Method for controlling driving force of vehicle

1. A method for controlling driving force of a vehicle, the method comprising:

determining, by a controller, a basic torque command on a basis of vehicle operation information collected while the vehicle is traveling;

obtaining, by the controller, tire vertical load information and vehicle pitch motion information in real time on a basis of information collected from the vehicle while the vehicle is traveling;

determining, by the controller, a final torque command using the determined basic torque command and the obtained tire vertical load information and vehicle pitch motion information; and

controlling, by the controller, a torque output of a driving device configured to drive the vehicle according to the determined final torque command.

2. The method of claim 1 , wherein the determining of the final torque command comprises:

determining, by the controller, a front-wheel torque upper limit value and a rear-wheel torque upper limit value using the tire vertical load information;

determining, by the controller, a front-wheel torque command and a rear-wheel torque command distributed according to a power distribution ratio determined from the basic torque command; and

determining, by the controller, a smaller value of the determined front-wheel torque command and the determined front-wheel torque upper limit value as a final front-wheel torque command for controlling a torque output of a front-wheel driving device, and determining, by the controller, a smaller value of the determined rear-wheel torque command and the determined rear-wheel torque upper limit value as a final rear-wheel torque command for controlling a torque output of a rear-wheel driving device.

3. The method of claim 2 , wherein the tire vertical load information comprises a front-wheel vertical load and a rear-wheel vertical load, and

wherein in the determining of the front-wheel torque command and the rear-wheel torque command, the power distribution ratio is determined to be a ratio of the front-wheel vertical load to the rear-wheel vertical load.

4. The method of claim 2 , wherein in the determining of the front-wheel torque command and the rear-wheel torque command, the power distribution ratio is determined to be a ratio of the determined front-wheel torque upper limit value to the determined rear-wheel torque upper limit value.

5. The method of claim 2 , wherein the tire vertical load information comprises a front-wheel vertical load and a rear-wheel vertical load, and the controller is configured to determine:

the front-wheel torque upper limit value from the front-wheel vertical load and the obtained vehicle pitch motion information; and

the rear-wheel torque upper limit value from the rear-wheel vertical load and the obtained vehicle pitch motion information.

6. The method of claim 5 , wherein the vehicle pitch motion information comprises a vehicle pitch angle that is a pitch direction angle of the vehicle, and a pitch angle change rate that is a rate of change of the vehicle pitch angle,

wherein the front-wheel torque upper limit value and the rear-wheel torque upper limit value are determined by Equations 1 and 2, respectively, below:

Front-wheel torque upper limit=σ1×front-wheel vertical load−σ2×pitch angle−σ3×pitch angle change rate,  [Equation 1]

Rear-wheel torque upper limit=σ1×Rear-wheel vertical load−σ2×Pitch angle−σ3×Pitch angle change rate,  [Equation 2]

wherein σ1 is a parameter value correspondingly determined to a maximum frictional coefficient of a road surface, and σ2 and σ3 are values preset to the controller.

7. The method of claim 1 , wherein the determining of the final torque command comprises:

determining, by the controller, a front-wheel torque command and a rear-wheel torque command distributed according to a power distribution ratio determined from the basic torque command; and

determining, by the controller, a final front-wheel torque command for controlling a torque output of a front-wheel driving device and a final rear-wheel torque command for controlling a torque output of a rear-wheel driving device using the determined front-wheel torque command, the determined rear-wheel torque command, the obtained tire vertical load information, and the obtained vehicle pitch motion information.

8. The method of claim 7 , wherein the tire vertical load information comprises a front-wheel vertical load and a rear-wheel vertical load,

wherein in the determining of the front-wheel torque command and the rear-wheel torque command, the power distribution ratio is determined to be a ratio of the front-wheel vertical load to the rear-wheel vertical load.

9. The method of claim 7 , wherein the tire vertical load information comprises a front-wheel vertical load and a rear-wheel vertical load,

wherein the vehicle pitch motion information comprises a vehicle pitch angle that is a pitch direction angle of the vehicle, and a pitch angle change rate that is a rate of change of the vehicle pitch angle, and

wherein the final front-wheel torque command and the final rear-wheel torque command are determined by Equations 3 and 4, respectively, below:

Final front-wheel torque command=Front-wheel torque command before correction+σ1×(Basic front-wheel vertical load−Current front-wheel vertical load)−σ2×Pitch angle−σ3×Pitch angle change rate,  [Equation 3]

Final rear-wheel torque command after correction=Rear-wheel torque command before correction+σ1×(Basic rear-wheel vertical load−Current rear-wheel vertical load)−σ2×Pitch angle−σ3×Pitch angle change rate,  [Equation 4]

wherein σ1 is a parameter value correspondingly determined to a maximum frictional coefficient of a road surface, and σ2, σ3, the basic front-wheel vertical load, and the basic rear-wheel vertical load are values preset to the controller.

10. The method of claim 1 , wherein the determining of the final torque command comprises:

determining, by the controller, a front-wheel torque upper limit value and a rear-wheel torque upper limit value using the tire vertical load information;

determining, by the controller, a front-wheel torque command and a rear-wheel torque command distributed according to a power distribution ratio determined from the basic torque command;

determining, by the controller, a smaller value of the determined front-wheel torque command and the determined front-wheel torque upper limit value as a front-wheel torque command before correction, and determining, by the controller, a smaller value of the determined rear-wheel torque command and the determined rear-wheel torque upper limit value as a rear-wheel torque before correction; and

determining, by the controller, a final front-wheel torque command for controlling a torque output of a front-wheel driving device and a final rear-wheel torque command for controlling a torque output of a rear-wheel driving device by using the determined front-wheel torque command before correction, the determined rear-wheel torque command before correction, the obtained tire vertical load information, and the obtained vehicle pitch motion information.

11. The method of claim 10 , wherein, in the controller, the front-wheel torque upper limit value and the rear-wheel torque upper limit value are determined by Equations 5 and 6, respectively, below:

Front-wheel torque upper limit=σ1×front-wheel vertical load,  [Equation 5]

Rear-wheel torque upper limit=σ1×rear-wheel vertical load,  [Equation 6]

wherein σ1 is a parameter value correspondingly determined to a maximum frictional coefficient of a road surface.

12. The method of claim 10 , wherein the tire vertical load information comprises a front-wheel vertical load and a rear-wheel vertical load,

wherein the vehicle pitch motion information comprises a vehicle pitch angle that is a pitch direction angle of the vehicle, and a pitch angle change rate that is a rate of change of the vehicle pitch angle, and

wherein the final front-wheel torque command and the final rear-wheel torque command are determined by Equations 7 and 8, respectively, below:

Final front-wheel torque command=Front-wheel torque command after applying the torque upper limit of Equation 5−σ2×Pitch angle−σ3×Pitch angle change rate,  [Equation 7]

Final rear-wheel torque command=Rear-wheel torque command after applying the torque upper limit of Equation 6−σ2×Pitch angle−σ3×Pitch angle change rate,  [Equation 8]

wherein σ1 is a parameter value as determined according to a maximum frictional coefficient of a road surface, and σ2 and σ3 are values preset to the controller.

13. The method of claim 1 , wherein the vehicle pitch motion information comprises a vehicle pitch angle that is a pitch direction angle of the vehicle and a pitch angle change rate that is a rate of change of the vehicle pitch angle.

14. The method of claim 13 , wherein the vehicle pitch angle is a suspension pitch angle that is an angle in the vehicle pitch direction according to strokes of a front-wheel suspension and a rear-wheel suspension.

15. The method of claim 1 , wherein, the obtaining of the tire vertical load information and the vehicle pitch motion information in real time includes obtaining, by a transfer function preset to the controller, the tire vertical load information and the vehicle pitch motion information, wherein the transfer function uses the information collected from the vehicle as input.

16. The method of claim 1 , wherein the determining of the final torque command comprises:

determining, by the controller, a driving wheel torque upper limit value using tire vertical load information of a driving wheel that is any one of a front-wheel and a rear-wheel of the vehicle;

comparing, by the controller, the determined basic torque command and the determined driving wheel torque upper limit value; and

determining, by the controller, the basic torque command as the final torque command when the basic torque command is no greater than the driving wheel torque upper limit value, and determining, by the controller, the driving wheel torque upper limit value as the final torque command when the basic torque command exceeds the driving wheel torque upper limit value.