Optimal Torque Allocation for Energy Efficient Operation of Dual E-Axle Based Powertrain for Heavy Duty Electric Vehicles

Heavy-duty vehicles (i.e. class- 8 trucks) are the backbone of the freight movement in the United States. The electrification of heavy-duty vehicles brings huge benefits in the form of reduced greenhouse Gas (GHG) emissions, reduced annual energy consumption, and annual fuel costs. The efficiency improvement of battery-powered electric trucks will make them more attractive as compared to conventional counterparts. Battery-powered electric trucks have dual e-axle-based powertrains to fulfill the traction power requirements. Currently, the dual e-axle control is based on the even torque split which fails to provide high efficiency at low power requests. This research paper proposes the optimal torque allocation technique for e-axle to minimize traction losses. It leads to a significant improvement in the overall energy efficiency of the powertrain. The optimal torque allocation routine is based on sequential quadratic programming(SQP) with constraints on torque split ratio range, gear number on axles, and battery State of Charge (SOC). The proposed technique is validated and compared with the conventional/even torque split strategy. Results show that energy losses at e-axle are reduced by 6.15% and overall energy efficiency is increased by <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{0. 6 8 2 \%}$</tex>.