Selective deceleration brake control system

• US RE33,486 E
• Filed: 03/05/1987
• Issued: 12/11/1990
• Est. Priority Date: 04/12/1972
• Status: Expired due to Term

• Current Assignee: Hydro-Aire Division of Crane Company
• Original Assignee: Hydro-Aire Division of Crane Company
• Inventors: Cook, Robert D., Hirzel, Edgar A.
• Primary Examiner(s): Lall, Parshotam S.
• Assistant Examiner(s): Dixon, Joseph L.
• Application Number:
  US07/022,488
• Time in Patent Office: 1,377 Days
• Field of Search: 364/424, 364/426, 364/424.02, 364/424.01, 188/181 A, 188/181 C, 244/110 A, 244/111, 303/20, 303/93, 303/106, 303/109, 303/100, 303/DIG. 3, 303/DIG. 4, 303/6 A, 303/33
• US Class Current: 701/75
• CPC Class Codes: B60T 8/1703 for aircrafts
• CPC Class Codes: B60T 8/325 Systems specially adapted for aircraft
• CPC Class Codes: B60T 8/3255 Systems in which the braking action is dependent on brake pedal data

Abstract

A selective deceleration brake control system which enables the operator of an aircraft or other vehicle to preselect a rate of deceleration for the vehicle. The system produces a velocity reference signal which decreases in value at a rate indicative of the rate of vehicle deceleration selected by the operator. A signal indicative of actual wheel velocity is continuously produced and compared with the velocity reference signal to generate an error signal. The error signal is processed and used to produce a brake control signal. The system continuously controls braking effort to cause the vehicle to decelerate at the rate selected by the operator. The selective deceleration circuit cooperates with an anti-skid brake control circuit such that at any instant the circuit providing the higher brake release command will control.

Claims

1. A brake control system for applying and controlling the brake application means for a wheel of a vehicle independently of operator brake application, comprising:

signal generating means for producing a wheel speed signal that is a function of the rotational speed of said wheel;

anti-skid control means for receiving and processing said wheel speed signal to provide an anti-skid brake control signal;

reference generating means for generating a reference velocity signal having a selectively variable rate of decrease;

rate selector means for manually selecting a rate of decrease of said reference velocity signal indicative of a desired rate of vehicle deceleration;

comparison means for comparing said wheel speed signal with said reference velocity signal for generating an error signal indicative of the difference between said wheel speed signal and said reference velocity signal;

control means for providing a signal to said brake application means to apply brake pressure to said wheel independently of operator brake application and response to said error signal to provide a selected deceleration control signal for controlling said brake pressure in order to maintain said desired rate of deceleration; and

means for preventing said brake application means from applying said brake pressure in response to said deceleration brake control signal and for applying brake pressure in response to said anti-skid brake control signal when said anti-skid brake control signal commands a lower brake pressure than does said deceleration brake control signal.

2. The invention defined in claim 1 wherein said reference generating means includes means for establishing an initial reference velocity signal value based on the maximum value attained by said wheel speed signal during wheel spin-up.

3. The invention defined in claim 1 wherein said brake control system further comprises a deceleration control turn-on means for energizing said deceleration control signal generating means and causing said deceleration control means to provide an initial deceleration control signal of maximum, value commanding a full brake release followed by a gradual decrease from said maximum value to permit a corresponding gradual increase in brake pressure.

4. The invention defined in claim 1 wherein said brake control system further comprises means for deactuating said deceleration control signal generating means and for causing said deceleration control signal generating means to provide incident to said de-actuation a deceleration control signal of gradually decreasing value to permit a gradual decrease in brake pressure.

5. The invention of claim 1 wherein said control means provides said signal initially upon the actuation of a switch means by the operator.

6. A brake control system for applying and controlling the brake application means associated with each wheel of a pair of brake loaded-bearing wheels of an aircraft independently of operator brake application, comprising:

signal generating means for each of said wheels for producing a wheel speed signal that is a function of the rotational speed of its associated wheel;

anti-skid control means for each of said wheels for receiving and processing said wheel speed signal to provide an anti-skid brake control .[.for control.]. signal .Iadd.for control .Iaddend.of its associated wheel;

reference generating means for generating a reference velocity signal having .[.a.]. selectively variable rate of decrease;

rate selector means for manually selecting a rate of decrease of said reference velocity signal indicative of a desired rate of vehicle deceleration;

averaging means responsive to the wheel speed signal associated with each of said wheels to form an average wheel speed signal therefrom;

comparison means for comparing said average wheel speed signal with said reference velocity signal for generating an error signal indicative of the difference between said average wheel speed signal and said reference velocity signal;

control means for providing a signal to said brake application means to apply brake pressure to each of said wheels independently of operator brake application and responsive to said error signal to provide a selected deceleration control signal for controlling said brake pressure in order to maintain said desired rate of deceleration; and

means for preventing said brake application means from applying said brake pressure in response to said brake control signal and for applying brake pressure in response to said anti-skid brake control signal when said anti-skid brake control signal commands a lower brake pressure than does said deceleration brake control signal.

7. The invention defined in claim 6 wherein said reference generating means includes means for establishing an initial reference velocity signal value based on the maximum value attained by said wheel speed signal during wheel spin-up.

8. The invention defined in claim 6 wherein said brake control system further comprises a deceleration control turn-on means for energizing said deceleration control signal generating means and causing said deceleration control means to provide an initial deceleration control signal of maximum value commanding a full brake release followed by a gradual decrease from said maximum value to permit a corresponding gradual increase in brake pressure.

9. The invention defined in claim 6 wherein said brake control system further comprises means for deactuating said deceleration control signal generating means and for causing said deceleration control signal generating means to provide incident to said de-actuation a deceleration control signal of gradually decreasing value to permit a gradual decrease in brake pressure.

10. The invention defined in claim 6 wherein said deceleration brake control signal comprises a time integral function of said error signal.

11. The invention defined in claim 10 wherein said deceleration control means includes circuit means having a predetermined actuation threshold level and wherein said time integral function is a time integral function of both positive and negative variation of said error signal from said threshold level.

12. The invention defined in claim 11 wherein said deceleration brake control signal further comprises a nonintegral, proportional function of said error signal.

17. attained by said average signal during wheel spin-up. 18. The .[.invention.]. .Iadd.deceleration control system .Iaddend.defined in claim .[.11.]. .Iadd.16 .Iaddend.wherein said .[.brake control system further comprises a control turn-on means for energizing said control means and causing said control.]. .Iadd.means for submitting an on-ramp signal includes .Iaddend.means .[.to provide.]. .Iadd.for providing .Iaddend.an initial deceleration .Iadd.brake .Iaddend.control signal of maximum value commanding a full brake release followed by a gradual decrease from said maximum value to permit a corresponding gradual increase in brake pressure. .[.19. The invention defined in claim 16 wherein said brake control system further comprises means for deactuating said control means and for causing said control means to provide incident to said deactuation a deceleration control signal of gradually decreasing

13. A brake control system, for an aircraft having .[.plural groups of braked load-bearing wheels for applying and controlling a brake application means for said wheels independently of operator brake application, said system.]. .Iadd.separate inboard and outboard wheel groups in which the wheels in each group are symmetrically mounted on opposite sides of the aircraft.Iaddend., comprising:

.Iadd.brake application means for providing brake pressure to each wheel;

.Iaddend.

anti-skid control means for providing an anti-skid brake control signal;

signal generating means associated with each of said wheels for producing a first signal that is .[.related.]. .Iadd.proportional .Iaddend.to the rotational speed of its associated wheel;

reference generating means for generating a .Iadd.velocity .Iaddend.reference signal .Iadd.having a selectively variable rate of decrease.Iaddend.;

rate selector means for manually .[.selecting said.]. .Iadd.modifying said reference generating means for producing a .Iaddend.reference signal indicative of .[.a.]. .Iadd.the .Iaddend.desired .[.rate of.]. vehicle deceleration;

.Iadd.separate .Iaddend.averaging means .[.in.]. .Iadd.for .Iaddend.each of said wheel groups responsive to the first signal associated with each of said wheels in said group .[.to form an average.]. .Iadd.for continuously determining the average speed of said wheels in each said group and for forming an analog .Iaddend.signal .[.therefrom.]. .Iadd.which is a function of said average speed of said wheels.Iaddend.;

comparison means for each of said wheel groups for comparing said .[.average.]. .Iadd.analog .Iaddend.signals for the associated wheel group with said reference signal for generating an error signal indicative of the difference between said .[.average.]. .Iadd.analog .Iaddend.signal for the associated wheel group and said reference signal;

.Iadd.modulating means for each of said wheel groups responsive to said error signal for producing a modulating brake signal when said error signal exceeds a predetermined threshold level, said modulating brake signal including a time integral function of both positive and negative variations of said error signal from said threshold level;

.Iaddend.

control means associated with each group of wheels .Iadd.and responsive to said modulating brake signal .Iaddend.for providing a .Iadd.deceleration brake control .Iaddend.signal to said brake application means .[.to apply brake pressure to said wheels.]. independently of operator brake application and .[.responsive to said error signal to provide a deceleration control signal.]. for controlling said brake pressure in order to maintain said desired rate of deceleration.Iadd., said control means including pressure balancing means associated with each of said modulating means for comparing the modulating brake signal of said associated modulating means with the modulating brake signal of another modulating means and causing the other modulating means to produce a modulating brake signal whose valve is not less than that of the associated modulating brake signal, thereby equalizing brake load distribution between said wheel groups.Iaddend.;

.[.and.].

means for preventing said brake application means from applying said brake pressure in response to said deceleration brake control signal for said group of wheels and for applying brake pressure in response to said anti-skid brake control signal when said anti-skid brake control signal commands a lower brake pressure than does said deceleration brake control signal.Iadd.;

means for submitting an on-ramp signal to said modulating means to cause said modulating means to provide an initial deceleration brake control signal to gradually increase brake pressure; and

means for submitting an off-ramp signal to said modulating means to cause said modulating means to provide a final deceleration brake control signal to gradually remove brake pressure.Iaddend.. .[.14. The invention defined in claim 13 further comprising;

a means associated with each of said control means for comparing the output thereof with the output of another of said control means associated with another wheel group to cause the output of the associated control means to command a brake pressure level

14. not less than that commanded by said other control means..]. 15. The .[.invention.]. .Iadd.brake control system .Iaddend.of claim 13 .[.where in.]. .Iadd.wherein .Iaddend.each of said control means provides said .Iadd.deceleration brake control .Iaddend.signal initially upon the

15. actuation of a switch means by the operator. 16. A deceleration control system for .[.applying and controlling the brake application means associated with each wheel of group of braked load-bearing wheels of.]. an aircraft, .[.independently of operator brake application,.]. comprising:

.Iadd.inboard and outboard wheels, each wheel having a brake;

separate brake application means for providing brake pressure to said wheels;

separate inboard and outboard wheel groups in which the wheels in each of said groups are mounted on opposite sides of the aircraft;

.Iaddend.

signal generating means for each of said wheels for producing a first signal that is .[.related.]. .Iadd.proportional .Iaddend.to the rotational speed of its associated wheel;

reference generating means for generating a .Iadd.velocity .Iaddend.reference signal .Iadd.having a selectively variable rate of decrease.Iaddend.;

rate selector means for manually .[.selecting said.]. .Iadd.modifying said reference generating means for producing a .Iaddend.reference signal indicative of .[.a.]. .Iadd.the .Iaddend.desired .[.rate of.]. vehicle deceleration;

.Iadd.separate .Iaddend.averaging means .Iadd.for each of said wheel groups .Iaddend.responsive to the first signal associated with each of said wheels .[.to form an.]. .Iadd.for continuously determining the .Iaddend.average .Iadd.speed of said wheels and for forming an analog .Iaddend.signal .[.therefrom.]. .Iadd.which is a function of said average speed of said wheels.Iaddend.;

comparison means for comparing said .[.average.]. .Iadd.analog .Iaddend.signal with said reference signal for generating an error signal indicative of the difference between said .[.average.]. .Iadd.analog .Iaddend.signal and said reference signal; and

.Iadd.modulating means responsive to said error signal for producing a modulating brake signal when said error signal exceeds a predetermined threshold level, said modulating brake signal including a time integral function of both positive and negative variations of said error signal from said threshold level;

.Iaddend.

control means .Iadd.responsive to said modulating brake signal .Iaddend.for providing a .Iadd.deceleration brake control .Iaddend.signal to said brake application means .[.to apply brake pressure to said wheels.]. independently of operator brake application and .[.responsive to said error signal to provide a selected deceleration control signal.]. for controlling said brake pressure in order to maintain said desired rate of deceleration.Iadd., said control means including separate pressure balancing means associated with each of said modulating means for comparing the modulating brake signal produced thereby with the modulating brake signal produced by another of said modulating means and producing an output that is applied to said other modulating means to command a deceleration brake control signal whose value is not less than the deceleration brake control signal commanded by said associated modulating means, thereby causing the braking load to be evenly distributed between wheel groups;

means for submitting an on-ramp signal to said modulating means to cause said modulating means to provide an initial deceleration brake control signal to gradually increase brake pressure; and

means for submitting an off-ramp signal to said modulating means to cause said modulating means to provide a final deceleration brake control signal

16. to gradually remove brake pressure.Iaddend.. 17. The .[.invention.]. .Iadd.deceleration control system .Iaddend.defined in claim 16 wherein .[.each of.]. said reference generating means includes means for establishing an initial reference signal value based on the maximum value

18. value to permit a gradual decrease in brake pressure..]. 20. The .[.invention.]. .Iadd.deceleration control system .Iaddend.defined in claim 16 wherein said deceleration brake control signal comprises a time

19. integral function of said error signal. 21. The .[.invention.]. .Iadd.deceleration control system .Iaddend.defined in claim 20 wherein said .[.control means includes circuit means having a predetermined actuation threshold level and wherein said.]. time integral function is a time integral function of both positive and negative variation of said

20. error signal from said threshold level. 22. The .[.invention.]. .Iadd.deceleration control system .Iaddend.defined in claim 21 wherein said deceleration brake control signal further comprises a .[.nonintegral.]. .Iadd.non-integral.Iaddend., proportional function of

21. said error signal. 23. The .[.invention.]. .Iadd.deceleration control system .Iaddend.of claim 16 wherein said control means provides said signal initially upon the actuation of a switch means by the operator.

22. A deceleration control system for an aircraft having .[.plural groups of brake load-bearing wheels,.]. .Iadd.separate inboard and outboard wheel groups in which the wheels in each said group are symmetrically mounted on opposite side of the aircraft, .Iaddend..[.for applying and controlling a brake application means for said wheels independently of operator brake application, said system.]. comprising:

.Iadd.brake application means for applying brake pressure to said wheels;

.Iaddend.

signal generating means associated with each of said wheels for producing a first signal that is .[.related.]. .Iadd.proportional .Iaddend.to the rotational speed of its associated wheel;

reference generating means for generating a .Iadd.velocity .Iaddend.reference signal .Iadd.having a selectively variable rate of decrease.Iaddend.;

rate selector means for manually .[.selecting said.]. .Iadd.modifying said reference generating means for producing a .Iaddend.reference signal indicative of .[.a.]. .Iadd.the .Iaddend.desired .[.rate of.]. vehicle deceleration;

.Iadd.separate .Iaddend.averaging means for each of said wheel groups responsive to the first signal associated with each of said wheels in said group .[.to form an.]. .Iadd.for continuously determining the .Iaddend.average .Iadd.speed of said wheels and for forming an analog .Iaddend.signal .[.therefrom.]. .Iadd.which is a function of said average speed of said wheels.Iaddend.;

comparison means for each of said wheel groups for comparing said .[.average.]. .Iadd.analog .Iaddend.signal for the associated wheel group with said reference signal for generating an error signal indicative of the difference between said .[.average.]. analog signal for the associated wheel group and said reference signal;

.[.and.].

.Iadd.modulating means for each of said wheel groups, each responsive to said error signal for producing a modulating brake signal when said error signal exceeds a predetermined threshold level, each of said modulating brake signals including a time integral function of both positive and negative variations of said error signal from said threshold level;

.Iaddend.

control means associated with each .Iadd.wheel .Iaddend.group .[.of wheels.]. .Iadd.and responsive to said modulating brake signal .Iaddend.for providing a .Iadd.deceleration brake control .Iaddend.signal to said brake application means .[.to apply brake pressure to said wheels.]. independently of operator brake application and .[.responsive to said error signal to provide a deceleration control signal.]. for controlling said brake pressure in order to maintain said desired rate of deceleration.Iadd., said control means including pressure balancing means associated with each of said modulating means for comparing the modulating brake signal of said associated modulating means with the modulating brake signal of another modulating means and causing the other modulating means to produce a modulating brake signal whose value is not less than that of the associated modulating brake signal, thereby equalizing brake load distribution between wheel groups;

means for submitting an on-ramp signal to said modulating means to cause said modulating means to provide an initial deceleration brake control signal to gradually increase brake pressure; and

means for submitting an off-ramp signal to said modulating means to cause said modulating means to provide a final deceleration brake control signal

24. attained by said average signal during wheel spin-up. 26. The .[.invention.]. .Iadd.deceleration control system .Iaddend.defined in claim 24 wherein said .[.brake control system further comprises for each of said wheel groups a control turn-on means for energizing said control means associated therewith and causing said associated control.]. .Iadd.means for submitting said on-ramp signal includes .Iaddend.means .[.to provide.]. .Iadd.for providing .Iaddend.an initial .Iadd.brake .Iaddend.deceleration control signal of maximum value commanding a full brake release followed by a gradual decrease from said maximum value to permit a corresponding gradual increase in brake pressure. .[.27. The invention defined in claim 24 wherein said brake control system further comprises for each of said wheel groups means for deactuating said control means associated therewith and for causing said associated control means incident to said deactuation to provide a deceleration control signal of gradually decreasing value to permit a gradual decrease in brake

23. to gradually remove brake pressure.Iaddend.. 25. The .[.invention.]. .Iadd.deceleration control system .Iaddend.defined in claim 24 wherein .[.each of.]. said reference generating means includes means for establishing an initial reference signal value based on the maximum value

25. pressure..]. 28. The .[.invention.]. .Iadd.deceleration control system .Iaddend.defined in claim 24 wherein each .[.said.]. deceleration brake control signal comprises a time integral function of said error signal.

28. control means..]. 32. A brake control system for controlling the brake application means for a wheel of a vehicle comprising:

analog signal generating means for producing a wheel speed signal that is a function of the rotational speed of said wheel;

anti-skid control means for receiving and processing said wheel speed signal to provide an anti-skid brake control signal;

reference generating means for generating a reference velocity signal having a selectively variable rate of decrease;

rate selector means for manually selecting a rate of decrease of said reference velocity signal indicative of a desired rate of wheel deceleration;

comparison means for comparing said wheel speed signal with said reference velocity signal for generating an error signal indicative of the difference between said wheel speed signal and said reference velocity signal;

deceleration control signal generating means responsive to said error signal to provide deceleration brake control signal;

gate means for receiving and comparing said anti-skid brake control signal and said deceleration brake control signal to transmit for control of said brake application means the control signal which commands the lower brake pressure; and

means for deactuating said deceleration control signal generating means and for causing said deceleration control signal generating means to provide incident to said deactuation a deceleration control signal of gradually

26. The .[.invention.]. .Iadd.deceleration control system .Iaddend.defined in claim 28 wherein .[.each said control means includes circuit means having a predetermined actuation threshold level and wherein.]. said time integral function is a time integral function of both positive and

29. decreasing value to permit a gradual decrease in brake pressure. 33. A brake control system for controlling the brake application means associated with each wheel of a pair of braked load-bearing wheels of an aircraft comprising:

analog signal generating means for each of said wheels for producing a wheel speed signal that is a function of the rotational speed of its associated wheel;

anti-skid control means for each of said wheels for receiving and processing said wheel speed signal to provide an anti-skid brake control signal for control of its associated wheel;

reference generating means for generating a reference velocity signal having a selectively variable rate of decrease;

rate selector means for manually selecting a rate of decrease of said reference velocity signal indicative of a desired rate of wheel deceleration;

averaging means responsive to the wheel speed signal associated with each of said wheels to form an average wheel speed signal therefrom;

comparison means for comparing said average wheel speed signal with said reference velocity signal for generating an error signal indicative of the difference between said average wheel speed signal and said reference velocity signal;

deceleration control signal generating means responsive to said error signal to provide a deceleration brake control signal;

gate means for each of said wheels for receiving and comparing said anti-skid brake control signal for its associated wheel and said deceleration brake control signal to transmit for control of the brake application means for its associated wheel the control signal which commands the lower brake pressure; and

means for deactuating said deceleration control signal generating means and for causing said deceleration control signal generating means to provide incident to said deactuation a deceleration control signal of gradually

27. negative variation of said error signal from said threshold level. 30. The .[.invention.]. .Iadd.deceleration control system .Iaddend.defined in claim 29 wherein .[.each.]. said deceleration brake control signal further comprises a non-integral, proportional function of said error signal. .[.31. The invention defined in claim 30 further comprising:

a means associated with each of said control means for comparing the time integral function formed thereby with the time integral function formed by another of said control means associated with another wheel group to cause the time integral function formed by said associated control means to command a brake pressure level not less than that commanded by said other

30. decreasing value to permit a gradual decrease in brake pressure. 34. A brake control system for an aircraft having plural groups of braked load-bearing wheels, said system comprising:

analog signal generating means associated with each of said wheels for producing a wheel speed signal that is a function of the rotational speed of its associated wheel;

anti-skid control means for each of said wheels receiving and processing said wheel speed signal to provide an anti-skid brake control signal for control of its associated wheel;

reference generating means for generating a reference velocity signal having a selectively variable rate of decrease;

rate selector means for manually selecting a rate of decrease of said reference velocity signal indicative of a desired rate of deceleration;

averaging means for each of said wheel groups for each of the wheels in its associated wheel group to form an average wheel speed signal therefrom;

comparison means for each of said wheel groups for comparing said wheel speed signal for the associated wheel group with said reference velocity signal for generating an error signal indicative of the difference between said average wheel speed signal for the associated wheel group and said reference velocity signal;

deceleration control signal generating means for each of said wheel groups responsive to said error signal for the associated wheel group to provide a deceleration brake control signal for the associated wheel group;

gate means for each of said wheels for receiving and comparing said anti-skid brake control signal for said wheel and said deceleration brake control signal for the associated wheel group to transmit for control of brake application means associated with said wheel the control signal which commands the lower brake pressure; and

a pressure balance means associated with each of said deceleration control signal generating means for comparing an output thereof with an output of another deceleration control signal generating means for another wheel group to cause the output of the associated deceleration control signal generating means to command a brake pressure level not less than that

31. commanded by said other deceleration control signal generating means. 35. A decelerational control system controlling the brake application means for a wheel of a vehicle comprising:

analog signal generating means for producing a wheel speed signal that is a function of the rotational speed of said wheel;

reference generating means for generating a reference velocity signal having a selectively variable rate of decrease;

rate selector means for manually selecting a rate of decrease of said reference velocity signal indicative of a desired rate of deceleration;

p1 comparison means for comparing said wheel speed signal with said reference velocity signal for generating an error signal indicative of the difference between said wheel speed signal and said reference velocity signal;

control means responsive to said error signal to provide a selected deceleration brake control signal; and

means for deactuating said deceleration control signal generating means and for causing said deceleration control signal generating means incident to said deactuation to provide a deceleration control signal of gradually

32. decreasing value to permit a gradual decrease in brake pressure. 36. A deceleration control system controlling the brake application means associated with each wheel of group of braked load-bearing wheels of an aircraft comprising:

analog signal generating means for each of said wheels for producing a wheel speed signal that is a function of the rotational speed of its associated wheel;

reference generating means for generating a reference velocity signal having a selectively variable rate of decrease;

rate selector means for manually selecting a rate of decrease of said reference velocity signal indicative of a desired rate of deceleration;

averaging means responsive to the wheel speed signal associated with each of said wheels to form an average wheel speed signal therefrom;

comparison means for comparing said average wheel speed signal with said reference velocity signal for generating an error signal indicative of the difference between said average wheel speed signal and said reference velocity signal;

deceleration control signal generating means responsive to said error signal to provide a deceleration brake control signal; and

means for deactuating said deceleration control signal generating means and for causing said deceleration control signal generating means to provide incident to said deactuation a deceleration control signal of gradually

33. decreasing value to permit a gradual decrease in brake pressure. 37. A deceleration control system for an aircraft having plural groups of braked load-bearing wheels, said system comprising:

analog signal generating means associated with each of said wheels for producing a wheel speed signal that is a function of the rotational speed of its associated wheel;

reference generating means for generating a reference velocity signal having a selectively variable rate of decrease;

rate selector means for manually selecting a rate of decrease of said reference velocity signal indicative of a desired rate of deceleration;

averaging means for each of said wheel groups for each of the wheels in its associated wheel group to form an average wheel speed signal therefrom;

comparison means for each of said wheel groups for comparing said wheel speed signal for the associated wheel group with said reference velocity signal for generating an error signal indicative of the difference between said average wheel speed signal for the associated wheel group and said reference velocity signal;

deceleration control signal generating means for each of said wheel groups responsive to said error signal for the associated wheel group to provide a deceleration brake control signal for the associated wheel group; and

means for each of said wheel groups for deactuating said deceleration control signal generating means associated therewith and for causing said associated deceleration control signal generating means incident to said deactuation to provide a deceleration control signal of gradually

34. decreasing value to permit a gradual decrease in brake pressure. 38. A deceleration control system for an aircraft having plural groups of braked load-bearing wheels, said system comprising:

analog signal generating means associated with each of said wheels for producing a wheel speed signal that is a function of the rotational speed of its associated wheel;

reference generating means for generating a reference velocity signal having a selectively variable rate of decrease;

rate selector means for manually selecting a rate of decrease of said reference velocity signal indicative of a desired rate of deceleration;

averaging means for each of said wheel groups for each of the wheels in its associated wheel group to form an average wheel speed signal therefrom;

comparison means for each of said wheel groups for comparing said wheel speed signal for the associated wheel group with said reference velocity signal for generating an error signal indicative of the difference between said average wheel speed signal for the associated wheel group and said reference velocity signal;

deceleration control signal generating means for each of said wheel groups responsive to said error signal for the associated wheel group to provide a deceleration brake control signal for the associated wheel group; and

a pressure balance means associated with each of said deceleration control signal generating means for comparing the signal formed thereby with the signal formed by another deceleration control signal generating means for another wheel group to cause the signal formed by said associated deceleration control signal generating means of the associated deceleration control signal generating means to command a brake pressure level not less than that commanded by said other deceleration control

35. signal generating means. 39. A brake control system for applying and controlling a brake application means for a wheel of a vehicle independently of operator brake application comprising:

signal generating means for producing a first signal that is proportional to the speed of said wheel;

reference generating means for generating a velocity reference signal having a selectively variable rate of decrease;

rate selector means for manually selecting a rate of decrease of said reference velocity signal indicative of a desired rate of vehicle deceleration;

comparison means for comparing said first signal with said reference signal for generating an error signal indicative of the difference between said first signal and said reference signal; and

control means for providing a signal to said brake application means to apply brake pressure to said wheel independently of operator brake application and responsive to said error signal to provide a selected deceleration brake control signal for controlling said brake pressure in

39. said error signal. 43. The invention defined in claim 39 wherein said deceleration control system further comprises a deceleration control turn-on means for energizing said control means and causing said control means to provide an initial deceleration control signal of maximum value commanding a full brake release followed by a gradual decrease from said maximum value to permit a corresponding gradual increase in brake

36. order to maintain said desired rate of deceleration. 40. The invention defined in claim 39 wherein said deceleration brake control signal

37. comprises a time integral function of said error signal. 41. The invention defined in claim 40 wherein said deceleration control means includes circuit means having a predetermined actuation threshold level and wherein said time integral function is a time integral function of both positive and negative variation of said error signal from said threshold level.

38. The invention defined in claim 40 wherein said deceleration brake control signal further comprises a non-integral, proportional function of

40. pressure. 44. The invention defined in claim 39 wherein said deceleration control system further comprises means for deactuating said control means and for causing said control means incident to said deactuation to provide a deceleration control signal of gradually decreasing value to permit a

41. gradual decrease in brake pressure. 45. The invention defined in claim 39 wherein said deceleration brake control signal comprises a time integral

44. nonintegral, proportional function of said error signal. 48. The invention of claim 39 wherein said control means provides said signal initially upon the actuation of a switch means by the operator.

42. function of said error signal. 46. The invention defined in claim 45 wherein said control means includes circuit means having a predetermined actuation threshold level and wherein said time integral function is a time integral function of both positive and negative variation of said

43. error signal from said threshold level. 47. The invention defined in claim 45 wherein said deceleration brake control signal further comprises a