A model predictive control scheme for regenerative braking in vehicles with hybridized architectures via aftermarket kits

Regenerative braking is an established technique that can improve the driving range of vehicles with full-electric or hybrid/hybridized powertrain, thus promoting their large-scale adoption. In this paper, the design of an MPC strategy for maximizing regenerative braking in a real vehicle that has been hybridized by means of a kit is presented. The kit is entirely built by the partners of the European Horizon2020 LIFE-SAVE (Solar Aided Vehicle Electrification – LIFE16 ENV/IT/000442) funded project, and features two in-wheel-motors placed on the rear axle, PV panels installed on the roof and the bonnet and a battery pack placed in the trunk. The proposed MPC strategy will serve as a baseline for the implementation of an additional algorithm to the actual version of the hybridized powertrain control such that the new kit will endow the vehicle also with regenerative braking. Since the kit cannot access the vehicle's ECU in order to avoid code infringements, the MPC relies only on information that can be retrieved via the vehicle's CAN. In addition to the maximization of the energy recovery during braking, the proposed strategy considers aspects such as the in-wheel-motors non-ideal efficiency and rated specifications, the constraints given by the brake operating region and possible comfort requirements that have a positive impact on the driver's experience. Furthermore, it also includes a penalty term to force the controller to trade-off with possible high-efficiency operations. The simulation outcomes show the effectiveness of the proposed MPC strategy, enabling the recovery up to approximately 18% of the vehicle's kinetic energy, and suggest that it can be fruitfully used as a baseline for an additional regenerative braking algorithm to be implemented onto the real vehicle.