U.S. patent application number 14/612557 was filed with the patent office on 2015-06-18 for method and apparatus for alignment harmonization.
The applicant listed for this patent is BAE Systems Information and Electronic Systems Integration Inc.. Invention is credited to Almond J. Cote, Kirby A. Smith.
Application Number | 20150168443 14/612557 |
Document ID | / |
Family ID | 52597907 |
Filed Date | 2015-06-18 |
United States Patent
Application |
20150168443 |
Kind Code |
A1 |
Cote; Almond J. ; et
al. |
June 18, 2015 |
METHOD AND APPARATUS FOR ALIGNMENT HARMONIZATION
Abstract
Techniques and architecture are disclosed for performing
alignment harmonization of a collection of electro-optical and/or
gimbaled componentry that is to operate within a common coordinate
frame. In some cases, the techniques and architecture can provide a
cost- and time-efficient approach to achieving alignment
harmonization that is compatible, for example, with field-test
and/or operational environments. In some instances, the techniques
and architecture can be used in concert with, error calibration
techniques to further improve the accuracy of the alignment
harmonization. The techniques and architecture can be utilized with
a wide range of components (e.g., sensors, armaments, targeting
systems, weapons systems, countermeasure systems, navigational
systems, surveillance systems, etc.) on a wide variety of
platforms. Numerous configurations and variations will be apparent
in light of this disclosure.
Inventors: |
Cote; Almond J.; (Auburn,
NH) ; Smith; Kirby A.; (Derry, NH) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
BAE Systems Information and Electronic Systems Integration
Inc. |
Nashua |
NH |
US |
|
|
Family ID: |
52597907 |
Appl. No.: |
14/612557 |
Filed: |
February 3, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13524081 |
Jun 15, 2012 |
8977512 |
|
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14612557 |
|
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61498199 |
Jun 17, 2011 |
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Current U.S.
Class: |
73/1.38 |
Current CPC
Class: |
G01C 25/005 20130101;
G01P 21/00 20130101 |
International
Class: |
G01P 21/00 20060101
G01P021/00 |
Goverment Interests
STATEMENT OF GOVERNMENT INTEREST
[0002] The invention was made with United States Government support
under Contract No. DAAE07-97-C-X073 awarded by the United States
Army. The United States Government has certain rights in this
invention.
Claims
1. A method of performing alignment harmonization, the method
comprising: operatively coupling an inertial measurement unit (IMU)
with a common reference surface of a platform and beginning
collection of a first set of angular rate data; uncoupling the IMU
from the common reference surface and transitioning the IMU to a
reference surface of a unit under alignment (UUA); and operatively
coupling the IMU with the UUA reference surface and stopping
collection of the first set of angular rate data.
2. The method of claim 1 further comprising using the first set of
angular rate data to determine a difference in attitude between the
common reference surface and the UUA reference surface.
3. The method of claim 2, wherein after operatively coupling the
IMU with the UUA reference surface and stopping collection of the
first set of angular rate data, the method further comprises:
uncoupling the IMU from the UUA reference surface, operatively
coupling the IMU with the common reference surface, and beginning
collection of a second set of angular rate data; uncoupling the IMU
from the common reference surface and transitioning the IMU to a
reference surface of a second UUA; and operatively coupling the IMU
with the reference surface of the second UUA and stopping
collection of the second set of angular rate data.
4. The method of claim 3 further comprising using the second set of
angular rate data output by the IMU to determine a difference in
attitude between the common reference surface and the reference
surface of the second UUA.
5. The method of claim 1, wherein the common reference surface and
the UUA reference surface operate within a common coordinate
frame.
6. The method of claim 1, wherein before operatively coupling the
IMU with the common reference surface of the platform, the method
former comprises calibrating the IMU.
7. The method of claim 6, wherein calibrating the IMU comprises:
determining a latitude and attitude of the common reference surface
of the platform, a heading of the common reference surface with
respect to true north, and gravitational direction; operatively
coupling the IMU with the common reference surface for a period of
time to capture angular rate error data; and uncoupling the IMU
from the common reference surface, rotating the IMU, and recoupling
the IMU with the common reference surface to capture rate scale
factor error data.
8. The method of claim 7, wherein the angular rate error data is
used to improve alignment harmonization.
9. The method of claim 1, wherein the rate scale factor error data
is used to improve alignment harmonization.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a division of U.S. Ser. No. 13/524,081
filed on Jun. 15, 2012 and claims the benefit of U.S. Provisional
Patent Application Ser. No. 61/498,199, filed on Jun. 17, 2011,
which is herein incorporated by reference in its entirety.
FIELD OF THE DISCLOSURE
[0003] The invention relates to componentry alignment, and more
particularly to alignment harmonization of electro-optical and
gimbaled componentry.
BACKGROUND
[0004] Component alignment on a given platform involves a number of
non-trivial challenges, and electro-optical and gimbaled
componentry have faced particular complications, such as those with
respect to alignment harmonization.
SUMMARY
[0005] One example embodiment of the present invention provides an
alignment harmonization system including an inertial measurement
unit (IMU) configured to output angular rate data relating to an
attitude of a common reference surface of a platform and an
attitude of a reference surface of a unit under alignment (UUA),
wherein the common reference surface and the UUA reference surface
operate within a common coordinate frame, and a processor
operatively coupled with the IMU and configured to interpret the
angular rate data to determine a difference in attitude between the
common reference surface and the UUA reference surface. In some
cases, the system further includes the common reference surface and
the UUA reference surface. In some such embodiments, the common
reference surface comprises a portion of the platform configured to
operatively couple with the IMU. In some other such embodiments,
the common reference surface comprises a reference plate
operatively coupled with the platform and configured to operatively
couple with the IMU. In some instances, the UUA reference surface
comprises a portion of the UUA configured to operatively couple
with the IMU. In some other such instances, the UUA reference
surface comprises a reference plate operatively coupled with the
UUA and configured to operatively couple with the IMU. In some
cases, the IMU is joined with an interface configured to
operatively couple with the common reference surface and with the
UUA reference surface. In some such cases, the common reference
surface is configured with an alignment slot and an alignment hole
configured to be operatively coupled with the interface, and
wherein the UUA reference surface is configured with an alignment
slot and an alignment hole configured to be operatively coupled
with the same interface. In some embodiments, the processor is
implemented in a laptop, a handheld electronic device, an on-board
computer of the platform, and/or the IMU. In some instances, the
IMU is calibrated to correct for at least one error associated with
the IMU.
[0006] Another example embodiment of the present invention provides
a method of performing alignment harmonization, the method
including the steps of operatively coupling an inertial measurement
unit (IMU) with a common reference surface of a platform and
beginning collection of a first set of angular rate data,
uncoupling the IMU from the common reference surface and
transitioning the IMU to a reference surface of a unit under
alignment (UUA), and operatively coupling the IMU with the UUA
reference surface and stopping collection of the first set of
angular rate data. In some cases, the method further includes using
the first set of angular rate data to determine a difference in
attitude between the common reference surface and the UUA reference
surface. In some such instances, the method further includes, after
operatively coupling the IMU with the UUA reference surface and
stopping collection of the first set of angular rate data, the
steps of uncoupling the IMU from the UUA reference surface,
operatively coupling the IMU with the common reference surface, and
beginning collection of a second set of angular rate data,
uncoupling the IMU from the common reference surface and
transitioning the IMU to a reference surface of a second UUA, and
operatively coupling the IMU with the reference surface of the
second UUA and stopping collection of the second set of angular
rate data. In some such embodiments, the method further includes
using the second set of angular rate data output by the IMU to
determine a difference in attitude between the common reference
surface and the reference surface of the second UUA. In some
embodiments, the common reference surface and the UUA reference
surface operate within a common coordinate frame. In some cases,
the method further includes, before operatively coupling the IMU
with the common reference surface of the platform, the step of
calibrating the IMU. In some such instances, calibrating the IMU
includes the steps of determining a latitude and attitude of the
common reference surface of the platform, a heading of the common
reference surface with respect to true north, and gravitational
direction, operatively coupling the IMU with the common reference
surface for a period of time to capture angular rate error data,
and uncoupling the IMU from the common reference surface, rotating
the IMU, and recoupling the IMU with the common reference surface
to capture rate scale factor error data. In some such embodiments,
the angular rate error data is used to improve alignment
harmonization. In some other such embodiments, the rate scale
factor error data is used to improve alignment harmonization.
[0007] Yet another example embodiment of the present invention
provides an alignment harmonization device including an inertial
measurement unit (IMU) configured to output angular rate data,
relating to an attitude of a common reference surface of a platform
and an attitude of a reference surface of a unit under alignment
(UUA), wherein the common reference surface and the UUA reference
surface operate within a common coordinate frame, a processor
operatively coupled with the IMU and configured to interpret the
angular rate, data to determine a difference in attitude between
the common reference surface and the UUA reference surface, and a
power source operatively coupled with the IMU and configured to
provide power to the IMU, wherein the device is configured to be
operatively coupled with the common reference surface and with the
UUA reference surface.
[0008] The features and advantages described herein are not
all-inclusive and, in particular, many additional features and
advantages will be apparent to one of ordinary skill in the art in
view of the drawings, specification, and claims. Moreover, it
should be noted that the language used in the specification has
been selected principally for readability and instructional
purposes and not to limit the scope of the inventive subject
matter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 is a schematic view of an alignment harmonization
system configured in accordance with an embodiment of the present
invention.
[0010] FIG. 2 is a side perspective view of an inertial measurement
unit (IMU) operatively coupled with an optional interface
configured in accordance with an embodiment of the present
invention.
[0011] FIG. 3A is a front perspective view of a common reference
surface/unit under alignment (UUA) reference surface having an
alignment slot and an alignment hole formed therein in accordance
with an embodiment of the present invention.
[0012] FIG. 3B is a cross-section view illustrating an IMU
operatively coupled with the common reference surface/UUA reference
surface of FIG. 3A.
[0013] FIG. 4A is a front perspective view of a reference plate
configured in accordance with an embodiment.
[0014] FIG. 4B is a cross-section view of an IMU operatively
coupled with the reference plate of FIG. 4A.
[0015] FIG. 5 is a schematic view of an example implementation of
an alignment harmonization system in accordance with an embodiment
of the present invention.
[0016] FIG. 6 is a flow diagram illustrating an example method of
performing alignment harmonization in accordance with an embodiment
of the present invention.
[0017] These and other features of the present embodiments will be
understood better by reading the following detailed description,
taken together with the figures herein described. The accompanying
drawings are not intended to be drawn to scale. In the drawings,
each identical or nearly identical component that is illustrated in
various figures is represented by a like numeral. For purposes of
clarity, not every component may be labeled in every drawing.
DETAILED DESCRIPTION
[0018] Techniques and architecture are disclosed for performing
alignment harmonization of a collection of electro-optical and/or
gimbaled componentry that is to operate within a common coordinate
frame. In some cases, the techniques and architecture can provide a
cost- and time-efficient approach to achieving alignment
harmonization that is compatible, for example, with field-test
and/or operational environments. In some instances, the techniques
and architecture can be used in concert with error calibration
techniques to further improve the accuracy of the alignment
harmonization. The techniques and architecture can be utilized with
a wide range of components (e.g., sensors, armaments, targeting
systems, weapons systems, countermeasure systems, navigational
systems, surveillance systems, etc.) on a wide variety of
platforms. Numerous configurations and variations will be apparent
in light of this disclosure.
[0019] General Overview
[0020] As previously indicated, there are a number of non-trivial
issues that can complicate component alignment. For instance, one
non-trivial issue pertains to the fact that, when a collection of
separate electro-optical and gimbaled functional components (e.g.,
such as may be implemented in sensors, countermeasures, navigation,
weapons systems and armaments, etc.) are to operate or otherwise be
used in concert within a common coordinate frame, it is necessary
to determine the alignments of their angular attitudes relative to
a common reference. The relative alignment of each component, is
determined during a process known as alignment harmonization.
[0021] Typical approaches involve making far-field measurements
using a theodolite as the common reference or making near-field
measurements requiring the complicated use of protractors and lines
drawn on the ground. However, these approaches are very time
consuming (e.g., harmonization can take several days to be properly
completed using this approach) and typically require a level
surface/platform on which to perform the alignment harmonization.
Other example approaches involve complex and prohibitively
expensive equipment. In addition, the aforementioned
techniques/approaches are notably error prone. Furthermore, such
extended alignment harmonization process times and expensive
equipment are both highly undesirable, for example, for field-test
and/or operational contexts. Other flaws and disadvantages inherent
to existing approaches/techniques will be apparent in light of this
disclosure.
[0022] Therefore, there is need for a way to directly and swiftly
perform alignment harmonization for a given collection of
electro-optical and/or gimbaled components on a given platform
while being compatible with field-test and/or operational
environments (e.g., without requiring a level platform, at
relatively low cost, in a time-efficient manner, etc.).
[0023] Thus, and in accordance with an embodiment of the present
invention, techniques and architecture are disclosed for a local
approach to directly measuring component alignment for achieving
alignment harmonization. The disclosed techniques and architecture
can be utilized to harmonize the alignment of a collection of
electro-optical and/or gimbaled components (e.g., such as may be
implemented in sensors, armaments, targeting systems, weapons
systems, countermeasure systems, navigational systems, surveillance
systems, etc.) that is to operate within a common coordinate frame.
In some cases, the techniques and architecture can provide a cost-
and time-efficient approach to achieving alignment harmonization
that is compatible, for example, with field-test and/or operational
environments.
[0024] In accordance with an embodiment of the present invention,
an alignment harmonization system is disclosed. In some such
embodiments, the alignment harmonization system includes an
inertial measurement unit (IMU) that Is operatively coupled with
one or more processors. In some instances, the alignment
harmonization system may include additional componentry (e.g.,
power supply, data cable, wireless interlacing, Bluetooth.RTM.
capability, compass, g sensor, GPS, etc.), as suitable for a given
application. In some cases, the alignment harmonization system can
be configured as a single, integral package/device, while in some
other cases one or more components of the device/system may be
discrete or otherwise separate.
[0025] In accordance with an embodiment, the IMU (whether discrete
or part of an integral package) can be passed from a common
reference surface of a given platform to a reference surface of a
unit under alignment (UUA) (e.g., the unit having the
electro-optical and/or gimbaled components to undergo alignment
harmonization). The resultant measured angular rate data output by
the IMU then can be provided to the one or more operatively coupled
processors, which interpret or otherwise analyze (e.g., integrate)
the data to determine the angular attitude differences between the
common reference surface and the UUA reference surface, thereby
permitting alignment harmonization of the UUA component(s).
[0026] In accordance with an embodiment, to help minimize or
otherwise reduce cost, a low-cost IMU may be utilized In the
alignment harmonization device/system. However, as will be
appreciated, some low-cost IMUs generally may have significant
sources of error which, upon interpretation (e.g., integration) by
an operatively coupled processor, normally would detract from
overall alignment accuracy. Such errors include, but are not
limited to: (1) 3.sigma. angular random walk; (2) insensitive drift
rate; (3) g-sensitive drift rate; (4) rate scale factor error; (5)
misalignment error; and (6) Earth's rate. Therefore, in accordance
with an embodiment, the disclosed alignment harmonization
techniques and architecture can be used in concert with one or more
error calibration techniques to minimize or otherwise reduce (e.g.,
such as by calibrating out) one or more of such errors to further
improve alignment accuracy and thereby improve alignment
harmonization. For instance, and in accordance with an embodiment,
the effects of one or more angular rate errors (e.g., g-insensitive
drift rate, g-sensitive drift rate, rate scale factor error, and/or
Earth's rate) may be minimized or otherwise reduced by using the
techniques/architecture described herein.
[0027] As will be appreciated in light of this disclosure, some
embodiments of the present invention may realize
advantages/benefits as compared to the existing alignment
harmonization equipment/approaches previously discussed. For
example, some embodiments of the present invention may realize a
substantial reduction in: (1) the amount of time required to
achieve alignment harmonization (e.g., less than one hour as
compared with existing approaches, which may take several days);
and/or (2) the cost of alignment harmonization (e.g., given that
the disclosed alignment harmonization system can utilize
inexpensive componentry). Also, some embodiments may realize a
substantial improvement in, for example: (1) alignment
harmonization accuracy and dependability (e.g., such as by
compensating for one or more errors); and/or (2) ease of
implementation in the field (e.g., given that the disclosed
alignment harmonization system can utilize a minimal number of
components). Furthermore, and in accordance with an embodiment, the
disclosed techniques and architecture can allow a user to harmonize
the alignment of various components at the site of any UUA without
having to activate the UUA and to do so rapidly in any host
platform orientation. Still further, in accordance with an
embodiment, the disclosed techniques/architecture may allow for a
user to perform a quick alignment check to ensure that alignment,
harmonization still holds true after a given period of time. Other
advantages/benefits associated with one or more embodiments of the
present invention will depend on a given application and will be
apparent in light of this disclosure.
[0028] As will be appreciated in light of this disclosure, the
alignment harmonization techniques and architecture described
herein may be utilized in a variety of contexts (e.g., experimental
research, laboratory, field-test, operations, deployment,
combat/warzone, etc.), in accordance with an embodiment. As will
further be appreciated in light of this disclosure, one or more
embodiments of the present invention may be implemented, for
example, with a variety of devices systems, and/or platforms
regardless of environment/context (air, land and/or sea vehicles,
etc.). Other suitable uses of one or more embodiments of the
present invention will depend on a given application and will be
apparent in light of this disclosure.
[0029] Alignment Harmonization System Architecture
[0030] FIG. 1 is a schematic view of an alignment harmonization
system 100 configured in accordance with an embodiment of the
present invention. As can be seen, alignment harmonization system
100 includes an inertial measurement unit (IMU) 110 that is
operatively coupled, for example, with a power supply 120 and one
or more processors 130. In general, an IMU is an electrical device
or apparatus that measures and reports angular rotation rates
about, and translational acceleration along, three orthogonal axes
(or a sub-set of those axes) using, for example, a combination of
accelerometers and gyroscopes. Other suitable instrumentation that
can effectively operate as an IMU can be used as well, as will be
appreciated in light of this disclosure. As will be further
appreciated in light of this disclosure, alignment harmonization
system 100 may include additional, fewer, and/or different elements
or components from those here described (e.g., user interfaces,
data cables, wireless interfacing, Bluetooth.RTM. capability,
compass, g sensor, GPS, etc.), and the claimed invention is not
intended to be limited to any particular system configurations, but
can be used with numerous configurations in numerous applications.
Also, as previously noted, and in accordance with one example
embodiment, alignment harmonization system 100 can be configured as
a single, integral package (e.g., all components are integrated
into a single die or device) in some cases. However, in accordance
with another example embodiment, alignment harmonization system 100
may be configured instead with one or more components that are
discrete or otherwise separate and populated, for example, onto a
printed circuit board. In some still other cases, and in accordance
with an embodiment, alignment harmonization system 100 may comprise
a discrete IMU 110 configured to be interfaced (e.g., via wired,
wireless, or other suitable connection) with processor 130.
Numerous degrees of functional integration can be implemented
depending on factors such as desired chip count and packaging
size.
[0031] In accordance with an embodiment of the present invention, a
number of factors may be considered in choosing a suitable IMU 110.
For example, it may be desirable, in accordance with an embodiment,
to ensure that IMU 110 has a suitable level of accuracy (e.g., a
sufficiently low initial error and/or error which may be
substantially calibrated out). As will be appreciated, providing
such an IMU 110 may assist with reducing/minimizing the amount of
lime required for achieving alignment harmonization. However, it
may be desirable to provide such an IMU 110, for example, without
incurring great expense, thus reducing/minimizing the overall cost
of alignment harmonization system 100. Furthermore, performance
characteristics such as functional temperature range, compatibility
with other componentry of alignment harmonization system 100 (e.g.,
processor 130), data output capabilities, and input power
requirements may be considered in choosing a suitable IMU 110 for a
given application. As will be appreciated in light of this
disclosure, and in accordance with an embodiment, IMU 110 may be a
standard, custom, or hybrid IMU, and in some instances may be
configured with one or more mechanical and/or solid state (e.g.,
ring laser, fiber optic, piezoelectric, etc.) gyroscopic
components. Other suitable configurations for IMU 110 will depend
on a given application and will be apparent in light of this
disclosure.
[0032] In some cases, it may be desirable to minimize or otherwise
reduce the need for field calibration of IMU 110, and thus reduce
the process time required to achieve alignment harmonization.
Therefore, in accordance with an embodiment, IMU 110 optionally may
be pre-calibrated (e.g., before receipt from the manufacturer or
otherwise before field/operational use), for example: (1) for a
wide range of operable temperature conditions; and/or (2) for one
or more of the principal sources of angular rate error (discussed
above). However, the claimed invention is not so limited, as an IMU
110 having sufficiently small or otherwise negligible errors may be
utilized without such optional pre-calibration, in accordance with
an embodiment. Furthermore, as previously noted, it may be
desirable in some instances to provide these and other
considerations without incurring great expense. Other
considerations for optional pre-calibration of IMU 110 will depend
on a given application and will be apparent in light of this
disclosure.
[0033] In accordance with an embodiment, it may be desirable to
ensure that IMU 110 is properly oriented and substantially flush,
for example, with a common reference surface 310 of a given
platform 300 and/or with a reference surface 410 of a given unit
under alignment (UUA) 400 to obtain accurate data. Thus, in some
embodiments, IMU 110 may be implemented with one or more features
configured to aid with proper interfacing.
[0034] For example, FIG. 2 is a side perspective view of an IMU 110
operatively coupled with an optional interface 210 configured in
accordance with an embodiment of the present invention. IMU 110 may
be permanently and/or removably joined with interface 210, for
example, to help ensure accurate and repeatable placement of IMU
110 on a common reference surface 310 and/or on a UUA reference
surface 410, in accordance with an embodiment. In some cases,
interface 210 may be configured with a series of alignment pins 212
and 214 (e.g., posts, tabs, protrusions, etc.) or other suitable
feature(s) configured to engage, respectively, a corresponding
alignment slot 222 and alignment hole 224 (discussed below).
Interface 210 may comprise any material having sufficient rigidity,
durability, and thermal expansion characteristics suitable for a
given application. For instance, interface 210 may comprise a
material such as, but not limited to, aluminum (Al), titanium (Ti),
steel, etc. As will be appreciated in light of this disclosure, it
may be desirable to ensure that interface 210 provides and retains
a flat/level surface to minimize or otherwise reduce the
possibility of introducing additional errors into the data obtained
by IMU 110.
[0035] FIG. 3A is a front perspective view of a common reference
surface 310/UUA reference surface 410 having an alignment slot 222
and an alignment hole 224 formed therein in accordance with an
embodiment of the present invention. FIG. 3B is a cross-section
view illustrating an IMU 110 operatively coupled with, the common
reference surface 310/UUA reference surface 410 of FIG. 3A. As can
be seen, in some embodiments alignment slot 222 and alignment hole
224 can be formed: (1) directly in a portion (e.g., a surface) of
platform 300 (e.g., common reference surface 310 is formed directly
in/on platform 300); and/or (2) directly In a portion (e.g., a
surface) of UUA 400 (e.g., UUA reference surface 410 is formed
directly in/on UUA 400). As can be seen with particular reference
to FIG. 3B, optional interface 210 may be inserted Into or
otherwise mated with common reference surface 310 and/or UUA
reference surface 410 (e.g., by placement of alignment pin 212 in
alignment slot 222 and alignment pin 214 in alignment hole
224).
[0036] In some cases, it may be desirable to configure alignment
slot 222 with at least one dimension that is different from
alignment hole 224. For instance, in one specific example
embodiment, alignment slot 222 and alignment hole 224 can be
configured to have different diameters, and alignment pins 212 and
214 can be correspondingly configured. As will be appreciated, the
alignment pin of greater diameter will not readily mate with the
alignment feature (e.g., alignment slot 222 or alignment hole 224)
of lesser diameter, and so such an embodiment may assist with
ensuring consistent, proper orientation of IMU 110 (with or without
optional interface 210) with a given surface having such alignment
features. Also, in another specific example embodiment, alignment
slot 222 can be configured with a longer length than alignment hole
224 to mitigate or otherwise compensate for the effects, if any, of
thermal expansion on achieving and maintaining operative coupling
between IMU 110 (with or without optional interface 210) and a
given surface having such alignment features.
[0037] In accordance with an embodiment, it may be desirable to
ensure that alignment slot 222 and alignment hole 224 are
configured/dimensioned to snugly receive alignment pin 212 and 214,
respectively, without requiring substantial application of force.
As will be appreciated in light of this disclosure, an
appropriately snug fit may minimize or otherwise reduce the
likelihood of introducing errors resulting from give/play in the
operative coupling of IMU 110 with a given surface. Other
configurations/considerations for alignment pins 21.2 and 214,
alignment slot 222, and/or alignment hole 224 will depend on a
given application and will be apparent in light of this
disclosure.
[0038] FIG. 4A is a front perspective view of a reference plate 220
configured in accordance with an embodiment. FIG. 4B is a
cross-section view of an IMU 110 operatively coupled with the
reference plate 220 of FIG. 4A. As can be seen, in some embodiments
an alignment slot 222 and an alignment hole 224 can be formed in a
reference plate 220. Alignment slot 222 and alignment hole 224 in
reference plate 220 may be configured in much the same way and may
serve much the same purpose as discussed above with reference to
FIGS. 3A and 3B. In accordance with an embodiment, reference plate
220 may be integrated into or otherwise operatively coupled, for
example: (1) with platform 300 (e.g., a reference plate 220 having
an alignment slot 222 and an alignment hole 224 provides a common
reference surface 310); and/or (2) with UUA 400 (e.g., a reference
plate 220 having an alignment slot 222 and an alignment hole 224
provides a UUA reference surface 410). However, the claimed
invention is not so limited: for instance, in accordance with an
embodiment, a bezel or other suitable mounting ring may be
configured to provide a common reference surface 310 and/or a UUA
reference surface 410. Other suitable configurations will depend on
a given application and will be apparent in light of this
disclosure.
[0039] Whether or not a reference plate 220 is utilized, alignment
pins 212 and 214 of interface 210 may be inserted into alignment
slot 222 and alignment hole 224, respectively. Once mated with
alignment slot 222 and alignment hole 224, interface 210 may be
manually and/or mechanically held in place, for instance, during
the collection of data by IMU 110. Also, in accordance with an
embodiment, it may be desirable to ensure that common reference
surface 310 and/or UUA reference surface 410 (whether provided by a
reference plate 220 or otherwise associated with platform 300/UUA
400) is substantially flat. As will be appreciated in light of this
disclosure, a suitably flat surface may minimize or otherwise
reduce the likelihood of introducing errors resulting from
wobble/tilting of IMU 110 when operatively coupled with such
surface.
[0040] Returning to FIG. 1, IMU 110 may be operatively coupled with
a power supply 120. In some embodiments, power supply 120 may be a
discrete unit/device operatively coupled with IMU 110 and
configured to provide power thereto, while in some other
embodiments power supply 120 may be integral to IMU 110. In some
specific example cases, power supply 120 may comprise one or more
electrochemical cells, photovoltaic/photoelectric cells, etc.,
configured to provide power to IMU 110. Other suitable
configurations for power supply 120 will depend on a given
application and will be apparent in light of this disclosure.
[0041] As previously noted, IMU 110 may be operatively coupled with
one or more processors 130. In accordance with an embodiment of the
present invention, processors) 130 may be chosen, at least in part,
based on: (1) the ability to interpret/analyze (e.g., integrate)
the angular rate data provided by IMU 110; and/or (2) compatibility
with software (e.g., commercially available and/or custom) suitable
for implementation with alignment harmonization system 100.
Furthermore, it may be desirable to provide processors) 130, for
example, without incurring great expense, thus reducing/minimizing
the overall cost of alignment harmonization system 100, in
accordance with art embodiment. Other suitable configurations for
processors) 130 will depend on a given application and will be
apparent in light of this disclosure.
[0042] In accordance with an embodiment, the one or more processors
130 may be implemented, for example: (1) in a handheld or other
portable computing device (e.g., PDA-like device, laptop, etc.);
(2) as part of an on-board computer of the host platform 300;
and/or (3) as an integral component of IMU 110. Furthermore, and in
accordance with an embodiment, operative coupling between IMU 110
and the one or more processors 130 may be achieved using any number
of suitable data interfacing techniques, such as, but not limited
to: (1) a wired connection (e.g., data cable, fiber optic, etc);
(2) a plug-and-play connection (e.g., USB, FireWire, etc); and/or
(3) a wireless connection (e.g., RF transmission, Bluetooth.RTM.,
etc.). Other suitable data interfacing techniques will depend on a
given application and will be apparent in light of this
disclosure.
[0043] Methodology
[0044] FIG. 5 is a schematic view of an example implementation of
an alignment harmonization system 100 in accordance with an
embodiment of the present invention. As can be seen, IMU 110 can be
passed or otherwise transitioned from a common reference surface
310 of a platform 300 to a reference surface 410 of a given UUA 400
that is operatively coupled with platform 300. As IMU 110 is so
transitioned, it outputs angular rate data to one or more
operatively coupled processors 130, which interpret/analyze (e.g.,
integrate) the data to account for one or more angular rate errors
that may be associated with IMU 110. In accordance with an
embodiment, this process may be repeated for any number of UUAs 400
(each with its own corresponding reference surface 410) operatively
coupled with platform 300, and the claimed invention is not
intended to be limited to implementation with only a single UUA
400. After correcting for any angular rate errors, an accurate
alignment harmonization of the one or more UUAs 400 may be
obtained.
[0045] As will be appreciated in light of this disclosure, platform
300 can be any system or vehicle (air, land, sea, etc) having one
or more UUAs 400 implementing, for example, electro-optical and/or
gimbaled componentry (e.g., sensors, armaments, targeting systems,
weapons systems, countermeasure systems, navigational systems,
surveillance systems, etc.) that is to operate within a common
coordinate frame.
[0046] In accordance with an embodiment, UUA reference surface 410
can be pre-calibrated, for example, with the boresight of UUA 400.
That is, before receipt from the manufacturer or otherwise before
field use/deployment, the alignment of the reference surface 410 of
a given UUA 400 (e.g., sensor, gimbaled componentry, etc.) with
respect to the boresight (e.g., optical, laser, gun, etc.) of that
UUA 400 can be calculated or otherwise determined. Similarly,
common reference surface 310 can be pre-calibrated with respect to
platform 300. In accordance with an embodiment, pre-calibration of
a given reference surface may help to reduce the process time
required to achieve alignment harmonization by minimizing or
otherwise reducing the need for in-the-field calibration. Other
pre-calibration considerations will depend on a given application
and will be apparent in light of this disclosure.
[0047] In accordance with an embodiment, the process time for
alignment harmonization via one or more of the disclosed
techniques/architecture may be substantially less than that
required by existing approaches (e.g., less than or equal to about
5%, less than or equal to about 10%, less than or equal to about
15%, etc., of the process time of existing approaches). For
instance, in one specific example embodiment, alignment
harmonization may be achieved with a process time of less than or
equal to about 1 hr. However, as will be appreciated in light of
this disclosure, a longer process time may result, for example,
depending on the total number of UUAs 400 and/or whether
pre-calibration (as previously described) was performed before
beginning alignment harmonization.
[0048] FIG. 6 is a flow diagram illustrating an example method of
performing alignment harmonization in accordance with an embodiment
of the present invention. The method of FIG. 6 can be implemented,
for example, to harmonize the alignment of one or more UUAs 400
that are operatively coupled with a platform 300. Numerous suitable
implementations for the disclosed, method will be apparent in light
of this disclosure.
[0049] Turning now to the method of FIG. 6, the method begins, as
in block 602, with operatively coupling an inertial measurement
unit (IMU) 110 with a common reference-surface 310 of a platform
300 and beginning collection of angular rate data. In accordance
with an embodiment, operative coupling of IMU 110 to common
reference surface 310 may be achieved by manually and/or
mechanically holding IMU 110 in place on common reference surface
310. In one specific example embodiment, IMU 110 may be optionally
joined with an interface 210, which may be mated with an alignment
slot 222 and an alignment hole 224 formed in platform 300 or
otherwise in a reference plate 220 that is operatively coupled with
platform 300. As will be appreciated in light of this disclosure,
and in accordance with an embodiment, it may be desirable to ensure
that IMU 110 is substantially flush/flat with common reference
surface 310 before beginning collection of angular rate data.
Furthermore, and in accordance with an embodiment, beginning or
otherwise initializing angular rate data collection may be achieved
using any of a wide variety of suitable techniques (e.g., hardware,
software, user interface, etc.), as will be apparent in light of
this disclosure. In some cases, it may be desirable to determine
the attitude of common reference surface 310 (e.g., before
beginning angular rate data collection) for subsequent use, for
instance, in determining the difference in attitude discussed below
with reference to block 608, in accordance with an embodiment.
[0050] As will be appreciated in light, of this disclosure, in some
instances IMU 110 initially may go through an optional calibration
(as discussed below with reference to optional block 601), at the
end of which IMU 110 remains operatively coupled with the common
reference surface 310. Thus, in some such instances, the operative
coupling described in block 602 may be provided already, and thus
IMU 110 need not be moved or otherwise adjusted at the end of the
optional calibration of block 601 before proceeding with block
604.
[0051] Next, the method continues, as in block 604, with uncoupling
IMU 110 from common reference surface 310 and then transitioning
IMU 110 to a reference surface 410 of a unit under alignment (UUA)
400. As previously noted, as IMU 110 is transitioned from common
reference surface 310 to UUA reference surface 410, it outputs
angular rate data which may be utilized (e.g., such as described
below with reference to block 608) to correct for one or more
angular rate errors that may be associated with IMU 110. As will be
appreciated in light of this disclosure, and in accordance with an
embodiment, it may be desirable to ensure that a relatively
steady/smooth transition is made, for instance, to minimize or
otherwise reduce the likelihood of introducing errors resulting
from jarring or otherwise disrupting IMU 110.
[0052] Subsequently, the method continues, as in block 606, with
operatively coupling IMU 110 to UUA reference surface 410 and
stopping collection of angular rate data. Operative coupling of IMU
110 with UUA reference surface 410 may be achieved in much the same
way as discussed above with common reference surface 310 in the
context of block 602. As will be appreciated in light of this
disclosure, and in accordance with an embodiment, it may be
desirable to ensure that IMU 110 is substantially flush/flat with
UUA reference surface 410 before stopping collection of angular
rate data. Furthermore, and in accordance with an embodiment,
stopping or otherwise terminating angular rate data collection may
be achieved using any of a wide variety of suitable techniques
(e.g., hardware, software, user interface, etc.), as will be
apparent in light of this disclosure.
[0053] Thereafter, the method may continue, as in block 608, with
using the angular rate data, output by the IMU 110 to determine a
difference in attitude between the common reference surface 310 and
the UUA reference surface 410. In accordance with an embodiment,
the angular rate data may he interpreted or otherwise analyzed
(e.g., integrated) by one or more processors 130 operatively
coupled with IMU 110. Such interpretation/analysis may be
performed, in part or in whole: (1) is real-time: and/or (2) at
some later time after collection. As will, be appreciated in light,
of this disclosure, and m accordance with an embodiment, the
angular attitude difference can be utilized in alignment
harmonization of common reference surface 310 of platform 300 and
reference surface 410 of UUA 400.
[0054] As previously discussed, a given. IMU 110 (e.g., a low-cost
IMU) may have a number of errors (e.g., angular rate error, rate
scale factor error, etc.) associated therewith which may hinder or
otherwise detract from the overall accuracy of alignment
harmonization. Thus, in accordance with an embodiment, the method
of FIG. 6 optionally may begin, as in block 601, with calibrating
the IMU 110 to be used in the alignment harmonization process.
[0055] To perform such optional IMU calibration, it may be
desirable first to determine: (1) the coordinates (e.g., latitude)
of the common reference surface 310 to which IMU 110 will be
operatively coupled; (2) the attitude of such common reference
surface 310; (3) the heading of such common reference surface 310
with respect to true north; and (4) the direction of gravity (e.g.,
determination of the downward direction). After such information is
gathered, the IMU 110 may be operatively coupled with the common
reference surface 310 for a period of time (e.g., in the range of
about 5 minutes) sufficient to capture angular rate error data.
Thereafter, the IMU 110 may be uncoupled from common reference
surface 310, rotated through a given angle (e.g., less than or
equal to about 360.degree., less than or equal to about 720.degree.
etc.), and then recoupled with common reference surface 310 to
capture rate scale factor error data. In accordance with an
embodiment, the obtained angular rate error and rate scale factor
error data can be used (e.g., interpreted/analyzed, such as
described above with reference to block 608) to correct for one or
more errors (e.g., Earth rate, g-sensitive drift rate,
g-insensitive drift rate, rate scale factor error, etc.) that may
be associated with IMU 110, thereby contributing to improving the
accuracy of alignment harmonization.
[0056] As will be appreciated in light of this disclosure, and in
accordance with an embodiment, the angular rate error and rate
scale factor error data can be used to calibrate IMU 110 and thus
establish an IMU reference which may be used as a baseline for all
subsequent UUA reference surface 410 attitude measurements.
However, as will be appreciated, some IMUs 110 may have minimal or
otherwise negligible/manageable errors, and thus the calibration of
IMU 110 discussed above with, reference to block 601, as previously
noted, may be entirely optional, in accordance with an
embodiment.
[0057] As previously noted, IMU 110 outputs angular rates as it is
transitioned from the common reference surface 310 to the
corresponding UUA reference surface 410. The resultant data (e.g.,
angular rates of yaw, pitch, and/or roll rotation) may be
transmitted from IMU 110 to one or more processors 130 that are
operatively coupled with IMU 110. Processors) 130 in turn may be
used to interpret or otherwise analyze (e.g., integrate) the
angular rate data, and in some cases the aforementioned angular
rate error and rate scale factor error data obtained during
optional calibration (block 601), to provide an accurate
measurement of the angular attitude difference between common
reference surface 310 of platform 300 and reference surface 410 of
UUA 400 within a common reference frame. Such
interpretation/analysis by processors) 130 may be performed, for
example: (1) using an on-board computer of platform 300, the IMU
110 itself (e.g., in some cases in which a processor 130 is
integral to IMU 110), and/or other suitable devices (e.g., laptop,
PDA-like device, etc.); and/or (2) with any suitable software
(e.g., standard, custom, etc.) which performs the desired
interpretations/analysis (e.g., integration).
[0058] As will be appreciated in light of this disclosure, the
longer the period of time between beginning (block 602) and
stopping (block 606) the collection of angular rate data, the
greater the magnitude of any accumulated angular rate error(s)
associated with IMU 110. However, in accordance with an embodiment,
such accumulation of error(s) can be substantially calibrated out
using the techniques/architecture described herein to improve the
accuracy of alignment harmonization of any given collection of UUAs
400.
[0059] Also, as previously noted, the techniques disclosed herein
may be readily used, in some instances, to achieve alignment
harmonization of multiple UUAs 400. For example, in some
embodiments IMU 110 may be passed from a common reference surface
310 to a reference surface 410 of a first UUA 400 (as described
above), then back to the common reference surface 310, then to a
reference surface 410 of a second UUA 400, and so on for any number
of UUAs 400. The steps denoted with respect to blocks 602, 604, and
606 may he repeated to achieve alignment harmonization for each
subsequent UUA 400 (e.g., a second UUA, a third UUA, a fourth UUA,
etc.) that is operatively coupled with a given platform 300.
However, the claimed invention is not so limited; for instance, in
some other embodiments in which IMU 110 has sufficiently small
errors, IMU 110 may be passed from a common reference surface 310
to a reference surface 410 of a first UUA 400 (as described above),
then to a reference surface 410 of a second UUA 400, and so on for
any number of UUAs 400, without returning to common reference
surface 310.
[0060] As will be appreciated in light of this disclosure, once a
given UUA reference surface 410 is aligned with UUA 400, further
adjustments to such, alignment may be unnecessary. However, in
accordance with an embodiment periodic checks/realignments using
the disclosed techniques/architecture may be performed to maintain
the accuracy of alignment harmonization.
[0061] The foregoing description of the embodiments of the
invention has been presented for the purposes of illustration and
description. It is not intended to be exhaustive or to limit the
invention to the precise form disclosed. Many modifications and
variations are possible in light of this disclosure. It is intended
that the scope of the invention be limited not by this detailed
description, but rather by the claims appended hereto.
* * * * *