Patent ID: 11872894
Assignee: VOLVO CAR CORPORATION
Field: Transport (Mechanical engineering)
Classification: CPC B  Y | IPC B

Claim 6:
7. A method for controlling a drive system of an electric vehicle, the drive system including a front wheel electric motor (EMF) and a rear wheel electric motor (EMR) of the same specification; a front wheel reducer (GF) whose output shaft is operatively coupled to a front wheel drive axle (SF) of the electric vehicle via the front wheel electric motor (EMF); and a rear wheel reducer (GR) whose output shaft is operatively coupled to a rear wheel drive axle (SR) of the electric vehicle via the rear wheel electric motor (EMR), the front wheel reducer (GF) having a transmission ratio different than that of the rear wheel electric motor (EMR), the method comprising:
determining, on the basis of the extent to which an accelerator pedal (AccPed) or a brake pedal (BrkPed) of the electric vehicle is pressed, a total torque (Tdemand) demanded to be exerted on the electric vehicle's wheels for accelerating it or for braking it respectively;
determining a rotating velocity (nF) of the output shaft of the front wheel electric motor (EMF) and a rotating velocity (nR) of the output shaft of the rear wheel electric motor (EMR) respectively on the basis of the vehicle's running velocity in combination of the transmission ratio (rF) of the front wheel reducer (GF) and the transmission ratio (rR) of the rear wheel reducer (GR); and
dividing the total torque (Tdemand) between torque outputs of the front wheel electric motor (EMF) and the rear wheel electric motor (EMR) as a function of the transmission ratio (rF) of the front wheel reducer (GF) and the transmission ratio (rR) of the rear wheel reducer (GR) respectively by a way as follows:
determining, according to a relationship between the electric motor torque, rotating speed and efficiency, combinations of a torque (TEMF) to be exerted or applied by the output shaft of the front wheel electric motor (EMF) and a torque (TEMR) to be exerted or applied by the output shaft of the rear wheel electric motor (EMR) at a given step size;
calculating and summing a power loss of the front wheel electric motor (EMF) and a power loss of the rear wheel electric motor (EMR) with regard to each determined torque combination; and
comparing the summing results for all the torque combinations and finding one torque combination corresponding to the minimum summing result; considering the torque of the one torque combination about the output shaft of the front wheel electric motor (EMF) and the torque of the one torque combination about the output shaft of the rear wheel electric motor (EMR) as a torque to be actually applied by the output shaft of the front wheel electric motor (EMF) and a torque to be actually applied by the output shaft of the rear wheel electric motor (EMR) respectively, and controlling the front wheel electric motor (EMF) and the rear wheel electric motor (EMR) correspondingly;

wherein the transmission ratio (rF) of the front wheel reducer (GF) is less than the transmission ratio (rR) of the rear wheel reducer (GR), thereby minimizing torque output waste.