System and method for controlling creep torque of an electric vehicle

1. A method for controlling creep torque of an electric vehicle, wherein a vehicle control unit controls a motor by calculating creep torque needed by the electric vehicle, and the method comprises the following steps:

1) reading a creep torque base value T q— creep_base of the electric vehicle;

2) reading an acceleration parameter and a basic information parameter of the electric vehicle and determining by calculation a creep torque slope resistance compensation value T q— slope of the electric vehicle according to the acceleration parameter and the basic information parameter;

3) determining a raw creep torque value T q— creep_raw according to the creep torque base value T q— creep_base read in step 1) and the creep torque slope resistance compensation value T q— slope determined in step 2);

4) reading a current gear of the electric vehicle and determining by calculation a creep torque compensation resistance value T q— creep_temp of the electric vehicle according to the gear; and

5) determining, according to the raw creep torque value T q— creep_raw determined in step 3) and the creep torque compensation resistance value T q— creep_temp determined in step 4), a creep torque T q— creep needed by the electric vehicle.

2. The method for controlling creep torque of an electric vehicle according to claim 1 , wherein step 2) further comprises the steps of:

21) reading the acceleration parameter and the basic information parameter of the electric vehicle and determining by calculation a raw creep torque slope resistance compensation value T q— slope_raw of the electric vehicle; and

22) performing linear attenuation on the raw creep torque slope resistance compensation value T q— slope_raw determined in step 21), to determine the creep torque slope resistance compensation value T q— slope.

3. The method for controlling creep torque of an electric vehicle according to claim 2 , wherein step 21) further comprises the steps of:

211) reading the acceleration parameter of the electric vehicle and determining by calculation a gravitational acceleration component Acc_g of the electric vehicle; and

212) reading the basic information parameter of the electric vehicle, and determining by calculation the raw creep torque slope resistance compensation value T q— slope_raw with reference to a gravitational acceleration component Acc_g of the electric vehicle determined in step 211).

4. The method for controlling creep torque of an electric vehicle according to claim 3 , wherein the acceleration parameter comprises an vehicle longitudinal acceleration sensor signal Acc_1gt and a wheel acceleration Acc_wheel, and the basic information parameter comprises a complete vehicle curb mass Mass_veh and a tire rolling radius R_tire.

5. The method for controlling creep torque of an electric vehicle according to claim 4 , wherein the gravitational acceleration component Acc_g is specifically:

Acc_ g =Acc_1 gt −Acc_wheel.

6. The method for controlling creep torque of an electric vehicle according to claim 4 , wherein the raw creep torque slope resistance compensation value T q— slope_raw is:

T q— slope_raw=Mass_ veh ×Acc_ g/R _tire.

7. The method for controlling creep torque of an electric vehicle according to claim 1 , further comprising the step of the determining creep torque compensation resistance value T q— creep_temp of the electric vehicle according to the motor reverse rotation speed.

8. The method for controlling creep torque of an electric vehicle according to claim 1 , wherein step 4) further comprises the steps of:

42) calculating, according to the current gear of the electric vehicle, a motor reverse rotation speed relative to a drive gear when the electric vehicle is in a creep working condition; and

43) determining the creep torque compensation resistance value T q— creep_temp of the electric vehicle according to the motor reverse rotation speed.

9. The method for controlling creep torque of an electric vehicle according to claim 1 , wherein step 5) further comprises the step of superposing the raw creep torque value T q— creep_raw determined in step 3) and the creep torque compensation resistance value T q— creep_temp determined in step 4), to determine the creep torque T q— creep needed by the electric vehicle.

10. A system for controlling creep torque of an electric vehicle, the system comprising:

a vehicle control unit;

an electrical motor in communication with the vehicle control unit, the vehicle control unit configured to control the electrical motor;

an accelerometer in communication with the vehicle control unit, the accelerometer configured to measure the lateral acceleration of the electric vehicle;

wherein the vehicle control unit is configured to:

1) read a creep torque base value T q— creep_base of the electric vehicle;

2) read an acceleration parameter and a basic information parameter of the electric vehicle and determining by calculation a creep torque slope resistance compensation value T q— slope of the electric vehicle according to the acceleration parameter and the basic information parameter;

3) determine a raw creep torque value T q— creep_raw according to the creep torque base value T q— creep_base read in step 1) and the creep torque slope resistance compensation value T q— slope determined in step 2);

4) read a current gear of the electric vehicle and determining by calculation a creep torque compensation resistance value T q— creep_temp of the electric vehicle according to the gear; and

5) determine, according to the raw creep torque value T q— creep_raw determined in step 3) and the creep torque compensation resistance value T q— creep_temp determined in step 4), a creep torque T q— creep needed by the electric vehicle.

11. The system for controlling creep torque of an electric vehicle of claim 10 , wherein the vehicle control unit is further configured to:

21) read the acceleration parameter and the basic information parameter of the electric vehicle and determining by calculation a raw creep torque slope resistance compensation value T q— slope_raw of the electric vehicle; and

22) perform linear attenuation on the raw creep torque slope resistance compensation value T q— slope_raw determined in step 21), to determine the creep torque slope resistance compensation value T q— slope.

12. The system for controlling creep torque of an electric vehicle according to claim 11 , wherein the vehicle control unit is further configured to:

211) read the acceleration parameter of the electric vehicle and determining by calculation a gravitational acceleration component Acc_g of the electric vehicle; and

212) read the basic information parameter of the electric vehicle, and determining by calculation the raw creep torque slope resistance compensation T q— slope_raw value q with reference to a gravitational acceleration component Acc_g of the electric vehicle determined in step 211).

13. The system for controlling creep torque of an electric vehicle according to claim 12 , wherein the acceleration parameter comprises a vehicle longitudinal acceleration sensor signal Acc_1gt and a wheel acceleration Acc_wheel, and the basic information parameter comprises a complete vehicle curb mass Mass_veh and a tire rolling radius R_tire.

14. The system for controlling creep torque of an electric vehicle according to claim 13 , wherein the gravitational acceleration component Acc_g is specifically:

Acc_ g =Acc_1 gt −Acc_wheel.

15. The system for controlling creep torque of an electric vehicle according to claim 13 , wherein the raw creep torque slope resistance compensation value T q— slope_raw is:

T q— slope_raw=Mass_ veh ×Acc_ g/R _tire.

16. The system for controlling creep torque of an electric vehicle according to claim 10 , wherein the vehicle control unit is further configured to determine the creep torque compensation resistance value T q— creep_temp of the electric vehicle according to the motor reverse rotation speed.

17. The system for controlling creep torque of an electric vehicle according to claim 10 , wherein the vehicle control unit is further configured to:

42) calculate, according to the current gear of the vehicle, a motor reverse rotation speed relative to a drive gear when the electric vehicle is in a creep working condition; and

43) determine the creep torque compensation resistance value T q— creep_temp of the electric vehicle according to the motor reverse rotation speed.

18. The system for controlling creep torque of an electric vehicle according to claim 10 , wherein the vehicle control unit is further configured to superpose the raw creep torque value T q— creep_raw determined in step 3) and the creep torque compensation resistance value T q— creep_temp determined in step 4), to determine the creep torque T q— creep needed by the electric vehicle.