U.S. patent number RE33,486 [Application Number 07/022,488] was granted by the patent office on 1990-12-11 for selective deceleration brake control system.
This patent grant is currently assigned to Hydro-Aire Div. of Crane Company. Invention is credited to Robert D. Cook, Edgar A. Hirzel.
United States Patent |
RE33,486 |
Hirzel , et al. |
December 11, 1990 |
Selective deceleration brake control system
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.
Inventors: |
Hirzel; Edgar A. (Granada
Hills, CA), Cook; Robert D. (Valencia, CA) |
Assignee: |
Hydro-Aire Div. of Crane
Company (Burbank, CA)
|
Family
ID: |
27382304 |
Appl.
No.: |
07/022,488 |
Filed: |
March 5, 1987 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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488525 |
Apr 28, 1983 |
|
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119381 |
Feb 7, 1980 |
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Reissue of: |
243251 |
Apr 12, 1972 |
04022513 |
May 10, 1977 |
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Current U.S.
Class: |
701/75; 244/111;
303/126; 303/178 |
Current CPC
Class: |
B60T
8/1703 (20130101); B60T 8/325 (20130101); B60T
8/3255 (20130101) |
Current International
Class: |
B60T
8/32 (20060101); B60T 8/17 (20060101); B60T
008/02 () |
Field of
Search: |
;364/424,426,424.02,424.01 ;188/181A,181C ;244/11A,111
;303/20,93,106,109,100,DIG.3,DIG.4,6A,33 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Lall; Parshotam S.
Assistant Examiner: Dixon; Joseph L.
Attorney, Agent or Firm: Fulwider, Patton, Lee &
Utecht
Parent Case Text
.Iadd.This is a continuation of application Ser. No. 488,525, filed
4/28/83 which is a combination of application Ser. No. 119,381,
filed 2/7/80 now both abandoned..Iaddend.
Claims
What is claimed is:
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.
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
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
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
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
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
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
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
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
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.
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
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
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
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.
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
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
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
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
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
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
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
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
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
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
order to maintain said desired rate of deceleration. 40. The
invention defined in claim 39 wherein said deceleration brake
control signal
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.
The invention defined in claim 40 wherein said deceleration brake
control signal further comprises a non-integral, proportional
function of
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
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
gradual decrease in brake pressure. 45. The invention defined in
claim 39 wherein said deceleration brake control signal comprises a
time integral
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
error signal from said threshold level. 47. The invention defined
in claim 45 wherein said deceleration brake control signal further
comprises a
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.
Description
BACKGROUND OF THE INVENTION
The present invention relates to a deceleration control system for
a vehicle and, more particularly, to a selective deceleration brake
control system which is effective to control braking effort to
cause the vehicle to decelerate at a rate selected and set by the
operator.
It has been the general practice to provide anti-skid brake control
systems on commercial aircraft to aid the aircraft in its
deceleration after land. Anti-skid systems have reached a point of
development beyond merely detecting and terminating wheel skids. A
modern anti-skid system functions to optimize braking efficiency by
continuously adapting to changing runway conditions and other
factors affecting braking to provide maximum braking effort
consistent with the level of brake pressure selected by pilot brake
pedal control. Such an anti-skid system is disclosed in U.S. patent
application Ser. No. 155,903, filed June 23, 1971, entitled Brake
Control System, which issued as U.S. Pat. No. 3,768,873 on Oct. 30,
1973, and in U.S. Pat. No. 3,724,916, issued Apr. 3, 1973, and U.S.
Pat. No. 3,729,234, issued Apr. 24, 1973. Despite the development
of superior anti-skid brake control systems, however, it remained
necessary for the pilot to continuously adjust the level of brake
pressure by manual brake pedal manipulation in order to accomplish
a smooth and comfortable deceleration of the aircraft. The present
invention relieves the pilot of this burden of constant attention
to brake pedal adjustment while providing a smooth comfortable
deceleration of the aircraft by automatically controlling brake
pressure to cause the aircraft to decelerate at a rate preselected
by the pilot.
SUMMARY OF THE INVENTION
As indicated, the general purpose of this invention is to provide a
selective deceleration system for decelerating a vehicle at a
preselected rate of deceleration. Briefly, the selective
deceleration system comprises analog means, including a transducer,
for generating an electrical analog signal indicative of the
velocity of the wheel or wheels being controlled by the system. A
reference generating means is provided for generating a reference
velocity signal having a preselectable rate of decrease or rundown.
A comparator means continuously compares the wheel velocity analog
signal with the reference velocity signal to provide an error
signal indicative of the difference between the wheel velocity
signal and the reference velocity signal. The error signal is
submitted to a modulation circuit which generates a modulation
signal which is a time integral function of the error signal. The
modulation signal and the error signal itself are continuously
summed to form a composite deceleration brake control signal for
transmission to the valve driver associated with the wheel or
wheels which are being controlled. The brake pressure level applied
is a proportional function of the deceleration control signal, and
in this way, braking is controlled to cause the vehicle to
decelerate in accordance with the preselected rate of deceleration
chosen by the operator of the vehicle.
To insure a smooth initial application of brakes by the selective
deceleration system following wheel spinup, the system includes an
ON-ramp circuit which provides an initial gradual increase of brake
pressure following wheel spin-up. Similarly, an OFF-ramp circuit is
included to provide a gradual decrease of brake pressure when the
selective deceleration control system is deactuated.
The complete brake control system for the vehicle preferably
includes an anti-skid system operation in conjunction with the
selected deceleration control system. In this circumstance, the
deceleration brake control signal is not transmitted directly to
the valve driver, but instead is continuously compared to an
anti-skid brake control signal transmitted from the output of the
anti-skid system. If at any time the anti-skid control signal would
provide a lower braking pressure than the selective deceleration
control signal, the anti-skid signal will be applied to the valve
driver instead of the selective deceleration control signal.
However, if the selective deceleration control signal would provide
a lower braking pressure, then it will be transmitted to the valve
driver. By utilizing the selective deceleration control circuit in
combination with an anti-skid control circuit in this manner,
greater safety is obtained. For example, if the operator of the
aircraft were to select a deceleration rate of 12 feet per second
per second, and the runway were extremely wet, be may be unable to
develop a ground coefficient of friction between the tire and
runway sufficient to obtain a deceleration rate of 12 feet per
second per second. As the tire began to skid, the selected
deceleration control circuit would continue to operate. However,
the braking control for the wheel would instead be provided by the
anti-skid control system. The anti-skid system would continue to
control the braking of the aircraft until the ground coefficient
necessary to give a deceleration of 12 feet per second per second
without skidding is again available. As an additional safety
feature, the pilot is given the option of immediately discontinuing
the use of the selected deceleration control circuit. He may either
throw a switch in the cockpit or may apply manually controlled
braking by touching his brake pedals. In either case, the selective
deceleration control circuit will be cut out and only the anti-skid
circuit would be effective to modify braking of the aircraft.
A single selected deceleration control circuit may be used to
control the deceleration braking of a single wheel or of a group of
wheels. For example, in the embodiment described in the following
detailed description, one selective deceleration circuit controls a
pair of symmetrically positioned inboard wheels of an aircraft and
a second selective deceleration circuit controls a pair of
symmetrically positioned outboard wheels. In such arrangements, a
common rate selector is used to select a single deceleration rate
for both deceleration control circuits, and a pressure balancing
circuit is preferably provided to equalize the brake load
distribution between the two wheel pairs or groups controlled by
the separate selective deceleration circuits.
The foregoing features and objects and many of the attendent
advantages of this invention will be more readily appreciated by
reference to the following detailed description when considered in
connection with the accompanying drawings wherein like reference
characters designate like or corresponding parts throughout the
several views.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a functional block diagram of an exemplary aircraft brake
control system embodying a preferred form of the invention.
FIG. 2 is a functional block diagram of the principal units of the
selective deceleration control circuit 10 from FIG. 1.
FIG. 3 is a functional block diagram of an anti-skid control
circuit which may be utilized in conjunction with the selective
deceleration control circuit as shown in FIG. 1.
FIGS. 4a, 4b, 4c, and 4d collectively depict in block and schematic
diagram form the circuit details of the selective deceleration
control circuit shown in FIG. 1.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to the drawing wherein like reference numerals
designate like or corresponding parts throughout the several views,
a preferred embodiment of the invention is illustrated as used in
an exemplary brake control system for an aircraft having four
braked wheels. One selective deceleration control circuit 10 is
used to control a pair of outboard wheels OW1 and OW2 symmetrically
mounted on opposite sides of the aircraft. The outboard wheels OW1
and OW2 are collectively referred to in FIGS. 1 and 2 as the Group
I wheels. A second selective deceleration control circuit 10b is
used to control a pair of inboard wheels IW1 and IW2 also
symmetrically mounted on opposite sides of the aircraft. The
inboard wheels IW1 and IW2 are collectively referred to herein as
the Group II wheels. In application to aircraft having a greater or
lesser number of braked wheels, the number of wheels included in
each group controlled by one selective deceleration circuit and the
number of such groups and associated selective deceleration control
circuits will vary in accordance with the requirements of the
particular aircraft. In some applications, it may be found
desirable to provide a selective deceleration control circuit for
each wheel.
Although the selective deceleration control system could be
utilized without associated anti-skid circuitry, a more effective
and safer braking system is provided by using the selective
deceleration control circuit in conjunction with an anti-skid
system such as that described in the aforementioned Hirzel U.S.
patent application Ser. No. 155,903.
Before describing the selective deceleration control circuit 10, it
will be helpful to briefly review the anti-skid control circuit
referred to and disclosed in detail in the above identified Hirzel
patent application. Referring to FIG. 3, the anti-skid control
circuit 12 is shown in a functional block diagram. The associated
circuitry for each of the functional blocks may be found in the
above identified Hirzel patent application. The transducer 14
produces an output wave signal which is shaped and limited by the
squaring circuit 16 into a square wave, the frequency of which is
proportional to the rotational speed of the wheel to which the
transducer 14 is connected. The constant amplitude square wave
output of the squaring circuit 16 is transmitted to the
velocity-to-DC converter 18 whose function is to convert the wheel
speed frequency output of the squaring circuit 16 into a DC
velocity analog voltage that varies directly with the wheel speed.
This wheel speed signal is then transmitted via the lead 20 to the
anti-skid control circuit 12. The anti-skid control circuit 12
comprises a deceleration reference control circuit 26, a velocity
reference control circuit 28, a velocity comparator 30, a pressure
bias modulator control circuit 32 (hereinafter referred to as PBM
control circuit 32), and a summing amplifier and transient control
circuit 34. The output from the summing amplifier and transient
control circuit 34 is an anti-skid brake control signal which is
transmitted via the lead 24 to a valve driver 36 to reduce brake
pressure in proportion to the magnitude of the anti-skid brake
control signal.
In operation, the velocity comparator 30 compares the analog wheel
speed voltage from the velocity-to-DC converter 18 with an aircraft
velocity reference voltage that is generated by the velocity
reference circuit 28. The velocity reference circuit 28 comprises
an operational integrator having an output which simulates aircraft
velocity. The velocity reference circuit 28 has a network which
provides a unilateral feedback 29 which forces the output of the
velocity reference circuit 28 to track the wheel speed voltage to
initial conditions at spin-up. During spin-up, the velocity
reference circuit 28 is driven by the output of the velocity
comparator 30. After the spin-up condition is reached, the velocity
comparator output returns to a quiescent level which, in turn,
prevents any further increase in the velocity reference voltage
transmitted by the velocity reference circuit 28.
The velocity reference circuit 28 during deceleration of the
aircraft is driven by the output signal from the deceleration
reference control circuit 26 which also receives the analog wheel
speed voltage signal from the velocity-to-DC converter 18. The
deceleration reference control circuit 26 functions as a low pass
differentiator and operates on the analog wheel speed voltage
signal from the velocity-to-DC converter 18. The resultant output
from the deceleration reference control circuit 26 in essence is a
derivative of the slow changing component of the wheel speed
voltage. Since the slow changing component of wheel speed is due to
the aircraft deceleration, the output signal from the deceleration
reference control circuit 26 is proportional to the aircraft
deceleration or drag force. This output signal is transmitted to
the velocity reference circuit 28 to reduce the reference velocity
signal.
As previously indicated, the output signal from the velocity
reference circuit 28 is transmitted to the velocity comparator 30
where it is compared to the wheel speed signal produced by the
velocity-to-DC converter 18. Thus, the velocity comparator circuit
30 continuously compares wheel speed with aircraft velocity. The
output of the velocity comparator circuit 109 represents an error
signal indicative of wheel slip. This slip signal is used to drive
the PBM control circuit 32.
The PBM control circuit 32 is the main controlling element for
normal brake pressure correction. The PBM control circuit 32
functions as an operational integrator that integrates departure of
the slip signal from a predetermined actuation threshold to provide
a smoothly modulating anti-skid control voltage. This smoothly
modulating control voltage is transmitted to the summing amplifier
and transient control circuit 34. The velocity error signal from
the velocity comparator circuit 30 is also transmitted to the
summing amplifier and transient control circuit 4. The output
signal from the PBM control circuit 32 as well as the velocity
error signal are then summed and provide a composite signal to the
valve driver circuit 36. The valve driver circuit 36 supplies valve
drive current to the coil of a servo valve which, in turn, controls
brake pressure on the wheel. The current provided is in inverse
proportion to the required brake pressure reduction and thus the
greater the current supplied, the more the brake pressure is
relieved or relaxes on the wheels. Thus, regardless of the amount
of brake pressure applied by the pilot of the aircraft, and
regardless of the runway conditions, the amount of braking pressure
applied to the wheels may be automatically controlled by the
anti-skid control system 12 to prevent skidding of the aircraft.
While the above description is necessarily brief and functional in
nature, a complete description including a complete schematic
diagram of one type of anti-skid control system 12 may be found in
the aforementioned Hirzel U.S. patent application Ser. No.
155,903.
Again referring to FIGS. 1 and 2, the selective deceleration
control circuit 10 will now be described. The selective
deceleration control circuit 10 compares wheel speed with a
reference velocity signal produced by a deceleration generator 40
which has a selectable rate of decrease of rundown indicative of a
desired rate of deceleration of the aircraft. The difference
between the wheel speed signal generated by the velocity-to-DC
converter 18 and the reference velocity signal is an error signal
which is processed and used to generate a control signal for
transmission to the valve drivers 36 and 36a associated with the
wheels being controlled. The selective deceleration control circuit
10 utilizes the same transducer 14, squaring circuit 16, and
velocity-to-DC converter 18 which were utilized in the anti-skid
control circuit 12. However, it will be recognized that separate
circuitry may be employed, and it is not necessary to utilize
circuitry common with the anti-skid control circuit 12.
As seen in FIGS. 1 and 2, the selective deceleration control
circuit 10 controls the deceleration of two wheels of the aircraft,
namely outboard wheel OW1 and outboard wheel OW2. A similar
deceleration control circuit 10b controls the deceleration of
inboard wheels IW1 and IW2. It will be recognized that the
selective deceleration control circuit 10 could be used to control
more than two wheels or alternatively could be used to control a
single wheel.
The selective deceleration control circuit 10 includes a comparator
and hold circuit 42 which sums the wheel speed information from the
velocity-to-DC converters 18 and 18a and compares their average
output with the reference velocity signal generated by the
deceleration generator 40.
The deceleration generator 40 generates a voltage ramp which
comprises the reference velocity signal that is capable of
producing a reference velocity signal having a selectively variable
rate of decrease or rundown. The rate of decrease of the reference
velocity signal determines the rate of deceleration of the
aircraft. Any desired deceleration rate may be manually selected by
the pilot through the use of a deceleration rate selector 44 which
may comprise a simple potentiometer or rheostat located in the
cockpit of the aircraft.
The pilot activates the selective deceleration control circuit 10
by applying an ON-ramp control voltage from an ON-ramp control
circuit 46. This may be achieved by merely closing an ON-ramp
selector switch 48 or by other suitable logic switching means. The
selective deceleration control circuit may be disengaged by
applying an OFF-ramp control voltage from an OFF-ramp control
circuit 50. This is accomplished by closing the OFF-ramp selector
switch 52 also located in the cockpit. The closing of the OFF-ramp
selector switch 52 will immediately disengage the selective
deceleration control circuit 10 and will return the braking control
of the aircraft to the pilot and to the anti-skid control circuitry
in a manner to be described below. The selective deceleration
control circuit 10 may be disengaged by means which respond to
actuation of the brake pedals by the pilot.
Upon initial spin-up of the wheels due to the initial contract of
the wheels with the runway, the output of the comparator and hold
circuit 42 is low. This forces the initial output of the
deceleration generator 40 to rise to a voltage level equivalent to
the wheel velocity transmitted from the velocity-to-DC converter
18. This initial spin-up velocity establishes the initial value for
the reference velocity signal generated by the deceleration
generator 40. This reference velocity signal is compared to the
wheel speed by the comparator and hold circuit 42 to generate an
error velocity signal which is transmitted to a pressure bias
modulation control circuit 54, hereinafter referred to as PBM
control circuit 54. The PBM control circuit 54 functions as an
operational integrator in an identical manner to the PBM control
circuit 32 associated with the anti-skid control circuit 12.
The PBM circuit 54 receives an initial full charge from the ON-ramp
hold circuit, causing an initial full-brake-release output signal
to be provided by the PBM circuit 54. This PBM signal begins to
decrease due to capacitor discharge within the PBM control circuit
54 to cause a gradually increasing brake pressure to be applied to
the wheels. When an error signal is generated by the comparator and
hold circuit 42 which exceeds the PBM circuit actuation threshold,
the PBM circuit output becomes a time-integral function of the
error signal increasing when the error signal is above the
threshold and decreasing when it drops below the threshold. Thus,
the PBM control circuit 54 provides a smoothly modulating control
voltage for brake pressure by providing gradual and alternating
brake application and relaxation. As described below, this gradual
brake application and relaxation is used to control aircraft
deceleration at a rate equal to the preselected rate of
deceleration chosen by the pilot and represented by the rundown
ramp of the reference velocity signal generated by the deceleration
generator 40.
The modulation signal from the PBM control circuit 54 drives the OR
amplifier circuit 56. In addition, the error velocity signal from
the comparator and hold circuit 42 is applied to the input of the
OR amplifier 56 and summed with the PBM signal. The composite
output signal from the OR amplifier 56, therefore, comprises a
modulating PBM signal which is an integral function of the error
signal plus a proportional or direct function of the error signal.
The PBM signal component is the main controlling component with the
component directly proportional to the error signal serving as a
transient correction signal. In some applications, the component
proportional to the error signal may not be necessary.
As can be seen in FIGS. 1 and 2, the output of the OR amplifier 56
consists of two isolated outputs 58 and 60. Each OR amplifier
output is OR-ed with the associated output from the anti-skid
control circuits 12 and 12a by an OR gate 62 and an OR gate 62a,
respectively. The output of the OR gates 62 and 62a is transmitted
to the valve drivers 36 and 36a, respectively, which, in turn,
control the wheel valves 38 and 38a thereby controlling the brake
pressure on the wheels OW1 and OW2.
The valve driver 36 is controlled by the output from either the
anti-skid control circuit 12 or from the OR amplifier 56, whichever
has the highest output level or value or, in other words, whichever
will command the lower braking pressure to be applied to the
selected wheel. For example, if the pilot selects a deceleration
rate of 12 feet per second per second and the runway is extremely
wet, he may be unable to develop a ground coefficient between the
tire and runway sufficient to obtain a deceleration rate of 12 feet
per second per second. As the tire begins to skid, the selected
deceleration system will continue to operate. However, the
anti-skid control circuit will provide a higher output or in other
words will demand a lower brake pressure and will therefore control
the operation of the valve driver 36. The system will remain in the
anti-skid mode until a ground coefficient necessary to give a
deceleration of 12 feet per second per second is again available,
and at this time the output from the OR amplifier 56 will become
greater than the output from the anti-skid control circuit 12 and
will therefore control the valve driver 36.
Referring again to the ON-ramp hold circuit, it should be noted
that its output is connected to the ON-ramp hold circuit 62. The
initial closing by the pilot of the ON-ramp selector switch 48
connects a source of power 64 to the selective deceleration control
circuit 10 and also results in an initial 300 millisecond-wide
charging pulse from the ON-ramp hold circuit 62 to be applied to
the input of the PBM control circuit 54 to cause an initial full
brake release of all brake pressure on the wheels. Another function
of the ON-ramp control circuit 46 is to gate the output of the OR
amplifier 56. If the ON-ramp voltage is removed, the OR amplifier
outputs on the leads 58 and 60 are removed, and control of the
deceleration of the aircraft reverts to pilot manual brake control
with anti-skid control back-up.
The OFF-ramp control circuit 50 provides a gradual brake release
which may be initiated by the closing of the OFF-ramp selector
switch 52 or other suitable logic circuitry. Immediately upon the
closing of the OFF-ramp selector switch 52, a ramp voltage signal
is placed on the input of the PBM control circuit 54 to effectively
replace the error velocity signal as the input control to the PBM
control circuit 54. This new ramp signal causes a gradual release
of brake pressure to pilot-applied brake pressure level or
quiescent valve level before deactuating the ON-ramp control
circuit to return the control of the aircraft to manual braking
with anti-skid back-up.
Corresponding ON-ramp control, ON-ramp hold, and OFF-ramp control
circuits are provided in the inboard selective deceleration circuit
106 for simultaneous action under the control of the same switching
logic represented by switches 48 and 52. Pressure balance
amplifiers 66 and 66b are provided to function as balancing means
for equalizing the brake load distribution between the two
selective deceleration circuits 10 and 10b. This is accomplished by
comparing the outputs from the two selective deceleration PBM
control circuits 54 and 54b and forcing the control toward the
higher brake pressure.
Before describing the detailed circuitry of the selective
deceleration control circuit 10, it should be reiterated by
reference to FIG. 1 that the selective deceleration control circuit
10 is used to control the deceleration of a first group of wheels,
outboard wheels OW1 and OW2, controlled by valves 38 and 38a, and
that the second selective deceleration control circuit 10b is used
to control a second group of wheels, inboard wheels IW1 and IW2,
controlled by wheel valves 38b and 38c. For clarity, only portions
of the selective deceleration control circuit 20 are shown in FIG.
2 and in FIGS. 4a through 4d. However, it should be understood that
the control circuitry for the inboard wheels is identical to the
control circuitry of the outboard wheels.
It may be noted at this juncture that the selective deceleration
control circuits 10 and 10b are substantially electrically separate
from their associated anti-skid control circuits 12, 12a, 12b, and
12c which are fully described in the aforementioned Hirzel patent
application. The only common components utilized are the
transducers 14, 14a, 14b, 14c, the squaring circuits 16, 16a, 16b,
16c, the velocity-to-DC converters 18, 18a, 18b, 18c, the valve
drivers 36, 36a, 36b, 36c, and the wheel valves 38, 38a, 38b, 38c.
By maintaining the selective deceleration control circuits
substantially electrically separate from the anti-skid control
system 12, assurance is provided that a failure within the
selective deceleration control circuits will not impair the
anti-skid operation.
Now referring to FIGS. 4a through 4d, a complete schematic of the
selective deceleration control circuit 10 will be described. The
comparator and hold circuit 42 takes the wheel speed information
from the two wheels in a wheel pair at its inputs 72 and 74 from
the velocity-to-DC converters 18 and 18a, respectively, along the
leads 22 and 22a. A reference velocity voltage or signal which is
generated by the deceleration generator 40 is applied to the input
76 of the comparator and hold circuit 42 via a lead 41. This
reference velocity voltage is then compared to the average of the
two wheel velocity signals on the input points 72 and 74, and an
error signal is produced at the output of an operational amplifier
78. The operational amplifier 78 amplifies this error velocity
signal, and the output signal of the operational amplifier 78 is
applied through a voltage follower amplifier 80 to the input of the
PBM control circuit 54 via the lead 43. The transistor 82 is
normally off except when an OFF-ramp voltage is applied in which
case transistor 82 is turned on. The turning on of transistor 82
back biases a controlled rectifier 84 which then disconnects the
comparator and hold circuit 42 from the PBM control input. Thus,
whenever there is an off-ramp control signal generated by the
pilot, the error velocity signal no longer is transmitted to the
PBM control circuit 54.
As mentioned previously, the deceleration generator 40 generates a
reference velocity signal having a variable rate of decrease which
is indicative of the desired rate of deceleration of the aircraft.
This reference velocity signal is transmitted via the lead 41 to
the input of the comparator and hold circuit 42. The reference
velocity signal generated by the deceleration generator 40 is a
voltage ramp that is used as a measure of the .Iadd.desired
deceleration of the .Iaddend.aircraft and appears at the output 86
of the deceleration generator 40.
When wheel spin-up occurs, the output of the comparator and hold
circuit 42 is initially low. This forward biases controlled
rectifier 88 and charges capacitor 90 through operational amplifier
92 until the output signal (the reference velocity) is close to the
wheel velocity. When this happens, the output of the comparator and
hold circuit 42 will then rise until controlled rectifier 88 is
back biased, thereby preventing any further rise in this reference
velocity or, in other words, in the voltage on capacitor 90.
Capacitor 90 will now start to discharge at the rate determined by
the voltage at input 94 of the deceleration generator 40. The
voltage at the input 94 is determined by the pilot's setting of the
deceleration rate selector 44. In other words, the deceleration
rate selector 44 is a voltage source the output voltage of which
may be selected by the pilot to set the desired deceleration
rate.
To increase the accuracy of the rundown rate of the reference
velocity voltage, a small precision capacitor 96 is used together
with an operational amplifier 98 in a capacitance multiplier
configuration. Assuming that the operational amplifiers are ideal,
the capacitance .Iadd.multiplier .Iaddend.functions as follows. If
an operational amplifier is in linear region, then its inputs are
at the same potential. Therefore, current through the resistor 102
is the same as the current through the resistor 104, and the
current through resistor 106 is the same as the sum of the current
through resistors 108 and 110. The voltage of operational amplifier
98 at output point 112 must be the same as at its inputs, and
therefore the voltage drop across resistor 108 is the same as
across resistor 110, and the current through resistor 110 may be
computed from the following formula: ##EQU1## but I.sub.110 is the
discharge current of capacitor 90 and therefore, multiplying
I.sub.total by ##EQU2## has the same effect as multiplying
capacitor 90 by ##EQU3##
The PBM control circuit 54 functions to insure gradual brake
reapplication after an initial brake release. Initially upon the
application of an ON-ramp signal caused by the pilot closing his
ON-ramp selector switch 48, a 300 millisecond-wide pulse from the
ON-ramp control circuit 62 is applied to the input 126 of the PBM
control circuit 54 via the lead 128. This pulse will cause a
capacitor 132 to charge rapidly to the maximum PBM voltage. This
maximum PBM voltage is then applied via the leads 134, 136, and 138
to the OR amplifier 56. This causes the OR amplifier to have a
maximum output and will result in a maximum brake release. After
this initial pulse is removed from the capacitor, the capacitor 132
will start to discharge through a resistor 140. As the capacitor
discharges, the PBM voltage decreases and a gradual brake
application is obtained. This is what is referred to as the ON-ramp
brake application. Following this gradual ON-ramp brake
application, the only input to the PBM circuit 54 during normal
braking operation is from the comparator and hold circuit 42 via
the lead 43 through a resistor 142. This output from the comparator
and hold circuit 42 is the error velocity signal. The error
velocity signal from the comparator and hold circuit 42 is
integrated by the PBM control circuit 54 and more particularly by
the capacitor 132 and an operational amplifier 144. Resistors 146,
148, and 150 set the actuation threshold for the integration
process. A controlled rectifier 152 is a clamping diode that limits
the PBM voltage when there is no input.
The OR amplifier 56 is the output circuit for the entire selective
deceleration control circuit 10. The output of the OR amplifier 56
occurs at the output points 162 and 164. The signals at these
output points 162 and 164 are transmitted via the leads 58 and 60
to the valve drivers 36 and 36a, respectively. As mentioned
previously, the output signal from the PBM control circuit 54,
which in essence is an integral function of the error velocity
signal from the comparator and hold circuit 42, is applied to the
OR amplifier 56 via the lead 138 through the resistors 166 and 168,
and finally to operational amplifiers 170 and 172. In addition, the
error velocity signal from the comparator and hold circuit 42 is
applied directly to the OR amplifier 56 at input point 174 through
the capacitor 176 from the output of the operational amplifier 78
of the comparator and hold circuit 42 via the lead 178. Thus, the
deceleration brake control output signal of the OR amplifier
circuit 56 is a composite signal comprising the deceleration
control signal which is an integral function of the error velocity
signal as the main control component and a direct or proportional
function of the error velocity signal as a transient correcting
component. As mentioned previously, the output of the OR amplifier
56 is transmitted to the valve drivers 36 and 36a through an OR
gate 62 and an OR gate 62a (FIG. 1), and this signal is OR-ed with
the output signal from the anti-skid control circuits 12 and 12a.
If the OR amplifier output is higher than the output of the
anti-skid control circuits 12 or 12a, then the OR amplifier output
will control the valve driver 36 or 36a, but if the output from the
anti-skid control circuit is higher, then the anti-skid control
circuit signal will control the valve driver 36. This occurs
because the controlled rectifiers 178 and 180 are back biased.
To assure proper operation, a zener diode 182 is provided which
regulates the B plus voltage on the operational amplifiers 170 and
172 and maintains them at 18 volts in the preferred embodiment. A
capacitor 185 prevents power loss transients from affecting the
outputs of the OR amplifier 56. A pair of resistors 184 and 186 set
the OR amplifier threshold, i.e. the PBM voltage required to cause
an OR amplifier output that exceeds the valve driver threshold. The
OR amplifier 56 receives its B plus voltage from the ON-ramp
voltage circuit 40, and thus the ON-ramp voltage circuit 40 serves
to gate the output of the OR amplifier 56. This is done so that no
failure on the selective deceleration circuit 10 can cause a brake
release if the ON-ramp voltage is removed.
In normal operation, when the ON-ramp voltage is applied either by
the pilot closing the switch 48 or by suitable logic circuitry, the
transistor 206 is on and the transistor 208 is off, thereby
permitting normal operation of the OR amplifier 56. If the ON-ramp
voltage is removed, then the transistor 206 will begin to turn off
and when the breakdown voltage of the zener diode 210 is exceeded,
the transistor 208 will then turn off. This removes the OR
amplifier output from the valve driver input by grounding the point
212 of the OFF-ramp ramp circuit 50 and thereby also the outputs of
the operational amplifier 170 and 172 of the OR amplifier 56. A
capacitor 184 external to the OR amplifier circuit 56 introduces a
delay of approximately 100 milliseconds between the time of the
removal of the ON-ramp voltage and the removal of the OR amplifier
output.
Immediately upon the application of an ON-ramp voltage from the
ON-ramp control circuit 40, the ON-ramp hold circuit 62 generates
an output pulse at the output point 228. This pulse is applied to
the input of the PBM control circuit 54 via the leads 230, 130, and
128 and causes the PBM control circuit 54 to generate maximum PBM
voltage thereby creating an initial brake release prior to ON-ramp
brake application and prior to the generation of the error velocity
signal by the comparator and hold circuit 42.
The reference velocity voltage from the deceleration generator 40
is applied to the ON-ramp hold circuit 62 at point 232 via the
leads 234 and 41. Since during spin-up this voltage will change in
a positive direction, the normally off transistor 236 will turn on
and discharge the capacitor 238. After spin-up, the voltage at the
point 232 will no longer change in a positive direction and
therefore will turn off the transistor 236. The capacitor 238 will
now start to charge and when its voltage exceeds the breakdown
voltage of the zener diode 240 and the forward voltage of the
controlled rectifier 242 and the base emitter voltage of the
transistor 244, the transistor 244 will turn on. Transistors 244
and 246 are in a latching configuration so once they have turned
on, they will remain on so long as the ON-ramp voltage is applied.
When the transistors 244 and 246 turn on, the pulse in the PBM
control circuit 54 is terminated. The time delay between the
ON-ramp application and the turn on of transistors 244 and 246 is
approximately 300 milliseconds. A zener diode 248 provides
additional voltage regulation (transient protection). The capacitor
238 prevents the transistors 244 and 246 from unlatching during any
power loss transients.
The OFF-ramp control circuit 50 functions to cause a gradual brake
release after an OFF-ramp input voltage is applied due to the pilot
closing the OFF-ramp selector switch 52. The OFF-ramp control
circuit 50 is in a closed loop differentiator configuration. In
normal braking operation when there is an ON-ramp input but no
OFF-ramp input, the transistor 282 is held on. This will force the
output of the operational amplifier 284 to approximately plus 4
volts and since there is no OFF-ramp input, the controlled
rectifier 282 will be back biased thereby preventing the loading of
the input of the PBM control circuit 54.
When the OFF-ramp is applied, the transistor 282 is turned off, and
this permits normal operation of the OFF-ramp control circuit 50.
The OFF-ramp voltage is now applied to the output point 288 and
through the output of the point 290 to the input of the PBM control
circuit 54 via the leads 292, 130, and 128. The PBM voltage will
now increase at a rate proportional to the input current, and this
will therefore also be the case of the output of the OR amplifier
56 thus causing a release of brake pressure. This output from the
OR amplifier 56 is transmitted via lead 294 to the OFF-ramp control
circuit 50 where it is differentiated by the capacitor 296 and the
resistor 290 and is amplified by the operational amplifier 284. The
output of the operational amplifier 284 will therefore have a
voltage amplitude that is proportional to the slope of the output
of the OR amplifier circuit 56. Since the output of the operational
amplifier 144 of the PBM control circuit 54 will go in a negative
direction from the reference, part of the input current through the
resistor 150 of the PBM control circuit 54 will now be shunted from
the PBM control circuit input into the operational amplifier 144.
Equilibrium will therefore be established, and the rate of brake
release will be constant. Controlled rectifiers 302 and 304 form a
part of the gate for the OR amplifier 56. When the ON-ramp is
removed, the point 212 is grounded, and this removes the OR
amplifier output from the valve driver circuit 36 as described
above.
As mentioned previously, the function of the pressure balance
amplifiers 66 and 66b is to equalize the brake load distribution of
the outboard and inboard wheel groups which are controlled by the
selective deceleration circuits 10 and 10b, respectively (see FIG.
1). If this were not done, then one wheel group could carry all or
most of the brake load while the other wheel group carried only a
small brake load. The brake load information (the PBM voltage) from
the outboard wheel group is applied to the input point 330 of the
balance amplifier 66 via the leads 134 and 136. This PBM voltage is
also applied to the input of the balance amplifier 66b via the
leads 134 and 136b. The brake load information from the inboard
wheel group is applied to the input point 332 of the balance
amplifier 66 via the leads 334 and 336 and is also applied to the
input of the balance amplifier 66b via the lead 336b (FIG. 1). The
output from the pressure balance amplifier 66 is applied to the
input of the PBM control circuit 54b via the lead 359. Similarly,
the output of pressure balance amplifier 66b is applied to the
input of PBM control circuit 54 via the leads 357 and 128. If the
two inputs to the pressure balance amplifier 6 are approximately
the same, the output of the operational amplifier 338 is less than
4 volts and will not affect the PBM control circuit 54b associated
with the inboard wheels. But if the voltage at the points 330 is
less than that at point 332, then the output of the operational
amplifier 338 goes higher than 4 volts and will cause an increase
of the PBM voltage in PBM control circuit 54b (FIG. 1) until the
input at the points 330 and 332 is again in balance. It should be
noted here that the PBM reference is plus 4 volts, and therefore,
plus 4 volts with respect to ground out of the PBM control circuit
54 means zero PBM voltage and zero volts with respect to ground
means maximum PBM voltage. A similar balancing control takes place
in the pressure balance amplifier 66b (FIG. 1) which if an
inbalance occurs, controls the PBM voltage in PBM control circuit
54.
As mentioned heretofore, the transistor 82 of the comparator and
hold circuit 42 is off at all times except for a short time
(approximately 300 milliseconds) at the beginning of the ON-ramp.
Its function is to assure that there is no PBM voltage buildup due
to pressure balance amplifier unbalance until the entire system has
stabilized and thus the pressure balance amplifiers 66 and 66b only
affect the selective deceleration control circuits 10 and 10b after
stabilization.
The voltage regulator circuit 70 does not appear in FIGS. 1 and 3
and is disclosed to show one method for obtaining the various
voltages needed to operate the selective deceleration control
circuit 10. However, it will be recognized that several other
methods may be utilized to obtain the required operating voltages.
The voltage regulator circuit 70 takes the 24 volt DC input voltage
and converts it to a 15 volt DC source. The voltage regulator is of
the series type (emitter follower) where the voltage at the base of
a path transistor 364 is determined by the voltage across the
controlled rectifier 366 and the zener diode 368. Zener diode 368
is rated at 14.6 volts, and the forward voltage of the controlled
rectifier 370 is 0.7 volts. Therefore, the base voltage of the
transistor 364 will be approximately 15.3 volts where the voltage
at the emitter (output voltage) will be approximately 14.6 volts.
Transistors 372 and 374 form a voltage follower that supplies the
plus 4 volt DC to the rest of the selective deceleration control
circuit 10. The 4 volts from the main power source of the aircraft
enter the voltage regulator circuit 70 at the points 376 and 378
and are applied to the base of the transistor 372 through the
resistors 380 and 382. Since the base emitter voltage drops, the
transistors 372 and 374 cancel each other, the voltage at the
emitter of the transistor 374 (output voltage) will be
approximately the same as the input voltage or plus 4 volts. The
capacitors 384 and 386 provide additional filtering. The resistor
388 reduces the power dissipation in the transistor 364 and also
provides isolation from the 24 volt input.
It will be recognized that the schematic diagrams shown in FIGS.
4a, 4b, 4c, and 4d represent one illustrative embodiment of the
invention. The various circuit elements are tabulated below as to
value or type number. It will be recognized, however, that these
values are exemplary and are merely illustrative of the invention,
and various modifications may be made without departing from the
spirit and scope of the invention. All capacitor values are in
microfarads except as otherwise noted. All resistor values are in
ohms or kilo except as otherwise noted.
______________________________________ DECELERATION GENERATOR-40
VALUE OR ELEMENT NUMBER TYPE NUMBER
______________________________________ 90 1 .mu.f 96 .0022 .mu.f
102 57.6K 104 57.6K 106 4.99K 108 4.99K 110 511K 114 8.87K 116
1.62K 118 178K 120 0.1 .mu.f 122 511K 124 10K 125 909 .OMEGA. 127
3.74K 88 CD5645 92 S101 98 LM207
______________________________________ COMPARATOR AND HOLD
CIRCUIT-42 VALUE OR ELEMENT NUMBER TYPE NUMBER
______________________________________ 71 4.7 .mu.f 73 2.37K 75
13.3K 77 150K 79 150K 83 301K 85 2K 87 IN751A 78 S101 80 S101 82
2N956 ______________________________________ PBM CONTROL CIRCUIT-54
VALUE OR ELEMENT NUMBER TYPE NUMBER
______________________________________ 132 2.2 .mu.f 140 499K 142
40.2K 146 24.3K 148 130K 150 1K 160 100 pF 144 42-15570
______________________________________ OR AMPLIFIER-56 VALUE OR
ELEMENT NUMBER TYPE NUMBER ______________________________________
166 150K 168 150K 176 .047 .mu.f 184 150K 185 150 .mu.f 186 280K
188 1K 190 1K 192 10K 198 150K 200 46.4K 202 280K 204 1K 196 IN649
182 UZ818 170 S101 172 S101 ______________________________________
ON-RAMP CONTROL CIRCUIT-46 VALUE OR ELEMENT NUMBER TYPE NUMBER
______________________________________ 214 20K 216 5.11K 218 4.53K
220 10K 222 2.2 .mu.f 224 7.5K 226 IN649 210 IN5234 208 2N956 206
2N956 ______________________________________ ON-RAMP HOLD
CIRCUIT-62 VALUE OR ELEMENT NUMBER TYPE NUMBER
______________________________________ 258 3.32K 262 1K 264 10K 268
15K 270 6.8 .mu.f 271 10K 272 6.8 274 2K 276 2K 252 CD5645 266
IN649 240 IN5230 248 UZ5720 236 2N956 246 2N2605 244 2N930
______________________________________ OFF-RAMP CONTROL CIRCUIT-50
VALUE OR ELEMENT NUMBER TYPE NUMBER
______________________________________ 296 22 .mu.f 298 49.9 206 2K
310 750 312 .68 .mu.f 316 383K 317 249K 318 68.1K 322 1.21K 324
200K 284 S101 282 2N930 286 CD5645 323 CD5645
______________________________________ PRESSURE BALANCE
AMPLIFIER-62 VALUE OR ELEMENT NUMBER TYPR NUMBER
______________________________________ 340 51.1K 342 51.1K 344 2.2
.mu.f 346 10K 348 10K 350 200K 352 2.2 .mu.f 354 200K 358 49.9K 360
2K 362 1M 338 ______________________________________ VOLTAGE
REGULATOR-70 VALUE OR ELEMENT NUMBER TYPE NUMBER
______________________________________ 380 2K 382 2K 384 6.8 .mu.f
386 0.1 .mu.f 388 150 .OMEGA. 392 750 .OMEGA. 394 1.5K 396 4.32K
364 2N1893 372 2N930 374 2N2605 368 1N4058
______________________________________
It should be understood, of course, that the foregoing disclosure
relates to only a preferred embodiment of the invention and that
numerous modifications or alterations may be made therein without
departing from the spirit and scope of the invention as set forth
in the appended claims.
* * * * *