Note: Descriptions are shown in the official language in which they were submitted.
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CONTROL PROCESS AND DEVICE FOR AN AIRCRAFT ROLL OR
PITCH CONTROL SURFACE
DESCRIPTION
Technical field
This invention relates to a process and device for
controlling an aircraft roll or pitch control surface.
For the purposes of this invention, a roll control
surface is a contro7_ surface that causes the aircraft
to =rotate about its roll axis. For example the roll
control surface in an aircraft may actually be an
ailE~ron, a canard surface, spoilers or a banking
control surface.
A pitch control surface is a control surface that
cau~;es the aircraft t:o rotate about its pitch axis.
Note also that a:n aircraft elevon is considered to
act as a pitch control surface and roll control surface
at the same time.
More precisely, the invention relates to an
electrical control device intended for use on transport
aircraft that simultaneously satisfies precision,
reliability and lightweight requirements in force for
this type of aircraft:.
State of prior art
Document (1) FR--A-2 604 685 describes a control
device for an aircraft pitch control surface equipped
with. two electrohydraulic actuators with an electric
input and one hydromechanical actuator with one
mechanical input. In this device, each actuator is
supplied by a specific hydraul,~c circuit.
Electrohydraulic actuators receive electrical
control orders output by computers associated with
them.
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Furthermore, only one of the three actuators is
controlled at any one time to maneuver the control
surf=ace. If there is a failure in the control system
of any one of the actuators, the control system for the
next. priority actuator is triggered according to a
predetermined hierarchy. The control system for the
hydromechanical actuator has the lowest triggering
priority. It thus acts as a mechanical standby if
there is an electric failure in the other control
systems .
With a device conform with document (1), if a
fai7_ure makes it impossible to use an actuator, for
example in the case of a failure causing a pressure
drop in the hydraulic circuit supplying the
elec:trohydraulic actuator, or if the actuator itself
fai7_s or if the actuator control fails, the control
surface is maneuvered either with the electrohydraulic
actuator remaining in operation, or possibly with the
hydromechanical actuator.
However, it is found that it is impossible to
actuate the control. surface with a hydromechanical
actuator and an electrohydraulic actuator
simultaneously, on aircraft equipped with a control
surface control device in accordance with document (1).
Thug>, if a failure makes it impossible to use an
actuator with an electrical control, it is no longer
pos~~ible to actuate the two remaining actuators
simultaneously. Therefore each actuator has to be
sized to output the maximum force necessary for
specific maneuvers.
This type of rneasure increases the size, and
con~:equently the mass of actuators and the
corresponding hydraulic circuits.
Therefore one of the purposes of this invention is
to propose a control surface control device that weighs
less; than the device in. document (1), and which is
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capable of maneuvering t:he control surface even under
the worst cases in which high forces are applied to the
control surface.
Yet another purpose is to propose a device that
remains operational even if there is a failure in the
actuator electrical control systems.
Yet another purpose of the invention is to propose
a control device that can be used to maneuver the
control surface with a significantly higher precision
than is possible with mechanically controlled devices.
Another purpose of t=he invention is to propose a
perfected control process for the pitch or roll control
surface that satisfies strict reliability and safety
requirements.
Dis~~losure of the invention
In order to achieve these purposes, the precise
objective of the invention is a device for controlling
the roll or pitch control surface of an aircraft
comprising at least two actuators, each actuator having
at least one electrical control input, and an
electrical control s~ystern for the actuators capable of
being in a first or "normal flight" state, in which at
lea;~t one of the actuators is controlled to actuate the
control surface . Accord:ing to the invention, at least
one of the actuator;, called the hybrid actuator, also
comprises a mechanical control input, and the actuator
electrical control ~~ystem may be in a second state or
the "maneuver" state in which at least two of the
actuators are controlled to simultaneously actuate the
control surface, and a third state or the "electrical
cont=rol failure" state in which the hybrid actuator is
cont=rolled from the wechanical control input to actuate
the control surface.
For the purposes of: this invention, the normal
fli<~ht state means the state in which there is no roll
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or pitch control, or a state in which the roll or pitch
controls are applied to initiate very small amplitude
mov~=_ments of the control surface for normal trajectory
corrections .
In the normal flight state, the control surfaces
occupy "at rest" positions, or are carrying out low
amplitude movements about: their "at rest" position.
The "maneuver" state is a state in which the
aircraft is carrying out a maneuver, for example such
as a vertical acceleration, a turn or a recovery in
which there is a large load on the control surfaces)
in question. The si=ate of the maneuver may also be a
stare in which the aircraft is not carrying out any of
the maneuvers mentioned above, but is subject to
turbulence increasing the forces applied on the control
sur:=aces .
In the maneuver state, the control surfaces usually
make movements in which. the amplitude from the "at
rest." position exceE=ds the amplitude of movements in
the normal flight state.
According to the invention, a larger number of
actuators is controlled to actuate the pitch or roll
cont=rol surface in t:he maneuver state.
This can increase the aircraft maneuvering speed,
for example to avoid an obstacle.
Furthermore, this makes it possible to reduce the
size of the actuators.
During normal flight, a single actuator may be
cuff=icient to hold the control surface in position.
Dur__ng the maneuver state, the fact of using two or
more active actuators simultaneously can provide
sufj_icient power to maneuver the control surface
without oversizing t:he actuators.
Note that this possibility is not available in the
case of the device described in document (1), since,
for example, it is not possible to actuate the actuator
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with a mechanical input and one or two actuators with
electrical inputs simultaneously.
If three actuators are used for each control
sur:Eace, this invention makes it possible to reduce the
5 size of the actuators so that they are smaller than the
solution described in document (1). If only two
actuators are used per control surface, the device
according to the invention enables maneuvering cases
sim_~lar to those possible with the device in document
(1); by using one actuator less.
The "electrical control failure" state is a state
in which the electrical control system no longer
generates any flight control orders, for example due to
one or more electrical failures or one or more computer
fai=_ures .
Thus in the "electrical control failure" state, the
dev=_ce according to the invention provides the safety
of ~~ mechanical control.
According to one aspect of the invention, the
electrical control system for the actuators may include
a calculation unit as:~ociated with each actuator
respectively.
Each calculation. unit may be equipped with only
one, or preferably with several redundant computers.
There computers generate control orders to actuators.
The computers also control actuator operating modes
that. are described in more detail later in the
remainder of the description.
According to another aspect of the invention,
actuators with elE:ctrical inputs may comprise a
hydraulic jack with two chambers, and a servovalve
connected to a hydraulic circuit to output a hydraulic
fluid flow to the chambers depending on an electrical
ordEer from the calc:ulat.ion unit associated with the
actuator.
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According to one aspect of the invention, actuators
with an electrical control input and without
mechanically controlled inputs can operate in two
mode's .
A first mode is the "electrical active" mode. A
solenoid valve in the actuator is excited by a computer
designed to control the actuator and the jack chambers
are put into communication with the servovalve. The
servovalve then outputs a hydraulic fluid flow that
depends on the electrical orders output by a computer
in the electrical control system.
A second mode is the "damped" mode. In this
operating mode, the ~~olenoid valve is disexcited by the
control computer and the actuator jack chambers are put
into mutual communication through a restrictor. This
restrictor slows the passage of the hydraulic fluid as
it passes from one jack to the other thus damping
movements of the control surface. A damped mode can
also be provided with several degrees of damping.
Slight damping only slightly effects the actuating
performances of the control surface when the aircraft
is being maneuvered. Higher damping may be provided
for actuators which do not participate in actuating the
control surface when there is a failure or in the
normal operating state of the aircraft.
According to one embodiment of the invention, the
device may comprise three actuators with electrical
inputs, including at :Least one hybrid actuator.
Actuators with hybrid inputs may also operate in the
"active", "electric", and "damped" modes. They may
also operate in a "mechanical active" mode. According
to ~. first embodiment of the hybrid control actuator,
it comprises a first solenoid valve controlled by the
calculation unit respectively associated with it, the
first solenoid valve being capable of occupying an
excited state corre:~ponding to an "electric active"
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operating mode of the j ack in which the j ack chambers
are put into commun_Lcation with the servovalve, and a
disexcited state. T:he hybrid actuator also comprises a
second and third :solenoid valve controlled by the
calculation units associated with the other two
actuators in the device respectively, and capable of
alternately being in an excited state and a disexcited
stage, the chambers of the hybrid actuator jack being
put into communication with each other in a "damped"
operating mode of the jack when the first solenoid
valve is in a disexcited state and at least one of the
second and third solenoid valves is in an excited
stage, and the chambc=rs of the hybrid actuator jack are
put into communication with a distributor connected to
the mechanical input of the actuator in a "mechanical
active" operating mode, when the first, second and
third solenoid valves are in a disexcited state.
When the jack chambers are in communication with
the servovalve, the servovalve outputs a flow of
hydraulic fluid to them that depends on electrical
control orders generated by the electrical control
system and applied to the servovalve. Similarly, when
the jack chambers are in communication with the
distributor, the distributor outputs a flow of
hydraulic fluid into them that depends on mechanical
orders applied on the mechanical control input.
According to another embodiment of the hybrid
actuator, it may also comprise a first, second and
third solenoid valve controlled by a calculation unit
associated with thE: said hybrid actuator, and by
calculation units associated with the other two
actuators in the device, each capable of alternately
being in an excited state and a disexcited state, the
actuator operating i_n a "damped" mode, in which the
jack chambers are put into communication when at least
one of the second and third solenoid valves is in an
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excited state; the actuator operating according to an
"electric active" mode in which the jack chambers are
put into communication with the servovalve, and in
which the servovalve is controlled through the
electrical control input, when the first solenoid valve
is excited and the second and third solenoid valves are
disE~xcited, and the actuator operating according to a
"mechanical active" mode in which the jack chambers are
put into communication with the servovalve and in which
the actuator is controlled through the mechanical
control input, when the first, second and third
solenoid valves are in a disexcited state.
According to a particular embodiment with two
actuators, one of the actuators of the hydrostatic type
with an electrical control input may be an EHA
(Electro-Hydrostatic Actuator) type actuator with an
electrical power supply.
This type of actuator may comprise an integrated
hydraulic circuit specific to it and pressurized by an
internal electric pump powered by an electric current.
Furthermore, the device may comprise at least one
EBHA (Electrical Back-up Hydraulic Actuator) type
actuator with two e~_ectrical control inputs, the said
actuator having a first electrical control input to
control a servovalve and a second electrical control
input to control an integrated and independent
hydraulic generation system.
The hydraulic generation system integrated into the
actuator in the case of EHA and EBHA type actuators may
outs>ut a variable flow of hydraulic fluid into the jack
chambers, as a function of the electrical control
orders generated by the control system in order to
maneuver the control surface.
This type of hydi-auli~ generation system is used on
hydrostatic type actuators. It makes it possible to
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operate the actuator independently of the aircraft
hydraulic circuits.
Loss of pressure in a hydraulic circuit makes the
corresponding actuator inoperative. Hydrostatic (EHA)
typ~=_ actuators anct actuators with two electrical
inputs, one of which controls an independent hydraulic
generation system (EBHA) therefore remains in an
operating state even if there is a failure in the
hydraulic circuit.
A device according to the invention may comprise
two, three or more actuators.
According to another embodiment, the device
according to the invention may include two actuators
with one electrical control input and a hybrid actuator
with an electrical control input and a mechanical
control input.
The invention also relates to a process for
controlling a devicE: for controlling an aircraft roll
or pitch control surface comprising an actuator with an
electrical control input and a hybrid actuator with an
electrical control input and a mechanical control
input. According to this process:
- one of the actuators is controlled electrically in a
"normal flight" st;~te,
- at. least two actuators are controlled electrically
and simultaneously in a "maneuver" state, and
- the hybrid actuator is controlled mechanically in an
"electrical control system failure" state of the
actuators .
Other characteristics and advantages of this
invention will become clear from the following
description with reference to the attached drawings,
given for illustrative purposes only and in no way
restrictive.
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Brief description of the Figures
- Figure 1 is a simplified schematic representation of a
control device for a control surface according to a first
embodiment of the invention,
5 - Figure 2 is a simplified schematic representation of an
actuator with an electrical control input to be used with the
device in Figure 1,
- Figure 3 is a simplified schematic representation of a
hybrid actuator that can be used with the device 10 in Figure 1,
10 - Figure 4 is a simplified schematic representation of
another type of hybrid actuator that can be used with the device
in Figure 1,
- Figure 5 is a simplified schematic representation 15 of a
control device for a control surface according to a second
embodiment of the invention,
- Figure 6 is a simplified schematic representation of a
control device for a control surface according to a third
embodiment of the invention.
Description of embodiments of the invention
In the following description, identical or similar elements
in the different Figures have the same references in order to
facilitate understanding.
Figure 1 is ~ a simplified view of a first embodiment of the
control surface control device according to the invention.
The device comprises three actuators 110, 112 and 114
equipped with jacks 111, 113 and 115 to maneuver a roll or pitch
control surface 116. Actuators 110 and 112 are actuators with
electrical control inputs 111a and 113a and actuator 114 is a
hybrid actuator with an electrical control input 115a and a
mechanical control input 115b. Actuators are of the "single body"
type, in other words each actuator is connected to a single
hydraulic circuit and only comprises a single jack.
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The jack for each actuator is supplied by a
diff=erent hydraulic circuit. The hydraulic circuits
for jacks 111, 113 and 115 are partly shown, and are
mar~:ed with references 128, 130 and 132 respectively.
Hydraulic circuit=s are equipped with pressurization
pumps (not shown? which are driven or supplied with
energy from one or more than one of the various
aircraft propulsion units .
As an alternative, one or several actuators may
comprise an internal hydraulic circuit specific to
them, and which is pressurized by an internal electric
pump. In this case, the actuators are supplied with
electrical energy, a:nd hydraulic circuits 128, 130 and
132 are replaced by electricity power supply circuits.
An electrical actuator control system with general
reference 127 includes three calculation units 150, 152
and 154 to control actuators 110, 112 and 114
respectively. Each calculation unit may include a
computer or several redundant computers, namely 150a,
150b, 152a, 152b, 154a, 154b, respectively, operating
in parallel to increase the reliability of the
calculation units.
Calculation unite 150, 152 and 154 are connected to
the actuators through electrical connections 151a, 153a
and 155 respectively, shown in a simplified manner
particularly to transmit control signals on the
electrical control inputs llla, 113a and 115a. These
control signals inc:Lude orders corresponding to the
position of a control device 126 such as a stick or a
wheel installed in the cockpit.
Electrical connections 151a, 151b, 153a, 153b and
155 transmit signals controlling an actuator operating
mode.
The position of control devices 126 detected by
position sensors is electrically transmitted to the
system 127 through an electrical connection 148.
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A mechanical linkage system 124 is also capable of
app_Lying controls exerted on the control device
directly to the mechanical control input 115b of
actuator 115, through a declutchable transmission 125.
An artificial force sensation device 140 and an
actuator 142 for adjusting the zero force controlled
through the electrical control system 127, are also
provided to restore a force on the control device that
depends on the applied control.
During normal flight, control orders are
transmitted electrically to one of the actuators. For
exarnple, the calcu7_ation unit 150 supplies control
orders to actuator 1:10. In the case of a maneuver, two
(or three) actuators are actuated simultaneously.
Note that in the case of a maneuver, whenever a
fai7_ure or another malfunction causes a loss of
hydraulic pressure in the hydraulic circuit of one of
the actuators, for example actuator 110, the control
surf=ace is actuated by the two actuators 112, 114, for
which the hydraulic circuit is not pressurized from the
circuit in failure .
Similarly, in the "normal flight" state, a failure
cau~~ing a problem in one of the actuators will trigger
control of another actuator that is in an operating
condition.
According to one variant of the device in Figure 1,
one of the actuators with an electrical input 110, 112,
for example actuator 112, may be replaced by an "EHA"
(Electro Hydrostatic Actuator), comprising an
integrated and independent hydraulic generation system.
The external hydraulic circuit 130 is then eliminated
and the weight of the device can be reduced.
If a failure occurs causing a pressure drop in one
of the hydraulic circuits 128 or 132, one of the
external hydraulic c-~~rcuit actuators 110 or 114 and the
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indE~pendent EHA actuator 112, remains in operation to
actuate the control surface.
Figure 2 schematically shows the main elements of
an actuator with an electrical control input, also
called an electrohyd:raulic actuator.
The actuator marked with general reference 110
comprises a jack 111 and a control unit 200 with an
electrical control input llla.
Jack 111 has one end 202 connected to a fixed
support and one end 204 connected to a roll or pitch
control surface, not shown. A piston 206 rigidly fixed
to a piston rod 208 separates the jack cylinder into
two chambers 210 and 211.
A solenoid valve 212 electrically connected to a
calculation unit (not shown?, associated with the
actuator, selects an operating mode of the actuator.
When the solenoid valve is excited by an electrical
signal, a slide known as "mode slide" 220 is moved into
position so that chambers 210 and 211 are put into
communication with a servovalve 222, through a double
pas~:age portion 227 of the slide.
Servovalve 222, electrically connected to the
calculation unit, then outputs a hydraulic fluid flow
to :jack 111 that depends on orders generated by the
calculation unit. The actuator then operates in the
electrical active mode already described. The
hydraulic fluid flow is provided by a hydraulic circuit
128, which is not shown except for the high pressure
inlet 224 and low pressure outlet 226.
When solenoid valve 212 is disexcited, if there is
no Electrical signal, the mode slide 220 is set so as
to isolate the jack chambers from servovalve 222 and to
put chambers 210 and 211 into communication with other
thrcugh a restricto== 228. This position, shown in
Figure 2, corresponds to damped mode operation of the
actuator already described.
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Figure 3 schematically shows a hybrid actuator such
as actuator 114 used in control device illustrated in
Figure 1. Many of t:he elements are identical to those
in the actuator in Figure 2. These elements have the
sam~=_ references, and therefore the explanations about
them given above can be referred to. Furthermore, the
actuator jack in Figure 3 is marked as reference 115,
the same as in Figure 1, and the electrical and
mechanical control inputs are marked with references
115a and 115b respectively.
The hybrid actuator mode slide 220 may be in one of
thrc=_e positions, and it is actuated by three solenoid
valves 212, 214 and 216 controlled by calculation units
154, 152 and 150 respectively, shown in Figure 1.
When solenoid valve 212 is excited, the slide 220
is in a position in which chambers 210, 211 are put in
communication with the servovalve 222 through a double
pas:~age portion 227 of the slide. The actuator then
operates in the electrical active mode described above.
When solenoid valve 212 is disexcited and at least
one of solenoid valves 214 and 216 is excited, the mode
slide occupies a position in which chambers 210 and 211
are put into communication through a restrictor 228 to
operate in damped mode. This position corresponds to
the slide position shown in Figure 3.
When none of the solenoid valves 212, 214 and 216
is excited, the mode slide is in a third position in
which chambers 210 and 211 are put into communication
with a distributor 230 through a double passage portion
229 of the slide. In this position, a clutch 232 is
engaged and connects distributor 230 to the mechanical
control input 115b .
The distributor 230 then outputs a hydraulic fluid
flow to the jack, that depends on the mechanical
control applied on input 115b. The actuator operates
in mechanical active: modes. This mode is triggered by
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default if there is a failure in the electrical control
system, in other words when none of the solenoid valves
is receiving signals from a calculation unit.
For example and in the normal flight state,
5 referring to Figure :L, it is obvious that if there is a
fai7_ure in the first electrical system 150, 150a, 150b,
151a, 151b associated with actuator 110, then solenoid
valve 216 will be disexcited. The second electrical
system 152, 152a, 152b, 153a, 153b associated with
10 actuator 112 is then activated to control actuator 112.
If there is an electrical failure in this second
system, then sole:zoid valve 214 will also be
desE:xcited. The third electrical system comprising
elements 154, 154a, 154b, 155 is then activated to
15 control actuator 114.
Finally, if there is an electrical failure in the
three systems, the three solenoid valves 212, 214 and
216 are disexcited and the mechanical control of the
hybrid actuator is automatically activated.
Clutch 232 is disengaged for normal operation of
the control surface control device. This prevents
orders such as stabilization orders output by computers
from being mechanically retransmitted onto the control
device. According t:o one alternative embodiment, the
mec~:.anical control input may also be fitted with a
spring or cam operated connecting rod system capable of
absorbing the entire stroke of the actuator, in order
to prevent orders from being retransmitted to control
devices.
Figure 4 schematically shows another type of hybrid
actuator that can be used in the device according to
the invention.
The actuator comprises a mode slide 220 with only
two positions. If at least one of the two solenoid
valves 214 and 216, controlled by calculation units 152
and 150 respectively shown in Figure 1, are excited,
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the mode slide i~; positioned to mutually create
comrnunication between jack chambers 210, 211 through
the restrictor 228 a.nd the actuator operates in damped
mode. Excitation of solenoid valve 212 also puts
clutch 232 into a declutched state which makes
servovalve 222 independent of the mechanical control
115b.
When solenoid valves 214 and 216 are disexcited,
the mode slide 220 moves into a position to put the
jack: chambers 115 into communication with servovalve
222 through a double passage portion 227 of the slide.
The actuator is then capable of operating either in
electrical active mode or in mechanical active mode.
Electrical active mode is activated if solenoid
valve 212 is excited. The mechanical control is then
decl_utched and fixed in place, and the electrical
control input 115a o. the servovalve is controlled.
When solenoid valve 212 is disexcited, either
intentionally or following electrical failures like
tho~~e described above, the mechanical control is
coupled to the servovalve through clutch 232 and the
servovalve outputs a flow to jack chambers that depends
on t:he mechanical control input 115b. Therefore, this
corresponds to the mechanical active mode.
In the envisaged application, and by construction,
there is no provision for controlling the servovalve
thrc>ugh the mechanical control input and through the
electrical control input simultaneously.
Figure 5 shows an alternative embodiment of the
invention in which the control device is equipped with
two or three hybrid actuators.
In the example :shown, actuators 110, 112 and 114
comprise electrical ~~ontrol inputs llla, 113a and 115a
respectively connectE=_d to the electrical control input
127, and mechanical control inputs (lllb), 113b and
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115b connected to the mechanical linkage 124 through
transmissions (325), 225 and 125 respectively.
The redundant nature of this configuration provides
additional operating safety.
- 5 Figure 6 shows another alternative embodiment of
the invention in which only two actuators are used.
The device comprises a hybrid actuator 115 with an
electrical control input 115a connected to an
electrical control system 127, and a mechanical control
input 115b connected to control devices 126 through
mechanical linkage 124 and transmission 125. Actuator
115 is supplied throwgh a hydraulic circuit 300.
The second actuator is shown under 109. It is an
"EBHA" (Electrical Back-up Hydraulic Actuator) with two
electrical inputs 109a and 109b also connected to the
control system 127.
The electrical input 109a can send control orders
to a servovalve (not shown) of the type described above
and supplied by a hydraulic circuit 302. The second
electrical input 10!ab can send control orders to an
integrated and independent hydraulic generation system
to maneuver the cont:col surface.
This embodiment can save one actuator and possibly
one hydraulic circuit, compared for example with the
embodiment shown in Figure 1. This can result in a
significant weight saving.
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