Role of Regenerative Braking in Velocity Trajectory Optimization of Electrified Powertrains over varying Road Grades

Abstract

Eco-driving via velocity trajectory optimization and regenerative braking can both reduce the energy demand of an electric vehicle (EV). However, eco-driving can save more energy than can be recovered via regenerative braking due to the total roundtrip efficiency of the motor/generator. The optimal velocity trajectory would always avoid braking if the constraints allow. This paper investigates energy optimal velocity profiles for various electric ground vehicles over varying road grades, where the autonomous vehicles can adjust their velocity trajectory. The optimal velocity trajectories, numerically obtained from Dynamic Programming, significantly reduce the total energy demand by the motor compared to a constant cruising operation for the same travel distance and time. The optimized velocity trajectories, thus increase vehicle range without a change in battery size or trip time.