U.S. patent application number 15/003193 was filed with the patent office on 2016-07-28 for rapid high-resolution magnetic field measurements for power line inspection.
This patent application is currently assigned to Lockheed Martin Corporation. The applicant listed for this patent is Lockheed Martin Corporation. Invention is credited to Stephen M. SEKELSKY.
Application Number | 20160216304 15/003193 |
Document ID | / |
Family ID | 56432336 |
Filed Date | 2016-07-28 |
United States Patent
Application |
20160216304 |
Kind Code |
A1 |
SEKELSKY; Stephen M. |
July 28, 2016 |
RAPID HIGH-RESOLUTION MAGNETIC FIELD MEASUREMENTS FOR POWER LINE
INSPECTION
Abstract
Methods and configurations are disclosed for DNV application in
rapid and cost-effective inspection of power transmission and power
distribution lines.
Inventors: |
SEKELSKY; Stephen M.;
(Princeton, NJ) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Lockheed Martin Corporation |
Bethesda |
MD |
US |
|
|
Assignee: |
Lockheed Martin Corporation
Bethesda
MD
|
Family ID: |
56432336 |
Appl. No.: |
15/003193 |
Filed: |
January 21, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62109551 |
Jan 29, 2015 |
|
|
|
62109006 |
Jan 28, 2015 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B60L 53/32 20190201;
Y02T 90/128 20130101; B60L 2240/622 20130101; G01R 1/06705
20130101; G05D 1/0265 20130101; Y02T 10/72 20130101; B60L 2200/10
20130101; G01R 31/085 20130101; Y02T 90/122 20130101; Y02T 10/7072
20130101; G01C 21/20 20130101; G01R 31/58 20200101; Y02T 90/12
20130101; Y02T 10/7291 20130101; Y02T 90/121 20130101; Y02T 10/7005
20130101; Y02T 90/14 20130101; H02G 1/02 20130101; B64C 39/024
20130101; B64C 2201/141 20130101; B64C 2201/146 20130101; Y02T
10/70 20130101; Y02T 90/16 20130101; B64C 2201/021 20130101; Y02T
90/162 20130101; H02J 7/025 20130101; B60L 53/126 20190201; B64C
2201/066 20130101; G01R 33/032 20130101; B64C 2201/042
20130101 |
International
Class: |
G01R 31/02 20060101
G01R031/02; G01R 33/032 20060101 G01R033/032; G01C 21/20 20060101
G01C021/20; G01R 1/067 20060101 G01R001/067 |
Claims
1. A system for inspecting electric power lines comprising: one or
more diamond nitrogen vacancy (DNV) components mounted on a movable
object relative to a power line, such DNV components being included
as part of a magnetometer configured to detect a magnetic vector of
a magnetic field generated as electric power flows along a power
line, said magnetometer determining a magnetic vector being
generated at intervals along the power line; one or more electronic
processors configured to receive the magnetic vector of the
magnetic field from the magnetometer, compare the magnetic vector
to a predetermined magnetic vector of a power line, and determine a
presence of an anomaly related to the power line based upon the
comparison.
2. The system of claim 1, wherein the one or more electronic
processors are further configured to determine a presence of the
power line based upon the magnetic vector.
3. The system of claim 2, wherein the one or more electronic
processors are further configured to identify a type of power line
based upon the magnetic vector.
4. The system of claim 3, wherein the one or more electronic
processors are further configured to determine the predetermined
magnetic vector of the power line based upon the type of power
line.
5. The system of claim 4, further comprising a navigation control
configured to navigate the vehicle based upon the presence of the
power line and the magnetic vector.
6. The system of claim 5, wherein the navigation control is further
configured to navigate to an initial position.
7. The system of claim 6, wherein the navigation control is further
configured to navigate the vehicle in a pattern over an area.
8. The system of claim 7, wherein the one or more electronic
processors are further configured to: receive a plurality of
real-time magnetic vectors from the magnetometer; determine a
course correction for the vehicle based upon the plurality of
magnetic vectors.
9. The system of claim 8, wherein the course correction follows a
curve of the power line.
10. The system of claim 1, wherein the vehicle is a flying
vehicle.
11. The system of claim 1, wherein the vehicle is a ground
vehicle.
12. The system of claim 1, wherein the vehicle is a submersible
vehicle.
13. The system of claim 1, further comprising a plurality of
magnetometers configured to detect a plurality of magnetic vectors
of the magnetic field.
14. The system of claim 13, wherein the one or more processors are
further configured to determine a presence of the power line based
upon the magnetic vector and the plurality of magnetic vectors.
15. A method for inspecting power lines comprising: detecting,
using a magnetometer, a magnetic vector of a magnetic field;
receiving the magnetic vector of the magnetic field from the
magnetometer; comparing the magnetic vector to a predetermined
magnetic vector of a power line; and determining a presence of an
anomaly related to the power line based upon the comparison.
16. The method of claim 15, further comprising determining a
presence of the power line based upon the magnetic vector.
17. The method of claim 16, further comprising identifying a type
of power line based upon the magnetic vector.
18. The method of claim 17, further comprising determining the
predetermined magnetic vector of the power line based upon the type
of power line.
19. The method of claim 18, further comprising navigating, using a
navigation control, the vehicle based upon the presence of the
power line and the magnetic vector.
20. The method of claim 19, further comprising navigating, using
the navigation control, to an initial position.
21. The method of claim 20, further comprising navigating, using
the navigation control, the vehicle in a pattern over an area.
22. A method comprising: detecting, using a magnetometer, a
magnetic vector of a magnetic field; receiving a plurality of
real-time magnetic vectors from the magnetometer; comparing the
magnetic vector to a predetermined magnetic vector of a power line;
determining a course correction for the vehicle based upon the
plurality of magnetic vectors; and determining a presence of an
anomaly related to the power line based upon the comparison.
23. The method of claim 22, wherein the course correction follows a
curve of the power line.
24. The method of claim 15, wherein the vehicle is a flying
vehicle.
25. The method of claim 15, wherein the vehicle is a ground
vehicle.
26. The method of claim 15, wherein the vehicle is a submersible
vehicle.
27. The method of claim 15, further comprising detecting, using a
plurality of magnetometers, a plurality of magnetic vectors of the
magnetic field.
28. The method of claim 27, further comprising determining a
presence of the power line based upon the magnetic vector and the
plurality of magnetic vectors.
29. A system for inspecting electric power lines comprising: one or
more magnetic sensor means mounted on a movable object relative to
a power line, the one or more magnetic sensor means configured to
detect a magnetic vector of a magnetic field generated as electric
power flows along a power line, said magnetic sensor means
determining a magnetic vector being generated at intervals along
the power line; one or more processor means configured to receive
the magnetic vector of the magnetic field from the magnetometer,
compare the magnetic vector to a predetermined magnetic vector of a
power line, and determine a presence of an anomaly related to the
power line based upon the comparison.
30. A non-transitory computer-readable medium having instructions
stored thereon, the instructions comprising: instructions to detect
using a magnetometer, a magnetic vector of a magnetic field;
instructions to receive the magnetic vector of the magnetic field
from the magnetometer; instructions to compare the magnetic vector
to a predetermined magnetic vector of a power line; and
instructions to determine a presence of an anomaly related to the
power line based upon the comparison.
31. The non-transitory computer-readable medium of claim 30,
further comprising instructions to determine a presence of the
power line based upon the magnetic vector.
32. The non-transitory computer-readable medium of claim 31,
further comprising instructions to identify a type of power line
based upon the magnetic vector.
33. The non-transitory computer-readable medium of claim 32,
further comprising instructions to determine the predetermined
magnetic vector of the power line based upon the type of power
line.
34. The non-transitory computer-readable medium of claim 33,
further comprising instructions to navigate the vehicle based upon
the presence of the power line and the magnetic vector.
35. The non-transitory computer-readable medium of claim 34,
further comprising instructions to navigate to an initial
position.
36. The non-transitory computer-readable medium of claim 35,
further comprising instructions to navigate the vehicle in a
pattern over an area.
37. The non-transitory computer-readable medium of claim 36,
further comprising: instructions to receive a plurality of
real-time magnetic vectors from the magnetometer; instructions to
determine a course correction for the vehicle based upon the
plurality of magnetic vectors.
38. The non-transitory computer-readable medium of claim 37,
wherein the course correction follows a curve of the power
line.
39. The non-transitory computer-readable medium of claim 30,
wherein the vehicle is a flying vehicle.
40. The non-transitory computer-readable medium of claim 30,
wherein the vehicle is a ground vehicle.
41. The non-transitory computer-readable medium of claim 30,
wherein the vehicle is a submersible vehicle.
42. The non-transitory computer-readable medium of claim 30,
further comprising instructions to detect, using a plurality of
magnetometers, a plurality of magnetic vectors of the magnetic
field.
43. The non-transitory computer-readable medium of claim 42,
further comprising instructions to determine a presence of the
power line based upon the magnetic vector and the plurality of
magnetic vectors.
Description
[0001] The present application claims the benefit of U.S.
Provisional Application Nos. 62/109,006, filed Jan. 28, 2015, and
62/109,551, filed Jan. 29, 2015, each of which is incorporated by
reference herein in its entirety. The present application is
related to co-pending U.S. Application No. __/___,___, filed Jan.
21, 2016, titled "MAGNETIC NAVIGATION METHODS AND SYSTEMS UTILIZING
POWER GRID AND COMMUNICATION NETWORK," which is incorporated by
reference herein in its entirety. The present application is also
related to co-pending U.S. Application No. __/___,___, filed Jan.
21, 2016, titled "IN-SITU POWER CHARGING", which is incorporated by
reference herein in its entirety.
FIELD
[0002] The disclosure generally relates to magnetometer systems,
and more particularly, to diamond nitrogen-vacancy (DNV)
magnetometer systems to inspection of human infrastructure such as
power lines and cellular communications networks.
BACKGROUND
[0003] Transmission lines, such as power lines, can acquire defects
over time and use. These defects can adversely affect transmission
of current and ultimately lead to failure of the transmission line.
Current methods of inspecting transmission lines include manually
inspecting transmission lines. For example, a helicopter can be
used to position the inspector close enough to visually inspect
transmission lines. Given the safety considerations of such an
inspection, the inspector is not able to get extremely close to the
power lines and thus, the visual inspection is limited.
SUMMARY
[0004] Methods and systems are described for exploiting magnetic
signature characteristics of electrical power transmission,
distribution lines and other magnetic sources for inspection of
these items for defects. In the following description, reference is
made to the accompanying attachments that form a part thereof, and
in which are shown by way of illustration, specific embodiments in
which the subject technology may be practiced. It is to be
understood that other embodiments may be utilized and changes may
be made without departing from the scope of the subject technology.
For example, the same principals disclosed apply to ground
autonomous vehicles that can follow the same overhead and buried
power lines, and to undersea autonomous vehicles that can follow
submerged power cables and other infrastructure. In addition,
groups of unmanned systems may improve the scope, accuracy and
types of features represented in the magnetic database described
below. Magnetic metadata for way-point determination and other
applications such as homing can be collected at will with the
system described. Metadata can be compiled in a central database
and/or shared in real-time with other platforms and sensors for
navigation and homing. In addition, platforms may coordinate their
information other platforms to allow those more distant platforms,
with or without a magnetic sensor, to more accurately locate their
positions.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] The foregoing and other features of the present disclosure
will become more fully apparent from the following description and
appended claims, taken in conjunction with the accompanying
drawings. Understanding that these drawings depict only several
implementations in accordance with the disclosure and are,
therefore, not to be considered limiting of its scope, the
disclosure will be described with additional specificity and detail
through use of the accompanying drawings.
[0006] FIG. 1 illustrates a low altitude flying object in
accordance with some illustrative implementations.
[0007] FIG. 2A illustrates a ratio of signal strength of two
magnetic sensors, A and B, attached to wings of the UAS 102 as a
function of distance, x, from a center line of a power in
accordance with some illustrative implementations.
[0008] FIG. 2B illustrates a composite magnetic field (B-field) in
accordance with some illustrative implementations.
[0009] FIG. 3 illustrates a high-level block diagram of an example
UAS navigation system in accordance with some illustrative
implementations.
[0010] FIG. 4 illustrates an example of a power line
infrastructure.
[0011] FIGS. 5A and 5B illustrate examples of magnetic field
distribution for overhead power lines and underground power
cables.
[0012] FIG. 6 illustrates examples of magnetic field strength of
power lines as a function of distance from the centerline.
[0013] FIG. 7 illustrates an example of a UAS equipped with DNV
sensors in accordance with some illustrative implementations.
[0014] FIG. 8 illustrates a plot of a measured differential
magnetic field sensed by the DNV sensors when in close proximity of
the power lines in accordance with some illustrative
implementations.
[0015] FIG. 9 illustrates an example of a measured magnetic field
distribution for normal power lines and power lines with anomalies
according to some implementations.
[0016] FIGS. 10A and 10B are block diagrams of a system for
detecting deformities in transmission lines in accordance with an
illustrative embodiment
[0017] FIG. 11 illustrates current paths through a transmission
line with a deformity in accordance with an illustrative
embodiment.
[0018] FIG. 12 illustrates power transmission line sag between
transmission towers in accordance with an illustrative
embodiment.
[0019] FIG. 13 illustrates vector measurements indicating power
transmission line sag in accordance with an illustrative
embodiment.
[0020] FIG. 14 illustrates vector measurements along a path between
adjacent towers in accordance with an illustrative embodiment.
[0021] FIG. 15 is a diagram illustrating an example of a system for
implementing some aspects of the subject technology in accordance
with some implementations.
DETAILED DESCRIPTION
[0022] In some aspects of the present technology, methods and
configurations are disclosed for diamond nitrogen-vacancy (DNV)
application to detection of defects in power transmission or
distribution lines. A characteristic magnetic signature of power
infrastructure may be used for inspection of the infrastructure.
For example, power lines without defects have characteristic
magnetic signatures. The magnetic signature of a power line can be
measured and compared to the expected magnetic signature. Measured
differences can indicate that there is a defect in the transmission
line.
[0023] In some implementations, a magnetic sensor may be used to
measure the magnetic signature of a transmission line. For example,
the magnetic sensor can be equipped on a manned vehicle. The manned
vehicle can move along the transmission line to measure the
magnetic signature of the transmission line. In other
implementations, the magnetic sensor can be included in an unmanned
vehicle. The transmission line can then also be used to navigate
the unmanned vehicle, allowing for unmanned inspection of the
transmission line. An unmanned vehicle can maneuver using power
lines and can also inspect the same power lines for defects.
[0024] Because the magnetic fields are being measured, the
measurements of these magnetic fields are not hindered by
vegetation or poor visibility conditions that impact other
inspection methods such as a visual, optical, and laser inspection
methods. Accordingly, the detection of defects such as a downed
power line can proceed in poor visibility weather or when
vegetation has overgrown the power lines.
[0025] In some implementations, the subject technology can include
one or more magnetic sensors, a magnetic navigation database, and a
feedback loop that can control an unmanned vehicle's position and
orientation. High sensitivity to magnetic fields of DNV magnetic
sensors for magnetic field measurements can be utilized. The DNV
magnetic sensor can also be low cost, space, weight, and power
(C-SWAP) and benefit from a fast settling time. The DNV magnetic
field measurements allow UAS systems to align themselves with the
power lines, and to rapidly move along the power-line
infrastructure routes. Navigation is enabled in poor visibility
conditions and/or in GPS-denied environments. Further, the UAS
operation may occur in close proximity to power lines facilitating
stealthy transit. DNV-based magnetic sensors can be approximately
100 times smaller than conventional magnetic sensors and can have a
reaction time that that is approximately 100,000 times faster than
sensors with similar sensitivity.
[0026] FIG. 1 is a conceptual diagram illustrating an example of an
UAS 102 navigation along power lines 104, 106, and 108, according
to some implementations of the subject technology. The UAS 102 can
exploit the distinct magnetic signatures of power lines for
navigation such that the power lines can serve as roads and
highways for the UAS 102 without the need for detailed a priori
knowledge of the route magnetic characteristics. As shown in FIG.
2A, a ratio of signal strength of two magnetic sensors, A and B
(110 and 112 in FIG. 1), attached to wings of the UAS 102, varies
as a function of distance, x, from a center line of an example
three-line power transmission line structure 104, 106, and 108.
When the ratio is near 1, point 222, the UAS 102 is centered over
the power transmission line structure, x=0 at point 220.
[0027] A composite magnetic field (B-field) 206 from all (3) wires
shown in FIG. 2B. This field is an illustration of the strength of
the magnetic field measured by one or more magnetic sensors in the
UAS. In this example, the peak of the field 208 corresponds to the
UAS 102 being above the location of the middle line 106. When the
UAS 102 has two magnetic sensors, the sensors would read strengths
corresponding to points 202 and 204. A computing system on the UAS
or remote from the UAS, can calculate combined readings. Not all of
the depicted components may be required, however, and one or more
implementations may include additional components not shown in the
figure. Variations in the arrangement and type of the components
may be made, and additional components, different components, or
fewer components may be provided.
[0028] As an example of various implementations, a vehicle, such as
a UAS, can include one or more navigation sensors, such as DNV
sensors. The vehicle's goal could be to travel to an initial
destination and possibly return to a final destination. Known
navigation systems can be used to navigate the vehicle to an
intermediate location. For example, a UAS can fly using GPS and/or
human controlled navigation to the intermediate location. The UAS
can then begin looking for the magnetic signature of a power
source, such as power lines. To find a power line, the UAS can
continually take measurements using the DNV sensors. The UAS can
fly in a circle, straight line, curved pattern, etc. and monitor
the recorded magnetic field. The magnetic field can be compared to
known characteristics of power lines to identify if a power line is
in the vicinity of the UAS. For example, the measured magnetic
field can be compared with known magnetic field characteristics of
power lines to identify the power line that is generating the
measured magnetic field. In addition, information regarding the
electrical infrastructure can be used in combination with the
measured magnetic field to identify the current source. For
example, a database regarding magnetic measurements from the area
that were previously taken and recorded can be used to compare the
current readings to help determine the UAS's location.
[0029] In various implementations, once the UAS identifies a power
line the UAS positions itself at a known elevation and position
relative to the power line. For example, as the UAS flies over a
power line, the magnetic field will reach a maximum value and then
begin to decrease as the UAS moves away from the power line. After
one sweep of a known distance, the UAS can return to where the
magnetic field was the strongest. Based upon known characteristics
of power lines and the magnetic readings, the UAS can determine the
type of power line.
[0030] Once the current source has been identified, the UAS can
change its elevation until the magnetic field is a known value that
corresponds with an elevation above the identified power line. For
example, as shown in FIG. 6, a magnetic field strength can be used
to determine an elevation above the current source. The UAS can
also use the measured magnetic field to position itself offset from
directly above the power line. For example, once the UAS is
positioned above the current source, the UAS can move laterally to
an offset position from the current source. For example, the UAS
can move to be 10 kilometers to the left or right of the current
source.
[0031] The UAS can be programmed, via a computer 306, with a flight
path. In various implementations, once the UAS establishes its
position, the UAS can use a flight path to reach its destination.
In various implementations, the magnetic field generated by the
transmission line is perpendicular to the transmission line. In
these implementations, the vehicle will fly perpendicular to the
detected magnetic field. In one example, the UAS can follow the
detected power line to its destination. In this example, the UAS
will attempt to keep the detected magnetic field to be close to the
original magnetic field value. To do this, the UAS can change
elevation or move laterally to stay in its position relative to the
power line. For example, a power line that is rising in elevation
would cause the detected magnetic field to increase in strength as
the distance between the UAS and power line decreased. The
navigation system of the UAS can detect this increased magnetic
strength and increase the elevation of the UAS. In addition, on
board instruments can provide an indication of the elevation of the
UAS. The navigation system can also move the UAS laterally to the
keep the UAS in the proper position relative to the power
lines.
[0032] The magnetic field can become weaker or stronger, as the UAS
drifts from its position of the transmission line. As the change in
the magnetic field is detected, the navigation system can make the
appropriate correction. For a UAS that only has a single DNV
sensor, when the magnetic field had decreased by more than a
predetermined amount the navigation system can make corrections.
For example, the UAS can have an error budget such that the UAS
will attempt to correct its course if the measured error is greater
than the error budget. If the magnetic field has decreased, the
navigation system can instruct the UAS to move to the left. The
navigation system can continually monitor the magnetic field to see
if moving to the left corrected the error. If the magnetic field
further decreased, the navigation system can instruct the UAS to
fly to the right to its original position relative to the current
source and then move further to the right. If the magnetic field
decreased in strength, the navigation system can deduce that the
UAS needs to decrease its altitude to increase the magnetic field.
In this example, the UAS would originally be flying directly over
the current source, but the distance between the current source and
the UAS has increased due to the current source being at a lower
elevation. Using this feedback loop of the magnetic field, the
navigation system can keep the UAS centered or at an offset of the
current source. The same analysis can be done when the magnetic
field increases in strength. The navigation can maneuver until the
measured magnetic field is within the proper range such that the
UAS in within the flight path.
[0033] The UAS can also use the vector measurements from one or
more DNV sensors to determine course corrections. The readings from
the DNV sensor are vectors that indicate the direction of the
sensed magnetic field. Once the UAS knows the location of the power
line, as the magnitude of the sensed magnetic field decreases, the
vector can provide an indication of the direction the UAS should
move to correct its course. For example, the strength of the
magnetic field can be reduced by a threshold amount from its ideal
location. The magnetic vector of this field can be used to indicate
the direction the UAS should correct to increase the strength of
the magnetic field. In other words, the magnetic field indicates
the direction of the field and the UAS can use this direction to
determine the correct direction needed to increase the strength of
the magnetic field, which could correct the UAS flight path to be
back over the transmission wire.
[0034] Using multiple sensors on a single vehicle can reduce the
amount of maneuvering that is needed or eliminate the maneuvering
all together. Using the measured magnetic field from each of the
multiple sensors, the navigation system can determine if the UAS
needs to correct its course by moving left, right, up, or down. For
example, if both DNV sensors are reading a stronger field, the
navigation system can direct the UAS to increase its altitude. As
another example if the left sensor is stronger than expected but
the right sensor is weaker than expected, the navigation system can
move the UAS to the left.
[0035] In addition to the current readings from the one or more
sensors, a recent history of readings can also be used by the
navigation system to identify how to correct the UAS course. For
example, if the right sensor had a brief increase in strength and
then a decrease, while the left sensor had a decrease, the
navigation system can determine that the UAS has moved to far to
the left of the flight path and could correct the position of the
UAS accordingly.
[0036] FIG. 3 illustrates a high-level block diagram of an example
UAS navigation system 300, according to some implementations of the
subject technology. In some implementations, the UAS navigation
system of the subject technology includes a number of DNV sensors
302a, 302b, and 302c, a navigation database 304, and a feedback
loop that controls the UAS position and orientation. In other
implementations, a vehicle can contain a navigation control that is
used to navigate the vehicle. For example, the navigation control
can change the vehicle's direction, elevation, speed, etc. The DNV
magnetic sensors 302a-302c have high sensitivity to magnetic
fields, low C-SWAP and a fast settling time. The DNV magnetic field
measurements allow the UAS to align itself with the power lines,
via its characteristic magnetic field signature, and to rapidly
move along power-line routes. Not all of the depicted components
may be required, however, and one or more implementations may
include additional components not shown in the figure. Variations
in the arrangement and type of the components may be made, and
additional components, different components, or fewer components
may be provided.
[0037] FIG. 4 illustrates an example of a power line
infrastructure. It is known that widespread power line
infrastructures, such as shown in FIG. 4, connect cities, critical
power system elements, homes and businesses. The infrastructure may
include overhead and buried power distribution lines, transmission
lines, railway catenary and 3.sup.rd rail power lines and
underwater cables. Each element has a unique electro-magnetic and
spatial signature. It is understood that, unlike electric fields,
the magnetic signature is minimally impacted by man-made structures
and electrical shielding. It is understood that specific elements
of the infrastructure will have distinct magnetic and spatial
signatures and that discontinuities, cable droop, power consumption
and other factors will create variations in magnetic signatures
that can also be leveraged for navigation.
[0038] FIGS. 5A and 5B illustrate examples of magnetic field
distribution for overhead power lines and underground power cables.
Both above-ground and buried power cables emit magnetic fields,
which unlike electrical fields are not easily blocked or shielded.
Natural Earth and other man-made magnetic field sources can provide
rough values of absolute location. However, the sensitive magnetic
sensors described here can locate strong man-made magnetic sources,
such as power lines, at substantial distances. As the UAS moves,
the measurements can be used to reveal the spatial structure of the
magnetic source (point source, line source, etc.) and thus identify
the power line as such. In addition, once detected the UAS can
guide itself to the power line via its magnetic strength. Once the
power line is located its structure is determined, and the power
line route is followed and its characteristics are compared to
magnetic way points to determine absolute location. Fixed power
lines can provide precision location reference as the location and
relative position of poles and towers are known. A compact on-board
database can provide reference signatures and location data for
waypoints. Not all of the depicted components may be required,
however, and one or more implementations may include additional
components not shown in the figure. Variations in the arrangement
and type of the components may be made, and additional components,
different components, or fewer components may be provided.
[0039] FIG. 6 illustrates examples of magnetic field strength of
power lines as a function of distance from the centerline showing
that even low current distribution lines can be detected to
distances in excess of 10 km. Here it is understood that DNV
sensors provide 0.01 uT sensitivity (1e-10 T), and modeling results
indicates that high current transmission line (e.g. with 1000
A-4000 A) can be detected over many tens of km. These strong
magnetic sources allow the UAS to guide itself to the power lines
where it can then align itself using localized relative field
strength and the characteristic patterns of the power-line
configuration as described below.
[0040] FIG. 7 illustrates an example of a UAS 702 equipped with DNV
sensors 704 and 706. FIG. 8 is a plot of a measured differential
magnetic field sensed by the DNV sensors when in close proximity of
the power lines. While power line detection can be performed with
only a single DNV sensor precision alignment for complex wire
configurations can be achieved using multiple arrayed sensors. For
example, the differential signal can eliminate the influence of
diurnal and seasonal variations in field strength. Not all of the
depicted components may be required, however, and one or more
implementations may include additional components not shown in the
figure. Variations in the arrangement and type of the components
may be made, and additional components, different components, or
fewer components may be provided.
[0041] In various other implementations, a vehicle can also be used
to inspect power transmission lines, power lines, and power utility
equipment. For example, a vehicle can include one or more magnetic
sensors, a magnetic waypoint database, and an interface to UAS
flight control. The subject technology may leverage high
sensitivity to magnetic fields of DNV magnetic sensors for magnetic
field measurements. The DNV magnetic sensor can also be low cost,
space, weight, and power (C-SWAP) and benefit from a fast settling
time. The DNV magnetic field measurements allow UASs to align
themselves with the power lines, and to rapidly move along
power-line routes and navigate in poor visibility conditions and/or
in GPS-denied environments. It is understood that DNV-based
magnetic sensors are approximately 100 times smaller than
conventional magnetic sensors and have a reaction time that that is
approximately 100,000 times faster than sensors with similar
sensitivity such as the EMDEX LLC Snap handheld magnetic field
survey meter.
[0042] The fast settling time and low C-SWAP of the DNV sensor
enables rapid measurement of detailed power line characteristics
from low-C-SWAP UAS systems. In one or more implementations, power
lines can be efficiently surveyed via small unmanned aerial
vehicles (UAVs) on a routine basis over long distance, which can
identify emerging problems and issues through automated field
anomaly identification. In other implementations, a land based
vehicle or submersible can be used to inspect power lines. Human
inspectors are not required to perform the initial inspections. The
inspections of the subject technology are quantitative, and thus
are not subject to human interpretation as remote video solutions
may be.
[0043] FIG. 9 illustrates an example of a measured magnetic field
distribution for normal power lines 904 and power lines with
anomalies 902 according to some implementations. The peak value of
the measured magnetic field distribution, for the normal power
lines, is in the vicinity of the centerline (e.g., d=0). The
inspection method of the subject technology is a high-speed anomaly
mapping technique that can be employed for single and multi-wire
transmission systems. The subject solution can take advantage of
existing software modeling tools for analyzing the inspection data.
In one or more implementations, the data of a normal set of power
lines may be used as a comparison reference for data resulting from
inspection of other power lines (e.g., with anomalies or defects).
Damage to wires and support structure alters the nominal magnetic
field characteristics and is detected by comparison with nominal
magnetic field characteristics of the normal set of power lines. It
is understood that the magnetic field measurement is minimally
impacted by other structures such as buildings, trees, and the
like. Accordingly, the measured magnetic field can be compared to
the data from the normal set of power lines and the measured
magnetic field's magnitude and if different by a predetermined
threshold the existence of the anomaly can be indicated. In
addition, the vector reading between the difference data can also
be compared and used to determine the existence of anomaly.
[0044] FIGS. 10A and 10B are block diagrams of a system for
detecting deformities in a transmission line in accordance with an
illustrative embodiment. An illustrative system 100 includes a
transmission line 1005 and a magnetometer 1030. The magnetometer
can be included within a vehicle.
[0045] Current flows through the transmission line 1005 as
indicated by the arrow labeled 1020. FIGS. 10A and 10B illustrate
the direction of a current through the transmission line 1005. As
the current 1020 passes through the transmission line 1005 a
magnetic field is generated 1025. The magnetometer 1030 can be
passed along the length of the transmission line 1005. FIGS. 10A
and 10B include an arrow parallel to the length of the transmission
line 1005 indicating the relative path of the magnetometer 1030. In
alternative embodiments, any suitable path may be used. For
example, in some embodiments in which the transmission line 1005 is
curved, the magnetometer 1030 can follow the curvature of the
transmission line 1005. In addition, the magnetometer 1030 does not
have to remain at a constant distance from the transmission line
1005.
[0046] The magnetometer 1030 can measure the magnitude and/or
direction of the magnetic field along the length of the
transmission line 1005. For example, the magnetometer 1030 measures
the magnitude and the direction of the magnetic field at multiple
sample points along the length of the transmission line 1005 at the
same orientation to the transmission line 1005 at the sample
points. For instance, the magnetometer 1030 can pass along the
length of the transmission line 1005 while above the transmission
line 1005.
[0047] Any suitable magnetometer can be used as the magnetometer
1030. In some embodiments, the magnetometer uses one or more
diamonds with NV centers. The magnetometer 1030 can have a
sensitivity suitable for detecting changes in the magnetic field
around the transmission line 1005 caused by deformities. In some
instances, a relatively insensitive magnetometer 1030 may be used.
In such instances, the magnetic field surrounding the transmission
line 1005 should be relatively strong. For example, the
magnetometer 1030 can have a sensitivity of about 10.sup.-9 Tesla
(one nano-Tesla). Transmission lines can carry a large current,
which allows detection of the magnetic field generated from the
transmission line over a large distances. For example, for high
current transmission lines, the magnetometer 1030 can be 10
kilometers away from the transmission source. The magnetometer 1030
can have any suitable measurement rate. For example, the
magnetometer 1030 can measure the magnitude and/or the direction of
a magnetic field at a particular point in space ten thousand times
per second. In another example, the magnetometer 1030 can take a
measurement fifty thousand times per second. Further description of
operation of a DNV sensor is described in U.S. Patent Application
No. __/___,___, entitled "Apparatus and Method for Hypersensitivity
Detection of Magnetic Field," filed on the same day as this
application, the contents of which are hereby incorporated by
reference.
[0048] In some embodiments in which the magnetometer 1030 measures
the direction of the magnetic field, the orientation of the
magnetometer 1030 to the transmission line 1005 can be maintained
along the length of the transmission line 1005. As the magnetometer
1030 passes along the length of the transmission line 1005, the
direction of the magnetic field can be monitored. If the direction
of the magnetic field changes or is different than an expected
value, it can be determined that a deformity exits in the
transmission line 1005.
[0049] In some embodiments, the magnetometer 1030 can be maintained
at the same orientation to the transmission line 1005 because even
if the magnetic field around the transmission line 1005 is uniform
along the length of the transmission line 1005, the direction of
the magnetic field is different at different points around the
transmission line 1005. For example, referring to the magnetic
field direction 1025 of FIG. 10A, the direction of the magnetic
field above the transmission line 1005 is pointing to the right of
the transmission line 1005 (e.g., according to the "right-hand
rule"). A vehicle carrying the magnetometer would know the
magnetometer's relative position to the transmission line 1005. For
example, an aerial vehicle would know it's relative position would
be above or a known distance offset from the transmission line
1005, while a ground based vehicle would now it's relative position
to be below or a known offset from the transmission line 1005.
Based upon the relative position of the magnetometer to the
transmission line 1005, the direction magnetic vector can be
monitored for indicating defects in the transmission line 1005.
[0050] In some embodiments in which the magnetometer 1030 measures
magnitude of the magnetic field and not the direction of the
magnetic field, the magnetometer 1030 can be located at any
suitable location around the transmission line 1005 along the
length of the transmission line 1005 and the magnetometer 1030 may
not be held at the same orientation along the length of the
transmission line 1005. In such embodiments, the magnetometer 1030
may be maintained at the same distance from the transmission line
1005 along the length of the transmission line 1005 (e.g., assuming
the same material such as air is between the magnetometer 1030 and
the transmission line 1005 along the length of the transmission
line 1005).
[0051] FIG. 10A illustrates the system in which the transmission
line 1005 does not contain a deformity. FIG. 10B illustrates in
which the transmission line 1005 includes a defect 1035. The defect
1035 can be a crack in the transmission line, a break in the
transmission line, a deteriorating portion of the transmission
line, etc. A defect 1035 is a condition of the transmission line
that affects the current flow through a defect free transmission
line. As shown in FIG. 10B, a portion of the current 1020 is
reflected back from the defect 1035 as shown by the reflected
current 1040. As in FIG. 10B, the magnetic field direction 1025
corresponds to the current 1020. The reflected current magnetic
field direction 1045 corresponds to the reflected current 1040. The
magnetic field direction 1025 is opposite the reflected current
magnetic field direction 1045 because the current 1020 travels in
the opposite direction from the reflected current 1040.
Accordingly, the magnetic field measured in the transmission line
would be based upon both the current 1020 and the reflected current
1040. This magnetic field is different in magnitude and possibly
direction from the magnetic field 1025. The difference between the
magnetic fields 1020 and 1040 can be calculated and used to
indicate the presence of the defect 1035. In some instances, as the
magnetometer 1030 travels closer to the defect 1035, the magnitude
of the detected magnetic field reduces. In some embodiments, it can
be determined that the defect 1035 exists when the measured
magnetic field is below a threshold value. In some embodiments, the
threshold value may be a percentage of the expected value, such as
.+-.5%, .+-.10%, .+-.15%, .+-.50%, or any other suitable portion of
the expected value. In alternative embodiments, any suitable
threshold value may be used.
[0052] In some embodiments in which the defect 1035 is a full break
that breaks conductivity between the portions of the transmission
line 1005, the magnitude of the current 1020 may be equal to or
substantially similar to reflected current 1040. Thus, the combined
magnetic field around the transmission line 1005 will be zero or
substantially zero. That is, the magnetic field generated by the
current 1020 is canceled out by the equal but opposite magnetic
field generated by the reflected current 1040. In such embodiments,
the defect 1035 may be detected using the magnetometer 1030 by
comparing the measured magnetic field, which is substantially zero,
to an expected magnetic field, which is a non-zero amount.
[0053] In some embodiments in which the defect 1035 allows some of
the current 1020 to pass through or around the defect 1035, the
magnitude of the reflected current 1040 is less than the magnitude
of the current 1020. Accordingly, the magnitude of the magnetic
field generated by the reflected current 1040 is less than the
magnitude of the magnetic field generated by the current 1020.
Although the magnitudes of the current 1020 and the reflected
current 1040 may not be equal, the current magnetic field direction
1025 and the reflected current magnetic field direction 1045 are
still opposite. Thus, the net magnetic field will be a magnetic
field in the current magnetic field direction 1025. The magnitude
of the net magnetic field is the magnitude of the magnetic field
generated by the current 1020 reduced based upon the magnitude of
the magnetic field generated by the reflected current 1040. As
mentioned above, the magnetic field measured by the magnetometer
1030 can be compared against a threshold. Depending upon the
severity, size, and/or shape of the defect 1035, the net magnetic
field sensed by the magnetometer 1030 may or may not be less than
(or greater than) the threshold value. Thus, the threshold value
can be adjusted to adjust the sensitivity of the system. That is,
the more that the threshold value deviates from the expected value,
the larger the deformity in the transmission line 1005 is to cause
the magnitude of the sensed magnetic field to be less than the
threshold value. Thus, the closer that the threshold value is to
the expected value, the finer, smaller, less severe, etc.
deformities are detected by the system 100.
[0054] As mentioned above, the direction of the magnetic field
around the transmission line 1005 can be used to sense a deformity
in the transmission line 1005. FIG. 11 illustrates current paths
through a transmission line with a deformity 1135 in accordance
with an illustrative embodiment. FIG. 11 is meant to be
illustrative and explanatory only and not meant to be limiting with
respect to the functioning of the system.
[0055] A current can be passed through the transmission line 1105,
as discussed above. The current paths 1120 illustrate the direction
of the current. As shown in FIG. 11, the transmission line 1105
includes a deformity 1135. The deformity 1135 can be any suitable
deformity, such as a crack, a dent, an impurity, etc. The current
passing through the transmission line 1105 spreads uniformly around
the transmission line 1105 in portions that do not include the
deformity 1135. In some instances, the current may be more
concentrated at the surface of the transmission line 1105 than at
the center of the transmission line 1105.
[0056] In some embodiments, the deformity 1135 is a portion of the
transmission line 1105 that does not allow or resists the flow of
electrical current. Thus, the current passing through the
transmission line 1105 flows around the deformity 1135. As shown in
FIG. 10A, the current magnetic field direction 1025 is
perpendicular to the direction of the current 1020. Thus, as in
FIG. 10A, when the transmission line 1005 does not include a
deformity, the direction of the magnetic field around the
transmission line 1005 is perpendicular to the length of the
transmission line 1005 all along the length of the transmission
line 1005.
[0057] As shown in FIG. 11, when the transmission line 1105
includes a deformity 1135 around which the current flows, the
direction of the current changes, as shown by the current paths
1120. Thus, even though the transmission line 1105 is straight, the
current flowing around the deformity 1135 is not parallel to the
length of the transmission line 1105. Accordingly, the magnetic
field generated by the current paths corresponding to the curved
current paths 1120 is not perpendicular to the length of the
transmission line 1105. Thus, as a magnetometer such as the
magnetometer 1030 passes along the length of the transmission line
1105, a change in direction of the magnetic field around the
transmission line 1105 can indicate that the deformity 1135 exits.
As the magnetometer 1030 approaches the deformity 1135, the
direction of the magnetic field around the transmission line 1105
changes from being perpendicular to the length of the transmission
line 1105. As the magnetometer 1030 passes along the deformity
1135, the change in direction of the magnetic field increases and
then decreases as the magnetometer 1030 moves away from the
deformity 1135. The change in the direction of the magnetic field
can indicate the location of the deformity 1135. In some instances,
the transmission line 1105 may have a deformity that reflects a
portion of the current, as illustrated in FIG. 10B, and that
deflects the flow of the current, as illustrated in FIG. 11.
[0058] The size, shape, type, etc. of the deformity 1135 determines
the spatial direction of the magnetic field surrounding the
deformity 1135. In some embodiments, multiple samples of the
magnetic field around the deformity 1135 can be taken to create a
map of the magnetic field. In an illustrative embodiment, each of
the samples includes a magnitude and direction of the magnetic
field. Based on the spatial shape of the magnetic field surrounding
the deformity 1135, one or more characteristics of the deformity
1135 can be determined, such as the size, shape, type, etc. of the
deformity 1135. For instance, depending upon the map of the
magnetic field, it can be determined whether the deformity 1135 is
a dent, a crack, an impurity in the transmission line, etc. In some
embodiments, the map of the magnetic field surrounding the
deformity 1135 can be compared to a database of known deformities.
In an illustrative embodiment, it can be determined that the
deformity 1135 is similar to or the same as the closest matching
deformity from the database. In an alternative embodiment, it can
be determined that the deformity 1135 is similar to or the same as
a deformity from the database that has a similarity score that is
above a threshold score. The similarity score can be any suitable
score that measures the similarity between the measured magnetic
field and one or more known magnetic fields of the database.
[0059] In various implementations, a vehicle that includes one or
magnetometers can navigate via the power lines that are being
inspected. For example, the vehicle can navigate to an known
position, e.g., a starting position, identify the presence of a
power line based upon the sensed magnetic vector. Then the vehicle
can determine the type of power line and further determine that the
type of power line is the type that is to be inspected. The vehicle
can then autonomously or semi-autonomously navigate via the power
lines as described in detail above, while inspecting the power
lines at the same time.
[0060] In various implementations, a vehicle may need to avoid
objects that are in their navigation path. For example, a ground
vehicle may need to maneuver around people or objects, or a flying
vehicle may need to avoid a building or power line equipment. In
these implementations, the vehicle can be equipment with sensors
that are used to locate the obstacles that are to be avoided.
Systems such as a camera system, focal point array, radar, acoustic
sensors, etc., can be used to identify obstacles in the vehicles
path. The navigation system can then identify a course correction
to avoid the identified obstacles.
[0061] Power transmission lines can be stretched between two
transmission towers. In these instances, the power transmission
lines can sag between the two transmission towers. The power
transmission line sag depends on the weight of the wire, tower
spacing and wire tension, which varies with ambient temperature and
electrical load. Excessive sagging can cause shorting when the
transmission line comes into contact with brush or other surface
structures. This can caused power transmission lines to fail.
[0062] FIG. 12 illustrates power transmission line sag between
transmission towers in accordance with an illustrative embodiment.
A transmission line 1210 is shown with "normal" sag 1222. Here sag
is determined based upon how far below the transmission line is
from the tower height. The transmission line 1210 is stretched
between a first tower 1202 and a second tower 1204. A second
transmission line 1220 is shown with excessive sag. When this
occurs the transmission line 1220 can come into contact with
vegetation 1230 or other surface structures that can cause on or
failure to the line.
[0063] A vector measurement made with a magnetometer mounted on a
UAV can measure the wire sag as the UAV flies along the power
lines. FIG. 13 depicts the instantaneous measurement of the
magnetic field at point X' as the UAV flies at a fixed height above
the towers. A larger horizontal (x) component of the magnetic field
indicates more sag. FIG. 14 depicts the variation in magnetic field
components for the wire with nominal sag, and for the wire with
excessive sag as the UAV transits between towers 1 and 2. The X and
Z components for a transmission line under normal/nominal sag are
shown (1408 and 1402 respectively). In addition, the X component
1406 and the Z component 1404 of a line experiencing excessive sag
is also shown.
[0064] The cable sag may be measured by flying the UAV along the
cable from tower to tower. FIG. 14 shows the modulation in vector
components of the magnetic field for different sag values. A
look-up table can be constructed to retrieve the sag from these
measurements for wires between each pair of towers along the UAV
flight route. Alternatively a database of prior vector measurements
can be compared with measurements. In general the flatter the
curves the less sag. The exact value of the sag depends on the
distance between towers and, which is measured by the UAV, and the
angle of the vector at the tower. Combined with weather information
and potentially historical data or transmission line sag models,
the vector measurements can be used to determine if the power line
is experiencing greater or lesser sag as expected. When this
occurs, an indication that the power line is experiencing a sag
anomaly can be indicated and/or reported.
[0065] FIG. 15 is a diagram illustrating an example of a system
1000 for implementing some aspects of the subject technology. The
system 1500 includes a processing system 1502, which may include
one or more processors or one or more processing systems. A
processor can be one or more processors. The processing system 1502
may include a general-purpose processor or a specific-purpose
processor for executing instructions and may further include a
machine-readable medium 1519, such as a volatile or non-volatile
memory, for storing data and/or instructions for software programs.
The instructions, which may be stored in a machine-readable medium
1510 and/or 1519, may be executed by the processing system 1502 to
control and manage access to the various networks, as well as
provide other communication and processing functions. The
instructions may also include instructions executed by the
processing system 1502 for various user interface devices. The
processing system 1502 may include an input port 1522 and an output
port 1524. Each of the input port 1522 and the output port 1524 may
include one or more ports. The input port 1522 and the output port
1524 may be the same port (e.g., a bi-directional port) or may be
different ports.
[0066] The processing system 1502 may be implemented using
software, hardware, or a combination of both. By way of example,
the processing system 1502 may be implemented with one or more
processors. A processor may be a general-purpose microprocessor, a
microcontroller, a Digital Signal Processor (DSP), an Application
Specific Integrated Circuit (ASIC), a Field Programmable Gate Array
(FPGA), a Programmable Logic Device (PLD), a controller, a state
machine, gated logic, discrete hardware components, or any other
suitable device that can perform calculations or other
manipulations of information.
[0067] A machine-readable medium can be one or more
machine-readable media. Software shall be construed broadly to mean
instructions, data, or any combination thereof, whether referred to
as software, firmware, middleware, microcode, hardware description
language, or otherwise. Instructions may include code (e.g., in
source code format, binary code format, executable code format, or
any other suitable format of code).
[0068] Machine-readable media (e.g., 1519) may include storage
integrated into a processing system such as might be the case with
an ASIC. Machine-readable media (e.g., 1510) may also include
storage external to a processing system, such as a Random Access
Memory (RAM), a flash memory, a Read Only Memory (ROM), a
Programmable Read-Only Memory (PROM), an Erasable PROM (EPROM),
registers, a hard disk, a removable disk, a CD-ROM, a DVD, or any
other suitable storage device. Those skilled in the art will
recognize how best to implement the described functionality for the
processing system 1502. According to one aspect of the disclosure,
a machine-readable medium is a computer-readable medium encoded or
stored with instructions and is a computing element, which defines
structural and functional interrelationships between the
instructions and the rest of the system, which permit the
instructions' functionality to be realized. Instructions may be
executable, for example, by the processing system 1502 or one or
more processors. Instructions can be, for example, a computer
program including code for performing methods of the subject
technology.
[0069] A network interface 1516 may be any type of interface to a
network (e.g., an Internet network interface), and may reside
between any of the components shown in FIG. 15 and coupled to the
processor via the bus 1504.
[0070] A device interface 1518 may be any type of interface to a
device and may reside between any of the components shown in FIG.
15. A device interface 1518 may, for example, be an interface to an
external device (e.g., USB device) that plugs into a port (e.g.,
USB port) of the system 1500.
[0071] The foregoing description is provided to enable a person
skilled in the art to practice the various configurations described
herein. While the subject technology has been particularly
described with reference to the various figures and configurations,
it should be understood that these are for illustration purposes
only and should not be taken as limiting the scope of the subject
technology.
[0072] One or more of the above-described features and applications
may be implemented as software processes that are specified as a
set of instructions recorded on a computer readable storage medium
(alternatively referred to as computer-readable media,
machine-readable media, or machine-readable storage media). When
these instructions are executed by one or more processing unit(s)
(e.g., one or more processors, cores of processors, or other
processing units), they cause the processing unit(s) to perform the
actions indicated in the instructions. In one or more
implementations, the computer readable media does not include
carrier waves and electronic signals passing wirelessly or over
wired connections, or any other ephemeral signals. For example, the
computer readable media may be entirely restricted to tangible,
physical objects that store information in a form that is readable
by a computer. In one or more implementations, the computer
readable media is non-transitory computer readable media, computer
readable storage media, or non-transitory computer readable storage
media.
[0073] In one or more implementations, a computer program product
(also known as a program, software, software application, script,
or code) can be written in any form of programming language,
including compiled or interpreted languages, declarative or
procedural languages, and it can be deployed in any form, including
as a stand-alone program or as a module, component, subroutine,
object, or other unit suitable for use in a computing environment.
A computer program may, but need not, correspond to a file in a
file system. A program can be stored in a portion of a file that
holds other programs or data (e.g., one or more scripts stored in a
markup language document), in a single file dedicated to the
program in question, or in multiple coordinated files (e.g., files
that store one or more modules, sub programs, or portions of code).
A computer program can be deployed to be executed on one computer
or on multiple computers that are located at one site or
distributed across multiple sites and interconnected by a
communication network.
[0074] While the above discussion primarily refers to
microprocessor or multi-core processors that execute software, one
or more implementations are performed by one or more integrated
circuits, such as application specific integrated circuits (ASICs)
or field programmable gate arrays (FPGAs). In one or more
implementations, such integrated circuits execute instructions that
are stored on the circuit itself.
[0075] In some aspects, the subject technology is directed to DNV
application to magnetic navigation via power lines. In some
aspects, the subject technology may be used in various markets,
including for example and without limitation, advanced sensors and
mobile space platforms.
[0076] The description of the subject technology is provided to
enable any person skilled in the art to practice the various
embodiments described herein. While the subject technology has been
particularly described with reference to the various figures and
embodiments, it should be understood that these are for
illustration purposes only and should not be taken as limiting the
scope of the subject technology.
[0077] There may be many other ways to implement the subject
technology. Various functions and elements described herein may be
partitioned differently from those shown without departing from the
scope of the subject technology. Various modifications to these
embodiments may be readily apparent to those skilled in the art,
and generic principles defined herein may be applied to other
embodiments. Thus, many changes and modifications may be made to
the subject technology, by one having ordinary skill in the art,
without departing from the scope of the subject technology.
[0078] Phrases such as an aspect, the aspect, another aspect, some
aspects, one or more aspects, an implementation, the
implementation, another implementation, some implementations, one
or more implementations, an embodiment, the embodiment, another
embodiment, some embodiments, one or more embodiments, a
configuration, the configuration, another configuration, some
configurations, one or more configurations, the subject technology,
the disclosure, the present disclosure, other variations thereof
and alike are for convenience and do not imply that a disclosure
relating to such phrase(s) is essential to the subject technology
or that such disclosure applies to all configurations of the
subject technology. A disclosure relating to such phrase(s) may
apply to all configurations, or one or more configurations. A
disclosure relating to such phrase(s) may provide one or more
examples. A phrase such as an aspect or some aspects may refer to
one or more aspects and vice versa, and this applies similarly to
other foregoing phrases
[0079] A reference to an element in the singular is not intended to
mean "one and only one" unless specifically stated, but rather "one
or more." The term "some" refers to one or more. Underlined and/or
italicized headings and subheadings are used for convenience only,
do not limit the subject technology, and are not referred to in
connection with the interpretation of the description of the
subject technology. All structural and functional equivalents to
the elements of the various embodiments described throughout this
disclosure that are known or later come to be known to those of
ordinary skill in the art are expressly incorporated herein by
reference and intended to be encompassed by the subject technology.
Moreover, nothing disclosed herein is intended to be dedicated to
the public regardless of whether such disclosure is explicitly
recited in the above description.
* * * * *