Abstract:

The limited torque capacity of the electric motor (EM) is a major concern for regenerative braking systems (RBS). Therefore, several strategies have been designed to coordinate the electric motor (EM) and hydraulic friction brake (HFB). However, these strategies drastically decrease the amount of energy recovered per braking to ensure braking safety and comfort. An optimal control plant was designed to calculate the duty ratio using the mathematical model of the switch-mode architecture. The design inherited from an analogy of the DC-DC booster used a clutch, a torsion spring and a brake actuator to couple the vehicle and the EM. Like for the DC-DC booster, a variating duty ratio was used to modulate the braking torque while optimizing the energy recovered. The model was built in Matlab/Simulink with the algorithm being testified by simulation. The results show a more stable output torque while conserving high regeneration performance.

Key words: electric vehicles (EV), regenerative braking systems (RBS), optimal control