Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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FEEDBACK DEVICE WITH DIFFERING MAGNETIC PERMEABILITY ZONES
TECHNICAL FIELD
[0001] The present disclosure relates generally to engines, and more
specifically to
blade angle position feedback systems.
BACKGROUND OF THE ART
[0002] On featherable aircraft propeller systems, it is desirable to
accurately measure
the propeller blade pitch (or beta) angle to ensure that the blade angle is
controlled
according to the engine power set-point requested, such as in reverse and low
pitch
situations, also known as the beta operating region. For this purpose, some
propeller
feedback systems use a beta or feedback device, sometimes referred to as a
phonic
wheel, which rotates with the engine. The feedback device has multiple
readable raised
markers disposed on an outer surface thereof, and a sensor can be used to
measure
the rotation of the feedback device via the markers, providing a proxy value
for the
rotational velocity of the engine, as well as measure blade angle. The
configuration of
existing feedback devices however results in reduced signal quality, in
addition to
requiring complex and costly manufacture.
[0003] Therefore, improvements are needed.
SUM MARY
[0004] In accordance with a broad aspect, there is provided a blade angle
feedback
assembly for an aircraft-bladed rotor, the rotor rotatable about a
longitudinal axis and
having an adjustable blade pitch angle. The assembly comprises a feedback
device
coupled to rotate with the rotor with adjustment of the blade pitch angle, the
feedback
device comprising a non-magnetically permeable body defining a root surface
and a
plurality of magnetically permeable position markers circumferentially
disposed on the
root surface, and at least one sensor mounted adjacent the feedback device and
configured to detect a passage of the plurality of position markers as the
feedback
device rotates about the longitudinal axis.
[0005] In some embodiments, the plurality of position markers are embedded in
the
feedback device.
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[0006] In some embodiments, the plurality of position markers comprises a
first plurality
of position markers circumferentially spaced from one another and oriented
along a first
direction, and at least one second position marker positioned between two
adjacent first
position markers and oriented along a second direction angled relative to the
first
direction.
[0007] In some embodiments, the first and second directions are angled
relative to the
longitudinal axis.
[0008] In some embodiments, the first and second directions are substantially
parallel
to the longitudinal axis.
[0009] In some embodiments, the at least one sensor comprises a first end
section and
a second end section opposite the first end section, a first magnetic pole
provided at the
first end section and a second magnetic pole provided at the second end
section, and
the at least one sensor is mounted adjacent the feedback device with the first
and
second magnetic poles positioned on either side of the root surface.
[0010] In some embodiments, the first and second magnetic poles are configured
to
align with any given one of the plurality of position markers as the given
position marker
passes through the sensor.
[0011] In some embodiments, the first and second magnetic poles are diamond-
shaped.
[0012] In some embodiments, the at least one sensor further comprises a first
protective bumper and a second protective bumper for preventing damage to the
at
least one sensor in the event of contact between the feedback device and the
at least
one sensor, the first bumper surrounding the first magnetic pole and the
second bumper
surrounding the second magnetic pole.
[0013] In some embodiments, the at least one sensor has a C-shaped cross
section.
[0014] In accordance with another broad aspect, there is provided an aircraft-
bladed
rotor system, comprising a rotor rotatable by a shaft about a longitudinal
axis, the rotor
having blades with adjustable blade pitch angle, and a feedback device coupled
to
rotate with the rotor with adjustment of the blade pitch angle, the feedback
device
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having a non-magnetically permeable body defining a root surface, and a
plurality of
magnetically permeable position markers circumferentially disposed on the root
surface.
[0015] In some embodiments, the plurality of position markers are embedded in
the
feedback device.
[0016] In some embodiments, the plurality of position markers comprises a
first plurality
of position markers circumferentially spaced from one another and oriented
along a first
direction, and at least one second position marker positioned between two
adjacent first
position markers and oriented along a second direction angled relative to the
first
direction.
[0017] In some embodiments, the first and second directions are angled
relative to the
longitudinal axis.
[0018] In some embodiments, the first and second directions are substantially
parallel
to the longitudinal axis.
[0019] In some embodiments, the system further comprises at least one sensor
mounted adjacent the feedback device and configured to detect a passage of the
plurality of position markers as the feedback device rotates about the
longitudinal axis.
[0020] In some embodiments, the at least one sensor comprises a first end
section and
a second end section opposite the first end section, a first magnetic pole
provided at the
first end section and a second magnetic pole provided at the second end
section, and
the at least one sensor is mounted adjacent the feedback device with the first
and
second magnetic poles positioned on either side of the root surface.
[0021] In some embodiments, the first and second magnetic poles are configured
to
align with any given one of the plurality of position markers as the given
position marker
passes through the sensor.
[0022] In some embodiments, the at least one sensor further comprises a first
protective bumper and a second protective bumper for preventing damage to the
at
least one sensor in the event of contact between the feedback device and the
at least
one sensor, the first bumper surrounding the first magnetic pole and the
second bumper
surrounding the second magnetic pole.
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[0023] In some embodiments, the at least one sensor has a C-shaped cross
section.
[0024] Features of the systems, devices, and methods described herein may be
used
in various combinations, in accordance with the embodiments described herein.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] Reference is now made to the accompanying figures in which:
[0026] FIG. 1 is a schematic cross-sectional view of an example gas turbine
engine, in
accordance with an embodiment;
[0027] FIG. 2 is a schematic diagram of an example feedback sensing system, in
accordance with an embodiment;
[0028] FIG. 3A and FIG. 3B respectively illustrate a schematic front view and
a
schematic top view of the feedback device of FIG. 2, in accordance with an
embodiment;
[0029] FIG. 4A and FIG. 4B respectively illustrate a schematic side view and a
schematic front view of the sensor of FIG. 2, in accordance with an
embodiment; and
[0030] FIG. 5A is a schematic front view of the feedback device of FIG. 3A
with the
sensor of FIG. 4 positioned adjacent the feedback device, in accordance with
an
embodiment;
[0031] FIG. 5B is a schematic top view of the feedback device of FIG. 5A
showing a
pole piece of the sensor of FIG. 3A, in accordance with an embodiment; and
[0032] FIG. 6 illustrates a schematic diagram of a sensor, in accordance with
another
embodiment.
[0033] It will be noted that throughout the appended drawings, like features
are
identified by like reference numerals.
DETAILED DESCRIPTION
[0034] FIG. 1 depicts a gas turbine engine 110 of a type typically provided
for use in
subsonic flight. The engine 110 comprises an inlet 112 through which ambient
air is
propelled, a compressor section 114 for pressurizing the air, a combustor 116
in which
the compressed air is mixed with fuel and ignited for generating an annular
stream of
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hot combustion gases, and a turbine section 118 for extracting energy from the
combustion gases.
[0035] The turbine section 118 comprises a compressor turbine 120, which
drives the
compressor assembly and accessories, and at least one power or free turbine
122,
which is independent from the compressor turbine 120 and rotatingly drives a
rotor
shaft (also referred to herein as a propeller shaft or an output shaft) 124
about a
propeller shaft axis 'A' through a reduction gearbox (RGB) 126. Hot gases may
then be
evacuated through exhaust stubs 128. The gas generator of the engine 110
comprises
the compressor section 114, the combustor 116, and the turbine section 118.
[0036] Rotation of the output shaft 124 is facilitated by one or more bearing
assemblies
(not illustrated), which can be disposed within the RGB 126 or at any other
suitable
location. The bearing assemblies are electrically isolating during operation
due to an oil
film which is present at the bearing assemblies where they rotate.
[0037] A rotor, in the form of a propeller 130 through which ambient air is
propelled, is
hosted in a propeller hub 132. The rotor may, for example, comprise the
propeller 130
of a fixed-wing aircraft, or a main (or tail) rotor of a rotary-wing aircraft
such as a
helicopter. The propeller 130 may comprise a plurality of circumferentially-
arranged
blades 134 connected to the hub 132 by any suitable means and extending
radially
therefrom. The blades 134 are also each rotatable about their own radial axes
through
a plurality of adjustable blade angles, which can be changed to achieve
various modes
of operation. The blade angle is the angle between the chord line (i.e. a line
drawn
between the leading and trailing edges of the blade 134) of the propeller
blade section
and a plane perpendicular to the axis of propeller rotation. In some
embodiments, the
propeller 130 is a reversing propeller, capable of operating in a variety of
modes of
operation, including feather, full reverse, and forward thrust. Depending on
the mode of
operation, the blade angle may be positive or negative: the feather and
forward thrust
modes are associated with positive blade angles, and the full reverse mode is
associated with negative blade angles.
[0038] With reference to FIG. 2, FIG. 3A, and FIG. 3B, a feedback sensing
system 200
for pitch-adjustable blades of bladed rotors of aircraft will now be
described. The system
200 may be used for sensing a feedback device (also referred to as a feedback
ring or
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phonic wheel) of an aircraft propeller. It should however be understood that,
although
the system 200 is described and illustrated herein with reference to an
aircraft propeller,
such as the propeller 130 of FIG. 1, the system 200 may apply to other types
of rotors,
such as those of helicopters. The systems and methods described herein are
therefore
not limited to being used for aircraft propellers.
[0039] In some embodiments, the system 200 provides for detection and
measurement
of rotational velocity of one or more rotating elements of the engine 110 and
of propeller
blade angle on propeller systems, such as the propeller 130 of FIG. 1. In
other
embodiments, the system 200 may be used for synchronization of propeller
blades on
multiple propeller aircrafts. The system 200 may interface to existing
mechanical
interfaces of typical propeller systems to provide a digital detection for
electronic
determination of the propeller blade angle. It should be noted that, although
the present
disclosure focuses on the use of the system 200 and the feedback device 204 in
gas-
turbine engines, similar techniques can be applied to other types of engines,
including,
but not limited to, electric engines and hybrid electric propulsion systems
having a
propeller driven in a hybrid architecture (series, parallel, or
series/parallel) or
turboelectric architecture (turboelectric or partial turboelectric).
[0040] The system 200 comprises an annular member 204 and one or more sensors
206 positioned proximate the annular member 204. Annular member 204 (also
referred
to herein as a feedback device) is a non-magnetically permeable conductive
ring made
of any suitable non-magnetically conductive material, including, but not
limited to,
aluminum and Polyether ether ketone (PEEK). The feedback device 204
illustratively
has a C-shaped cross-section, as shown in FIG. 2. The feedback device 204 has
a
plurality of detectable features 208 (also referred to herein as position
markers)
disposed circumferentially thereon for detection by sensor(s) 206. As will be
discussed
further below, the position markers 208 are magnetically permeable and are
embedded
within the feedback device 204, so as to be flush with a surface (not shown)
thereof.
The feedback device 204 may therefore comprise zones of different magnetic
permeability, including zones (i.e. position markers 208) arranged to indicate
propeller
position via axial position of the feedback device 204.
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[0041] In some embodiments, the feedback device 204 is mounted for rotation
with the
propeller 130, which rotates about the longitudinal axis 'A' (as illustrated
by arrow `B').
The feedback device 204 is also supported for longitudinal sliding (or 'beta')
movement
along the axis A (as illustrated by arrow 'C'). In other words, the feedback
device 204 is
supported to move axially with adjustment of the blade angle of the blades
(reference
134 in FIG. 1) of the propeller 130, e.g. by support members, such as a series
of
circumferentially spaced feedback rods 210 that extend along the axis A. A
compression spring (not shown) illustratively surrounds an end portion of each
rod 210.
The feedback rods 210 may be mounted to a flange 212, secured for example to a
housing of the reduction gearbox 126 or to any other static element of the
engine
(reference 110 in FIG. 1), as appropriate.
[0042] In one embodiment, the one or more sensors 206 are fixedly mounted to a
static
portion of the engine 110. In other embodiments, the or more sensors 206 are
mounted
for rotation with the propeller 130 and to move axially with adjustment of the
blade
angle of the blades 134 of the propeller 130, and the feedback device 204 is
fixedly
mounted to a static portion of the engine 110. In some embodiments, a single
sensor
206 is mounted in close proximity to the feedback device 204 and the position
markers
208. In some other embodiments, one or more additional sensors, which may be
similar
to the sensor 206, are provided.
[0043] The system 200 also includes a controller 220 communicatively coupled
to the
sensor(s) 206. The one or more sensors 206 are configured for producing a
sensor
signal which is transmitted to or otherwise received by the controller 220,
for example
via a detection unit 222 thereof. The sensor signal can be an electrical
signal, digital or
analog, or any other suitable type of signal. In some embodiments, each sensor
206
produces a series of signal pulses in response to detecting the presence of a
position
marker 208 in a sensing zone of the sensor 206. For example, the sensor 206 is
a
variable reluctance magnetic sensor that operates on detecting changes in
magnetic
flux, and has a sensing zone which encompasses a circular or rectangular area
or
volume in front of the sensor 206. When a position marker 208 is present in
the sensing
zone, or passes through the zone during rotation of the feedback device 204,
the
magnetic flux in the sensing zone is varied by the presence of the position
marker 208,
and the sensor 206 can produce a signal pulse, which forms part of the sensor
signal.
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Accordingly, the position markers 208 may be made of any suitable magnetically
permeable material (e.g., a ferromagnetic material, Mu-Metal, or the like)
which would
cause the passage of the position markers 208 near the sensor 206 to provide a
change in magnetic permeability within the magnetic field generated by the
sensor 206.
In addition, it should be understood that, although the sensor 206 is
illustrated with
straight lines, this need not be the case in all embodiments and the sensor
206 may
have other suitable shape(s). The sensor 206 may for example be curve-shaped,
which
may allow to vary the sensitivity for axial position of the feedback device
204.
[0044] As shown in FIG. 3A and FIG. 3B, in some embodiments the feedback
device
204 is embodied as a circular disk which rotates as part of the engine
(reference 110 in
FIG. 1), for example with the propeller shaft (reference 124 in FIG. 1) or
with the
propeller (reference 130 in FIG. 1). The feedback device 204 comprises
opposing faces
(references 2141, 2142 in FIG. 2) having outer edges 3021, 3022 and defines a
root
surface 304 which extends between the opposing faces 2141, 2142 and
circumscribes
them. Put differently, the root surface 304 of the feedback device 204 is the
outer
periphery of the circular disk which spans between the two opposing faces
2141, 2142
and the root surface 304 intersects the faces 2141, 2142 at the edges 3021,
3022. In
these embodiments, the position markers 208 are embedded in the feedback
device
204, flush with the root surface 304 such that the feedback device 204 has a
substantially smooth or uniform root surface 304.
[0045] In one embodiment, the position markers 208 are integrally formed with
the
feedback device 204 so that the feedback device 204 may have a unitary
construction.
Each position marker 208 may be a portion of the feedback device 204 which is
made
of a different material, or to which is applied a layer of a different
material. The position
markers 208 may then be applied to the root surface 304, for instance as
strips of
material for detection by the sensor 206. The position markers 208 may be
applied to
the root surface 304 via bonding or any other suitable technique.
[0046] Still referring to FIG. 3A and FIG. 3B, the position markers 208 may
comprise a
plurality of first position markers 3061 arranged along a first direction
(direction D1' in
FIG. 3B) relative to the opposing faces 2141, 2142 of the feedback device 204
and
substantially equally spaced from one another on the root surface 304. The
position
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markers 208 may also comprise a plurality of second position markers 3062,
each
positioned between two adjacent first position markers 3061. Each second
position
marker 3062 is illustratively oriented along a direction D2', which is at an
angle relative
to the direction D1 along which the first position markers 3061 are arranged.
In this
manner, the time of flight between passes of the sensor 206 varies with the
axial
position of the feedback device 204. The angle between the directions D1 and
D2 can
have any suitable value between 1 and 89 , for example 30 , 45 , 60 , or any
other
value, as appropriate. The angle between the directions D1 and D2 as well as
the
number of pairs of position markers 3061, 3062 may be determined based on a
number
of factors including, but not limited to, processing speed (e.g., of the
controller 220),
required update rate, selected gap (or distance) between the sensor 206 and
the
feedback device 204, pole piece dimensions, overall magnetic circuit
considerations,
axial travel to be measured, and rotor diameter.
[0047] In one embodiment, all position markers 3061 may be oriented along the
same
direction D1 and all position markers 3062 may be oriented along the same
direction D2,
such that the angle between the directions D1 and D2 remains substantially the
same
around the circumference of the feedback device 204 (as illustrated in FIG.
3B). It
should however be understood that other embodiments may apply. Indeed, in
another
embodiment, the angle between the directions D1 and D2 may be varied at each
pair of
position markers 3061, 3062. For example, the angle between the directions D1
and D2
may be varied (e.g., by a predetermined amount) for each successive pair of
position
markers 3061, 3062. In this manner, the time of flight (as the sensor 206
passes
adjacent a pair of position markers 3061, 3062) varies with the axial position
of the
feedback device 204. Still, any suitable combination of positions for pairs of
position
markers 3061, 3062 or individual position markers 3061, 3062 may apply. In one
embodiment, asymmetric features may further permit marking a particular
position (also
referred to as a "rotor position" or "index"), such as the "12 o'clock"
position of the rotor,
which can be useful for balance monitoring. Varying the angular position or
divergence
of pairs of position markers 3061, 3062 may also be used to detect wobble or
axial
runout of the feedback device 204.
[0048] As shown in FIG. 3B, each position marker 3061, 3062 extends axially
(along
longitudinal direction D1 for position marker 3061 and along longitudinal
direction D2 for
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position marker 3062), from a first axial end or termination (not shown) to a
second
termination (not shown), which is opposite the first termination. Each
termination is
adjacent a corresponding edge 3021, 3022 of the feedback device 204. In other
words,
the position markers 3061, 3062 extend between the opposing faces 2141, 2142
of the
feedback device 204, while maintaining the smooth surface of the feedback
device 204,
from one edge 3021, 3022 to the other. Each position marker 3061, 3062 has a
substantially rectangular profile (with substantially parallel longitudinal
edges, not
shown) when viewed from the direction of the magnetic field generated by the
sensor
206.
[0049] In some embodiments, the feedback device 204 includes only a single
second
position marker 3062 while, in other embodiments, the feedback device 204 can
include
more than one second position marker 3062. Each second position marker 3062
can be
located at substantially a midpoint between two adjacent first position
markers 3061 or
can be located close to a particular one of two adjacent first position
markers 3061 (as
shown in FIG. 3A and FIG. 3B).
[0050] As described above, as the feedback device 204 rotates, varying
portions
thereof enter, pass through, and then exit the sensing zone of the sensor 206.
The
resulting signal pulses produced by the sensor 206, which form part of the
electrical
signal received by the control system 220, can be used to determine various
operating
parameters of the engine 110 and the propeller 130. For example, a speed of
rotation of
the feedback device 204 and a blade angle of the propeller 130 can be
determined.
[0051] Referring now to FIG. 4A and FIG. 4B, the configuration of the sensor
206 in
accordance with one embodiment will be discussed in more detail. The sensor
206
comprises a body 402 that is generally C-shaped and has a first (or upper) end
portion
4041 and a second (or lower) end portion 4042, the second end portion 4042
being
opposite to and spaced from the first portion 4041. The sensor 206 further
comprises
two magnetic poles 4061, 4062, with the pole 4061 being provided at the first
end portion
4041 and the pole 4062 being provided at the second end portion 4042. Each
magnetic
pole 4061, 4062 is illustratively shaped and oriented so as to align with a
given position
marker 208 as the feedback device 204 is displaced. This in turn minimizes
pole
shading, which relates to the effect of a portion of the magnetic flux being
conducted
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through adjacent position markers 208 and results in a less defined change in
sensor
signal (i.e. in a diluted signal) as a given position marker 208 passes the
pole 4061,
4062. Indeed, as illustrated in FIG. 5A and FIG. 5B, the sensor 206 is mounted
relative
to the feedback device 204 such that the poles 4061, 4062 are on either side
of the
feedback device 204 (i.e. on either side of the root surface 304), in a spaced
relationship therewith. As a result, when the poles 4061, 4062 are shaded by a
position
marker 208 as the feedback device 204 is displaced, a small total air gap may
be
experienced. Large and fast changes of flux may then be created within the
magnetic
circuit, so as to obtain a desired sensor signal.
[0052] In one embodiment, the sensor 206 further comprises two protective
bumpers
as in 408, each protective bumper 408 surrounding a given pole piece 4061,
4062 such
that any deflection which may occur (with the feedback device 204 or the
sensor 206)
will not result in a destructive contact between the feedback device 204 and
the sensor
206. The protective bumpers 408 may prevent any galling or damage to the
sensor 206
if such a contact were to occur. The protective bumpers 508 may be made of any
suitable material. In one embodiment, the protective bumpers 508 may be made
from a
low friction impact resistant material including, but not limited to, Teflon,
VespelTM,
Nylon, brass, and other sintered metals where the filler is a lubricant such
as oil,
graphite, Teflon, and Molybdenum Disulfide (MoS2). In another embodiment where
the
rotor (and accordingly the feedback device 204) is made of VespelTM, the
protective
bumpers 508 may be made of ceramic composites suited for intermittent
operation
against VespelTM. The choice of the material for the protective bumpers 508
may
depend on factors including, but not limited to, avoiding fracture, ignition,
high friction,
and related undesired events to allow momentary contact with minimal damage
and
wear.
[0053] In operation, the sensor 206 provides a completed (or closed) magnetic
flux
circuit, where the upper pole 4061 can be said to emit the magnetic flux and
the bottom
pole 4062 to receive the magnetic flux. A closed magnetic path is indeed
created when
the position markers 208 pass through the poles 4061, 4062 as the feedback
device 204
rotates. It should be noted that the total air gap of the magnetic circuit is
substantially
equal to the sum of the spacing (or airgap) between an outer surface
(reference 216 in
FIG. 2) of the feedback device 204 and the upper pole 4061 and the spacing
between
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an inner surface (reference 2162 in FIG. 2) of the feedback device 204 and the
bottom
pole 4062. It can therefore be seen that, in one embodiment, the total airgap
remains
substantially constant as the position of the feedback device 204 varies.
There is
accordingly less variation in signal strength, as may arise due to different
thermal
expansions, dimensional runout of the feedback device 204, and vibration. As
such, the
signal amplitude is increased and the clarity of the definition of the
waveform of the
sensor signal received at the controller (reference 220 in FIG. 2) is improved
as a given
position marker 208 passes a given pole 4061, 4062 (referred to herein as a
"position
marker passing" or "on" state).
[0054] In one embodiment, the spacing between the poles 4061, 4062 is set
(i.e. the
poles 4061, 4062 are sufficiently close and the feedback device 204 is
suitably thin)
such that a significant magnetic flux is transferred even when the position
markers 208
are not positioned adjacent the poles 4061, 4062 (i.e. when the non-
magnetically
permeable portions of the feedback device 204 pass through the poles 4061,
4062,
referred to herein as a "non-shaded portion of operation" or "off' state). A
relatively
closed magnetic path is therefore created in the "off' state. In one
embodiment, by
having significant magnetic flux transfer in both the "on" and "off' states,
the state
changes may have a pronounced and distinct shape in the resulting waveform. In
addition, since a failed sensor 206 or pole 4061, 4062 would result in an open
flux
circuit, the proposed configuration may provide for an additional means of
error
proofing.
[0055] In one embodiment, optimization of the sensor signal waveform may also
be
achieved by ensuring that the poles 4061, 4062 of the sensor 206 are far from
saturation
and otherwise working to minimize stray field. Indeed, if the sensor 206 is
arranged with
a magnet that is too strong for the flux guides (i.e. the poles 4061, 4062 of
the sensor
206), extra magnetic flux will overflow from the sensor body and may flow away
from
the sides of the poles 4061, 4062 (i.e. magnetic flux lines may not be
constrained only at
the gap between the sensor 206 and the feedback device 204). The stray
magnetic flux
may then find a path, leading to a partial circuit and a partial, but
unwanted, signal
being formed. In one embodiment, it is proposed herein to ensure that the
poles 4061,
4062 are able to carry substantially all of the magnetic flux, such that more
magnetic flux
flows away from the poles 4061, 4062 and into the position markers 3061, 3062,
with a
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crisp transition. As such, the expected shape of the magnetic flux lines in
the non-
shaded portion of operation may be reasonably constrained, so that position
markers
208 that are advancing towards and departing from the sensor 206 do not
conduct large
amounts of magnetic flux. The resulting sensor signal may therefore be as near
to a
square wave as possible.
[0056] Optimization of the sensor signal waveform may further be achieved by
providing poles 4061, 4062 with diamond-shaped ends, as shown in FIG. 5B. The
poles
4061, 4062 may be shaped to replicate the angles on the position markers 208,
and
oriented such that the poles 4061, 4062 align with each position marker 208 as
the
position marker 208 passes through the sensor 206. As previously described,
the
position markers 208 may also be shaped with substantially razor sharp
parallel faces
and edges (not shown), so as to create fast magnetic rates of change of
permeability.
This in turn creates steep signal slopes (as the position markers 208 pass
within the
sensing zone of the sensor 206), thereby allowing to obtain more accurate
measurement of axial position (hence beta angle) and greater precision of
speed
calculation.
[0057] In one embodiment, the C-shaped sensor 206 may be substituted for a so-
called
"dual tip" (or "bi-polar") probe (not shown) having one tip corresponding to
magnetic
north and another tip corresponding to magnetic south. The C-shaped sensor 206
may
also be replaced with a dual tip probe having an alternating magnetic signal
induced
between the poles. In other words, the sensor 206 may have an upside-down U-
shaped
cross-section (rather than a C-shaped cross-section), as shown in FIG. 6
(where the
spacing of the poles 4061, 4062 of the sensor 206 is illustratively the same
as the
spacing of the position markers 208). In yet another embodiment, the variable
reluctance magnetic sensor 206 may be replaced with an optical probe, a Hall-
effect
sensor, or any other suitable sensor capable of detecting the passage of the
position
markers 208.
[0058] In one embodiment, the proposed feedback sensing system 200 may be
configured to produce electrical power. There may indeed be a use for
generated power
to perform work, such as de-ice an engine inlet sensor. The power generated
may then
be used to either supplement or replace a permanent magnet alternator (PMA)
typically
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driven by the engine 110. The creation of steep changes of magnetic flux
conduction
and the use of small air gaps at the shaded portion along with permeable
materials in
the magnetic circuit may also allow to provide signal power. The signal power
may in
turn be exploited in terms of obtaining advantageous signal to noise levels
for system
robustness, thus requiring less shielding to attain an intended immunity from
high-
intensity radiated field (HIRF) and related threats. The signal power
generated by the
feedback device 204 and sensor 206 may also result in only minimal
amplification being
required within the sensor 206, resulting in a less expensive and fragile
sensor 206,
while reducing the susceptibility of the sensor signal to electromagnetic
interference
and distortion.
[0059] Unwanted ambient electromagnetic noise may be further passively
cancelled
through the use of dual coils and magnets at the sensor 206. For example, a
first coil
(not shown) may be wrapped on one end portion (reference 4041 in FIG. 4A) of
the C-
shaped sensor body (reference 402 in FIG. 4A) and a second coil (not shown)
may be
wrapped on the other end portion (reference 4042 in FIG. 4A) of the sensor
body 702.
The coils may be wound in opposite directions and polarity so their signals
add
together. Any electromagnetic pulse travels through the coils would then be
cancelled.
[0060] Moreover, because the proposed arrangement permits for a smooth
feedback
device 204 (and sensor 206) configuration, all operating surfaces of the
feedback
device 204 (and of the sensor 206) may be coated with abrasion resistant and
low
friction material. Momentary contact, such as from hard landings, bird strike,
and the
like, may become tolerable and any risk of catastrophic collision with the
sensor 206
may be reduced. The smooth feedback device 204 may further allow the sensor
206 to
comprise glides, rollers, skids, or any other such feature so as to
accommodate
collision events as may arise after hard landings, bird strike, ground strike,
lightning
blast compression wave, weapons fire, or the like. The configuration of the
feedback
device 204 and sensor 206 may further allow for suspension-like features to be
incorporated in (either intrinsic to or arranged in a mount of) the sensor 206
to
accommodate for distortion or deflection that may arise from sustained turns
due the
gyroscopic forces on the propeller 130.
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[0061] In one embodiment, due to the availability of permeable alloys (e.g.,
Permendur)
and magnets of great energy product (e.g., samarium¨cobalt (Sa-CO) or other
rare
earth types), it becomes possible for the sensor 206 to be made small relative
to typical
small gas turbine variable reluctance probes. The position markers 208 may
also be
made small, thus permitting to decrease the weight of the overall system. The
configuration of the position markers 208 may also allow them to be traded for
many
samples per revolution without magnetic crosstalk (or interference). Magnetic
crosstalk
between position markers 208 may indeed tend to occur if the position markers
208 are
spaced too closely, such that magnetic flux lines begin to flow to two
position markers
208 when the sensor 206 is positioned between the position markers 208. This
creates
a design space limit. Hence, it can be seen that the smaller the sensor poles
4061,
4062, and the smaller the position markers 208, the more position markers 208
can be
placed on a given rotor before crosstalk becomes a problem. In one embodiment,
it
may be desirable to provide several position markers 208 (rather than
providing fewer
position markers 208) in order for more samples per revolution, and
accordingly more
samples per unit time for a given rotor at a given speed, to be obtained. As a
result, it
may be possible to calculate speed, position, and rate of change of speed and
position
sooner, which may in turn provide system control advantages. The proposed
arrangement may also facilitate the use of non-metallic materials (e.g.,
durable high-
performance polyimide-based plastics like VespelTM) for the feedback device
204.
[0062] From the above description, it can also be seen that the position
markers 208
are relatively slender with large surface area and low weight, thus allowing
them to be
readily bonded onto a feedback device 204 made of aluminum or any other
suitable
non-magnetically permeable alloy, without any challenging bond or retention
tasks. The
proposed arrangement may also make it possible to manufacture the feedback
device
204 using three-dimensional (3D) printing using 3D printed permeable media,
allowing
the feedback device 204 to be manufactured with reduced machining time and
resources. Other suitable manufacturing techniques may apply.
[0063] In one embodiment, the feedback device 204 may be 3D printed with
position
markers 208 made of ferritic resin being printed in the feedback device 204. A
one
piece feedback device 204 may therefore be printed from at least two powders,
one
which is structural and not magnetically permeable (e.g., to form the feedback
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204 itself) and another that is highly magnetically permeable (e.g., to form
the position
markers 208). Such a 3D printed feedback device 204 would be expected to be
able to
withstand considerable strain without rupture and to have low weight compared
to
feedback devices made from magnetic steel.
[0064] Referring back to FIG. 1 in addition to FIG. 2, as the output shaft 124
rotates,
electrical charge generates on the output shaft 124. For example, the output
shaft 124
can be struck by lightning or other electrical discharges, or can be subjected
to
triboelectric charge accumulation. In one embodiment, the proposed
configuration for
the feedback device 204, as described herein, may allow to prevent lightning
strikes on
the feedback device 204. Indeed, the fact that the feedback device 204 may be
made
from non-electrically conductive materials (e.g., PEEK) prevents electrical
discharge to
the feedback device 204. In particular, the proposed configuration of the
feedback
device 204 prevents the possibility for lightning to be conducted from a
propeller
attachment to the feedback device and then to the sensor 206 or other point on
the
engine 110.
[0065] The above description is meant to be exemplary only, and one skilled in
the art
will recognize that changes may be made to the embodiments described without
departing from the scope of the invention disclosed. Still other modifications
which fall
within the scope of the present invention will be apparent to those skilled in
the art, in
light of a review of this disclosure.
[0066] Various aspects of the systems and methods described herein may be used
alone, in combination, or in a variety of arrangements not specifically
discussed in the
embodiments described in the foregoing and is therefore not limited in its
application to
the details and arrangement of components set forth in the foregoing
description or
illustrated in the drawings. For example, aspects described in one embodiment
may be
combined in any manner with aspects described in other embodiments. Although
particular embodiments have been shown and described, it will be apparent to
those
skilled in the art that changes and modifications may be made without
departing from
this invention in its broader aspects. The scope of the following claims
should not be
limited by the embodiments set forth in the examples, but should be given the
broadest
reasonable interpretation consistent with the description as a whole.
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