Method and system to increase electric brake clamping force accuracy

1. A method and system for increasing accuracy of clamping force of electric aircraft carbon brakes of an aircraft having a plurality of wheels and a corresponding plurality of wheel brakes for the plurality of wheels to reduce brake wear when the aircraft is taxiing, comprising the steps of:

providing a first portion of a plurality of electric brake actuators of each brake with a first range of low brake clamping force responsive to low brake clamping force commands, and a second portion of the plurality of electric brake actuators of each brake with a second range of high brake clamping force responsive to high brake clamping force commands;

monitoring commanded initiation of braking of any of the plurality of wheel brakes of the aircraft;

setting a residual brake clamping force to a predetermined minimum residual brake clamping force for the plurality of wheel brakes in response to said commanded initiation of braking of any of the plurality of wheel brakes;

actuating said first portion of electric brake actuators to apply said predetermined minimum residual brake clamping force once wheel braking is commanded and maintaining said predetermined minimum residual brake clamping force despite a commanded release of braking of any of the plurality of wheel brakes; and

actuating said second portion of electric brake actuators only when the commanded braking force is in the second high range of brake clamping force.

2. The method of claim 1 , further comprising the step of discontinuing applying said predetermined minimum residual brake clamping force in response to at least one control logic condition.

3. The method of claim 2 , further comprising the steps of determining an average wheel speed and comparing said average wheel speed with a predetermined wheel speed threshold, and wherein said at least one control logic condition comprises when said average wheel speed is below said predetermined wheel speed threshold.

4. The method of claim 3 , wherein said predetermined wheel speed threshold is in the range of about 2 knots to about 15 knots.

5. The method of claim 3 , wherein said predetermined wheel speed threshold is in the range of about 2 knots to about 10 knots.

6. The method of claim 3 , wherein said aircraft has left and right landing gear, and said step of determining an average wheel speed comprises determining an average wheel speed of the left landing gear and an average wheel speed of the right landing independently, comparing said average wheel speeds of the left and right landing gear, and comparing the lesser of the average wheel speeds of the left and right landing gear with said predetermined wheel speed threshold.

7. The method of claim 2 , wherein said aircraft includes at least one engine thrust lever, further comprising the step of monitoring engine thrust lever position, and wherein said at least one control logic condition comprises when said at least one engine thrust lever is in an advanced position.

8. The method of claim 2 , further comprising the step of detecting wheel speed acceleration, and comparing said wheel speed acceleration with a predetermined acceleration threshold, and wherein said at least one control logic condition comprises when said wheel speed acceleration exceeds said acceleration threshold.

9. The method of claim 2 , further comprising monitoring temperature of said plurality of wheel brakes, and comparing said temperature of said plurality of wheel brakes with a temperature threshold, and wherein said at least one control logic condition comprises when said temperature of said plurality of wheel brakes exceeds said temperature threshold.

10. The method of claim 2 , further comprising determining distance rolled with said predetermined minimum residual brake clamping force applied, comparing said distance rolled with a predetermined distance threshold, and wherein said at least one control logic condition comprises when said distance rolled exceeds said predetermined distance threshold.

11. The method of claim 1 , wherein said predetermined minimum residual brake clamping force comprises about 1-10% of a maximum brake clamping force of said plurality of wheel brakes.

12. The method of claim 1 , wherein said predetermined minimum residual brake clamping force comprises about 2-5% of a maximum brake clamping force of said plurality of wheel brakes.

13. A system for increasing accuracy of clamping force of electric aircraft carbon brakes of an aircraft having a plurality of wheels and a corresponding plurality of wheel brakes for the plurality of wheels to reduce brake wear when the aircraft is taxiing, the system comprising:

a first portion of a plurality of electric brake actuators of each brake with a first range of low brake clamping force responsive to low brake clamping force commands;

a second portion of a plurality of electric brake actuators of each brake with a second range of high brake clamping force responsive to high brake clamping force commands;

means for monitoring commanded initiation of braking of any of the plurality of wheel brakes of the aircraft;

means for setting a residual brake clamping force to a predetermined minimum residual brake clamping force for the plurality of wheel brakes in response to said commanded initiation of braking of any of the plurality of wheel brakes;

means for actuating said first portion of electric brake actuators to apply said predetermined minimum residual brake clamping force once wheel braking is commanded and maintaining said predetermined minimum residual brake clamping force despite a commanded release of braking of any of the plurality of wheel brakes; and

means for actuating said second portion of electric brake actuators only when the commanded braking force is in the second high range of brake clamping force.

14. The system of claim 13 , further comprising means for discontinuing applying said predetermined minimum residual brake clamping force in response to at least one control logic condition.

15. A method and system for increasing accuracy of clamping force of electric aircraft carbon brakes of an aircraft having a plurality of wheels and a corresponding plurality of wheel brakes for the plurality of wheels to reduce brake wear when the aircraft is taxiing, comprising the steps of:

providing a first pair of electric brake actuators of each brake with a first range of low brake clamping force responsive to low brake clamping force commands, and a second pair of electric brake actuators of each brake with a second range of high brake clamping force responsive to high brake clamping force commands;

monitoring commanded initiation of braking of any of the plurality of wheel brakes of the aircraft;

setting a residual brake clamping force to a predetermined minimum residual brake clamping force for the plurality of wheel brakes in response to said commanded initiation of braking of any of the plurality of wheel brakes;

actuating said first pair of electric brake actuators to apply said predetermined minimum residual brake clamping force once wheel braking is commanded and maintaining said predetermined minimum residual brake clamping force despite a commanded release of braking of any of the plurality of wheel brakes; and

actuating said second pair of electric brake actuators only when the commanded braking force is in the second high range of brake clamping force.

16. The method of claim 15 , further comprising the step of discontinuing applying said predetermined minimum residual brake clamping force in response to at least one control logic condition.

17. The method of claim 16 , further comprising the steps of determining an average wheel speed and comparing said average wheel speed with a predetermined wheel speed threshold, and wherein said at least one control logic condition comprises when said average wheel speed is below said predetermined wheel speed threshold.

18. The method of claim 17 , wherein said predetermined wheel speed threshold is in the range of about 2 knots to about 15 knots.

19. The method of claim 17 , wherein said predetermined wheel speed threshold is in the range of about 2 knots to about 10 knots.

20. The method of claim 17 , wherein said aircraft has left and right landing gear, and said step of determining an average wheel speed comprises determining an average wheel speed of the left landing gear and an average wheel speed of the right landing independently, comparing said average wheel speeds of the left and right landing gear, and comparing the lesser of the average wheel speeds of the left and right landing gear with said predetermined wheel speed threshold.

21. The method of claim 16 , wherein said aircraft includes at least one engine thrust lever, further comprising the step of monitoring engine thrust lever position, and wherein said at least one control logic condition comprises when said at least one engine thrust lever is in an advanced position.

22. The method of claim 16 , further comprising the step of detecting wheel speed acceleration, and comparing said wheel speed acceleration with a predetermined acceleration threshold, and wherein said at least one control logic condition comprises when said wheel speed acceleration exceeds said acceleration threshold.

23. The method of claim 16 , further comprising monitoring temperature of said plurality of wheel brakes, and comparing said temperature of said plurality of wheel brakes with a temperature threshold, and wherein said at least one control logic condition comprises when said temperature of said plurality of wheel brakes exceeds said temperature threshold.

24. The method of claim 16 , further comprising determining distance rolled with said predetermined minimum residual brake clamping force applied, comparing said distance rolled with a predetermined distance threshold, and wherein said at least one control logic condition comprises when said distance rolled exceeds said predetermined distance threshold.

25. The method of claim 15 , wherein said predetermined minimum residual brake clamping force comprises about 1-10% of a maximum brake clamping force of said plurality of wheel brakes.

26. The method of claim 15 , wherein said predetermined minimum residual brake clamping force comprises about 2-5% of a maximum brake clamping force of said plurality of wheel brakes.

27. A system for increasing accuracy of clamping force of electric aircraft carbon brakes of an aircraft having a plurality of wheels and a corresponding plurality of wheel brakes for the plurality of wheels to reduce brake wear when the aircraft is taxiing, the system comprising:

a first pair of electric brake actuators of each brake with a first range of low brake clamping force responsive to low brake clamping force commands;

a second pair of electric brake actuators of each brake with a second range of high brake clamping force responsive to high brake clamping force commands;

means for monitoring commanded initiation of braking of any of the plurality of wheel brakes of the aircraft;

means for setting a residual brake clamping force to a predetermined minimum residual brake clamping force for the plurality of wheel brakes in response to said commanded initiation of braking of any of the plurality of wheel brakes;

means for actuating said first pair of electric brake actuators to apply said predetermined minimum residual brake clamping force once wheel braking is commanded and maintaining said predetermined minimum residual brake clamping force despite a commanded release of braking of any of the plurality of wheel brakes; and

means for actuating said second pair of electric brake actuators only when the commanded braking force is in the second high range of brake clamping force.

28. The system of claim 27 , further comprising means for discontinuing applying said predetermined minimum residual brake clamping force in response to at least one control logic condition.