Systems and methods for low speed braking operation

1. A brake control system, comprising:

an accelerometer coupled to an axle;

a servo valve configured to receive a hydraulic fluid and provide the hydraulic fluid to apply a braking force to a wheel via a hydraulic line; and

a brake control unit in electronic communication with the servo valve;

wherein the brake control unit is configured to:

receive an axle acceleration signal indicative of at least one of an axle acceleration or an axle deceleration from the accelerometer;

determine whether an aircraft speed is less than a threshold speed value;

monitor acceleration oscillations by determining whether the axle acceleration is greater than a threshold acceleration value, in response to the aircraft speed being less than the threshold speed value, and determining whether the axle deceleration is greater than the threshold acceleration value, in response to the aircraft speed being less than the threshold speed value; and

decrease a braking command pressure in response to the axle acceleration and the axle deceleration being greater than the threshold acceleration value, wherein the braking force applied to the wheel is reduced in response to the brake control unit decreasing the braking command pressure.

2. The brake control system of claim 1 , wherein the brake control unit is further configured to increase the braking command pressure at a predetermined rate.

3. The brake control system of claim 2 , wherein the brake control unit is further configured to:

determine whether the braking command pressure is equal to or greater than a pedal command pressure; and

switch from using the braking command pressure to using the pedal command pressure, in response to the braking command pressure being equal to or greater than the pedal command pressure.

4. The brake Control system of claim 1 , wherein the brake Control unit is further configured to decrease the braking command pressure to a contact pressure in response to the axle acceleration being greater than the threshold acceleration value.

5. The brake control system of claim 1 , wherein the brake control unit is further configured to:

monitor a brake pedal position to determine whether at least one of:

i) a pedal deflection is greater than a threshold deflection value;

ii) a pedal deflection is decreasing; and

iii) a pedal apply rate is greater than a threshold apply rate; and

switch from using the braking command pressure to using a pedal command pressure, in response to at least one of a criteria in i)-iii) being true.

6. The brake control system of claim 3 , wherein the brake control unit is further configured to continue increasing the braking command pressure at the predetermined rate, in response to the braking command pressure being less than the pedal command pressure.

7. A method for brake control, comprising:

receiving, by a brake control unit, an axle acceleration signal indicative of at least one of an axle acceleration or an axle deceleration from the accelerometer;

determining whether an aircraft speed is less than a threshold speed value;

monitoring acceleration oscillations by determining whether the axle acceleration is greater than a threshold acceleration value, in response to the aircraft speed being less than the threshold speed value, and determining whether the axle deceleration is greater than the threshold acceleration value, in response to the aircraft speed being less than the threshold speed value; and

decreasing, by the brake control unit, a braking command pressure in response to the axle acceleration and the axle deceleration being greater than the threshold acceleration value, wherein a braking force applied to a wheel is reduced in response to the brake control unit decreasing the braking command pressure.

8. The method of claim 7 , further comprising increasing, by the brake control unit, the braking command pressure at a predetermined rate.

9. The method of claim 8 , further comprising:

determining, by the brake control unit, whether the braking command pressure is equal to or greater than a pedal command pressure; and

switching, by the brake control unit, from using the braking command pressure to using the pedal command pressure, in response to the braking command pressure being equal to or greater than the pedal command pressure.

10. The method of claim 7 , further comprising decreasing, by the brake control unit, the braking command pressure to a contact pressure in response to the axle acceleration being greater than the threshold acceleration value.

11. The method of claim 7 , further comprising:

monitoring, by the brake control unit, a brake pedal position to determine whether at least one of:

i) a pedal deflection is greater than a threshold deflection value;

ii) a pedal deflection is decreasing; and

iii) a pedal apply rate is greater than a threshold apply rate; and

switching, by the brake control unit, from using the braking command pressure to using a pedal command pressure, in response to at least one of a criteria in i)-iii) being true.

12. A brake control system that is configured for use with an aircraft, comprising:

a brake control unit comprising a processor; and

a tangible, non-transitory memory configured to communicate with the processor, the tangible, non-transitory memory having instructions stored thereon that, in response to execution by the processor, cause the brake control unit to perform operations comprising:

receiving an axle acceleration signal indicative of at least one of an axle acceleration or an axle deceleration from the accelerometer;

determining whether an aircraft speed is less than a threshold speed value;

monitoring acceleration oscillations by determining whether the axle acceleration is greater than a threshold acceleration value, in response to the aircraft speed being less than the threshold speed value, and determining whether the axle deceleration is greater than the threshold acceleration value, in response to the aircraft speed being less than the threshold speed value; and

decreasing a braking command pressure in response to the axle acceleration and the axle deceleration being greater than the threshold acceleration value, wherein a braking force applied to a wheel of the aircraft is reduced in response to the brake control unit decreasing the braking command pressure.

13. The brake control system of claim 12 , wherein the instructions cause the brake control unit to perform further operations comprising:

increasing the braking command pressure at a predetermined rate.

14. The brake control system of claim 11 , wherein the instructions cause the brake control unit to perform further operations comprising:

determining whether the braking command pressure is equal to or greater than a pedal command pressure; and

switching from using the braking command pressure to using the pedal command pressure, in response to the braking command pressure being equal to or greater than the pedal command pressure.

15. The brake control system of claim 12 , wherein the brake control unit is configured to decrease the braking command pressure to a contact pressure in response to the axle acceleration being greater than the threshold acceleration value.

16. The brake control system of claim 12 , wherein the instructions cause the brake control unit to perform further operations comprising:

monitoring a brake pedal position to determine whether at least one of:

i) a pedal deflection is greater than a threshold deflection value;

ii) a pedal deflection is decreasing; and

iii) a pedal apply rate is greater than a threshold apply rate; and

switching from using the braking command pressure to using a pedal command pressure, in response to at least one of a criteria in i)-iii) being true.

17. The brake control system of claim 14 , wherein the instructions cause the brake control unit to perform further operations comprising:

increasing the braking command pressure at the predetermined rate, in response to the braking command pressure being less than the pedal command pressure.