Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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BLADE ANGLE POSITION FEEDBACK SYSTEM WITH PROFILED MARKER
TERMINATIONS
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This patent application claims priority of US provisional Application
Serial No.
62/831,252, filed on April 9, 2019, the entire contents of which are hereby
incorporated
by reference.
TECHNICAL FIELD
[0002] The present disclosure relates generally to engines, and more
specifically to
blade angle position feedback systems.
BACKGROUND OF THE ART
[0003] 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. Existing
feedback
devices are however vulnerable to a so-called "edge-effect" that leads to an
increase in
reading error as the sensor approaches the edges of the feedback device.
[0004] Therefore, improvements are needed.
SUMMARY
[0005] 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, the feedback device having a root surface
having a first
edge, a first plurality of position markers extending from the root surface
and oriented
substantially parallel to the longitudinal axis, the first plurality of
position markers
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circumferentially spaced from one another, at least one second position marker
extending from the root surface and positioned between two adjacent first
position
markers at an angle thereto, the at least one second position marker having an
end
positioned adjacent to the first edge and non-flush therewith, and at least
one sensor
mounted adjacent the feedback device and configured to detect a passage of the
first
plurality of position markers and the at least one second position marker as
the
feedback device rotates about the longitudinal axis.
[0006] In some embodiments, the end of the at least one second position marker
is
beveled at an angle with respect to the first edge.
[0007] In some embodiments, the end of the at least one second position marker
comprises a second edge, the second edge having a first edge section
substantially
aligned with the first edge and a second edge section angled relative to the
first edge.
[0008] In some embodiments, the first edge section and the second edge section
connect at a geometric centerline of the at least one second position marker,
the first
edge section forming a first acute angle with the centerline and the second
edge section
forming a second acute angle with the centerline, the first angle
substantially equal to
the second angle.
[0009] In some embodiments, a notch is formed in the root surface adjacent the
second
edge section.
[0010] In some embodiments, the end of the at least one second position marker
comprises a second edge, the second edge having a rounded shape.
[0011] 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, the feedback device having a root surface having a
first edge, a
first plurality of position markers extending from the root surface and
oriented
substantially parallel to the longitudinal axis, the first plurality of
position markers
circumferentially spaced from one another, and at least one second position
marker
extending from the root surface and positioned between two adjacent first
position
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markers at an angle thereto, the at least one second position marker having an
end
positioned adjacent to the first edge and non-flush therewith.
[0012] In some embodiments, the system further comprises at least one sensor
mounted adjacent the feedback device and configured to detect a passage of the
first
plurality of position markers and the at least one second position marker as
the
feedback device rotates about the longitudinal axis.
[0013] In accordance with yet another 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, the feedback device having a root
surface
having a first edge, a first plurality of position markers extending from the
root surface
and oriented substantially parallel to the longitudinal axis, the first
plurality of position
markers circumferentially spaced from one another, at least one second
position marker
extending from the root surface and positioned between two adjacent first
position
markers at an angle thereto, the at least one second position marker having an
end
positioned adjacent to the first edge and substantially flush therewith, an
extrusion of
material provided at the end to make the end substantially symmetrical about a
geometric centerline of the at least one second position marker, and at least
one sensor
mounted adjacent the feedback device and configured to detect a passage of the
first
plurality of position markers and the at least one second position marker as
the
feedback device rotates about the longitudinal axis.
[0014] In accordance with yet 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, the feedback device having a root surface
having a first
edge, a first plurality of position markers extending from the root surface
and oriented
substantially parallel to the longitudinal axis, the first plurality of
position markers
circumferentially spaced from one another, and at least one second position
marker
extending from the root surface and positioned between two adjacent first
position
markers at an angle thereto, the at least one second position marker having an
end
positioned adjacent to the first edge and substantially flush therewith, an
extrusion of
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material provided at the end to make the end substantially symmetrical about a
geometric centerline of the at least one second position marker.
[0015] 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
[0016] Reference is now made to the accompanying figures in which:
[0017] FIG. 1 is a schematic cross-sectional view of an example gas turbine
engine;
[0018] FIG. 2 is a schematic diagram of an example feedback sensing system;
[0019] FIG. 3 is a schematic diagram of the propeller of FIG. 1 with the
feedback
device of FIG. 2, in accordance with an embodiment;
[0020] FIG. 4A is a schematic bottom view of the feedback device of FIG. 2
showing
the shape of position marker terminations, in accordance with one embodiment;
[0021] FIG. 4B is a schematic bottom view of the feedback device of FIG. 2
showing
the shape of position marker terminations, in accordance with another
embodiment;
[0022] FIG. 4C is a schematic bottom view of the feedback device of FIG. 2
showing
the shape of position marker terminations, in accordance with yet another
embodiment;
and
[0023] FIG. 5 is a schematic bottom view of the feedback device of FIG. 2,
showing the
shape of position marker terminations, in accordance with yet another
embodiment.
[0024] It will be noted that throughout the appended drawings, like features
are
identified by like reference numerals.
DETAILED DESCRIPTION
[0025] 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
hot combustion gases, and a turbine section 118 for extracting energy from the
combustion gases.
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[0026] 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.
[0027] 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 connected to a hub by any suitable means and extending radially
therefrom. The
blades are also each rotatable about their own radial axes through a plurality
of blade
angles, which can be changed to achieve modes of operation, such as feather,
full
reverse, and forward thrust.
[0028] With reference to FIG. 2, 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 phonic
wheel) 204
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.
[0029] 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. 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
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propulsion systems having a propeller driven in a hybrid architecture (series,
parallel, or
series/parallel) or turboelectric architecture (turboelectric or partial
turboelectric).
[0030] The system 200 comprises an annular member 204 and one or more sensors
212 positioned proximate the annular member 204. Annular member 204 (referred
to
herein as a feedback device) has a plurality of detectable features (also
referred to as
position markers or teeth) 202 disposed thereon for detection by sensor 212.
In some
embodiments, the feedback device 204 is mounted for rotation with propeller
130 and to
move axially with adjustment of the blade angle of the blades of the propeller
130, and
the sensor 212 is fixedly mounted to a static portion of the engine 110. In
other
embodiments, the sensor 212 is mounted for rotation with propeller 130 and to
move
axially with adjustment of the blade angle of the blades of the propeller 130,
and the
feedback device 204 is fixedly mounted to a static portion of the engine 110.
[0031] The system 200 also includes a controller 220 communicatively coupled
to the
sensor 212. The sensor 212 is 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, the sensor 212 produces a
series
of signal pulses in response to detecting the presence of a position marker
202 in a
sensing zone of the sensor 212. For example, the sensor 212 is an inductive
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
212. When
a position marker 202 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 202, and the sensor 212 can produce a
signal
pulse, which forms part of the sensor signal. Accordingly, the position
markers 202 may
be made of any suitable material (e.g., a ferromagnetic material, Mu-Metal, or
the like)
which would cause the passage of the position markers 202 near the sensor 212
to
provide a change in magnetic flux within the magnetic field generated by the
sensor
212.
[0032] In the example illustrated in FIG. 2, a side view of a portion of
feedback device
204 and sensor 212 is shown. The sensor 212 is mounted to a flange 214 of a
housing
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of the reduction gearbox 126, so as to be positioned adjacent the plurality of
position
markers 202. In some embodiments, the sensor 212 is secured to the propeller
130 so
as to extend away from the flange 214 and towards the position markers 202
along a
radial direction, identified in FIG. 2 as direction 'IT. Sensor 212 and flange
214 may be
fixedly mounted, for example to the housing of the reduction gearbox 126, or
to any
other static element of the engine 110, as appropriate.
[0033] In some embodiments, a single sensor 212 is mounted in close proximity
to the
feedback device 204 and the position markers 202. In some other embodiments,
in
order to provide redundancy as well as dual-signal sources at multiple
locations, one or
more additional sensors, which may be similar to the sensor 212, are provided.
For
example, an additional sensor 212 may be mounted in a diametrically opposite
relationship, or at any angle, relative to the position markers 202, which
extend away
from the feedback device 204 and towards the sensor(s) 212. In yet another
embodiment, several position markers 202 may be spaced equiangularly about the
perimeter of the feedback device 204. Other embodiments may apply.
[0034] With additional reference to FIG. 3, in some embodiments the feedback
device
204 is embodied as a circular disk which rotates as part of the engine 110,
for example
with the propeller shaft 124 or with the propeller 130. The feedback device
204
comprises opposing faces 3011, 3012 having outer edges 3021, 3022 and defines
a root
surface 304 which extends between the opposing faces 3011, 3012 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
3011, 3022
and the root surface 304 intersects the faces 3011, 3012 at the edges 3021,
3022. In
these embodiments, the position markers 202 can take the form of projections
which
extend from the root surface 304.
[0035] The position markers 202 may comprise a plurality of first projections
(not
shown) arranged along a direction substantially transverse to the opposing
faces and
substantially equally spaced from one another on the root surface 304. The
position
markers 202 may also comprise one or more second projections (not shown) each
positioned between two adjacent first projections. Each second projection is
illustratively oriented along a direction, which is at an angle relative to
the direction
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along which the first projections are arranged. The angle can be any suitable
value
between 1 and 89 , for example 30 , 45 , 60 , or any other value, as
appropriate. It
should be noted, however, that in some other embodiments the second
projection(s)
can be co-oriented with the first projections. It should also be noted that in
some
embodiments, each second projection can be substituted for a groove or inward
projection, as appropriate. In addition, in some embodiments, the feedback
device 204
includes only a single second projection while, in other embodiments, the
feedback
device 204 can include more than one second projection. In the latter case,
the second
projections can be oriented along a common orientation or along one or more
different
orientations and each second projection can be located at substantially a
midpoint
between two adjacent first projections or can be located close to a particular
one of two
adjacent first projections.
[0036] In one embodiment, the position markers 202 are integrally formed with
the
feedback device 204 so that the feedback device 204 may have a unitary
construction.
In another embodiment, the position markers 202 are manufactured separately
from the
feedback device 204 and attached thereto using any suitable technique, such as
welding or the like.
[0037] It should also be noted that, although the present disclosure focuses
primarily
on embodiments in which the position markers 202 are projections, other
embodiments
are also considered. The position markers 202 may, for example, comprise one
or more
of protrusions, teeth, walls, voids, recesses, and/or other singularities. For
instance, in
some embodiments, the position markers 202 may be embedded in the circular
disk
portion of the feedback device 204, such that the feedback device 204 has a
substantially smooth or uniform root surface 304. A position marker 202 can
then 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 202 may then be
applied to
the root surface 304, for instance as strips of metal or other material for
detection by the
sensor 212, which can be which can be an inductive sensor capable of sensing
changes in magnetic flux (as discussed above) or any other suitable sensor
such as a
Hall sensor or a variable reluctance sensor as discussed herein above. Still
other
embodiments are considered.
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[0038] The signal pulses produced by the sensor 212, 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. The regular spacing of the
first
projections can, for example, be used to determine a speed of rotation of the
feedback
device 204. In addition, the second projection(s) can be detected by the
sensor 212 to
determine a blade angle of the propeller 130.
[0039] With continued reference to FIG. 3, the feedback device 204 is
supported for
rotation with the propeller 130, which rotates about the longitudinal axis
'A'. The
feedback device 204 is also supported for longitudinal sliding movement along
the axis
A, e.g. by support members, such as a series of circumferentially spaced
feedback rods
306 that extend along the axis A. A compression spring 308 surrounds an end
portion
of each rod 306.
[0040] As depicted in FIG. 3, the propeller 130 comprises a plurality of
angularly
arranged blades 310, each of which is rotatable about a radially-extending
axis 'R'
through a plurality of adjustable blade angles, the blade angle being the
angle between
the chord line (i.e. a line drawn between the leading and trailing edges of
the blade) 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.
[0041] Referring now to FIG. 4A, the feedback device 204 illustratively
comprises
position markers 202, which, in one embodiment, can take the form of
projections which
extend from the root surface 304. As the feedback device 204 rotates, varying
portions
thereof enter, pass through, and then exit the sensing zone of the sensor 212.
From the
perspective of the sensor 212, the feedback device 204 moves axially along
axis A and
rotates about direction 'F'. However, as the sensor 212 moves towards and is
positioned adjacent to the edges 3021, 3022 of the feedback device 204 as a
result of
movement of the feedback device 204, the markers' magnetic centerline is
shifted. As
will be discussed further below, this results in a so-called "edge-effect"
that leads to an
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increase in reading error (also referred to herein as beta error) in the
measured position
of the feedback device 204 at the edges 3021, 3022. In order to permit the
sensor 212 to
accurately detect the passage of the position markers 202 without any (or with
reduced)
edge-related effects, it is proposed herein to modify the geometry of the
position
markers 202, as will be discussed further below.
[0042] In one embodiment illustrated in FIG. 4A, the position markers 202
include a
plurality of projections 402 (also referred to herein as 'straight'
projections) which are
arranged along a direction 'D', which is substantially transverse to the
opposing edges
3021, 3022. Although only two projections 402 are illustrated in FIG. 4A, it
should be
understood that any suitable number of projections 402 may be present across
the
whole of the root surface 304. The projections 402 can be substantially
equally spaced
from one another on the root surface 304. In addition, the projections 402 are
of
substantially a common shape and size, for example having a common volumetric
size.
[0043] The feedback device 204 also includes at least one supplementary (or
'angled')
projection 404 which is positioned between two adjacent ones of the
projections 402. In
the embodiment depicted in FIG. 4A, the projection 404 is oriented along a
direction 'E',
which is at an angle relative to direction 'D'. The angle between directions
'ID' and 'E'
can be any suitable value between 1 and 89 , for example 30 , 45 , 60 , or
any other
value, as appropriate. In some embodiments, the feedback device 204 includes
only a
single supplementary projection 404. In other embodiments, the feedback device
204
can include two, three, four, or more supplementary projections 404. In
embodiments in
which the feedback device 204 includes more than one supplementary projection
404,
the supplementary projections can all be oriented along a common orientation,
for
instance direction 'E', or can be oriented along one or more different
orientations. The
projection 404 can be located at substantially a midpoint between two adjacent
projections 402, or, as shown in FIG. 4A, can be located close to a particular
one of two
adjacent projections 402.
[0044] As shown in FIG. 4A, each projection 402, 404 extends axially (along
longitudinal direction `D' for projection 402 and along longitudinal direction
'E' for
projection 404), from a first axial end or termination 406 to a second
termination 408
(opposite the first termination 406), such that each termination 406, 408 is
adjacent a
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corresponding edge 3021, 3022 of the feedback device 204. Each projection 402,
404
has a first longitudinal edge 4101, a second longitudinal edge 4102 opposite
and
substantially parallel to the first longitudinal edge 4101, and opposite axial
edges (also
referred to as 'tips') 412 where the projection 402, 404 terminates. In other
words, each
termination 406, 408 ends at an edge 412.
[0045] In the embodiment of FIG. 4A, for each projection 402, the edge 412 of
each
termination 406, 408 is substantially parallel to the edge 3021, 3022 of the
feedback
device 204 the termination 412, 414 is adjacent to, such that each projection
402 is
symmetrical about its geometrical centerline 'C' from one termination 406, 408
to the
other. However, if the edges 412 of the angled projection 404 were to also be
substantially parallel to the edges 3021, 3022, this would result in the
angled projection
404 being asymmetrical about its geometrical centerline 'C' adjacent the edges
3021,
3022. Indeed, at each termination 406, 408, more material would be provided on
one
side of the centerline 'C' (referred to herein as the 'obtuse angle" side)
than on the other
side (referred to as the 'acute angle' side). For example, for a termination
406 having an
edge 412 substantially parallel with the feedback device's edge 3021, the
portion of the
termination 406 delimited by the centerline C, the edge 412, and the second
longitudinal edge 4102 (obtuse angle side) would have a greater volumetric
size than
the portion of the termination 406 defined by the centerline C, the edge 412,
and the
first longitudinal edge 4101 (acute angle side). This asymmetric distribution
of material
on the angled projection 404 would then lead to a distortion of the angled
projection's
magnetic centerline (away from the geometric centerline C) due to magnetic
flux
asymmetry. As the sensor 212 approaches the edges 3021, 3022 of the feedback
device
204, this asymmetry would result in an increase in the time interval between
the
passage of the straight projection 402 and the passage of the angled
projection 404, as
detected by the sensor 212. This would in turn increase the reading error (or
edge-
effect) and lead to inaccurate measurement of the position of the feedback
device 204
(since the position of the feedback device 204 is determined by the relative
timing
between the straight projections 402 and the angled projection 404), and thus
to
inaccurate blade pitch (or beta) angle measurement by the sensor 212.
[0046] In order to reduce any edge-related effects, it is proposed herein to
modify the
geometry of the terminations 406, 408 of each angled projection 404 such that
the
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terminations 406, 408 are symmetrical about the geometric centerline C. As a
result, as
the sensor 212 approaches the edges 3021, 3022 of the feedback device 204, the
angled projection 404 appears magnetically symmetrical about the geometric
centerline
C, thus improving the accuracy of the beta measurement system 200.
[0047] For this purpose, in one embodiment, the terminations 406, 408 of each
angled
projection 404 are shaped so as to be non-flush with the plane defined by a
corresponding feedback device face 3011, 3012 the termination 406, 408 is
adjacent to,
as illustrated in FIG. 4A, FIG. 4B, and FIG. 4C. In other words, for each
angled
projection 404, the edge 412 of each termination 406, 408 is not flush or
aligned with
(i.e., not parallel to) the edge 3021, 3022 that the termination 406, 408 is
adjacent to.
This can be achieved by removing material from the terminations 406, 408,
using any
suitable manufacturing technique such as milling. In this manner, the angled
projection
404 remains symmetrical about the centerline C throughout its length, i.e.
from one
termination 406, 408 to the other.
[0048] In the embodiment shown in FIG. 4A, material is removed from the
terminations
406, 408 of the angled projection 404 to achieve beveled chamfered
terminations 406,
408. The edge 412 of each termination 406, 408 is indeed beveled at an angle
with
respect to the edge 3021, 3022 the termination 406, 408 is adjacent to. In
particular,
each angled projection termination (illustrated by termination 406 in FIG. 4A)
is profiled
such that its edge 412 comprises a first section 4121 that is substantially
aligned with
the feedback device's edge 3021 and a second section 4122 that is at an angle
relative
to the first edge section 4121 and to the edge 3021. The first and second edge
sections
4121, 4122 connect at the centerline C and the angle between the second edge
section
4122 and the feedback device edge 3021 is set such that the termination 406 is
symmetrical about the centerline C. In particular, the first edge section 4121
forms a first
acute angle 81 with the centerline C and the second edge section 4122 forms a
second
acute angle 82 with the centerline C, the first angle 01 substantially equal
to the second
angle 02.
[0049] Referring now to FIG. 4B in addition to FIG. 4A, in accordance with
another
embodiment, in addition to profiling the terminations 406, 408 of the angled
projection
404 in the manner described above with reference to FIG. 4A, the feedback
device 204
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is also beveled adjacent the angled projection's terminations 406, 408. For
this
purpose, material may be removed from the feedback device 204 adjacent the
second
edge section 4122, thereby creating notches as in 414 along the edges 3021,
3022. In
one embodiment, provision of the notches as in 414 may further decrease
reading error
by further reducing the asymmetric distribution of material on the angled
projection 404.
[0050] Referring now FIG. 4C, although the edges 412 are illustrated and
described
herein as being straight, it should be understood that the terminations 406,
408 may
also be shaped with arcuate (e.g., rounded) edges 412. The arcuate shape of
the
edges 412 is illustratively selected to ensure that the angled projection 404
remains
symmetrical about the centerline C at the terminations 406, 408. In one
embodiment,
provision of the arcuate shape at the edges 412 may allow to simplify
manufacture and
inspection of the feedback device 204 (e.g., by providing all markers 402, 404
with a
similar configuration at their terminations as in 406, 408).
[0051] Referring now to FIG. 5, it should also be understood that, in another
embodiment, the angled projection 404 may be made symmetrical about the
centerline
C with the terminations 406, 408 being substantially flush with (i.e.
substantially parallel
to) the plane defined by a corresponding feedback device face 3011, 3012 that
the
termination 406, 408 is adjacent to (and accordingly substantially flush with
the
corresponding edges 3021, 3022). For this purpose, material may be added to
the
terminations 406, 408 to create an extrusion of material 416 on the acute
angle side of
the termination 406, 408 (without extending the terminations 406, 408 beyond
the
edges 3021, 3022). This is in contrast with the embodiments of FIGs. 4A, 4B,
and 4C,
where material is removed on the obtuse angle side of the terminations 406,
408. For
example, the geometry of the termination 406 is modified to add the extrusion
of
material 416 at the longitudinal edge 4101, thereby increasing the volumetric
size of the
portion of the termination 406 provided at acute angle side. The amount of
extrusion of
material 416 to be added is such that the volumetric size of the termination
406 at the
acute angle side is substantially similar to the volumetric size of the
termination at the
obtuse angle side, thereby achieving symmetry about the centerline C. In one
embodiment, the extrusion of material 416 is integral with the feedback device
204,
whereby the extrusion is machined from solid. In another embodiment, the
extrusion of
material 416 is added to the feedback device 204 by welding. It should however
be
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understood that any suitable manufacturing method including, but not limited
to,
additive manufacturing, casting, forging, extrusion, powder metallurgy,
blanking,
broaching, milling, and grinding, may apply.
[0052] It should be understood that, although FIGs. 4A to 5 only detail the
configuration
of the termination 406 (for clarity purposes), the termination 408 is shaped
similarly to
termination 406 in each embodiment. It should also be understood that the
shape of the
terminations 412, 414 will be modified differently depending on the
configuration of the
feedback device 204. Additional factors including, but not limited to, the
amount of beta
error, the available space according to clearances and tolerance stackup of
the
feedback system, and the accuracy required by the feedback system, may also
come
into play.
[0053] From the above description, it can be seen that, in one embodiment, the
feedback device 204 may be configured to allow for the sensor 212 to be
positioned
near or at the edges 3021, 3022 of the feedback device 204 while accurately
detecting
the passage of the position markers 202, thereby mitigating any edge-related
effects
that may influence the sensor 212.
[0054] 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.
[0055] 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
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limited by the embodiments set forth in the examples, but should be given the
broadest
reasonable interpretation consistent with the description as a whole.
CA 3077916 2020-04-08
