Method for electric vehicle simulating combustion engine braking

1 . A motor-vehicle, comprising:

a first and a second wheel forming a first axle of said motor-vehicle arranged at a rear of the motor vehicle in use;

a third and a fourth wheel forming a second axle of said motor-vehicle arranged at a front of the motor vehicle in use;

a first and a second electric machine reversible and operatively connected respectively with said first and second wheels;

a third and a fourth electric machine reversible and operatively connected respectively with said third and fourth wheels; and

an electrical power source that is rechargeable and electrically connected with said first, second, third and fourth electric machines;

each of said first, second, third and fourth electric machines being actuatable as an electric motor to exert respectively a first and second, third and fourth driving torque respectively on said first, second, third and fourth wheels, and as an electric generator to use at least a portion of the kinetic energies of respective said first and second, third and fourth wheels and to generate an electrical current that recharges, in use, said electrical power source;

said motor-vehicle further comprising:

a first accelerator command actuatable by a driver to request an acceleration of said motor-vehicle;

a second brake command actuatable by a driver to request a deceleration of said motor-vehicle;

a control unit programmed, upon a release of said first command, to:

process values of a first, second, third and fourth electrical power available for a regenerative simulation of an engine brake for respective said first, second, third and fourth electric machines based on an amount of electrical power still storable in said electrical power source and first operating parameters (of said motor-vehicle;

communicate said first, second, third, and fourth electrical power available for the regenerative simulation to the respective said first, second, third and fourth electric machines and receive from said first, second, third and fourth electric machines respective values of a first, second, third and fourth available torque for the regenerative simulation of said engine brake associated with second operating parameters of respective said first, second, third and fourth electric machines themselves;

process a first, second, third and fourth torque to be implemented for the regenerative simulation of the engine brake for the respective first, second, third and fourth electric machines;

each said first, second, third and fourth torque to be implemented for the respective first, second, third and fourth electric machines being associated with corresponding said values of the first, second, third and fourth available torque for the regenerative simulation of said engine brake;

wherein said control unit is further programmed to:

store a table that associates a target torque that simulates the effect of the engine brake with a forward speed of said motor-vehicle;

distribute said target torque over said first, second, third and fourth electric machines, so as to process respective first, second, third and fourth target torques; and

process said first, second, third and fourth torques to be implemented as a minimum value between absolute values of each said first, second, third and fourth target torques and the corresponding said first, second, third and fourth available torques for the regenerative simulation of said engine brake.

2 . The motor-vehicle according to claim 1 , wherein said control unit is further programmed to:

communicate said first, second, third and fourth torques to be implemented to the respective said first, second, third and fourth electric machines;

receive from said first, second, third and fourth electric machines the respective first, second, third and fourth electrical power to be regenerated;

process values of said third and fourth electrical power available for the regenerative braking for said third and fourth electric machines, based also on a sum of said first and second electrical power regenerated) by the respective said first and second electric machines the regenerative simulation of said engine brake.

3 . The motor-vehicle according to claim 2 , wherein said control unit is further programmed, upon actuating a second command, to:

process a sum of the first, second, third and fourth electrical power regenerated by said first, second, third and fourth electric machines for the regenerative simulation of said engine brake; and

process values of a seventh and eighth available electrical power for the regenerative braking for respective said third and fourth electric machines based on the amount of electrical power still storable in said electrical power source, of third operating parameters of said motor-vehicle and of said sum of said first, second, third and fourth electrical power regenerated by said first, second, third and fourth electric machines for the regenerative simulation of said engine brake.

4 . The motor-vehicle according to claim 3 , wherein said control unit is programmed to:

receive a current value of a sum of the third and fourth electrical power implemented by said third and fourth electric machines; and

process the values of a fifth and sixth electrical power available for the regenerative braking for respective said first, second electric machines, based on the amount of electrical power still storable in said electrical power source, of said sum of said third and fourth electrical power implemented by said third and fourth electric machines, and of the sum of the first, second, third and fourth power regenerated by said first, second, third and fourth electric machines the regenerative simulation of said engine brake.

5 . The motor-vehicle according to claim 4 , wherein said first, second, third and fourth electric machines are programmed to:

receive from said control unit, at input, respective said fifth, sixth, seventh and eighth electrical power available for the regenerative braking;

process a first and second available torque for the regenerative braking, based on the respective said fifth and sixth electrical power and said second operating parameters of said first and second electric machines;

process a third and a fourth available torque for the regenerative braking, based on respective said seventh and eighth electrical power and said second operating parameters of said third and fourth second electric machines;

process a first maximum regenerable torque for said first axle, based at least on said amount of electrical power still storable in said electrical power source, and on an angular velocity and an electromechanical efficiency of said first and second electric machines;

process a second maximum regenerable torque for said second axle, based at least on said amount of electrical power still storable in said electrical power source, and on an angular velocity and an electromechanical efficiency of said third and fourth electric machines;

process a first maximum regenerable torque for said first axle as the minimum value between the absolute values of:

said first available torque for the regenerative braking for said first axle equal to the sum of said first and second available torques for the regenerative braking, and

the difference between a maximum torque regenerated at said first axle for said first axle and a sum of said first and second torques to be implemented for the regenerative simulation of said engine brake; and

process a second maximum regenerable torque for said second axle as the minimum value between the absolute values of:

said second available torque for the regenerative braking for said second axle (equal to the sum of said third and a fourth available torque for the regenerative braking, and

the difference between said second maximum available torque for the regenerative braking for said second axle and a sum of said third and fourth regenerated torques for the regenerative simulation of said engine brake.

6 . The motor-vehicle according to claim 5 , further comprising:

a braking device adapted to exert a braking torque by friction on said first, second, third and fourth wheels;

a brake control unit programmed, in the case of activation of said second command, to:

receive said first maximum regenerable torque for the regenerative braking by said first and second electric machines and said second maximum regenerative torque for the regenerative braking by said third and fourth electric machines;

process a fifth and a sixth torque implemented for the regenerative braking for the respective said first and second electric machines, based on said first maximum regenerable torque for the regenerative braking;

process a seventh and eighth torque implemented for the regenerative braking for the respective third and fourth electric machines, based on said second maximum regenerable torque for the regenerative braking;

communicate said fifth, sixth, seventh, and eighth torques to be implemented for the regenerative braking to said control unit; and

process a braking torque value for said braking device based on said command set, in use, on said second pedal and said first, second, third, fourth, fifth, sixth, seventh and eighth torque values implemented for said regenerative braking.

7 . The motor-vehicle according to claim 6 , wherein said control unit is further programmed to command:

said first electric machine to sum said first torque to be implemented for the simulation of said engine brake and the fifth torque to be implemented for the regenerative braking;

said second electric machine to sum said second torque to be implemented for the simulation of said engine brake and the sixth torque to be implemented for the regenerative braking;

said third electric machine to sum said third torque to be implemented for the simulation of said engine brake and said seventh torque to be implemented for the regenerative braking; and

said fourth electric machine to implement said fourth torque to be implemented for the simulation of said engine brake and said eighth torque to be implemented for the regenerative braking.

8 . The motor-vehicle according to claim 1 , wherein the motor vehicle is without a heat engine.

9 . A method to control a first, second, third and fourth reversible electric machine of a motor-vehicle, comprising:

store a table that associates a target torque that simulates the effect of the engine brake with a forward speed of said motor-vehicle;

operatively connecting a first and a second electric machine respectively with a first and a second wheel of said motor-vehicle forming a first axle of said motor-vehicle arranged at a rear of the motor vehicle in use;

operatively connecting a third and a fourth electric machine respectively with a third and a fourth wheel of said motor-vehicle forming a second axle of said motor-vehicle arranged at a front of the motor vehicle in use;

electrically connecting a rechargeable electrical power source electrically connected with said first, second, third and fourth electric machines;

operating each said first, second, third and fourth electric machines as an electric motor to exert respectively a first and second, third and fourth driving torque respectively on said first, second, third and fourth wheels, in the case of actuating a first accelerator command of said motor-vehicle;

operating each said first, second, third and fourth electric machines as an electric generator to use at least a portion of the kinetic energies of respective said first, second, third and fourth wheels and to generate an electrical current that recharges, in use, said rechargeable electrical power source, upon actuating a second brake command of said motor-vehicle;

wherein the method further comprises, upon release of said first command, of:

processing values of a first, second, third and fourth electrical power available for a regenerative simulation of an engine brake for respective said first, second, third and fourth electric machines based on an amount of electrical power still storable in said rechargeable electrical power source and first operating parameters of said motor-vehicle, upon release of said first command;

communicate said first, second, third and fourth electrical power available for the regenerative simulation to the respective said first, second, third and fourth electric machines and receive from said first, second, third and fourth electric machines respective values of a first, second, third and fourth available torque for the regenerative simulation of said engine brake associated with second operating parameters of respective said first, second, third and fourth electric machines themselves; and

distribute said target torque over said first, second, third and fourth electric machines, so as to process respective first, second, third and fourth target torques; and

process a first, second, third and fourth torque to be implemented for the regenerative simulation of the engine brake for the respective first, second, third and fourth electric machines;

wherein said first, second, third and fourth torques are to be implemented as a minimum value between absolute values of each said first, second, third and fourth target torques and the corresponding said first, second, third and fourth available torques for the regenerative simulation of said engine brake;

each said first, second, third and fourth torque to be implemented for the respective first, second, third and fourth electric machines being associated with the corresponding said first, second, third and fourth available torque values for the regenerative simulation of said engine brake.