetrain losses. The minimizing-losses strategy leverages the dynamic engagement and disengagement of the RAD on this architecture with different gear reductions on the axles to optimize efficiency. It also offers better acceleration performance than FWD-only by engaging the rear axle during high-torque demands. Results show that demandbased rear axle engagement delivers the best balance of efficiency and performance. Simulation results, validated by vehicle-in-theloop testing, show that the minimizing-losses strategy reduces energy use by over 8% compared to 50/50 split strategy.