Optimal Electric Vehicle Braking Control for Maximum Energy Regeneration

This paper presents an optimal controller for an electric vehicle’s mechanical braking system to maximize energy regeneration during braking. First an EV powertrain system model is developed using a DC motor, an equivalent circuit battery, and a vehicle dynamics model. An open-loop speed controller is then derived for precise drive cycle tracking. Using the electromechanical DC motor equations, an optimal control policy is developed for motor voltage and the friction brake system to maximize motor power during energy regeneration. Simulation results indicate that the addition of the mechanical brake in an optimal way can improve energy recovery during braking periods. However, the amount of energy recovery is highly dependent on the deceleration rate and the parameters of the electric motor including the back-emf constant and the coil resistance.