Method for estimating master cylinder pressure during brake apply

1. A method for estimating master cylinder pressure during brake apply of a brake system of a vehicle, wherein the brake system includes a brake pedal, and wherein the method comprises:

a) determining a first master cylinder pressure from brake pedal position during brake apply;

b) determining a second master cylinder pressure from vehicle deceleration during brake apply;

c) estimating the master cylinder pressure during brake apply to be equal to the first master cylinder pressure when the vehicle deceleration is below a predetermined deceleration value;

d) estimating the master cylinder pressure during brake apply to be equal to a value which is less than the first master cylinder pressure and greater than or equal to the second master cylinder pressure when the vehicle deceleration is at or above the predetermined deceleration value; and

e) using at least the estimated master cylinder pressure during brake apply to control the vehicle.

2. The method of claim 1 , wherein step a) determines brake pedal position, at least in part, from a brake pedal travel sensor.

3. The method of claim 2 , wherein step b) determines vehicle deceleration, at least in part, from at least one wheel speed sensor.

4. The method of claim 3 , wherein step a) includes using an empirically-determined first look-up table of stored master cylinder pressure values and corresponding stored brake pedal position values.

5. The method of claim 4 , wherein step b) includes using an empirically-determined second look-up table of stored master cylinder pressure values and corresponding stored vehicle deceleration values.

6. The method of claim 5 , wherein step a) includes interpolating a master cylinder pressure value for a brake pedal position value between two closest stored brake pedal position values.

7. The method of claim 6 , wherein step b) includes interpolating a master cylinder pressure value for a vehicle deceleration value between two closest stored vehicle deceleration values.

8. The method of claim 1 , wherein the predetermined deceleration value is equal to substantially 0.2 g, wherein g is gravitational acceleration.

9. The method of claim 1 , wherein step d) estimates the master cylinder pressure during brake apply to be equal to the second master cylinder pressure when the vehicle deceleration is at or above the predetermined deceleration value.

10. The method of claim 1 , wherein step d) estimates the master cylinder pressure during brake apply to be equal to the first master cylinder pressure minus a fixed percentage of the second master cylinder pressure when the vehicle deceleration is at or above the predetermined deceleration value, wherein the percentage is between 1% and 99%.

11. The method of claim 1 , wherein step e) includes sending an input signal based on the estimated master cylinder pressure to an electronic stability control system of the vehicle.

12. A method for estimating master cylinder pressure during brake apply of a brake system of a vehicle, wherein the brake system includes a brake pedal, and wherein the method comprises:

a) determining a first master cylinder pressure from brake pedal position during brake apply;

b) determining a second master cylinder pressure from vehicle deceleration during brake apply;

c) estimating the master cylinder pressure during brake apply to be equal to the first master cylinder pressure when the vehicle deceleration is below a predetermined deceleration value;

d) calculating an error to be equal to the first master cylinder pressure minus the second master cylinder pressure when the vehicle deceleration is at or above the predetermined deceleration value;

e) estimating the master cylinder pressure during brake apply to be equal to the first master cylinder pressure minus a value of a variable percentage of the error when the vehicle deceleration is at or above the predetermined deceleration value, wherein the value of the variable percentage is adaptively learned over time; and

f) using at least the estimated master cylinder pressure during brake apply to control the vehicle.

13. The method of claim 12 , wherein step a) determines brake pedal position, at least in part, from a brake pedal travel sensor.

14. The method of claim 13 , wherein step b) determines vehicle deceleration, at least in part, from at least one wheel speed sensor.

15. The method of claim 14 , wherein step a) includes using an empirically-determined first look-up table of stored master cylinder pressure values and corresponding stored brake pedal position values.

16. The method of claim 15 , wherein step b) includes using an empirically-determined second look-up table of stored master cylinder pressure values and corresponding stored vehicle deceleration values.

17. The method of claim 16 , wherein step a) includes interpolating a master cylinder pressure value for a brake pedal position value between two closest stored brake pedal position values.

18. The method of claim 17 , wherein step b) includes interpolating a master cylinder pressure value for a vehicle deceleration value between two closest stored vehicle deceleration values.

19. The method of claim 12 , wherein the predetermined deceleration value is equal to substantially 0.2 g, wherein g is gravitational acceleration.

20. The method of claim 12 , wherein step f) includes sending an input signal based on the estimated master cylinder pressure to an electronic stability control system of the vehicle.