Regenerative braking strategy for hybrid electric vehicles based on regenerative torque optimization control

A regenerative torque distribution (RTD) strategy is proposed to make maximum use of the braking energy to improve fuel economy for hybrid electric vehicles, in which the available regenerative braking force, the demand of the front wheel braking force, and the front wheel lock-up force are all explicitly taken into account. The actual front wheel cylinder pressure, which is reduced by the amount of the actual regenerative braking force, is supplied from the electronic hydraulic brake system. An emulated engine compression braking (EECB) is suggested during coasting, and the electric motor provides a negative torque to emulate the internal combustion engine drag torque to charge the ultracapacitor. In addition, a regenerative torque optimization strategy (RTO) is implemented to maximize the actual electric power recuperated by the ultracapacitor. The simulation results show that both the RTD with RTO and the EECB with RTO are able to offer improved ultracapacitor voltages.