Energy-Efficient Straight-Line Driving Torque Vectoring for Electric Vehicles with Disconnect Clutches and Unequal Front/Rear Motors

This paper investigates potential of energy efficiency improvement for electric vehicle (EV) equipped with unequal front/rear-axle e-motors and disconnect clutches under straight-line driving conditions. First, a static optimization of front/rear torque distribution is performed for various driving cycles, which provides insights into energy efficiency gains and optimal powertrain operation including optimal torque switching curve for two- and four-wheel drive modes. Disconnect clutches enable inactive motors to be switched off when operating in the 2WD mode to avoid their drag losses. A dynamic programming (DP)-based optimization of torque vectoring control trajectories is carried out to find the globally optimal energy saving potential. For clutch durability reasons, the number of clutch state changes is minimized along with energy consumption. Finally, a rule-based (RB) control strategy is proposed and verified against the DP Pareto optimal frontier benchmark for different certification driving cycles.