Comparison of regenerative braking capacity for an independent-axle all-wheel-drive electric vehicle using different torque distribution strategies

This work examines the regenerative braking capacity using different torque distribution strategies for an independent-axle all-wheel-drive electric vehicle. A single-motor rear-wheel drive Cadillac LYRIQ provided by General Motors and modeled by MathWorks is being modified into an all-wheel drive architecture. The architecture under study has independently driven front and rear axles, driven by a 50 kW (peak power) front motor and a 182 kW (peak power at 350V) rear motor. The goal of the study is to evaluate and compare the regenerative braking capacity for different regenerative braking strategies. This study aims to assist in the development of the energy management algorithm for the Propulsion Supervisory Controller (PSC). Firstly, two variants of optimal regenerative torque distribution strategies are studied. One without power rate penalties and the other with a power rate penalty. Secondly, a torque-assist strategy is assessed, wherein the rear motor only contributes to the total regenerative braking torque when the full regenerative braking capacity of the front motor is already being used. In the case of forward torque, the front motor only contributes to the total torque command, when the rear motor is already using its full capacity in the forward direction. Thirdly, a fixed ratio strategy is studied. In this, both axles contribute with a fixed torque ratio, which for forward torque, is calculated based on the maximum total forward torque capacity available, and for braking, is calculated based on the ideal braking curve for the vehicle. The results can be used to assess whether it would be worth using a computationally heavier optimal regenerative braking torque split strategy as compared to using a simpler fixed-ratio strategy.