Comparison of torque-split strategies for an independent axle, dual-motor all-wheel drive electric vehicle

In this study, torque distribution strategies for a modified all-electric Cadillac LYRIQ SUV are investigated. The base vehicle, provided by General Motors and modeled by MathWorks, is being modified into a dual-motor, all-wheel drive architecture including a main rear motor and a smaller front motor. The objective is to assess and compare three distinct torque-split strategies. This will support development of the energy management system software on the Propulsion Supervisory Controller (PSC) for the vehicle. Firstly, an optimal strategy with and without power-rate penalties is explored, which distributes the torque request to minimize the total energy consumption (losses) in both motors. Secondly, a fixed-ratio strategy is considered where both axles contribute with predetermined torque ratios to meet the total torque demand. Thirdly, a torque-assist approach is examined, wherein the front motor contributes to the total torque request, only after the rear motor reaches instantaneous peak torque, i.e., the accelerator pedal input crosses a certain threshold. This study gives an insight into the feasibility of deploying sophisticated computational algorithms in the propulsion controller for enhanced efficiency. The optimal strategy reduces energy consumption by 1 kWh/100-miles as compared to the fixed ratio strategy for the Urban Dynamometer Driving Schedule (UDDS).