Note: Descriptions are shown in the official language in which they were submitted.
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STRUCTURAL DEFLECTION AND LOAD MEASURING DEVICE
FIELD OF THE INVENTION
[0001] The present invention provides a means for measuring the
bending/shear
deflection of a structure, and through knowledge of the type of structure,
provides means to
determine the loads/forces applied to the structure. The present invention
provides means for
measuring structural deflections in general, and axle deflections in
particular. More
particularly, the present invention provides means to measure the deflections
of aircraft
landing gear axles and for determining the loads applied thereto.
BACKGROUND OF THE INVENTION
[0002] An axle is generally described as a supporting shaft for a
rotating wheel(s) or
gear(s). Axles are used in many different environments, including in
automobiles and aircraft.
In general use, an axle may be required to sustain varying weights placed upon
it and
therefore its structural integrity may be important to its lifespan. For
example, in an aircraft
application there will be an increase in the load placed on the axle when the
plane is
stationary and being loaded with passengers, cargo and fuel. An even greater
load will be
placed on the axle when the wheels and the axle to which they are attached
come into contact
with the runway upon landing. It is therefore desirable to monitor the
condition of the axle to
ensure that it is not damaged or in need of servicing or maintenance.
[0003] Knowing the forces applied to aircraft landing gear axles provides
for the
determination of aircraft weight and balance, which is of interest to aircraft
operators. The
weight (mass of the aircraft, fuel, occupants, and cargo) and balance (the
position of the
centre of gravity of the aircraft) are critical factors that require
measurement or calculation
prior to every flight. Currently, almost every aircraft departs using
calculated weight and
balance values. These calculated values are based on average weights, not the
actual weights
of passengers and baggage, so aircraft operators must limit the usage of their
aircraft to a
narrower band of weight and balance values than that set by the aircraft
manufacturer. This
limits the utilisation of the aircraft, and reduces its potential revenue. In
addition, the
calculations are performed manually in some instances, and in others by
central calculation
departments. If a method of measuring the weight and centre of gravity existed
that could
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reliably determine these values, the usage of the aircraft would increase
(more
passengers/cargo) could be carried, and the costs to aircraft operators to
determine the values
could be significantly reduced.
[0004] A number of attempts to determine the weight of aircraft have been
tried, with
various degrees of success. The benchmark are stationary scales that an
aircraft rolls onto,
such that each landing gear or landing gear wheel is weighed. This method
provides the
standard to which all others are compared, but since the scales are not
carried aboard the
aircraft, and since the weighing procedure typically takes a significant
amount of time, this
method is not appropriate for the determination of the aircraft weight and
balance prior to
each flight. A number of flyable approaches have been attempted. In all these
methods the
landing gear, or portions thereof, form the element on which the measurement
will be made
since the landing gear, and its associated wheels and tires, are where the
aircraft's weight is
reacted by the ground. One of the earliest approaches to determining the
weight over a
landing gear was by measuring the pressure of the gas in the gas spring that
supports the
aircraft. This method suffers from a lack of accuracy due to the friction of
the gas and oil
seals in the strut which carry some of the load. Methods exist (Nance) to
account for this
friction, but these are either based on empirical data or require complicating
the gas oil strut
of the landing gear with various valves, tubes, and actuators that by their
existence reduce the
reliability of the landing gear system.
[0005] Other methods have been tried that more directly relate to the
present
invention ¨ they work by attempting to measure the deflection of the landing
gear axles. A
direct approach uses strain gauges, either bonded to the axle, or bonded to a
sensor fitted
within the axle. Strain gauges use conductive metal that when stretched or
compressed will
cause an increase or decrease in electrical resistance across the material.
The amount of
change in the electrical resistance can be used as a measurement of the strain
or deflection
that the component to which the strain gauge is attached to is under. Such
gauges have
limitations based on the constriction of the elastic limits of the material
used and the lack of
high accuracy that can occur in the measurement readings. In addition, strain
gauged based
systems suffer from a lack of longevity in landing gear applications related
to their reliance
on mechanical bonding (gluing) of the gauge to the area of interest. Another
point of failure
of strain gauges is through corrosion where the electrical leads are
terminated to the gauge.
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These terminations are by necessity in a harsh environment (the aircraft
landing gear axle)
and typically do not survive long in service.
[0006] A further attempt to measure the shear deflection of the axle has
been fielded.
This system employs a variable reluctance sensor which operates by measuring
directly the
displacement of the landing gear axle. The sensor is bolted to specially
machined lugs on the
exterior of the landing gear axle. In practice the system is expensive due to
the requirement
for machining lugs on a part which would be normally have been turned in a
lathe and
difficult to calibrate and use.
[0007] Other systems, which have been contemplated or demonstrated,
include
systems that directly measure material properties of a component to which they
are attached,
i.e. the axle. Such measurements (such as Barkhausen noise and other magnetic
domain
measurements) are then compared to predetermined material measurements and can
be used
to determine any potential stress on the component material. Many of these
systems are
experimental and have not had their reliability proven. In addition, there are
questions as to
how certain material properties of interest to these sensors change naturally
with time. For
instance, the Barkhausen noise properties of steel may change naturally over
the life of a
landing gear, confounding the original calibration.
[0008] In addition to the interest in measuring the weight of an
aircraft, it is of interest
to measure the forces acting on a landing gear in order to better determine
the structural life
and integrity of said landing gear. A method to measure axle deflections could
provide a
significant amount of information towards the determination of landing gear
structural life.
SUMMARY OF THE INVENTION
[0009] The present invention provides a structural deflection and load
measuring
device for mounting on an axle comprising at least one light beam emitting
device connected
to the axle and operable to emit at least one light beam and at least one
light position sensing
device connected to the axle and located relative to the light beam emitting
device. The at
least one light position sensing device comprising at least two independent
locations for
receiving an incident beam and operable to measure the at least two
independent locations.
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The at least two independent locations may be located on the same or different
light position
sensing devices.
[0010] The present invention further provides a refractive optical
device located
between the at least one light position sensing device and the at least one
light emitting
device and within the path of the light beam for refracting the light beam
prior to being
received on the light position sensing device.
[0011] The present invention further provides a device that
includes at least one light
beam emitting device and at least one light position sensing device being
located proximal to
each other, for example within the same plane, and a reflective optical device
which is
located at a position distal from the at least one light beam emitting device
and the at least
one light position sensing device and positioned to reflect the beam emitted
from the at least
one emitting device onto the at least one position sensing device.
[0012] The present invention further provides a housing to contain
the structural
deflection and load measuring device described herein and for mounting on or
within an axle.
[0013] The present invention further provides a structural
deflection and load
measuring device comprising a first light beam emitting device operable to
emit, at least one
light beam and a first light position sensing device for receiving the first
light beam and a
second light beam emitting device operable to emit at least one light beam and
a second light
position sensing device located relative to the second light beam emitting
device for receiving
at least one light beam emitted from the second light beam emitting device
thereon. The
device further comprises a refractive optical device located between the
second light emitting
device and the second light position sensing device for enhancing the
deflection of the
= second light beam.
[0014] The present invention further provides transmitting means
connected to the at
least one light position sensing device for transmitting the measured
locations of the light
beam. Preferably the device also comprises a processor which is connected to
the transmitting
means and operable to calculate at least one of weight, balance and load of
the aircraft using
the measured location(s) of the light beam.
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[0015] The present invention further comprises a method for measuring
axle
deflection using an optical axle deflection sensor comprising at least one
light emitting device
connected to the axle and at least one light position sensing device connected
to the axle and
located relative to the light beam emitting device for receiving at least one
light beam from
the light beam emitting device thereon, the method comprising the steps of
(i) measuring the position of the light beam from the light beam emitting
device on the light
position sensing device when no load is applied to the axle
(ii) applying a load to the axle and re-measuring the position of the light
beam on the sensing
device (iii) comparing the position of the light beam in (i) with (ii) and
calculating the light
beam deflection; and (iv) calculating the axle deflection using the light beam
deflection
calculated in (iii). The method further comprises using the calculated axle
deflection of step
(iv) to determine at least one of weight, balance and load on the axle.
[0016] The present invention further comprises a structural deflection
and load
measuring device for mounting on a dual wheel axle comprising
a housing for mounting on the axle; at least one mirror assembly for mounting
on the inside
of at least one wheel hub cap connected to the wheel axle, at least one light
beam emitting
device contained within the housing and operable to emit at least one light
beam towards the
mirror assembly and at least one light position sensing device contained
within the housing
and located adjacent the light beam emitting device for receiving the at least
one deflected
light beam from the mirror assembly thereon and operable to calculate the
position of the
light beam received thereon.
[0017] The present invention further provides a mirror assembly
comprising a
plurality of light absorbing elements. The light absorbing elements may be
radially extending
elements, for example radially extending stripes. The mirror assembly may
include at least
one mirror and at least one of a reflective lens and a refractive lens.
[0018] The present invention further provides a system for measuring the
weight,
balance and/or load of an aircraft comprising at least one structural
deflection and load
measuring device described herein located on each axle of the aircraft. The
present invention
further provides a system for measuring the weight, balance and/or load of an
aircraft
including additional structural deflection and load measuring devices mounted
at
predetermined positions on the aircraft landing gear, for example on a bogie
beam.
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[0019] The present invention further provides a structural deflection and
load
measuring device for mounting on an axle, comprising a housing for mounting on
the axle
a first light beam emitting device contained within the housing and operable
to emit at least
one light beam, a first light position sensing device contained within the
housing and located
relative to the light beam emitting device for receiving at least one light
beam from the first
light beam emitting device thereon and operable to calculate the position of
the light beam
received thereon, a second light beam emitting device contained within the
housing and
located adjacent the first light beam emitting device, a second light position
sensing device
contained within the housing and located relative to the second light beam
emitting device for
receiving the light beam emitted from the second light beam emitting device
and operable to
calculate the position of the light beam received thereon and
a refractive optical device located between the second light emitting device
and the second
light position sensing device.
[0020] The present invention further provides a structural deflection and
load
measuring device for mounting on a dual wheel axle comprising a housing for
mounting on
the axle, at least one mirror assembly for mounting on the inside of at least
one wheel hub
cap connected to the wheel axle, at least one light beam emitting device
contained within the
housing and operable to emit at least one light beam towards the mirror
assembly, at least one
light position sensing device contained within the housing and located
adjacent the light
beam emitting device having at least two independent locations for receiving
an incident
beam and operable to measure the at least two locations. The present invention
further
provides the device above wherein the at least two independent locations are
located on either
the same light sensing device or different light sensing devices.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] Embodiments of the present invention will be described in further
detail
below, with reference to the accompanying figures in which:
[0022] Figure 1 is a side view of one embodiment of the optical axle
deflection sensor
of the present invention;
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[0023] Figure 2 is a side view of the optical axle deflection sensor of
Figure 1 shown
in a deflected state, with a load applied on the axle;
[0024] Figure 3 is a schematic of the an alternative embodiment of the
optical axle
deflection sensor of the present invention;
[0025] Figure 4 is a side view of the optical deflection sensor of Figure
1 using a
prism to amplify the deflection of the light beam.
[0026] Figures 5A-C illustrate three separate measurement states for a
further
embodiment of the optical axle deflection sensor of the present invention;
[0027] Figure 6 illustrates a further alternative embodiment of the
optical axle
deflection sensor of the present invention using a reflecting device;
[0028] Figure 7 illustrates an additional embodiment of the optical axle
deflection
sensor of the present invention including a thermal heater and cooler element;
and
[0029] Figures 8A and B illustrates a further embodiment of the present
invention for
mounting on a dual wheel axle.
[0030] Figure 9a is an example of nose landing gear of an aircraft.
[0031] Figure 9b is an example of main landing gear of an aircraft.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0032] The present invention will now be described in further detail with
reference to
Figures 1 through 6. The present invention provides a structural deflection
and load
measuring device, also referred to herein as an optical axle deflection sensor
or a deflection
sensor, having at least one light beam emitting device and at least one light
position sensing
device. The at least one emitting device and the at least one sensing device
are mounted on an
axle at a spaced apart distance from each other. The position of the at least
one light beam
emitting device relative to the at least one sensing device provides that the
light beam emitted
from the at least one light beam emitting device projects onto the at least
one sensing device
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when no axle deflection is occurring. Preferably the light beam is projected
on to an area of
the at least one sensing device at a position that maximises the useful
resolution of the sensor.
The initial position being chosen when no axle deflection is occurring. For
example, the
position of the light beam/dot may be chosen to be fairly close to the edge of
the sensor for
measurements of weight/vertical force. This position may be chosen since the
magnitude of
the loads in the aircraft weight direction are significantly greater that the
loads in the opposite
direction which come mostly from the inertial loading of the wheels, tires,
and brakes during
free extension of the shock strut. However, for the fore/aft (drag load) the
position of the
light beam/dot may be in the centre.
[0033] One embodiment of the present invention will now be described with
reference to Figures 1 and 2 in which the optical axle deflection sensor is
indicated generally
at numeral 10. The optical axle deflection sensor 10 is mounted to an axle,
which is indicated
generally at numeral 12. The optical axle deflection sensor 10 uses a light
beam emitting
device 14 and a light position sensing device 16, which may also be referred
to as a detector
or sensor. The light beam emitting device 14 emits at least one light beam
which is received,
in the form of a light image or dot, on a surface of the light position
sensing device 16.
[0034] When no load is placed on the axle 12 the light beam emitted from
the
emitting device 14 projects an image or dot onto the centre of the surface of
the sensing
device 16. When a load is applied on the axle 12 the light beam will deflect
relative to the
amount of the load and will be received on the surface of the sensing device
at a position that
differs from the no load position. The deflection of the light beam may be
very small when
lighter loads are applied on the axle relative to the deflection that occurs
when heavy loads
are applied.
[0035] The light beam emitting device 14 may be any device from which at
least one
light beam is emitted. Examples of light beam emitting devices are known in
the art and may
be, but are not limited to, for example, a light emitting diode or laser. The
light position
sensing device 16 may be any device that is operable to detect, or sense, at
least one light
image received thereon, for example a light dot or a light image or shape,
such as a circle or
ellipse. Examples of light position sensing devices are known in the art and
may be, but are
not limited to, a position sensitive detectors (PSD) or an optical image
sensor such as a
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charge coupled device (CCD) or complementary metal oxide semiconductor (CMOS)
image
sensor.
[0036] Position-sensitive detectors are photodiodes that are able to
detect the position
of a light spot, or dot, projected onto its surface. The information relating
to the signal is
calculated from the magnitude of the photocurrent signals provided on the PSD.
Charge
coupled devices are integrated circuits containing an array of linked
capacitors which when
hit by light emit electrons which can in turn be measured and used to
calculate the position of
the image/dot. The information relating to the position of the image or dot
can then be
relayed to a processor or control system that is capable of manipulating this
information and
correlating the change in position of the image/dot, i.e. the deflection, into
information
relating to the vertical and drag load on the axle.
[0037] As stated above, the light beam emitting device 14 and the light
position
sensing device 16 are mounted to the axle such that they are spaced apart a
distance and
aimed at each other such that at no deflection of the axle the light beam
emitted from the
emitting device projects a dot, or image, at a position on the sensing device
16. The light
beam emitting device 14 and the light position sensing device 16 are mounted
in order that
both devices are held at fixed locations relative to the axle to ensure that
the movement of the
axle is reflected, and subsequently measured, in the projection of the light
beam.
[0038] Figure 3 illustrates one embodiment of the mounting of the sensor
10 to the
axle. In this embodiment the emitting device 14 and the sensing device 16 are
located within
a housing 17 that is mounted within the axle 12. The housing 17 is attached at
peripheral ends
to first and second rings 19 that are fitted within the internal portion of
the axle, through an
interference fit. It will be understood that this attachment is by no means
limiting and other
ways of attaching the housing 17 to the internal portion of the axle may be
used. For
example, the housing 17 may include flange portions at either end that can be
directly
attached to the internal portion of the axle, for example by welding or using
bolts.
Alternatively the housing 17 may be attached to the external surface of the
axle. The
attachment to the external surface may be through any means already discussed
and those
known to a person skilled in the art. For example, the housing may be attached
at peripheral
ends to rings that fit around the external surface of the axle, i.e. the axle
passes through the
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internal portion of the rings, or alternatively the rings may include flanges
or other attachment means by
which the rings are connected to the axle.
[0039] Any load that is applied on the axle 12 will cause a deflection in the
beam that is produced by the
light beam emitting device 14, relative to its stationary position when no
force is applied to the axle 12.
When the beam from the light beam emitting device 14 is deflected, the light
dot, or image on the sensing
device 16 moves proportional to the deflection. The measurement of the
position of the light dot and in
particular of the change in the position of the light dot relative to its
stationary position is used to
calculate the amount of deflection of the axle which in turn allows for the
determination of the axle load.
[0040] Since the deflection sensor 10 of the present invention may be used to
determine axle loads it will
be understood that the deflection sensor 10 may therefore be used in any
structure on which a load/force
is placed that causes a deflection of the structure relative to its at rest
state. For example, and as described
herein, the deflection sensor 10 may be used on an aircraft landing gear.
[0041] The use of a two dimensional light sensor 10 allows the beam
deflections to be characterized in
two dimensions, i.e. for instance up and down, and fore and aft. When used on
an aircraft landing gear,
these deflections may be correlated to, for example, aircraft vertical load or
weight and drag loads, for
example from braking.
[0042] Depending on the applied load, the relative movement of the light beam
emitted from the light
beam emitting device 14 compared to the original stationary, no load, position
may be quite small, for
example if a relatively small load is applied. Therefore in order to be able
to measure small movements in
the position of the light beam on the light position sensing device 16 it may
be beneficial to incorporate
within the sensor 10 an optical device that is capable of amplifying the
movement of the light beam.
[0043] In a further embodiment, illustrated in Figure 4, in the deflection
sensor 10 described above, the
light beam emitted from the at least one light beam emitting device 14 may
therefore be split using optics,
such as a prism or a refractive lens, to force the beam to travel a greater
distance across the light sensing
device 16, i.e. to amplify the deflection. In
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the embodiment illustrated a prism 20 is connected to the portion of the
sensor 10 that
includes the light position sensing device 16. Examples of other optical
devices that may be
used are known to persons skilled in the art.
[0044] An alternative embodiment is illustrated in Figures 5A-C in which
the optical
axle deflection sensor 10 includes two light beam emitting devices 14 and two
light position
sensing devices 16. The light beam emitting devices 14,14' are located at one
end of the axle
12 and the light position sensing devices 16,16' are located at a distance
from the emitting
devices 14,14', and close to the opposing end of the axle 12. One of the light
beam emitting
devices is located at a higher position, referred to as the "upper" device 14'
relative to the
second light beam emitting device 14. The upper emitting device 14' sends a
beam on a
direct path to one of the detectors 16' whereas the lower emitting device 14
sends a beam that
passes through an optical deflection device 20, shown in Figure 5 as a
spherical lens, and then
onto the second detector 16. The optical deflection device 20 may be any
optical device that
provides a magnification of the movement of the light beam, as discussed
earlier, i.e. a
magnification in the increase in the angle of deflection of the light beam.
[0045] When a large load is applied on the axle 12 the light beam emitted
from the
upper emitting device 14' will undergo a large deflection which can be
measured by sensing
device 16. However, if a small load is applied then only a small deflection in
the light beam
will occur. In this instance, the deflection of the light beam emitted from
the lower emitting
device will be amplified upon passing through the optical deflection device 20
and therefore a
large deflection may be measured on the second detector 16.
[0046] As discussed above, the deflection sensor may be used on an axle
in aircraft
landing gear. When the landing gear axle undergoes a large deflection, as is
the case when an
aircraft comes in for a landing, the detector 16' takes the direct
measurements, i.e. not
through the optical deflection device 20, may be used for the calculation of
the light beam
deflection. Axle deflection values in this case may range from 1 to 2 mm,
which may be an
easily detectable distance range for the detector 16' being used. When the
landing gear axle
12 undergoes a small deflection, as is the case when a plane is stationary on
the ground
during loading, the detector 16 takes measurements from the beam that passes
through the
optical deflection device 20. With the small deflection, the incident beam
coming from the
lower emitting device 14 moves only a small amount relative to the original
position.
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However, the refracted beam exiting the optical deflection device 20 moves a
much larger distance
against the detector's surface. For example, a 5 micrometer movement in the Y
direction of the incident
beam translates into a 500 micrometer movement along the detector's surface.
By using the optical
deflection device 20 to amplify the observed deflection, very small
deflections of the axle 12 can be
measured.
[0047] In a further embodiment, illustrated in Figure 6, the optical axle
deflection sensor 10 may include
the use of at least one mirror 26, either plane or having a specific
predefined curvature, in order that the
light beam emitting device 14 and the light position sensing device 16 may be
placed on the same side of
the axle 12. The placement of the emitting device 14 and the point sensing
device 16 being on the same
side allow for both devices to be connected to the same electronic circuit
board. The location of the
components on the same electronic circuit board allow for the possibility to
maintain all the components
at the same temperature since they are located within close proximity to each
other. Connection to the
same circuit board will also reduce the number of wires and power sources that
may be required for the
components. The use of a mirror, or other reflective device, with a specific
curvature may provide the
capability to combine the amplification of deflection function along with the
folding of the light beam
such that the electronics may be mounted together.
[0048] In a further embodiment, illustrated in Figure 7, the optical axle
deflection sensor 10 includes at
least one heating element 28. The heating element 28 may be used to either
provide heat to the sensor 10
or to cool the sensor 10. The heating element 28 may include at least one
thermal heater element and/or at
least one cooler element. The heating element 28 may be used to heat the
environment of the sensor
components when the sensor is used under extreme cold temperature conditions.
The heating element 28
may be used to cool the environment of the sensor components when the sensor
10 is used under extreme
heat conditions. The heater element 28 may be separate components or they may
be one component
having the capability to provide both hot and cold temperature variations, for
example a Peltier junction
may be used to stabilize, under electronic control, the temperature of the
emitter and detector.
Environments where large variations in temperature occur are, for example, on
aircraft landing gear
where severe cold, due to high elevations during flight, and severe heat, due
to braking, can occur. The
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heating element 28 may be used to maintain the sensor 10 at a constant
temperature when in use.
[0049] It will be understood that the sensor 10 described above can be used in
many different
applications. When used in aircraft landing gear, the sensor 10 may be used to
measure weight/balance
and therefore may only be used during loading of the plane. Alternatively, the
sensor 10 may be used for
health monitoring purposes, i.e. to monitor the applied loads placed on the
axle during loading and during
landing of the plane. The requirements for power and monitoring of the sensor
10 in each system will
therefore vary. For example, if the sensor 10 is only being used to monitor
the weight/balance during
loading of the plane then power is only required for a short pre-determined
period of time. The power
source may therefore be supplied through ground control systems or the sensor
10 may be battery
powered. In situations where the sensor 10 is being used to monitor the health
of the aircraft landing gear
then power may be supplied through a connection to the aircraft power system.
[0050] The embodiments described above generally refer to a light image or dot
located on the surface of
the point sensing device. The light image may be any shape that can project
onto the surface of the
sensing device and that can be measured by the sensing device to calculate a
deflection from the original
projected position. Examples of alternative shapes include circles that when
deflected change shape to
form an ellipse which indicates a deflection has occurred and the measurement
taken can then be
translated into an applied force on the axle. The use of certain images, for
example a cross-like image
may reflect torsional movement in the projected image on the sensing device.
Image analysis software
may then be used to correlate the change in image to a torsional force that
has been applied to the axle.
[0051] The information obtained by the light position sensing device 16, i.e.
the location of the light
beam, may be transmitted to an on-board control system, or processor, for
further manipulation or may be
temporarily stored in or near the sensor 10 or may be transmitted to a ground
control system. Systems and
methods of relaying such information include the use of processors and
transmitters and are known by
persons skilled in the art.
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[0052] The embodiment described above, includes a housing 17 that is used to
contain the at least one
light emitting device 14 and the at least one point sensing device 16 therein.
The housing 17 may be a
container which is closed and then attached by external means to the axle.
Alternatively the housing 17
may be a cover that is positioned over the at least one light emitting device
14 and the at least one light
sensing device 16. In this embodiment the light emitting device 14 is attached
directly to the surface of
the axle at a first point and the light sensing device 16 is attached directly
to the surface of the axle at a
second point, with all of the requirements of the positioning of the devices
relative to each other, as
described above. The cover may then be placed over the device to keep the
devices 14,16 protected and to
reduce the possibility of foreign bodies interfering with the light beam
projection and measurements.
[0053] In yet another embodiment, illustrated in Figures 8A-B, a sensor
package 30 is mounted at the
midpoint of a dual wheel axle 32. The sensor package 30 contains a plurality
of light emitting devices 14
and a plurality of light sensing devices 16. The package 30 is installed
through a hole at the midpoint of
the axle such that at least one set of light emitting devices 14 and light
sensing devices 16 face towards
one end of the axle shaft, and at least one other set of light emitting
devices 14 and light sensing devices
16 face towards the other end of the axle shaft. By placing the sensor package
30 in such a way that it is
insertable through the hole in the axle shaft 32, the sensor package 30 may be
replaced or repaired in the
field. A mirror or mirror and lens assembly is mounted to the inside of the
hub cap, not shown, (which is
rigidly attached to the wheel which rotates on the axle). This mounting
arrangement allows for rapid and
simple removal and replacement of the components while an aircraft is in
service.
[0054] In a further embodiment, an additional light emitting device 14 and a
light sensing device 16 can
be added to the sensor package 30 of the embodiment above, with the additional
light emitting device 14
axis offset from the neutral axis of the axle 32. A plane mirror or other
optical device 36 mounted to the
inside of the hubcap 38, of wheel 40, will have a series of radial strips 42
etched or painted on to reduce
or eliminate the reflectivity of the optical device 36. This would cause the
light sensing device 16 to
receive a series of pulses during wheel rotation that would be proportional to
the wheel speed and the
number of strips (a fixed constant). This system would allow the incorporation
of wheel speed
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CA 02576805 2007-02-05
WO 2006/024146 PCT/CA2005/001304
measuring equipment within the axle load detecting system in order to simplify
the
equipment currently mounted in an aircraft axle.
[0055] The invention will now be described in further detail with regard
to the use of
the structural deflection and load measuring device of the present invention
in an aircraft
landing gear. In a typical tricycle arrangement of landing gear there is
included a left main
landing gear and a right main landing gear and a nose landing gear. An example
of the
left/right main landing gear is illustrated in Figure 9A and an example of the
nose landing
gear is illustrated in Figure 9B. To achieve a weight and balance calculation
for an aircraft
the vertical force acting upon each axle is required. The weight of the
aircraft is the sum of all
the vertical loads and constant weights for the wheels, brakes and tires.
[0056] In a cantilever arrangement, the axle remains in a fixed position
relative to the
ground. The axle translates across the ground and its orientation remains
stable. In this type
of arrangement a one dimensional axle sensor, as known in the prior art, may
be used.
However, many landing gear arrangements are of the Bogie or articulated style.
In these
arrangements the angle that the vertical force acts on the axle varies with
axle position, this is
generally even more evident on an articulated landing gear. One dimensional
sensors will
therefore not read the vertical load accurately. However, the two dimensional
sensor device
of the present invention is operable to measure this load.
[0057] As will be understood by a person skilled in the art, using x and
y force
measurements and using the formula Vertical Load =I x' + y2 the true vertical
load may be
measured whenever the aircraft is static.
[0058] In a first application used to calculate the weight and balance of
an aircraft the
system is preferably dual redundant. This means that the system includes two
light emitting
devices and two light sensing devices. For example, the system may include the
light emitting
devices and the light sensing devices located on the same electronics board
and preferably
having separate power supplies. In this embodiment, the two light emitting
devices are
located in the same plane as the two light sensing devices and are positioned
opposite an
optical deflector, e.g. a mirror. Alternatively, the system may include two
light emitting
devices located in the same plane and opposite two light sensing devices. In
both of these
systems the dual light emitting and sensing devices are located within one
housing. In a
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CA 02576805 2012-08-29
õ
system for measuring weight and load balance of an aircraft one of the
embodiments described above
containing the dual emitting and sensing devices is attached to each axle of
the aircraft.
[0059] In a second application used to monitor the load on the aircraft it is
preferable to also include a
measurement of the side loads. Therefore, in a bogie gear, additional sensor
systems, as described above,
are also included in the bogie beam, for example at position A illustrated in
Figure 9B, the measurement
axes are indicated at arrows B and C. In a cantilever system, additional
sensor systems, as described
above, may be included in the piston.
[0060] While this invention has been described with reference to illustrative
embodiments and examples,
the description is not intended to be construed in a limiting sense. Thus,
various modifications of the
illustrative embodiments, as well as other embodiments of the invention, will
be apparent to persons
skilled in the art upon reference to this description. It is therefore
contemplated that the appended claims
will cover any such modifications or embodiments. Further, all of the claims
are hereby incorporated by
reference into the description of the preferred embodiments.
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