Regenerative Braking Control with Gear Downshifting for Energy Efficiency and Motion Stability Improvement of an Electrical-four-wheel-drive Hybrid Vehicle

A regenerative braking control strategy is proposed for an electrical-four-wheel-drive (e-4WD) hybrid vehicle. The e-4WD powertrain consists of an engine, a motor/generator (MG), and an automatic transmission (AT) on the front axle, and two in-wheel motors (IWMs) on the rear axle. Pure regenerative braking with the MG and two IWMs is focused in this article, which is very common in mild braking scenario. Energy efficiency and vehicle motion stability are both considered in the design of the braking control strategy. With quadratic programming (QP)-based control allocation algorithm, downshifting decision of the AT is coordinated with the torque allocation of the MG and two IWMs, achieving high regenerative energy efficiency as well as good vehicle motion dynamics. Co-simulations with Matlab/Simulink® and CarSim® show the effectiveness of the proposed algorithm.