System and method for correcting friction coefficient of brake pad for vehicle

1. A system for correcting a friction coefficient of a brake pad for a vehicle, comprising:

a brake controller;

a G sensor for inputting a deceleration signal to the brake controller;

a wheel speed sensor for inputting a wheel speed signal to the brake controller;

a wheel pressure sensor for inputting a wheel pressure signal to the brake controller at braking; and

an upper level controller for inputting regenerative braking torque and coasting traveling braking torque signals to the brake controller,

wherein the brake controller is configured to:

determine an activation condition for estimating a brake factor;

estimate the brake factor, when the brake factor estimation activation condition is satisfied;

calculate a brake factor offset by operating a difference in value between the estimated brake factor and a previous brake factor;

update the previous brake factor with the calculated brake factor offset; and

correct the friction coefficient of the brake pad based on the updated brake factor offset.

2. The system of claim 1 ,

wherein the brake controller determines that the activation condition for estimating the brake factor is satisfied when a driver request braking torque, a wheel speed, a wheel pressure, a regenerative braking torque, and a regenerative braking torque slope are equal to or greater than a reference value, respectively.

3. The system of claim 1 ,

wherein the brake controller estimates the brake factor in a manner of inversely calculating braking force and wheel dynamics, or estimates the brake factor by using a Kalman filter and the wheel dynamics,

wherein the brake controller estimates the brake factor by

C

p

=

-

J

·

dw

dt

+

r

×

F

b

-

T

reg

P

wheel

,

and

wherein Cp: the estimated brake factor,

-

J

·

dw

dt

:

an inertia torque, r: an effective radius, which is the distance from the wheel center to the point where the brake pad contacts a disk, Fb: the braking force generated by the brake pad contacting the disk, r×Fb: the braking force torque, Treg: the regenerative braking torque, and Pwheel: the wheel pressure.

4. The system of claim 1 ,

wherein the brake controller calculates the brake factor offset by a difference between the estimated brake factor and the previous brake factor,

wherein the brake controller determines that convergence of the brake factor offset has been completed when the calculated brake factor offset falls within a certain range for a certain time, and

wherein, when the brake factor offset of which the convergence has been completed is equal to or greater than a reference value, the brake controller decides the brake factor offset, which is equal to or greater than the reference value, to be the brake factor offset to be calculated.

5. The system of claim 1 ,

wherein the brake controller updates the brake factor offset in real time considering that the friction coefficient of the brake pad is changed according to a brake temperature, or updates the brake factor offset for each predetermined period considering that the friction coefficient of the brake pad has a deviation according to a seasonal temperature.

6. A method for correcting a friction coefficient of a brake pad for a vehicle, comprising steps of:

determining, by a brake controller, an activation condition for estimating a brake factor;

estimating, by the brake controller, the brake factor when the brake factor estimation activation condition is satisfied;

calculating, by the brake controller, a brake factor offset by operating a difference in value between the estimated brake factor and a previous brake factor;

updating, by the brake controller, the previous brake factor with the calculated brake factor offset; and

correcting, by the brake controller, the friction coefficient of the brake pad based on the updated brake factor offset.

7. The method of claim 6 ,

wherein, in the step of determining an activation condition, the brake controller determines that the activation condition for estimating the brake factor is satisfied when a driver request braking torque, a wheel speed, a wheel pressure, a regenerative braking torque, and a regenerative braking torque slope are equal to or greater than a reference value, respectively.

8. The method of claim 6 ,

wherein, in the step of estimating a brake factor, the brake controller estimates the brake factor in a manner of inversely calculating braking force and wheel dynamics, or estimates the brake factor by using a Kalman filter and the wheel dynamics,

wherein the brake controller estimates the brake factor by

C

p

=

-

J

·

dw

dt

+

r

×

F

b

-

T

reg

P

wheel

,

and

wherein Cp: the estimated brake factor,

-

J

·

dw

dt

:

an inertia torque, r: an effective radius, which is the distance from the wheel center to the point where the brake pad contacts a disk, Fb: the braking force generated by the brake pad contacting the disk, r×Fb: the braking force torque, Treg: the regenerative braking torque, and Pwheel: the wheel pressure.

9. The method of claim 6 ,

wherein the brake controller calculates the brake factor offset by a difference between the estimated brake factor and the previous brake factor,

wherein the brake controller determines that convergence of the brake factor offset has been completed when the calculated brake factor offset falls within a certain range for a certain time, and

wherein, when the brake factor offset of which the convergence has been completed is equal to or greater than a reference value, the brake controller decides the brake factor offset, which is equal to or greater than the reference value, to be the brake factor offset to be calculated.

10. The method of claim 6 ,

wherein, in the step of updating the calculated brake factor offset, the brake controller updates the brake factor offset in real time considering that the friction coefficient of the brake pad is changed according to a brake temperature, or updates the brake factor offset for each predetermined period considering that the friction coefficient of the brake pad has a deviation according to a seasonal temperature.

11. A system for correcting a friction coefficient of a brake pad for a vehicle, comprising:

a brake controller;

a G sensor for inputting a deceleration signal to the brake controller;

a wheel speed sensor for inputting a wheel speed signal to the brake controller;

a wheel pressure sensor for inputting a wheel pressure signal to the brake controller at braking; and

an upper level controller for inputting regenerative braking torque and coasting traveling braking torque signals to the brake controller,

wherein the brake controller is configured to:

determine an activation condition for estimating a brake factor;

estimate the brake factor, when the brake factor estimation activation condition is satisfied;

calculate a brake factor offset by operating a difference in value between the estimated brake factor and a previous brake factor, wherein the brake factor is a value calculated by multiplying a friction coefficient of a brake pad, a piston area of a caliper restricting the brake pad, and an effective radius, which is the distance from the wheel center to the point where the brake pad contacts a disk, and is defined as a braking torque generated per 1 bar of hydraulic pressure;

update the previous brake factor with the calculated brake factor offset; and

correct, the friction coefficient of the brake pad based on the updated brake factor offset,

wherein the brake controller updates the brake factor offset in real time considering that the friction coefficient of the brake pad is changed according to a brake temperature, or updates the brake factor offset for each predetermined period considering that the friction coefficient of the brake pad has a deviation according to a seasonal temperature.