U.S. patent application number 09/735959 was filed with the patent office on 2002-09-05 for hydraulic logic cross-coupling between physically-separate redundant servoactuators.
This patent application is currently assigned to Moog Inc.. Invention is credited to Flavell, David J..
Application Number | 20020121086 09/735959 |
Document ID | / |
Family ID | 27668429 |
Filed Date | 2002-09-05 |
United States Patent
Application |
20020121086 |
Kind Code |
A1 |
Flavell, David J. |
September 5, 2002 |
HYDRAULIC LOGIC CROSS-COUPLING BETWEEN PHYSICALLY-SEPARATE
REDUNDANT SERVOACTUATORS
Abstract
A redundant control actuation system (100) provides hydraulic
logic cross-coupling between physically-separate servoactuators
(101A, 101B). Each servoactuator has a control valve (102A, 102B)
arranged to provide a hydraulic output in response to a control
signal. Each actuator also has a hydraulic actuator (106A, 106B)
arranged to move a load in response to the hydraulic output from
its associated control valve. Logic valve means (103A, 104A, 105A,
103B, 104B, 105B) are operatively associated with the control
valves (102A, 102B) and actuators (106A, 106B). Each logic valve
means is supplied with hydraulic and electrical input signals. Each
logic valve means is operatively arranged between the associated
control valve and actuator to either (a) permit control operation
of the actuator in response to the control signal, (b) permit the
actuator to move freely and independently of the control signal, or
(c) restrain movement of the load independently of the control
signal, as a function of the supplied input signals. Each logic
valve means is operatively arranged to provide a hydraulic output
signal. The hydraulic output signal of each servoactuator is
provided as the hydraulic input signal to the other
servoactuator.
Inventors: |
Flavell, David J.; (Tierra
Verde, FL) |
Correspondence
Address: |
Peter K. Sommer, Esq.
Phillips, Lytle, Hitchcock, Blaine & Huber LLP
Intellectual Property Group
3400 HSBC Center
Buffalo
NY
14203
US
|
Assignee: |
Moog Inc.
|
Family ID: |
27668429 |
Appl. No.: |
09/735959 |
Filed: |
December 13, 2000 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09735959 |
Dec 13, 2000 |
|
|
|
09244708 |
Feb 4, 1999 |
|
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Current U.S.
Class: |
60/405 |
Current CPC
Class: |
B64C 13/503 20130101;
F15B 18/00 20130101; B64C 13/504 20180101 |
Class at
Publication: |
60/405 |
International
Class: |
F16D 031/02 |
Claims
What is claimed is:
1. A servoactuator for use in a redundant control actuation system,
said servoactuator having a body, said servoactuator comprising: a
control valve mounted on said body and arranged to provide a
hydraulic output in response to a control signal; a hydraulic
actuator mounted on said body and arranged to move a load in
response to the hydraulic output from said control valve; and logic
valve means mounted on said body and operatively associated with
said control valve and actuator, said body communicating with a
source of pressurized fluid and with a fluid return, said body
being provided with an external hydraulic signal, said logic valve
means being supplied with such hydraulic and electrical signals and
being operatively arranged between said control valve and said
actuator to either (a) permit control operation of said actuator in
response to said control signal, (b) permit said actuator to move
freely and independently of said control signal, or (c) restrain
movement of said load independently of said control signal, as a
function of said supplied input signals, said logic valve means
being arranged to provide a hydraulic output signal, said logic
valve means being arranged to provide a hydraulic output signal
external of said body which is a function of said hydraulic and
electrical signals.
2. A servoactuator as set forth in claim 1 wherein said control
valve is an electro-hydraulic servovalve.
3. A servoactuator as set forth in claim 1 and further comprising:
a first flow passageway arranged to selectively communicate the
opposing chambers of said actuator when said logic valve means
permits said actuator to move freely and independently of said
control signal.
4. A servoactuator as set forth in claim 3 and further comprising:
a second flow passageway having a restrictive orifice, said second
flow passageway being arranged to selectively communicate the
opposing chambers of said actuator when said logic valve means
causes said actuator to restrain movement of said load
independently of said control signal.
5. A servoactuator as set forth in claim 1 wherein said logic valve
means includes a bypass valve and a fail-safe valve connected
hydraulically between said control valve and said actuator.
6. A servoactuator as set forth in claim 5 wherein said bypass
valve is movable between a first position in which fluid is
permitted to flow between said control valve and actuator, and a
second position in which fluid is prevented from flowing between
said control valve and actuator but is freely bypassed between the
opposing chambers of said actuator, and wherein said bypass valve
is biased toward said second position.
7. A servoactuator as set forth in claim 6 wherein said bypass
valve includes a valve spool mounted for sealed sliding movement
within a body, and wherein a spring is operatively arranged to
cause said bypass valve spool to move toward said second position,
and wherein a fluid pressure is operatively arranged to cause said
bypass valve spool to move toward said first position.
8. A servoactuator as set forth in claim 7 and further comprising:
a source of pressurized fluid and a solenoid valve operatively
arranged between said source and said bypass valve, said solenoid
valve communicating with said source and being arranged such that
energization of said solenoid valve by said electrical input signal
will cause pressurized fluid from said source to move said bypass
valve spool to said first position and to provide said hydraulic
output signal.
9. A servoactuator as set forth in claim 5 wherein said fail-safe
valve is movable between an open position in which fluid is
permitted to flow between said bypass valve and said actuator, and
a closed position in which fluid is prevented from flowing between
said bypass valve and said actuator, and wherein said fail-safe
valve is biased toward said closed position.
10. A servoactuator as set forth in claim 9 wherein said fail-safe
valve includes a valve spool mounted for sealed sliding movement
within a body, and a spring operatively arranged to cause said
fail-safe valve spool to move toward said closed position, and
wherein a fluid pressure is supplied to said servoactuator as said
hydraulic input signal and is operatively arranged to cause said
fail-safe valve spool to move toward said open position.
11. A redundant control actuation system, comprising: first and
second servoactuators, each servoactuator having a body and having:
a control valve mounted on the associated body and arranged to
provide a hydraulic output in response to a control signal; a
hydraulic actuator mounted on said associated body and arranged to
move a load in response to the hydraulic output from said control
valve; and logic valve means mounted on said associated body and
operatively associated with said control valve and actuator, said
associated body communicating with a source of pressurized fluid
and with a fluid return, said associated body being provided with
an external hydraulic signal, said logic valve means being supplied
with such hydraulic and electrical signals and being operatively
arranged between said control valve and said actuator to either (a)
permit control operation of said actuator in response to said
control signal, (b) permit said actuator to move freely and
independently of said control signal, or (c) restrain movement of
said load independently of said control signal, as a function of
said supplied input signals, said logic valve means being arranged
to provide a hydraulic output signal, said logic valve means being
arranged to provide a hydraulic output signal external of said
associated body which is a function of said hydraulic and
electrical signals; and wherein the hydraulic output signal of each
servoactuator is provided as the hydraulic input signal to the
other servoactuator.
12. A redundant control actuation system as set forth in claim 11
wherein each control valve is an electrohydraulic servovalve.
13. A redundant control actuation system as set forth in claim 12
wherein said control valves are identical to one another
14. A redundant control actuation system as set forth in claim 11
wherein each servoactuator further comprises: a first flow
passageway arranged to selectively communicate the opposing
chambers of the associated actuator when the associated logic valve
means permits said associated actuator to move freely and
independently of said control signal.
15. A redundant control actuation system as set forth in claim 14
wherein each servoactuator further comprises: a second flow
passageway having a restrictive orifice, said second flow
passageway being arranged to selectively communicate the opposing
chambers of the associated actuator when said logic valve means
causes said associated actuator to restrain movement of said load
independently of said control signal.
16. A redundant control actuation system as set forth in claim 11
wherein said each logic valve means includes a bypass valve and a
fail-safe valve connected hydraulically between the associated
control valve and the associated actuator.
17. A redundant control actuation system as set forth in claim 16
wherein each bypass valve is movable between a first position in
which fluid is permitted to flow between the associated control
valve and the associated actuator, and a second position in which
fluid is pre-vented from flowing between said associated control
valve and said associated actuator but is freely bypassed between
the opposing chambers of said actuator, and wherein each bypass
valve is biased toward said second position.
18. A redundant control actuation system as set forth in claim 17
wherein each bypass valve includes a valve spool mounted for sealed
sliding movement within a body, and wherein a spring is operatively
arranged to cause said bypass valve spool to move toward said
second position, and wherein a fluid pressure is operatively
arranged to cause said bypass valve spool to move toward said first
position.
19. A redundant control actuation system as set forth in claim 18,
wherein each servoactuator further comprises a source of
pressurized fluid and a solenoid valve operatively arranged between
said source and the associated bypass valve, each solenoid valve
communicating with said source and being arranged such that
energization of said solenoid by said supplied electrical input
signal will cause pressurized fluid from said source to move the
associated bypass valve to said first position and to provide said
hydraulic output signal.
20. A redundant control actuation system as set forth in claim 15
wherein each fail-safe valve is movable between an open position in
which fluid is permitted to flow between the associated bypass
valve and the associated actuator, and a closed position in which
fluid is prevented from flowing between the associated bypass valve
and the associated actuator, and wherein each fail-safe valve is
biased toward said closed position.
21. A redundant control actuation system as set forth in claim 20
wherein each fail-safe valve includes a valve spool mounted for
sealed sliding movement within a body, and a spring operatively
arranged to cause said fail-safe valve spool to move toward said
closed position, and wherein a fluid pressure is supplied to said
servoactuator as said hydraulic input signal and is operatively
arranged to cause said fail-safe valve spool to move toward said
open position.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation-in-part of prior pending
U.S. patent application Ser. No. 09/244,708, filed Feb. 4, 1999,
now abandoned.
TECHNICAL FIELD
[0002] The present invention relates generally to servoactuators
for moving a load in response to a control signal, and, more
particularly, to an improved redundant control actuation system in
which physically-separate servoactuators, the outputs of which are
connected to a common load, are cross-coupled to exchange hydraulic
logic information therebetween.
BACKGROUND ART
[0003] Modern fly-by-wire ("FBW") aircraft use
hydraulically-powered electrically-controlled actuation systems,
typically dual-redundant, to operate flight control surfaces, and,
more recently, engine thrust-vectoring controls. As used herein,
the term "actuation system" refers to the total number of
electrohydraulic components required to move the surface with the
required functionality and performance. Many of these systems,
particularly those designed for military aircraft, take the form of
tandem-piston servoactuators that integrate the elements of a
dual-redundant actuation system into a single mechanical package
and have redundant sources supplying pressurized hydraulic fluid
independently to one or more integrated electrohydraulic
servovalves. On the other hand, in commercial aircraft, it is
generally desired that such dual-redundant actuator systems employ
physically- separated single-system servoactuators that are
connected to a common load and are provided with separate
connections to independent pressure sources and fluid returns.
[0004] In either case, these redundant actuation systems have been
typically arranged to operate cooperatively. More particularly, the
servovalves have been typically connected with respect to their
respective actuators with logic valves that permit three distinct
operating modes for each operable half of a dual servoactuator or
for each single-system servoactuator. The first of these modes
involves active control, in which the servovalve is used to
actively control the flows of fluid with respect to the associated
actuator. The second mode is known as a free-bypass mode, in which
the actuator is effectively disconnected from its associated
servovalve (e.g., because its control elements or power supplies
have failed) to permit continued control and operation of the load
by the other servoactuator. The third is known as a fail-safe mode,
in which the servovalve is disconnected from the associated
actuator, and in which the opposing chambers of the disconnected
actuator communicate with one another through a restricted orifice
to permit continued, albeit "damped", movement of the load.
[0005] Previous cross-coupling techniques for redundant
servoactuators have employed the exchange of electrical and/or
hydraulic signals. In general, these prior art devices have
involved pilot-operated solenoid valves and fail-safe valves to
accomplish mode switching in response to certain conditions. Some
devices have even employed a bypass valve in connection with a
fail-safe valve. Upon information and belief, each of these prior
systems has involved a compromise of performance, weight, size or
expense.
[0006] Accordingly, it would generally be desirable to provide an
improved redundant control actuation system, and servoactuator for
use in same, that avoids these compromises in the prior art.
DISCLOSURE OF THE INVENTION
[0007] With parenthetical reference to the corresponding parts,
portions or surfaces of the embodiment disclosed in FIGS. 4 and 4A,
merely for purposes of illustration and not by way of limitation,
the present invention broadly provides an improved servoactuator
(101A) for use in a redundant control actuation system (100), and
an improved redundant control actuation system employing such
servoactuators.
[0008] The improved servoactuator has a body and broadly includes:
a control valve (102A) mounted on the body and arranged to provide
a hydraulic output in response to a control signal; a hydraulic
actuator (106A) mounted on the body and arranged to move a load in
response to the hydraulic output from the control valve; and logic
valve means (103A, 104A, 105A) mounted on the body and operatively
associated with the control valve and actuator. The body
communicates with a source of pressurized fluid (P.sub.S1) and with
a fluid return (R.sub.1). The body is also provided with an
external hydraulic signal. The logic valve means is supplied with
such hydraulic signal and with electrical input signals, and is
operatively arranged between the control valve and the actuator to
either (a) control operation of the actuator in response to the
control signal, (b) permit the actuator to move freely and
independently of the control signal, or (c) restrain movement of
the load independently of the control signal. The selected mode is
a function of the supplied hydraulic and electrical input signals.
The logic valve means is operatively arranged to provide a
hydraulic output signal external of the body which is a function of
the supplied hydraulic and electrical signals..
[0009] The improved redundant control actuation system (100)
broadly comprises: first and second servoactuators (101A, 101B),
each servoactuator having a body and having: a control valve (102A,
102B) mounted on the associated body and arranged to provide a
hydraulic output in response to a control signal; a hydraulic
actuator (106A, 106B) mounted on the associated body and arranged
to move a load in response to the hydraulic output from the
associated control valve; and logic valve means (103A, 104A, 105A,
103B, 104B, 105B) mounted on the associated body and operatively
associated with the control valve and actuator. The associated body
communicates with a source of pressurized fluid (P.sub.S1,
P.sub.S2) and with a fluid return (R.sub.1, R.sub.2), and is
provided with an external hydraulic signal. The logic valve means
of each servoactuator is supplied with such hydraulic and
electrical input signals, and is operatively arranged between the
associated control valve and actuator to either (a) control
operation of the actuator in response to the control signal, (b)
permit the actuator to move freely and independently of the control
signal, or (c) restrain or impede free movement of the load
independently of the control signal. The selected mode is a
function of the supplied input signals. The logic valve means of
each servoactuator is arranged to provide a hydraulic output signal
external of the associated body which is a function of the
hydraulic and electrical signals. The hydraulic output signal of
one servoactuator is provided as the hydraulic input signal to the
other servoactuator.
[0010] In the preferred embodiment, each control valve (102A, 102B)
is an electro-hydraulic servovalve, and the two servovalves are
identical.
[0011] Each servoactuator (101A, 101B) may further include a first
flow passageway arranged to selectively communicate the opposing
chambers of its associated actuator when its logic valve means
permits the actuator to move freely and independently of the
control signal. Each servoactuator may further include a second
flow passageway having a restricted orifice (115A, 115B). The
second flow passageway is arranged to selectively communicate the
opposing chambers of its associated actuator when its logic valve
means causes the actuator to restrain movement of the load
independently of the control signal.
[0012] The logic valve means may include a bypass valve (104A,
104B) and a fail-safe valve (105A, 105B) connected hydraulically in
series between the associated control valve (102A) and actuator
(106A). The bypass valve is movable between a first position in
which fluid is permitted to flow between the associated control
valve and actuator, and a second position in which fluid is
prevented from flowing therebetween and is freely bypassed (i.e.,
without purposeful flow restriction) between the opposing chambers
of the associated actuator. The bypass valve may be biased toward
the second position. The bypass valve may include a valve spool
(110A, 110B) mounted for sealed sliding movement within a body, and
may further include a spring (111A, 111B) operatively arranged to
cause the spool to move toward the second position. The spool may
be caused to move toward the first position by a fluid
pressure.
[0013] The servoactuator may further include a port to which an
external source of pressurized fluid (P.sub.S1) is supplied, and a
solenoid valve (103A, 103B) operatively arranged between the port
and the bypass valve. The solenoid valve may communicate with the
port and be arranged such that energization of the solenoid valve
by the electrical input signal will cause pressurized fluid from
the port to move the bypass valve spool (110A, 110B) to the first
position and to provide the hydraulic output signal.
[0014] The fail-safe valve (105A, 105B) is movable between an open
position in which fluid is permitted to flow between the associated
bypass valve and the actuator, and a closed position in which fluid
is prevented from flowing between the associated bypass valve and
actuator. The fail-safe valve may be biased toward its closed
position. The fail-safe valve may further include a valve spool
(112A, 112B) mounted for sealed sliding movement within a body, and
a spring (113A, 113B) operatively arranged to cause the fail-safe
valve spool to move toward its closed position. A fluid pressure,
supplied to the servoactuator as its hydraulic input signal, may
urge the fail-safe valve spool to move toward its open
position.
[0015] Accordingly, the general object of the present invention is
to provide an improved servoactuator for use in a redundant control
actuation system.
[0016] Another object is to provide an improved redundant control
actuation system employing two such servoactuators.
[0017] Still another object is to provide an improved redundant
control actuation system which employs hydraulic logic
cross-coupling between physically-separate redundant servoactuators
to allow each servoactuator three modes of operation, as
appropriate, without electrical cross-coupling between them.
[0018] These and other objects and advantages will become apparent
from the foregoing and ongoing written specification, the drawings,
and the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1 is a schematic of a first prior art dual-redundant
control actuation system in which two control valves and associated
logic valve means are mounted on a common body, and are coupled to
a common tandem actuator to form an integrated dual-tandem
servoactuator.
[0020] FIG. 1A is a schematic view of the servoactuator shown in
FIG. 1 in association with an airfoil surface.
[0021] FIG. 2 is a schematic of a second prior art
servoactuator.
[0022] FIG. 2A is a schematic of a dual-redundant control actuation
system in which two physically-separate single-system
servoactuators of the type shown in FIG. 2 are coupled to a common
load.
[0023] FIG. 3 is a schematic of a third prior art
servoactuator.
[0024] FIG. 3A is a schematic of a dual-redundant control system in
which two physically-separate single-system servoactuators of the
type shown in FIG. 3 are coupled to a common load and are
electrically cross-coupled.
[0025] FIG. 4 is a schematic of an improved servoactuator.
[0026] FIG. 4A is a schematic of an improved dual-redundant control
actuation system according to the present invention, which provides
hydraulic logic cross-coupling between physically-separate
single-system servoactuators connected to a common load.
DESCRIPTION OF PREFERRED EMBODIMENT(S)
[0027] At the outset, it should be clearly understood that like
reference numerals are intended to identify the same structural
elements, portions or surfaces consistently throughout the several
drawing figures, as such elements, portions or surfaces may be
further described or explained by the entire written specification,
of which this detailed description is an integral part. Unless
otherwise indicated, the drawings are intended to be read (e.g.,
cross-hatching, arrangement of parts, proportion, degree, etc.)
together with the specification, and are to be considered a portion
of the entire written description of this invention. As used in the
following description, the terms "horizontal", "vertical", "left",
"right", "up", and "down", as well as adjectival and adverbial
derivatives thereof (e.g., "horizontally", "rightwardly ",
"upwardly", etc.), simply refer to the orientation of the
illustrated structure as the particular drawing figure faces the
reader. Similarly, the terms "inwardly" and "outwardly" generally
refer to the orientation of a surface relative to its axis or
elongation, or axis of rotation, as appropriate. In addition, the
expression "mounted on a body", and equivalents thereof, shall be
understood to encompass mounting on or within a body, and the term
"body" shall be understood to also encompass body assemblies
comprised of two or more parts.
[0028] The present invention broadly provides an improved
servoactuator (FIG. 4) for use in a redundant control actuation
system (FIG. 4A), and to a redundant control actuation system
employing such improved servoactuators. However, before proceeding
to a discussion of the present improvements, it is deemed advisable
to first review three prior art redundant control actuation systems
incorporating servoactuators, in order that the significance of the
present invention may be better understood.
[0029] First Prior Art Embodiment (FIGS. 1 and 1A)
[0030] Referring now to FIGS. 1 and 1A, a first prior art redundant
control actuation system is generally indicated at 20. As best
shown in FIG. 1, this control system is comprised of two actuators,
two control valves, and two logic valve means, all mounted on a
common body 19 to form an integrated dual-tandem servoactuator 21.
In this form, the servoactuator 21 comprises the entire control
actuation system. The two actuators are combined to form a common
tandem piston actuator, generally indicated at 22.
[0031] Actuator 22 is shown as having two axially-spaced pistons
23A, 23B mounted on a common rod 24. Left piston 23A is mounted for
sealed sliding movement within a left cylinder 25A, and right
piston 23B is mounted for sealed sliding movement within a right
cylinder 25B. The control valve and logic valve means coupled to
the left piston and cylinder 23A, 25A are identical to the control
valve and logic valve means coupled to the right piston and
cylinder 23B, 25B. Hence, only the left valve and actuator parts of
the servoactuator 21 will be explicitly described, it being
understood that the corresponding reference numeral, albeit
identified with suffix letter "B" rather than "A", refers to the
corresponding part, portion or surface of the right valve and
actuator component parts of servoactuator 21.
[0032] Servoactuator 21 is shown as broadly including two two-stage
four-way electro-hydraulic servovalves, generally indicated at 26A,
26B; two bypass valves 28A, 28B; two fail-safe valves 29A, 29B; and
two pilot solenoid valves 30A, 30B. An electrical feedback signal,
reflective of the position of rod 24 relative to the body 19, is
supplied from a suitable sensor, such as a linear variable
differential transformer ("LVDT") (not shown) or equivalent, via
line 27.
[0033] Servovalve 26A is arranged to be supplied with pressurized
hydraulic fluid P.sub.S1 from a suitable source (not shown), and is
connected to a first fluid return R.sub.1. Servovalve 26A may, for
example, be of the type disclosed in U.S. Pat. No. 3,023,782, the
aggregate disclosure of which is incorporated by reference. Suffice
it to say here that this servovalve is known, and includes an
electrical section 31A and a hydraulic section 32A. This type of
servovalve is used to produce a differential hydraulic output at
outlet ports C.sub.1, C.sub.2 in proportional response to an input
electrical signal supplied via conductors 33A to the electrical
section of the servovalve.
[0034] Bypass valve 28A is shown as having a three-lobed valve
spool 34A mounted for sealed sliding movement within a cylinder.
The spool is biased to move leftwardly to the position shown by a
spring 35A in the right spool right end chamber.
[0035] The fail-safe valve 29A is also shown as having a
three-lobed valve spool 36A mounted for sealed sliding movement
within a body or cylinder. The spool is biased to move leftwardly
by a spring 38A in the right spool end chamber. An actuator piston
39A is operatively arranged in a cylinder, and has a stub shaft
arranged to bear against the left end of spool 36A.
[0036] Solenoid valve 30A is also arranged to be provided with
pressurized fluid from source P.sub.S1, and communicates with
return R.sub.1. Solenoid valve 30A is a conventional three-way
two-position solenoid valve. When the solenoid is de-energized (as
shown), conduit 40A communicates with return R.sub.1. When the
solenoid is supplied with an energization current i.sub.1,
pressurized fluid from source P.sub.S1 is supplied to conduit 40A,
to the left spool end chamber of the fail-safe valve 29A, and to
the right piston end chamber of piston 39B for fail-safe valve 29B.
Conversely, another conduit 40B communicates solenoid valve 30B
with the right spool end chamber of the fail-safe valve 29B and the
left end chamber of actuator piston 39A.
[0037] The structure shown in FIG. 1 is in a depressurized and
de-energized condition.
[0038] When the system is energized and pressurized, supply
pressure P.sub.S1, and P.sub.S2 are provided to the servoactuator
21, where indicated. Similarly, the servoactuator return ports
communicate with separate fluid returns R.sub.1, R.sub.2. An
electrically-commanded hydraulic pressure differential is produced
at the outlet ports C.sub.1, C.sub.2 of each servovalve in response
to the electrical signal supplied to the associated servovalve via
conductors 33A, 33B.
[0039] Solenoid valves 30A, 30B are energized with currents
i.sub.1, i.sub.2respectively. Hence, supply pressure P.sub.S1
exists in conduit 40A, and is applied to the left spool end chamber
of the fail-safe valve 29A and to the right end chamber of piston
39B. This displaces fail-safe valve spools 36A rightwardly and 36B
leftwardly, compressing springs 38A and 38B. Conversely, supply
pressure P.sub.S2 exists in conduit 40B, and is applied to the
right spool end chamber of the fail-safe valve 29B and the left end
chamber of actuator piston 39A, to displace fail-safe valve spools
36A rightwardly and 36B leftwardly, compressing springs 38A, 38B.
When the two fail-safe valve spools are so displaced, the conduits
containing the restricted orifices, severally indicated at 41A,
41B, respectively, are covered. Thus, such energization and
pressurization overcomes the opposing bias of springs 39A, 39B, and
shifts each fail-safe valve spool hard-over to enable unrestricted
flow from the associated bypass valve through the associated
fail-safe valve to the opposing chambers of the associated
actuator.
[0040] Supply pressure is also supplied to the left and right spool
end chambers of bypass valves 28A, 28B, respectively. This shifts
each bypass valve spool hard-over, compressing springs 35A and 35B,
respectively. This displacement of each bypass valve spool
selectively communicates the servovalve outlet ports C.sub.1,
C.sub.2 with the opposing actuator chambers via the now-displaced
bypass and fail-safe valve spools. In this configuration, the
dual-redundant servoactuator operates in an active-active manner in
which both servovalves are simultaneously operated to control the
flows of fluid with respect to their respective actuator
chambers.
[0041] Suppose now that there is an energization or pressurization
failure of the right section of the servoactuator. Either situation
will cause conduit 40B to communicate with return R.sub.2 instead
of supply pressure P.sub.S2. The right spool end chamber of bypass
valve 34B, and the right spool end chamber of fail-safe valve 29B,
will both be vented to return R.sub.2. Hence, bypass valve 28B will
be shifted from its displaced or energized state, back to the
position shown in FIG. 1. However, because the left section of the
servoactuator is still operational in this example (i. e., is still
pressurized and energized), supply pressure P.sub.S1 will continue
to be provided through conduit 40A to the right end chamber of
fail-safe valve 29B and will keep the fail-safe valve spool 36B
shifted leftwardly. Hence, the opposing chambers of the right
actuator will communicate with one another through bypass valve 28B
and fail-safe valve 29B, the spool of which is still displaced. In
other words, the opposing chambers of the rightward actuator will
communicate via a plurality of series-connected passageways such
that the right actuator will be bypassed. Hence, it may move
freely, the only intended resistance being the pressure to move the
fluid through the series of connected passageways. Thus, in the
situation where there is a pressurization or energization failure
of servovalve B, control of the actuator will still be continued by
servovalve A, and actuator B will be in free-bypass mode. Of
course, if servovalve A were to be depressurized or de-energized,
while servovalve B continued to operate, the situation would be
reversed.
[0042] Alternatively, if there is a pressurization and/or
energization failure of both sections of the servoactuator,
solenoid valves 30A and 30B would communicate conduits 40A and 40B
with returns R.sub.1 and R.sub.2, respectively. Hence, the bypass
valve springs and the fail-safe valve springs would both expand to
urge their respective valve spools to move back to the positions
shown in FIG. 1. In this condition, the opposing chambers of both
sections of the tandem actuator communicate with their respective
fluid returns via passageways containing restricted orifices 41A,
41B, respectively. Hence, in this third fail-safe mode, neither
servovalve controls the operation of the load, but, passageways
containing restricted orifices communicate the actuator opposing
chambers with their respective returns. While not controlling the
movement of the load, this load restraint is customarily sized to
prevent "flutter" and other forms of dynamic instability of the
load.
[0043] Thus, in this first prior art system, two servovalves, two
sets of control logic valving and two actuators were mounted on a
common body to form a dual-redundant control actuation system in
the form of a tandem servoactuator assembly. The two actuators and
their respective control valving were not physically separate from
one another, but, to the contrary, were positioned immediately
adjacent one another in the common body. As best shown in FIG. 1A,
controlled movement of actuator rod 24 acted through an arm 42 to
selectively rotate an airfoil member 43 about its axis x-x.
[0044] This first embodiment offered three distinct modes of
operation for each operable half of the dual-tandem actuator.
However, such dual tandem servoactuators are generally large, heavy
and complex. This was acceptable for some applications, but not for
others.
[0045] Second Prior Art Embodiment (FIGS. 2 and 2A)
[0046] FIG. 2A depicts another prior art redundant control
actuation system, generally indicated at 50. This system included a
left servoactuator 51A and a physically-separate identical right
servoactuator 51B. Only the left servoactuator 51A illustrated in
FIG. 2 will be described, it being understood that the same
reference numeral, albeit with the suffix letter "B", will refer to
the corresponding part, portion or surface of the right
servoactuator 51B.
[0047] As shown in FIG. 2, servoactuator 51A includes a two-stage
electrohydraulic servovalve 53A, again having an electrical section
and a hydraulic section, as before. This servovalve may also be of
the type shown and described in U.S. Pat. No. 3,023,782.
Alternatively, other types of servovalves may be employed.
Servovalve 53A is adapted to be supplied with pressurized fluid
P.sub.S1 from a suitable source, and is adapted to communicate with
a fluid return R.sub.1. Servoactuator 51A also includes a pilot
solenoid valve 54A, a damped-bypass valve 55A, and an actuator 56A.
An LVDT (not shown) was operatively arranged to provide an
electrical feedback signal reflective of the position of the
actuator rod via line 57A. Solenoid valve 54A is a three-way
two-position solenoid-operated valve adapted to be energized by a
current i.sub.1. When solenoid valve 54A is de-energized, conduit
58A communicates with the fluid return R.sub.1. When solenoid valve
54A is energized, supply pressure P.sub.S1 is provided to conduit
58A. Bypass valve 55A is shown as having a three-lobed valve spool
59A mounted for sealed sliding movement within a body. A spring 60A
urges the spool 59A to move leftwardly to the position shown.
[0048] To avoid interchanging logic information between the two
separated servo-actuators, the system shown in FIG. 2A was operated
in an active-standby manner. In other words, during normal
operation, one servoactuator was energized and pressurized, while
the other was not. Hence, for example, if servoactuator 51A was
pressurized and energized, the supply pressure P.sub.S1 would be
applied through conduit 58A to shift bypass valve spool 59A
rightwardly, while compressing spring 60A. This enabled fluid
communication between servovalve control ports C.sub.1, C.sub.2
with the opposing chambers of actuator 56A. If servoactuator 51A
was used to control the movement of the load, servoactuator 51B was
normally de-energized, and the condition of its various parts was
as shown in FIG. 2. In other words, spring 60B expanded to urge
bypass valve spool 59B rightwardly. Hence, fluid could flow with
respect to other opposed chamber of actuator 56B via restricted
orifices, severally indicated at 61B. Thus, by virtue of these
restricted orifices, when one system was operated and the other was
not, the non-operable servoactuator provided additional dynamic
load that had to be overcome for the active servoactuator to
displace the load 52. Hence, the servoactuators were built
oversized to accommodate this additional load, and this unnecessary
size compromised weight and expense.
[0049] If servoactuator 51A failed by becoming depressurized or
de-energized, servoactuator 51B would be immediately energized. The
failure of servovalve 51A would cause spring 60A to expand to move
bypass valve spool 59A to the position shown in FIG. 2, while
servoactuator 51B was simultaneously energized. Thus, the situation
would be reversed with respect to that previously described, with
servoactuator 51B thereafter controlling movement of the load, and
servoactuator 51A being switched to a fail-safe or damped-bypass
mode.
[0050] Alternatively, if both servoactuators failed by being either
depressurized or de-energized, both bypass valve spools would move
to the position shown in FIG. 2. Hence, restricted orifices 61A and
61B would provide impedance to prevent dynamic instability of the
load, notwithstanding the fact that neither servoactuator
thereafter affirmatively controlled the load.
[0051] Thus, each half of the prior art embodiment shown in FIGS. 1
and 1A was adapted to operate in active, free-bypass and fail-safe
modes. These three modes were available when their use was
appropriate because hydraulic logic was exchanged between the two
sections of the servoactuator via lines 40A, 40B. This hydraulic
logic exchange was enabled by the fact that the dual-redundant
actuation elements of the system were positioned immediately
adjacent one another in a common body.
[0052] However, FIG. 2 represented the next step in the evolution
of such control systems. The redundant actuation elements were
moved physically apart to form two separate servoactuators, with
each servoactuator having its own body. Because of the physical
separation of the servoactuators, and the use of separate actuator
rods rather than a common tandem piston, the exchange of hydraulic
logic information between the two servoactuators was abandoned. In
the embodiment shown in FIG. 2, each servoactuator was adapted to
be operated in only two modes: active, and fail-safe or
damped-bypass.
[0053] Third Prior Art Embodiment (FIGS. 3 and 3A)
[0054] FIG. 3A illustrates a third prior art dual-redundant control
actuation system, generally indicated at 70, that also avoided the
interchange of hydraulic logic information between
physically-separate servoactuators 71A, 71B connected to a common
load 90. Only the left servoactuator 71A illustrated in FIG. 3 will
be explicitly described, it being understood that the corresponding
parts, portions or services of the right embodiment are indicated
by the same reference numeral, albeit with suffix letter "B".
[0055] Servoactuator 71A broadly included electrohydraulic
servovalve 72A, a bypass valve 73A, a two-position
solenoid-operated valve 74A, and a fail-safe valve 75A controlled
by the operation of a solenoid 76A. Solenoid valve 74A was adapted
to be energized with a current i,. Similarly, solenoid valve 74B
was adapted to be energized with a current i.sub.2. Solenoid 76A
was adapted to be energized with two separate summed currents,
i.sub.1+i.sub.2, where i.sub.2 was derived from the control
circuitry for servoactuator 71B and solenoid 76B was also adapted
to be energized with two separate summed currents, i.sub.1+i.sub.2,
where i.sub.1 was derived from the control circuitry for
servoactuator 71A. Thus, driving the solenoids 76A, 76B with summed
currents, as described provided an electrical cross-coupling
between servoactuators 71A, 71B. The two actuators 78A, 78B are
connected to a common load 79. An LVDT (not shown) was operatively
arranged to provide a feedback signal in lines 77A.
[0056] Here again, electrohydraulic servovalve 72A was a two-stage
four-way servovalve, such as shown in U.S. Pat. No. 3,023,782, and
was adapted to be supplied with a supply pressure P.sub.S1, to
communicate with a fluid return R.sub.1, and to selectively produce
a differential hydraulic output at its control ports C.sub.1,
C.sub.2. Servovalve 72B was similarly adapted to be supplied with a
supply pressure P.sub.S2, to communicate with a fluid return
R.sub.2, and to selectively produce a differential hydraulic output
at its control ports C.sub.1, C.sub.2, respectively.
[0057] When solenoid valve 74A was energized, supply pressure
P.sub.S1 existed in conduit 79A. Conversely, when solenoid valve
74A was de-energized, conduit 79A communicated with return R.sub.1.
Solenoid valve 74B operated in an analogous manner with respect to
conduit 79B.
[0058] Bypass valve 73A is shown as having a three-lobed valve
spool 80A mounted for sealed sliding movement within a body. The
valve spool is biased to move leftwardly relative to the body by a
spring 81A. Conduit 79A communicates solenoid valve 74A with the
spool left end chamber.
[0059] The fail-safe valve 75A is also shown as including a
three-lobed valve spool 82A mounted for sealed sliding movement
within a body. A spring 83A biases spool 82A to move leftwardly
toward the position shown. When solenoid 76A is energized, spool
82A will be displaced rightwardly, overcoming the compression of
spring 83A.
[0060] This redundant control system was adapted to be operated
primarily in an active-active manner. Normally, both servoactuators
would be energized (i.e., i.sub.1 and i.sub.2 were provided) and
pressurized (i. e., P.sub.S1 and P.sub.S2 were provided). Hence,
each of the respective logic valve spools would be shifted in the
appropriate direction against the urging of its associated return
spring. Hence, each servovalve would communicate directly with its
associated actuator.
[0061] Should there be a pressurization failure (i. e., P.sub.S1=0)
of servoactuator 71A, spring 81A would expand to move the bypass
valve spool 80A to the position shown in FIG. 3. However, since
both servoactuators would still be energized (i.e., i.sub.1 and
i.sub.2 would still be provided), the two summed energization
currents, i.sub.1+i.sub.2, would continue to hold valve spool 82A
in a rightwardly-displaced condition. Thus, in this arrangement,
when servoactuator 71A was depressurized but not de-energized, the
opposing chambers of actuator 78A could communicate with the
return. In effect, a depressurization of servoactuator 71A would
cause the actuator 78A to switch to a free-bypass mode, while
servovalve B would continue in an active mode to control movement
of the load.
[0062] Alternatively, if there was a de-energization of servovalve
A, but not a depressurization, then i.sub.1 would be lost. This
would cause solenoid valve 74A to move to its de-energized
position. Spring 81A would expand to shift valve spool 80A
leftwardly to the position shown. However, even though there was an
absence of current i.sub.1, current i.sub.2 from still-energized
servoactuator 71B would be sufficient to hold fail-safe valve spool
82A in a rightwardly-displaced condition. Hence, in this condition,
servoactuator A would be in a free-bypass mode.
[0063] Alternatively, if both servoactuators failed, either
electrically or hydraulically, currents i.sub.1 and i.sub.2 would
be removed from solenoids 76A and 76B, permitting the fail-safe
springs 83A, 83B to expand to urge the fail-safe valves 82A, 82B,
respectively, to move to the positions shown in FIG. 3. In this
condition, both actuators would be switched to their fail-safe or
damped-bypass modes such that flow with respect to the actuator
chamber would be constrained to pass through restricted orifices
84A, 84B.
[0064] Thus, in the system shown in FIG. 3A, because of the
electrical cross-coupling therebetween, each of the two
servoactuators was normally adapted to operate in active,
free-bypass and fail-safe (i.e., damped-bypass) modes, depending on
the nature of the energization and pressurization failure(s). As
with the form shown in FIG. 2A, the two servoactuators were
physically separate from one another, and there was no attempt to
exchange hydraulic logic information therebetween.
[0065] The Improved Control System (FIGS. 4-4A)
[0066] The improved redundant control actuation system according to
the present invention is generally indicated at 100 in FIG. 4A.
This arrangement also includes two identical separate
servoactuators, the left being indicated as servoactuator 101A and
the right being indicated as servoactuator 101B. Here again,
inasmuch as these two servoactuators are substantially identical,
the suffixes "A" and "B" will be used to distinguish the
corresponding parts, portions or surfaces of the two systems.
[0067] As best shown in FIG. 4, servoactuator 101A is shown as
including an electrohydraulic servovalve 102A provided with a
supply pressure P.sub.S1 communicating with a return R.sub.1 and
adapted to provide differential hydraulic output at its outlet
ports C.sub.1, C.sub.2, respectively. Servoactuator 101A also
includes a solenoid-operated valve 103A, a bypass valve 104A, a
fail-safe valve 105A and an actuator 106A. The two actuators are
coupled to a common load 108 (FIG. 4A). A conduit 109A communicates
the outlet of solenoid valve 103A with the spool left end chamber
of bypass valve 104A and the spool left end chamber of fail-safe
valve 105. When solenoid valve 103A is energized by current
i.sub.1, supply pressure will exist in conduit 109A and will shift
the bypass valve spool 110A rightwardly, overcoming the bias of
spring 111A, and will shift the fail-safe valve spool 112A
rightwardly, overcoming the bias of spring 113A. Conversely, when
solenoid valve 103A is de-energized, conduit 109A communicates with
return R.sub.1. In this condition, spring 111A expands to move
bypass valve spool 110A leftwardly to the position shown.
[0068] The fail-safe valve 105A is shown as having a three-lobed
valve spool 112A mounted for sealed sliding movement within a body.
A spring 113A urges valve spool 112A to move leftwardly toward the
position shown. An actuator 114A has a piston 115A arranged to act
against the left end of fail-safe valve spool 112A. The left end
chamber of actuator 114A is provided with the pressure in conduit
109B via conduit 116. Conversely, the pressure in conduit 109A is
provided by a conduit 118 to the left end chamber of actuator 114B.
The right chamber of actuator 114A, and the right chamber of
actuator 114B are vented to the atmosphere.
[0069] Thus, when servoactuator 101 A is both pressurized and
energized, supply pressure P.sub.S1 will exist in conduits 109A and
118, and will shift the bypass valve spool 110A rightwardly,
overcoming the bias of spring 111A, and the fail-safe valve spool
112A rightwardly, overcoming the bias of spring 113A. Conversely,
the pressure in conduit 109B will be transmitted by conduit 116 to
the left end chamber of actuator 114A, also displacing the
fail-safe valve spool rightwardly. Conversely, the pressure in
conduit 109A will be transmitted via conduit 118 to the left end
chamber of actuator 114B to shift fail-safe valve spool 112B
rightwardly from the position shown. Thus, when both servoactuators
are energized and pressurized, the bypass valve spools and
fail-safe valve spools are shifted from the positions shown in FIG.
4 to their displaced positions, thereby allowing control of each
actuator by its associated servovalve.
[0070] Should solenoid 103A be de-energized while servoactuator
101B remains pressurized and energized, conduit 109A will
communicate with the return. Hence, bypass valve spool 110A will
shift leftwardly to the position shown. This will isolate
servovalve 102A from actuator 106A, and the opposed chambers of
actuator 106A will communicate with the return. However, it should
be noted that the pressurized signal from conduit 109B is
transmitted via conduit 116 to keep fail-safe valve spool 112A
shifted rightwardly. This allows actuator 106A to operate in its
free-bypass mode.
[0071] Alternatively, should servoactuator 101A fail by being
depressurized (but not de-energized), then the pressure in conduit
109A will again fall to the return pressure R.sub.1. Spring 111A
will expand to urge the bypass valve spool 110A to move leftwardly
to the position shown in FIG. 4. However, the pressure of
still-functioning servoactuator 101B will be transmitted via
conduit 116 to the left end chamber of actuator 114A to hold
fail-safe valve spool 112A in its rightwardly-displaced position.
Thus, in this alternative situation, the opposing chambers of
actuator 106A will communicate with the return.
[0072] Alternatively, if both servoactuators become either
depressurized and/or de-energized, conduits 109A, 109B will
communicate with their returns R.sub.1, R.sub.2, respectively.
Hence, the bypass valve spool will be shifted back to the position
shown in FIG. 4. Conversely, loss of supply pressure in conduits
109A and 109B, will be transmitted via conduits 116, 118, and the
fail-safe valve spool springs 113A, 113B, will expand to move their
respective valve spools to the position shown. In this condition,
the opposed chambers of actuator 106A will communicate with return
R.sub.1 via restricted orifices 115A, 115A, while the opposed
chambers of actuator 106B will communicate with return R.sub.2 via
restricted orifices 115B, 115B.
[0073] Therefore, in summary, with the invention shown in FIGS. 4
and 4A, the two servoactuators may be operated simultaneously to
control movement of the load in an active-active manner.
Alternatively, only one servoactuator need be pressurized and
energized. The other will be in a free-bypass mode. Thus, if the
improved system is operated initially in an active-active manner,
and there is a pressurization or energization failure to either
servoactuator, the affected servoactuator will be immediately
shifted to a free-bypass mode, with the unaffected servoactuator
continuing to maintain control over the load. Alternatively, if
both servoactuators lose pressurization or energization, then both
servoactuators move to a fail-safe or damped-bypass mode in which
free movement of the load is restrained by passage of fluid through
the restricted orifices.
[0074] Thus, as demonstrated above, the prior art purposefully
avoided, and therefore taught away from, the exchange of hydraulic
logic information between two physically separate servoactuators.
The inventive improvement, however, defied this trend by
purposefully providing for the exchange of hydraulic logic signals
between the servoactuators.
[0075] Modifications
[0076] The present invention contemplates that many changes and
modifications may be made. For example, the servovalves may be
two-stage four-way electrohydraulic servovalves, such as shown and
described in U.S. Pat. No. 3,023,782. Alternatively, other types of
servovalves may be substituted therefor. In the aircraft
environment, it is generally desired that pressure sources P.sub.S1
and P.sub.S2 be independent of one another. However, while
desirable, this is not critical to the operation of the invention.
Fluid sources P.sub.S1 and P.sub.S2 may therefore be independent of
one another, or provided from a common source. Similarly, returns
R.sub.1 and R.sub.2 may connect with a common return, or may be
wholly independent of one another. The bypass and fail-safe valves
may be rearranged in position between the control valve and the
actuator and yet provide the same functions. The bypass valve and
fail-safe valve may be spool valves, as shown, or may be of some
other type or configuration. Similarly, the solenoid valves may be
pilot-type poppet or spool valves. They may be integrated with the
bypass valves, or the bypass function may be integrated with the
control valve. The manner in which the redundancy of the improved
actuation system is managed may be active-active or active-standby.
The fail-safe mode may be damped-bypass or may be arranged to cause
the servoactuator to drive to a preferred position.
[0077] Therefore, while the presently-preferred form of the
inventive redundant control system has been shown and described,
and several modifications thereof discussed, persons skilled in
this art will readily appreciate that various additional changes
and modifications may be made without departing from the spirit of
the invention, as defined and differentiated by the following
claims.
* * * * *