U.S. patent application number 13/542727 was filed with the patent office on 2013-02-07 for sea glider.
This patent application is currently assigned to iRobot Corporation. The applicant listed for this patent is Marc Jeremy Hoffman, Robert Eugene Hughes, Amber Kardes, Christopher R. Yahnker. Invention is credited to Marc Jeremy Hoffman, Robert Eugene Hughes, Amber Kardes, Christopher R. Yahnker.
Application Number | 20130032078 13/542727 |
Document ID | / |
Family ID | 46763163 |
Filed Date | 2013-02-07 |
United States Patent
Application |
20130032078 |
Kind Code |
A1 |
Yahnker; Christopher R. ; et
al. |
February 7, 2013 |
Sea Glider
Abstract
A sea glider that includes a pressure hull and fore and aft
fairings encapsulating the pressure hull. At least one of the fore
and aft fairings defines an Ogive profile.
Inventors: |
Yahnker; Christopher R.;
(Raleigh, NC) ; Hughes; Robert Eugene; (Chapel
Hill, NC) ; Hoffman; Marc Jeremy; (Clayton, NC)
; Kardes; Amber; (Durham, NC) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Yahnker; Christopher R.
Hughes; Robert Eugene
Hoffman; Marc Jeremy
Kardes; Amber |
Raleigh
Chapel Hill
Clayton
Durham |
NC
NC
NC
NC |
US
US
US
US |
|
|
Assignee: |
iRobot Corporation
Bedford
MA
|
Family ID: |
46763163 |
Appl. No.: |
13/542727 |
Filed: |
July 6, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61508385 |
Jul 15, 2011 |
|
|
|
Current U.S.
Class: |
114/331 |
Current CPC
Class: |
B63G 8/001 20130101;
B63G 8/22 20130101; B63G 8/18 20130101 |
Class at
Publication: |
114/331 |
International
Class: |
B63G 8/14 20060101
B63G008/14 |
Claims
1. A sea glider comprising: a pressure hull; and fore and aft
fairings encapsulating the pressure hull; wherein at least one of
the fore and aft fairings defines an Ogive profile.
2. The sea glider of claim 1, further comprising a straight section
joint connecting the fore fairing to the aft fairing.
3. The sea glider of claim 1, wherein the aft fairing defines a
convex shape.
4. The sea glider of claim 1, wherein the fore and aft fairings
comprise fiberglass.
5. The sea glider of claim 4, wherein the fore and aft fairings
each have a wall thickness of between about 2 mm and about 12
mm.
6. The sea glider of claim 1, further comprising: right and left
wings disposed opposite of each other on the aft fairing; a rudder
disposed on the aft fairing; and an antenna disposed on the aft
fairing.
7. The sea glider of claim 1, further comprising a flooded payload
section disposed aft of the pressure hull and at least partially
enclosed by the aft fairing.
8. The sea glider of claim 7, further comprising a bladder system
housed by the payload section for altering a buoyancy of the sea
glider.
9. The sea glider of claim 8, further comprising a controller in
communication with at least one of the bladder system, a removable
rudder disposed on the aft fairing, and an antenna.
10. The sea glider of claim 9, wherein the controller executes a
Kalman filter for predicting water currents.
11. The sea glider of claim 9, wherein the controller executes
waypoint navigation by using a depth averaged current navigation
algorithm.
12. A sea glider body comprising: fore and aft fairings for
encapsulating a pressure hull, at least one of the fore and aft
fairings defines an Ogive profile; a straight section defined
between the fore and aft fairings, the straight section having a
length of about 200 mm; wherein the fore and aft fairings have a
combined overall length of between about 1.8 meters and about 2.0
meters.
13. The sea glider body of claim 12, wherein the fore and aft
fairings comprise fiberglass.
14. The sea glider body of claim 13, wherein the fore and aft
fairings each have a wall thickness of between about 2 mm and about
12 mm.
15. The sea glider body of claim 12, wherein the aft fairing
defines a convex shape.
16. The sea glider body of claim 12, wherein the fore fairing
defines approximately 75 mm of the straight section and the aft
fairing defines the remaining portion of the straight section.
17. The sea glider body of claim 12, further comprising a flooded
payload section at least partially enclosed by the aft fairing.
18. A sea glider comprising: a pressure hull; fore and aft fairings
encapsulating the pressure hull, the fore and aft fairings each
defining an Ogive profile; right and left wings disposed opposite
of each other on the aft fairing; a rudder disposed on the aft
fairing; an antenna disposed on the aft fairing; a bladder system
disposed in a flooded payload section disposed aft of the pressure
hull and at least partially defined by the aft fairing, the bladder
system altering a buoyancy of the sea glider; and a controller in
communication with at least one of the bladder system, the rudder,
and the antenna.
19. The sea glider of claim 18, wherein the fore and aft fairings
together define a straight section about a joint connecting the
fairings.
20. The sea glider of claim 19, wherein the fore and aft fairings
have a combined overall length of between about 1.8 meters and
about 2.0 meters and the straight section has a length of about 200
mm.
21. The sea glider of claim 20, wherein the fore fairing defines
approximately 75 mm of the straight section and the aft fairing
defines the remaining portion of the straight section.
22. The sea glider of claim 18, wherein the aft fairing defines a
convex shape.
23. The sea glider of claim 18, wherein the fore and aft fairings
comprise fiberglass.
24. The sea glider of claim 23, wherein the fore and aft fairings
each have a wall thickness of between about 2 mm and about 12
mm.
25. The sea glider of claim 18, wherein the controller executes a
Kalman filter for predicting water currents.
26. The sea glider of claim 18, wherein the controller executes
waypoint navigation by using a depth averaged current navigation
algorithm.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This U.S. patent application claims priority under 35 U.S.C.
.sctn.119(e) to U.S. Provisional Application No. 61/508,385, filed
on Jul. 15, 2011, which is hereby incorporated by reference in its
entirety.
TECHNICAL FIELD
[0002] This disclosure relates to sea gliders.
BACKGROUND
[0003] Sea gliders travel through water with extremely modest
energy requirements using changes in buoyancy for thrust coupled
with a stable, low-drag, hydrodynamic shape. Sea gliders are
generally deep diving UUVs that may measure temperature, salinity,
and other quantities in the ocean, sending back data using global
satellite telemetry. Sea gliders can collect physical, chemical and
biological oceanographic data and performs a variety of missions
for researchers and military planners.
SUMMARY
[0004] A sea glider having fairings the define an Ogive profile
accommodate a relatively increased payload capacity, as compared to
fairings defining other profiles, thus allowing the sea glider to
carry relatively more and larger sensors. The fairings provide a
relatively larger overall length of the sea glider and the profile
of an aft fairing defines a convex shape, adding payload volume.
These two features combined give the fairings a 650% increase in
the volumetric payload capacity of the sea glider, as compared to a
typical sea glider. Moreover, the fairings provide a reduction in
total drag by as much as 25%, as compared to a typical sea glider,
which can improve endurance of the sea glider (since less thrust is
required to propel the sea glider).
[0005] One aspect of the disclosure provides a sea glider that
includes a pressure hull and fore and aft fairings encapsulating
the pressure hull. At least one of the fore and aft fairings
defines an Ogive profile.
[0006] Implementations of the disclosure may include one or more of
the following features. In some implementations, the sea glider
includes a straight section joint connecting the fore fairing to
the aft fairing. The aft fairing may define a convex shape.
Moreover, the fore and aft fairings may comprise fiberglass (e.g.,
fiberglass composite) and/or each have a wall thickness of between
about 2 mm and about 12 mm.
[0007] In some implementations, the sea glider includes right and
left wings disposed opposite of each other on the aft fairing, a
rudder disposed on the aft fairing, and an antenna disposed on the
aft fairing. The sea glider may include a flooded payload section
disposed aft of the pressure hull and at least partially enclosed
by the aft fairing. A bladder system may be housed by the payload
section for altering a buoyancy of the sea glider. The sea glider
may include a controller in communication with at least one of the
bladder system, a rudder disposed on the aft fairing, and an
antenna. The rudder may be movable and/or removable from the sea
glider. In some examples, the controller executes a Kalman filter
for predicting water currents. In additional examples, the
controller executes waypoint navigation by using a depth averaged
current navigation algorithm.
[0008] Another aspect of the disclosure provides a sea glider body
that includes fore and aft fairings for encapsulating a pressure
hull. At least one of the fore and aft fairings defines an Ogive
profile. A straight section defined between the fore and aft
fairings has a length of about 200 mm. The fore and aft fairings
have a combined overall length of between about 1.8 meters and
about 2.0 meters.
[0009] In some implementations, the fore and aft fairings comprise
fiberglass (e.g., fiberglass composite) and/or each have a wall
thickness of between about 2 mm and about 12 mm. The aft fairing
may define a convex shape. The fore fairing may define
approximately 75 mm of the straight section and the aft fairing may
define the remaining portion of the straight section. The sea
glider body may include a flooded payload section at least
partially enclosed by the aft fairing.
[0010] In yet another aspect, a sea glider includes a pressure hull
and fore and aft fairings encapsulating the pressure hull. The fore
and aft fairings each define an Ogive profile. The sea glider
includes right and left wings disposed opposite of each other on
the aft fairing, a rudder disposed on the aft fairing, an antenna
disposed on the aft fairing, and a bladder system disposed in a
flooded payload section disposed aft of the pressure hull and at
least partially defined by the aft fairing. The bladder system
alters a buoyancy of the sea glider. The sea glider also includes a
controller in communication with at least one of the bladder
system, the rudder, and the antenna.
[0011] In some implementations, the fore and aft fairings together
define a straight section about a joint connecting the fairings.
The fore and aft fairings may have a combined overall length of
between about 1.8 meters and about 2.0 meters and the straight
section may have a length of about 200 mm. In some examples, the
fore fairing defines approximately 75 mm of the straight section
and the aft fairing defines the remaining portion of the straight
section. The aft fairing may define a convex shape. The fore and
aft fairings may each comprise fiberglass (e.g., fiberglass
composite) and/or have a wall thickness of between about 2 mm and
about 12 mm.
[0012] In some instances, the controller executes a Kalman filter
for predicting water currents. In addition or alternatively, the
controller may execute waypoint navigation by using a depth
averaged current navigation algorithm.
[0013] The details of one or more implementations of the disclosure
are set forth in the accompanying drawings and the description
below. Other aspects, features, and advantages will be apparent
from the description and drawings, and from the claims.
DESCRIPTION OF DRAWINGS
[0014] FIG. 1 is a front perspective view of an exemplary sea
glider.
[0015] FIG. 2 is a top perspective view of an exemplary sea
glider.
[0016] FIG. 3 is a side view of an exemplary sea glider.
[0017] FIG. 4 is a graphical view of a tangent Ogive profile.
[0018] FIG. 5 is a side view of first and second exemplary sea
gliders.
[0019] FIG. 6 is a graphical view of results of an exemplary
computational fluid dynamics analysis of a sea glider.
[0020] FIGS. 7A is a graphical view of fluid flow over a sea glider
having fairings defining non-Ogive profiles.
[0021] FIGS. 7B is a graphical view of fluid flow over a sea glider
having fairings defining Ogive profiles.
[0022] FIG. 8 is a graphical view of horizontal versus vertical
speed of a sea glider in water.
[0023] FIG. 9 is a graphical view of metrics of a sea glider model
having fairings defining an Ogive profile
[0024] Like reference symbols in the various drawings indicate like
elements.
DETAILED DESCRIPTION
[0025] A sea glider can be used to expand hydrographic observations
at significantly less cost than using ships or moorings. The sea
glider can be used to monitor environmental conditions in and
around polar icecaps, study the impacts of deep-sea accidents, and
record and track marine mammals from Alaska to Hawaii, for
example.
[0026] Referring to FIGS. 1-3, in some implementations, a sea
glider 100 includes a pressure hull 110 (e.g., anodized aluminum
shell) surrounded by a glider body 120 having fore and aft fairings
120a, 120b. The fairings 120a, 120b can each have an external
surface 122a, 122b defining a smooth and hydrodynamic shaped that
allow seawater to pass between an inner surface 124a, 124b of the
fairing 120a, 120b and the outer surface 112 of the pressure hull
110. A flooded payload section 130 can be disposed aft of the
pressure hull 110 and at least partially enclosed by the aft
fairing 120b. The fairings 120a, 120b accommodate a flooded payload
section 130 having payload capacity to house a bladder system 140
to increase and decrease the buoyancy of the sea glider 100 and/or
provide sensor payload capacity. For example, the payload section
130 may house a global positioning sensor (GPS), current profilers,
PAR sensors, and acoustic modems, and/or a Glider Payload CTD 180
(GPCTD) (available from Sea-Bird Electronics, Inc. of 13431 NE 20th
Street, Bellevue, Wash. 98005). The glider payload CTD (GPCTD)
measures conductivity, temperature, and pressure, and dissolved
oxygen of the sea water.
[0027] In the examples shown, the sea glider 100 includes right and
left wings 150a, 150b (e.g., having a combined wing span of about 1
meter), a rudder 152, and an antenna 160 (e.g., about 1 meter long)
disposed on the aft fairing 120b for iridium satellite data
telemetry, for example. Each of the components can be used for
navigation of the sea glider 100 in water. The rudder 152 may be
movable and/or removable from the sea glider 100. The sea glider
100 may include a controller 105 in communication with one or more
of the bladder system 140, the right and left wings 150a, 150b, the
rudder 152, the antenna 160, a battery 190 (e.g., lithium), and any
sensors housed by the payload section 130. The controller 105 may
include at least includes a programmable or preprogrammed digital
data processor, e.g., a microprocessor, for performing program
steps, algorithms and/or mathematical and logical operations as may
be required. Moreover, the controller 105 may include digital data
memory in communication with the data processor for storing program
steps and other digital data therein. In some examples, the
controller 105 includes one or more clock elements for generating
timing signals, 256 MB Compact Flash memory, 8 serial data
channels, 4 frequency channels, 12 channels 12-bit A/D, and/or 5
digital outputs. For guidance control, the controller 105 may
execute a navigation routine that uses dead reckoning between GPS
fixes using pitch, roll, and heading. The navigation routine may
use a Kalman filter prediction for mean and oscillatory currents.
Moreover, in some examples, the navigation routine uses a
bathymetry map for surface to near-bottom dives.
[0028] The fairings 120a, 120b define a hydrodynamic shape while
optionally providing removable hatch cover(s) 170 for accessing the
payload section 130. The payload capacity of sea glider 100 is a
function of both mass and volume, and directly affects the maximum
change in buoyancy that the vehicle can achieve resulting in the
desired thrust. During fairing development, a number of different
profiles for the fairings 120a, 120b were analyzed for increasing
the payload volume without adversely affecting the hydrodynamics of
the sea glider 100. In some implementations, the fairings 120a,
120b define an Ogive profile, which provides advantageous
hydrodynamic results. The basic equations for an Ogive profile can
be modified to define the shape and size used by the sea glider
100. Specifically, the end conditions can be chosen so that the
shape is tangent to the fore fairing 120a and an antenna mount
162.
[0029] FIG. 4 graphically illustrates a tangent Ogive profile. The
profile of this shape is formed by a segment of a circle such that
the joint 126 is tangent to the curve of the fairing at its base;
and the base of the fairing is on the radius of the circle. The
radius of the circle that forms the Ogive is called the Ogive
Radius p and it is related to the length and base radius of the
fairing as expressed by the following formula.
.rho. = R 2 + L 2 2 R ( 1 ) ##EQU00001##
[0030] The radius y at any point x, as x varies from 0 to L is:
y= {square root over (.rho..sup.2-(L-x).sup.2)}+R-.rho. (2)
[0031] The fairing length, L, may be equal to, or less than the
Ogive Radius p. The fore and/or aft fairings 120a, 120b may define
tangent Ogive profiles. Moreover, the fore fairing 120a may define
a spherically blunted tangent Ogive.
[0032] Referring to FIG. 5, while a sea glider 10 having fairings
defining non-Ogive profiles can house a payload mass of
approximately 2 kg in water with a useable payload volume of
approximately 3,200 cm.sup.3, fairings 120a, 120b defining an Ogive
profile can accommodate a payload section 130 that can house
approximately 4 kg in water and provide a useable payload volume of
over 21,000 cm.sup.3.
[0033] Referring again to FIG. 3, to provide a relatively low
weight sea glider 100, the fairings 120a, 120b may be constructed
of fiberglass (e.g., a fiberglass composite) and have a wall
thickness T of between about 2 mm and about 12 mm. In some
examples, the fairings 120a, 120b are made of a fiberglass
composite that includes syntactic foam and fiberglass. Other
composites are possible as well, such as, but not limited to, a
composite of fiberglass, carbon fiber, and/or syntactic foam. An
overall length L.sub.All of sea glider 100 (without an antenna) may
be between about 1.8 meters and about 2.0 meters.
[0034] The sea glider 100 may include a fairing joint 126 joining
the first and second fairings 120a, 120b. The fairing joint 126 may
be configured as a straight section having a length L.sub.J of
about a 200 mm (8 inches). The straight section fairing joint 126
allows for a relatively larger payload section 130 while not having
any significant impact on drag on the sea glider 100, since a
parallel section on torpedo shaped bodies of revolution with a
length to diameter ratio of 6:1 to 11:1 have minimal effect on
total drag and cost less to manufacture than complex curves.
Approximately 75 mm (3 inches) of the straight section fairing
joint 126 may be added to the fore fairing 120a. The remaining 125
mm (5 inches) of the straight section fairing joint 126 may be
added to the aft fairing 120b.
[0035] The hatch cover(s) 170 extend to match the length extensions
for the fairings 120a, 120b, to enable full access to the flooded
payload section 130 and to increase the available space for
mounting sensors. The aft fairing 120b defines a convex shape,
rather than a typical concave shape, which allows the sea glider
100 to accommodates a relative larger payload section 130, by
significantly increases the payload volume by increasing the
flooded space. The increased volume provides greater clearance for
the bladder 140, cables, and tubing that reside in the flooded
payload section 130. It also allows for the mounting of relatively
larger sensors, GPCTD 180, echo sounders, and/or an Acoustic
Doppler Current Profiler (ADCP) inside the flooded payload section
130.
[0036] Computational Fluid Dynamics (CFD) may be used for
determining the shape and size of the fairings 120a, 120b. CFD
enables the import of various 3D CAD geometry for fairing shapes,
wings, and sensors and analysis of those components in a virtual
flow tank. Using CFD, profiles at different pitch angles and
velocities were analyzed to build up a comparison of hydrodynamic
performance. FIG. 6 illustrates an exemplary CFD analysis of the
sea glider 100. The CFD model provided direct estimates of the
drag, lift forces, and moments that act upon the vehicle during
operation. This data was used to compare and contrast different
flow shapes and profiles. In addition, the results allowed
observation of critical factors such as turbulence intensity and
boundary layer separation that are difficult to witness in
laboratory testing or detect in real world applications.
[0037] FIG. 7A illustrates the flow over sea glider fairings 120a,
120b of a sea glider 10 having a non-Ogive profile and a concave
profile for the aft fairing 120b, and gives an approximation of
where a boundary layer breaks and flow transitions from laminar to
turbulent. The colors represent the predicted degree of turbulence,
with lighter colors showing increasing levels of turbulence; darker
regions represent little to no turbulence and lighter regions are
highly turbulent flow. Similar to testing a model in a flow tank,
the virtual vehicle was held stationary and pitched at different
angles of attack to visualize the flow while calculating the
resulting forces and moments acting on the vehicle (FIG. 4). In
FIG. 7A, the boundary layer breaks around the joint 126 between the
fore and aft fairings 120a, 120b. This sets up a turbulent layer
over the back of the sea glider 10 where sensors protrude from the
hatch covers. It also creates a condition where roughly 40% of the
rudder 152 is in the turbulent wake of the sea glider 10 resulting
in decreased control authority.
[0038] FIG. 7B illustrates flow over the fairings 120a, 120b of a
sea glider 100 defining an Ogive shape. In this design, the
boundary layer separation point is moved aft by approximately 25 cm
(10 inches) with respect to the other sea glider 10 and creates a
relatively smaller turbulent region. Based on a number of analyses
run with different attack angles and flow velocities, the reduction
in total vehicle drag due to the reduced turbulence is as much as
25%. This reduction in drag may result in extended endurance for
the sea glider 100.
[0039] A combination of simulation runs can be used to determine
the hydrodynamic coefficients for lift HD_A, profile drag HD_B, and
induced drag HD_C. These coefficients may be the initial sea glider
control inputs and can be used by sea glider control algorithms for
navigation, stall angle calculations, and glide slope calculations,
each executable on the controller 105. FIG. 8 depicts a plot of the
sea glider performance model for a set of hydrodynamic coefficients
HD_A, HD_B, HD_C computed from the CFD results.
[0040] In FIG. 8, the MAX_BUOY line amidst the dark cluster of
points on the bottom of the plot represents the stall angle and the
Glide Slope line is the desired glide slope. The space between the
stall angle and glide slope defines valid operating points for
horizontal and vertical velocities depending on the desired thrust
and the maximum buoyancy of the sea glider 100. The greater the
separation between the stall angle and glider slope, the wider the
variety of options that is available to the pilot when operating
the sea glider 100 to maximize efficiency and endurance. A small
amount of asymmetry may have a significant impact on the control of
the sea glider 100.
[0041] FIG. 9 graphically illustrates parameters of a sea glider
model having valid solutions for hydrodynamic coefficients.
[0042] The sea glider 100 may use waypoint navigation by executing
a Depth Averaged Current (DAC) navigation algorithm on the
controller 105. As the sea glider 100 moves through the water
between waypoints, it is pushed by currents. As a part of its
navigation algorithms, the sea glider 100 attempts to compensate
for the currents by adjusting its target such that the currents
will push the sea glider 100 towards the desired waypoint. In some
implementations, the navigational control algorithm uses a Kalman
filter to estimate the currents. In additional implementations, the
navigation model uses depth-averaged current (DAC) calculations
specific to the hydrodynamics of the sea glider 100. This DAC
algorithm reduces the processor time required to calculate a
navigational heading and results in a power savings that can lead
to an increase in overall duration for a long-term mission.
[0043] A number of implementations have been described.
Nevertheless, it will be understood that various modifications may
be made without departing from the spirit and scope of the
disclosure. Accordingly, other implementations are within the scope
of the following claims.
* * * * *