Vehicle braking strategies based on regenerative braking boundaries of electric machines

Electric and hybrid-electric vehicles are capable of providing electrical braking to assist mechanical brakes during a braking event. Braking strategies can be formulated to dictate the manner in which the braking effort is shared between the electrical and mechanical brakes. Electrical braking capability is identified by regions in the braking quadrants of an electric machine´s torque-speed plane, and these capability regions may be further subdivided into regenerative and non-regenerative braking regions. Regenerative electrical braking adds energy to the energy storage system, whereas non-regenerative electrical braking subtracts energy from the energy storage system. This paper uses the concept of regenerative braking boundaries to define braking strategies that avoid operation in non-regenerative braking regions so as to recover as much electrical energy as possible during braking events.