U.S. patent application number 13/887239 was filed with the patent office on 2013-11-07 for smooth, spheroidal, appendage free underwater robot capable of 5 dof motions.
This patent application is currently assigned to Electric Power Research Institute. The applicant listed for this patent is Electric Power Research Institute. Invention is credited to Haruhiko Harry Asada, Aaron Michael Fittery, Martin Lozano, Anirban Mazumdar.
Application Number | 20130291782 13/887239 |
Document ID | / |
Family ID | 49511567 |
Filed Date | 2013-11-07 |
United States Patent
Application |
20130291782 |
Kind Code |
A1 |
Asada; Haruhiko Harry ; et
al. |
November 7, 2013 |
SMOOTH, SPHEROIDAL, APPENDAGE FREE UNDERWATER ROBOT CAPABLE OF 5
DOF MOTIONS
Abstract
An underwater robot includes a body including a first end, and a
second end, opposite the first end, and first and second actuation
units positioned inside the body. Each actuation unit includes a
pump and two valves connected to the pump. The first and second
actuation units generate jets of fluid that are discharged through
the first and second ends to propel the underwater robot, and the
first and second ends are smooth.
Inventors: |
Asada; Haruhiko Harry;
(Lincoln, MA) ; Mazumdar; Anirban; (Cambridge,
MA) ; Lozano; Martin; (Austin, TX) ; Fittery;
Aaron Michael; (Orange, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Electric Power Research Institute; |
|
|
US |
|
|
Assignee: |
Electric Power Research
Institute
Palo Alato
CA
|
Family ID: |
49511567 |
Appl. No.: |
13/887239 |
Filed: |
May 3, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61642007 |
May 3, 2012 |
|
|
|
61714290 |
Oct 16, 2012 |
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Current U.S.
Class: |
114/330 ;
114/337 |
Current CPC
Class: |
B63G 8/16 20130101; B63G
2008/004 20130101; B63G 8/08 20130101 |
Class at
Publication: |
114/330 ;
114/337 |
International
Class: |
B63G 8/16 20060101
B63G008/16; B63G 8/08 20060101 B63G008/08 |
Claims
1. An underwater robot comprising: a body comprising a first end,
and a second end, opposite the first end; and first and second
actuation units positioned inside the body, each actuation unit
comprising a pump and two valves coupled to the pump, wherein the
first and second actuation units generate jets of fluid that are
discharged through the first and second ends to propel the
underwater robot, and wherein the first and second ends are
smooth.
2. The underwater robot of claim 1 wherein each pump of the first
and second actuation units comprises: a first exit port; and a
second exit port, wherein an angle between the first and second
exit ports is 90 degrees.
3. The underwater robot of claim 1 wherein each pump of the first
and second actuation units comprises a centrifugal pump.
4. The underwater robot of claim 1 wherein each of the two valves
coupled to each pump of the first and second actuation units
comprises a Coanda effect valve.
5. The underwater robot of claim 1 wherein the first and second
ends do not include an appendage.
6. The underwater robot of claim 1 wherein the first and second
ends do not include a fin.
7. The underwater robot of claim 1 wherein a shape of the first end
is the same as a shape of the second end.
8. The underwater robot of claim 1 wherein a shape of the body
comprises a spheroid.
9. The underwater robot of claim 1 comprising: a camera positioned
inside the body.
10. A underwater robot comprising: a body having a shape of a
spheroid and comprising a first end, and a second end, opposite the
first end; a first actuation unit to propel the underwater robot,
the first actuation unit being positioned inside the body and
including: a first pump having a first outlet, and a second outlet;
a first valve coupled to the first outlet of the first pump; and a
second valve coupled to the second outlet of the first pump; and, a
second actuation unit to propel the underwater robot, the second
actuation unit being positioned inside the body and including: a
second pump having a third outlet, and a fourth outlet; a third
valve coupled to the third outlet of the second pump; and a fourth
valve coupled to the fourth outlet of the second pump, wherein an
angle between the first and second outlets of the first pump is 90
degrees, and an angle between the third and fourth outlets of the
second pump is 90 degrees.
11. The underwater robot of claim 10 wherein the first and second
ends do not include a fin.
12. The underwater robot of claim 10 wherein the first and second
ends are smooth surfaces.
13. The underwater robot of claim 10 wherein a length of the body
is about 146 millimeters and a width of the body is about 108
millimeters.
14. The underwater robot of claim 10 wherein the first and second
ends are symmetrical.
15. A method comprising: placing a robot in water, wherein the
robot comprises first and second actuation units to propel the
robot through the water, each actuation unit including a pump
having two outlets 90 degrees apart, and a valve coupled to each of
the two outlets of the pump; maneuvering the robot via at least one
of the first or second actuation units in a surge motion;
maneuvering the robot via at least one of the first or second
actuation units in a sway motion; maneuvering the robot via at
least one of the first or second actuation units in a heave motion;
maneuvering the robot via at least one of the first or second
actuation units in a pitch motion; and maneuvering the robot via at
least one of the first or second actuation units in a yaw
motion.
16. The method of claim 15 wherein the surge motion is
unaccompanied by the sway, heave, pitch, and yaw motions.
17. The method of claim 15 wherein the sway motion is unaccompanied
by the surge, heave, pitch, and yaw motions.
18. The method of claim 15 wherein the heave motion is
unaccompanied by the surge, sway, pitch, and yaw motions.
19. The method of claim 15 wherein the pitch motion is
unaccompanied by the surge, sway, heave, and yaw motions.
20. The method of claim 15 wherein the yaw motion is unaccompanied
by the surge, sway, heave, and pitch motions.
21. The method of claim 15 wherein a shape of the robot comprises a
spheroid.
22. The method of claim 15 wherein the robot does not include
external propellers.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This patent application claims priority to U.S. provisional
patent applications 61/642,007, filed May 3, 2012, and 61/714,290,
filed Oct. 16, 2012, which are all incorporated by reference along
with all other references cited in this application.
TECHNICAL FIELD
[0002] The present invention relates to the field of underwater
vehicles, including, more particularly, to underwater robots.
BACKGROUND OF THE INVENTION
[0003] To access complex underwater structures robots must be
tetherless, compact, highly maneuverable, and have a smooth body
shape with minimal appendages. These requirements are challenging
because few propulsive systems can be designed to fit into a
smooth, streamlined body. A moment referred to as the "Munk moment"
is destabilizing for elongated bodies. For example, the moment
tends to rotate them broadside to the flow.
[0004] Thus, there is a need to provide improved robotic systems
and techniques.
BRIEF SUMMARY OF THE INVENTION
[0005] A new 5 degree of freedom (DOF) underwater robot is
provided. This robot is propelled using a novel pump-valve system
and is therefore able to achieve a smooth, symmetric outside shape.
The yaw direction of the robot is stabilized using feedback
control. The pitch direction is designed to be passively stable by
placing the center of mass below the geometric center. The vehicle
therefore does not need external stabilizers and can have a smooth
outer shape. Due to its symmetry and unique design, the robot is
capable of unique motions and maneuvers such as turning in place,
sideways translation, and forward-stop-reverse motions. In
addition, due to the propulsion system being completely internal,
this robot is very quiet and creates relatively small disruptions
to the surrounding fluid.
[0006] In a specific embodiment, an underwater robot includes a
body including a first end, and a second end, opposite the first
end, and first and second actuation units positioned inside the
body, each actuation unit a pump and two valves coupled to the
pump. The first and second actuation units generate jets of fluid
that are discharged through the first and second ends to propel the
underwater robot, and the first and second ends are smooth.
[0007] In another specific embodiment, an underwater robot includes
a body having a shape of a spheroid and including a first end, and
a second end, opposite the first end, a first actuation unit to
propel the underwater robot, the first actuation unit being
positioned inside the body and including a first pump having a
first outlet, and a second outlet, a first valve coupled to the
first outlet of the first pump, and a second valve coupled to the
second outlet of the first pump; and, a second actuation unit to
propel the underwater robot, the second actuation unit being
positioned inside the body and including a second pump having a
third outlet, and a fourth outlet, a third valve coupled to the
third outlet of the second pump, and a fourth valve coupled to the
fourth outlet of the second pump. An angle between the first and
second outlets of the first pump is 90 degrees, and an angle
between the third and fourth outlets of the second pump is 90
degrees.
[0008] In a specific implementation, a method includes placing a
robot in water, where the robot includes first and second actuation
units to propel the robot through the water, each actuation unit
including a pump having two outlets 90 degrees apart, and a valve
coupled to each of the two outlets of the pump, maneuvering the
robot via at least one of the first or second actuation units in a
surge motion, maneuvering the robot via at least one of the first
or second actuation units in a sway motion, maneuvering the robot
via at least one of the first or second actuation units in a heave
motion, maneuvering the robot via at least one of the first or
second actuation units in a pitch motion, and maneuvering the robot
via at least one of the first or second actuation units in a yaw
motion.
[0009] Other objects, features, and advantages of the present
invention will become apparent upon consideration of the following
detailed description and the accompanying drawings, in which like
reference designations represent like features throughout the
figures.
BRIEF DESCRIPTION OF THE FIGURES
[0010] The patent or application file contains at least one drawing
executed in color. Copies of this patent or patent application with
color drawing(s) will be provided by the Office upon request and
payment of the necessary fee.
[0011] FIG. 1A shows a diagram of a fin stabilizing a prior art
underwater robot in a forward direction.
[0012] FIG. 1B shows a diagram of the fin destabilizing the prior
art robot in a reverse direction.
[0013] FIG. 2A shows a top view of a specific embodiment of a robot
having a smooth shape that is appendage free and capable of 5
DOF.
[0014] FIG. 2B shows an end view of the robot shown in FIG. 2A.
[0015] FIG. 2C shows a top view of another specific embodiment of a
robot.
[0016] FIG. 2D shows a bottom view of the other specific embodiment
of the robot.
[0017] FIG. 2E shows a front view of the other specific embodiment
of the robot.
[0018] FIG. 2F shows a back view of the other specific embodiment
of the robot.
[0019] FIG. 3 shows the vehicle body or robot fixed coordinate
frame.
[0020] FIG. 4 shows a CFD illustration of a 180 degree centrifugal
pump.
[0021] FIG. 5A shows a schematic of a centrifugal pump having a 90
degree configuration.
[0022] FIG. 5B shows the pump in FIG. 5A where the impeller
direction is reversed.
[0023] FIG. 5C shows a CFD illustration of the pump in FIG. 5A.
[0024] FIG. 5D shows a CFD illustration of the pump in FIG. 5B.
[0025] FIG. 6A shows a schematic of a valve.
[0026] FIG. 6B shows a CFD illustration of the valve in FIG.
6A.
[0027] FIG. 7 shows an example of a prototyped valve.
[0028] FIG. 8 shows an example of a prototyped actuation unit.
[0029] FIG. 9 shows the maneuvering architecture for the robot.
[0030] FIG. 10 shows the inside of the robot.
[0031] FIG. 11A shows a forward and reverse test of the robot.
[0032] FIG. 11B shows a sway direction translation of the
robot.
DETAILED DESCRIPTION
[0033] An underwater vehicle propulsion system is provided that
allows a smooth, symmetric underwater robot to move with 5 degrees
of freedom (DOF). Maneuvering forces and moments are provided by
using internal pumps and valves to eject fluid jets through various
exit ports. The degrees of freedom include surge, sway, heave,
pitch, and yaw. In a specific embodiment, the vehicle is entirely
symmetric and has no external appendages such as propellers or
fins. The use of an internal propulsion system allows the robot to
operate very quietly and create few disruptions to the surrounding
fluid. These robots can be used for a variety of applications
ranging from the inspection of water-filled piping structures, to
exploration of underwater infrastructure and wildlife, just to name
a few examples. In a specific embodiment, the robot is completely
or substantially smooth yet capable of stable motions in 5
translations or rotations.
[0034] In a specific embodiment, a smooth spheroidal robot is
capable of 5 degrees of freedom and has no external appendages such
as propellers or fins. In this specific embodiment, the smooth
outer shape and 5 degrees of freedom are achieved through the use
of a pump-valve architecture based on retrofitted centrifugal pumps
and fluidic valves. Angled jets are provided which enable
translations in surge, sway, and allows the system to be stabilized
through feedback control.
[0035] Developing these types of smooth, spheroidal vehicles is a
challenging task due to the fundamental fluid mechanics. Smooth,
streamlined robots are subjected to directional instability caused
by the Munk Moment. For this reason, streamlined underwater
vehicles often use fins at their rear to move their aerodynamic
center backwards and therefore make them passively stable. However,
the fins can add extra size making the robot less compact. Second,
at large angles of attack, fins can add substantial induced drag
that can inhibit the turning robot of the vehicle. Finally, while
fins in the rear of the vehicle will stabilize the vehicle in one
direction they will further destabilize the vehicle when the
direction is reversed. Therefore a robot with fins will be required
to turn around 180 degrees rather than simply being able to move in
reverse. This limits the maneuverability and omni-directional
properties of the robot. This phenomenon is illustrated with a
diagram in FIGS. 1A and 1B. FIGS. 1A and 1B show how fins can
provide stability in one direction (FIG. 1A) but instability in the
other (FIG. 1B).
[0036] The current development presented here introduces a
combination of a novel design and closed loop control that
overcomes the issue of instability and addresses the shortcomings
of previous systems. In a specific embodiment, a jet arrangement is
provided that enables the planar robot dynamics to be fully
controllable. Linear control system design techniques are used to
develop a closed loop controller capable of stabilizing the
robot.
[0037] To prove operability, a prototype of a robot was fully
built, tested, and verified to operate as intended. FIG. 2A shows a
top view of a specific embodiment of a robot 205 that was built as
a prototype. FIG. 2B shows an end view of the robot shown in FIG.
2A. This prototype may be referred to as the Omni-Egg or Omni-Egg
prototype. As shown in FIG. 2A, this specific embodiment of the
robot includes a body or housing 208 that define an interior space
210. The body includes a first end 211, a second end 215, and an
intermediate section 218. The first and second ends are opposite
each other. The intermediate section is between the first and
second ends. A length L indicates a length of the robot. A width W
indicates a width of the robot.
[0038] There are a set of openings 221 on the body. The openings
allow for the intake of a fluid, such as water, and the output of
the fluid as jets which propel the robot through the fluid. More
particularly, as shown in FIG. 2B, a first subset 225 of the
openings can be located at the first end. A second subset of the
openings can be located at the second end.
[0039] FIGS. 2C-2F show views of another specific embodiment of a
robot 250 that was built as a prototype. This robot is similar to
the robot shown in FIGS. 2A-2B, however, this robot does not
include a separate intermediate section. FIG. 2C shows a top view
of the robot. FIG. 2D shows a bottom view of the robot. FIG. 2E
shows a front or first end view of the robot. FIG. 2F shows a back
or second end view of the robot. A coordinate system 252 has been
included with the views to help indicate the orientation of the
robot. This specific embodiment includes first and second ejection
openings 255A, B (FIG. 2C), third and fourth ejection openings
255C, D (FIG. 2D), fifth and sixth ejection openings 255E, F (FIG.
2E), and seventh and eighth ejection openings 255G, H (FIG. 2F).
There is an intake opening 260 (FIG. 2D).
[0040] This example of the robot includes eight ejection openings
and one intake opening. The number of openings, however, can vary
depending on the factors such as the application of the robot,
number of pumps, number of valves, desired movements (e.g., degrees
of freedom), and so forth. For example, there can be fewer or more
than eight ejection openings. There can be more than one intake
opening. In a specific implementation, there are at least eight
ejection openings.
[0041] Actuation units can be positioned inside the body that suck
in the fluid and eject the fluid as jets through the openings. For
example, depending on the type of motion desired fluid may be
outputted through the first end, second end, or both. Further
discussion of the actuation units is provided below.
[0042] The body can further house other components of the robot
such as one or more cameras (e.g., two cameras), controller, RF
transmitter, RF receiver, antenna (e.g., for wireless operation),
power source (e.g., battery), motor, switch, storage device (e.g.,
hard drive or flash memory for recording images), sensors (e.g.,
temperature sensor, or depth sensor), lights (e.g., light emitting
diodes (LEDs)), measuring instruments, collection instruments, and
the like. The body can be designed to be watertight and may include
seals, o-rings, gaskets, and the like.
[0043] In a specific embodiment, the body is made of plastic.
Portions or sections of the body may include a transparent material
so that a camera inside the body can capture images. For example,
in a specific embodiment, the intermediate section includes a
transparent material (e.g., transparent piece of plastic) for
capturing images via the camera. Some examples of materials that
the body may be fabricated or made from include polymers, nylon,
rubber, carbon fiber, metal (e.g., steel, stainless steel, or
titanium), glass, or combinations of these.
[0044] In a specific embodiment, the length of the robot is about
146 millimeters and a width of the robot is about 108 millimeters.
The small size of the robot allows the robot to navigate through
tight spaces. The dimensions of the robot, however, can vary
greatly depending upon its application. For example, the length of
the robot may be greater or less than 146 millimeters. The width of
the robot may be greater or less than 108 millimeters.
[0045] As shown in FIG. 2A, in a specific embodiment, a shape of
the robot includes a spheroid. A spheroid is a quadric surface
obtained by rotating an ellipse about one of its principal axes; in
other words, an ellipsoid with two equal (opposing) semi-diameters.
In a specific embodiment, the shape is a prolate spheroid. A
prolate spheroid has the shape of an ellipse that is rotated about
its major axis. In this specific embodiment, the robot is
symmetrical. A shape of the first end is the same as the shape of
the second end. The shape of the first end can be a mirror image of
the shape of the second end. The ends can be dome-shaped. A shape
of a top half of the robot is the same as a shape of a bottom half
of the robot.
[0046] The symmetry of the robot shape facilitates movement of the
robot through the various directions or degrees of freedom. For
example, having the shape of the first end being the same as the
shape of the second end facilitates the robot's movement in a first
direction (e.g., forward direction) and a second direction (e.g.,
reverse direction), opposite the first direction.
[0047] In this specific embodiment, the robot does not include an
external propeller, fins, foils, stabilizing attachments, or other
appendages that may break off or snag on obstacles. For example, an
exterior surface of the robot may be smooth or substantially
smooth, continuous, or uninterrupted by an appendage.
[0048] The smooth, spheroidal robot shown in FIGS. 2A and 2B is
capable of 5 degrees of freedom and has a completely or
substantially smooth outer shape. This design was achieved by using
internal pumps which suck in water and then eject or exhaust out
pressurized jets. Fluidic valves are used to control the direction
of the pressurized jets. Based on the jet direction, the robot can
either purely translate in the "x" (surge) direction, the "y"
(sway) direction, or the "z" (heave) direction. In addition the
robot can purely rotate about either the "x" (pitch) axis or the
"z" (yaw) axis. An illustration of the coordinate frame is provided
in FIG. 3.
[0049] In other words, the surge motion may be unaccompanied or
substantially unaccompanied by the sway, heave, pitch, and yaw
motions. The sway motion may be unaccompanied or substantially
unaccompanied by the surge, heave, pitch, and yaw motions. The
heave motion may be unaccompanied or substantially unaccompanied by
the surge, sway, pitch, and yaw motions. The pitch motion may be
unaccompanied or substantially unaccompanied by the surge, sway,
heave, and yaw motions. The yaw motion may be unaccompanied or
substantially unaccompanied by the surge, sway, heave, and pitch
motions.
[0050] In a specific embodiment, an actuation unit includes a
centrifugal pump for the propulsive component. Centrifugal pumps
are advantageous because of their mechanical simplicity,
availability at centimeter (cm) size scales, and the ease of use
with electronic circuitry. However, one common issue with some
centrifugal pumps is that they are not reversible. This means that
the pump can only provide force in one direction and will need to
be combined with a second one in order to achieve bi-directional
forces. Ideally, the pump could be designed to provide forces in 2
directions 180 degrees apart. This would save substantial space and
weight. An example of this geometry is provided in FIG. 4. The pump
sucks water in through the plane of the page and then depending on
the direction of rotation of the impeller will eject water through
either Exit 1 or Exit 2. In this figure, the impeller is rotating
counterclockwise and therefore is ejecting fluid through Exit 1.
However, note that there is substantial flow out of Exit 2 as well.
This "backflow" serves to degrade the performance of the pump by
substantially reducing the output force.
[0051] Applicants have discovered that by orienting the two exit
ports adjacent to each other but 90 degrees apart, problems with
backflow can be eliminated or reduced. This outlet design may be
referred to a "90 degree retrofit." FIG. 5A shows a schematic
diagram of a pump 505 of an actuation unit. A set of coordinate
axis have been included with the figure to help indicate
orientation. The pump includes an impeller 510, a suction side 515,
a first exit (or first pressure side) 520, and a second exit (or
second pressure side) 525.
[0052] In this specific embodiment, an angle 530 between the first
exit and the second exit is about 90 degrees. That is, the angle is
a right angle. In the example shown in FIG. 5A, the impeller is
rotating in a counter-clockwise direction 535. As a result of the
counter-clockwise direction, fluid will exit through the exit 1
(520). FIG. 5B shows a schematic diagram of the pump shown in FIG.
5A. In FIG. 5B, however, the direction of the impeller is reversed
from the direction shown in FIG. 5A. That is, in FIG. 5B, a
direction 540 of the impeller is in a clockwise direction. As a
result of the clockwise direction, fluid will exit through the exit
2 (525).
[0053] Computational Fluid Dynamic (CFD) illustrations of the 90
degree retrofit are provided in FIGS. 5C and 5D. FIG. 5C shows the
CFD illustration for the pump direction shown in FIG. 5A. Note how
in this case there is no or a reduced backflow out the second exit
as compared to FIG. 4. In fact a small amount of suction occurs
which further improves the force output. This approach was verified
and shown to provide double the output force of the 180 degree
pump. FIG. 5D shows the CFD illustration for the pump direction
shown in FIG. 5B.
[0054] More particularly, in a specific embodiment, the unique
capabilities of the robot are enabled by three components:
retrofitted centrifugal pumps, use of fluidic valves to achieve
bidirectional in-line forces, and the use of angled jets to achieve
multi axis forces. Each of these three components will be discussed
in greater detail below.
[0055] In a specific embodiment, fluidic valves that achieve
bidirectional forces are provided. While the centrifugal pumps
combined with the 90 degree retrofit provide substantial forces in
2 directions, the 2 directions are 90 degrees apart rather than the
desired 180. This fact complicates vehicle design. One approach is
to use elbows to redirect the flow. Elbows, however, can cause
substantial losses. Thus, in this specific embodiment, custom
designed Coanda effect valves are provided. These valves are based
on bistable fluidic amplifiers that allow switching the direction
of a jet 180 degrees at high speeds.
[0056] FIG. 6A provides an illustration of how the Coanda effect
valve works. A jet is supplied to inlet 1610, while control ports
C1 and C2 can open to the ambient fluid or close and seal the port.
If port C1 is opened while C2 is closed the jet will exit the
nozzle, attach to the right side of the device, and exit through
exit E2 620. A CFD illustration of the fluid jet exiting exit E2 is
provided in FIG. 6B. Similarly, if C1 is closed and C2 is opened,
the jet will switch and exit through exit E1 615. Note that the
arrows associated with reference numbers 615 and 620 indicate exits
E1 and E2, respectively, rather than the direction of the fluid
output.
[0057] In a specific embodiment, Applicants have designed these
valves for the specific application of water jet propulsion.
Computational fluid dynamics (CFD) and experiments have allowed for
miniaturizing the design. In this specific embodiment, a special
switching mechanism has been designed that uses a small direct
current (DC) motor. The small DC motor is used to open and close
the control ports, and requires simple commercially available
electronics for control.
[0058] FIG. 7 shows an example of a built, tested, and verified
prototype of a valve 705 of an actuation unit. The valve includes
an inlet 710, a first exit 715, and a second exit 720. An angle
between the first and second exit is about 180 degrees.
[0059] One of these valves can be attached to each of the two exit
ports on the retrofitted pumps. This means that now a single pump
can be engineered to provide an output jet in one of two pairs of
directions or 4 directions total. This full manifestation may be
referred to as a 2DOF actuation unit. These units can serve as the
building blocks for robots, as they can be combined and rotated in
order to meet the user requirements. FIG. 8 shows an example of a
built, tested, and verified fully assembled 2DOF actuation
unit.
[0060] As shown in the example of FIG. 8, an actuation unit 805
includes a pump 810, a first valve 815, and a second valve 820. The
pump includes a first exit port 825 and a second exit port 830. An
angle between the first and second exit ports is about 90 degrees.
An inlet of the first valve is connected to the first exit port of
the pump. An inlet of the second valve is connected to the second
exit port of the pump. The valves have been mated to the pump such
that one valve is rotated 90 degrees with respect to another valve.
As a result, the exits of the valves are in different planes. For
example, as shown in FIG. 8 an exit 835 of the first valve is in a
different plane with respect to an exit 840 of the second valve.
The exit of the first valve may be in a first plane parallel to the
paper. The exit of the second valve may be in a second plane
perpendicular to the paper.
[0061] A specific embodiment provides for a 5 DOF underwater
vehicle design using pump-valve architecture and angled jets. In
this specific embodiment, this robot design incorporates two of the
actuation units. An illustration of the layout is provided in FIG.
9. Pump 1 can produce Jet 2 or Jet 4 depending on direction, and
Pump 2 can produce Jet 1 or Jet 3. Also note how Jets 1 and 2 are
angled at their outputs. This is a key innovation of the design.
This novel feature means that forces can be provided in both the
"x" and "y" directions. The Omni-Egg design is capable of 5 DOF
(surge (x), sway (y), heave (z), pitch (q), and yaw (r)). The
coordinate frame is illustrated in FIG. 3.
[0062] For example, Jet 1 is directed through a first channel 930.
The ends of the channel are angled 933A and 933B. In a specific
implementation, the angle is about 30 degrees from the x-axis. The
angle may range from about 15 degrees to about 45 degrees.
Similarly, Jet 2 is directed through a second channel 940. The
second channel may be similarly angled as the first channel. The
angle of the channels allows Jets 1 and 2 to be angled at their
outputs as shown by arrows 950A-B. Arrows 950A-B show the direction
of the fluid jets from the robot. The angled direction of the fluid
jets help to stabilize and control the movement of the robot.
[0063] During operation of the robot, the actuation units (e.g.,
pumps and valves) can be activated and deactivated to achieve the
desired movement. In a specific implementation, Pump 1 generates
one of Jet 2 or Jet 4. Pump 2 generates one of Jet 1 or Jet 3. The
opening and closing of the valve control ports associated with a
pump can be rapidly pulsed to achieve the desired movement.
[0064] Table A below provides a summary of maneuvering primatives
for how each of these DOFs can be achieved.
TABLE-US-00001 TABLE A DOF First Jet Second Jet +x +Jet 1 +Jet 2 -x
-Jet 1 -Jet 2 +z +Jet 3 +Jet 4 -z -Jet 3 -Jet 4 +q +Jet 4 -Jet 3 -q
-Jet 4 +Jet 3 +r +Jet 1 -Jet 2 -r -Jet 1 +Jet 2 +y +Jet 1 -Jet 1 -y
+Jet 2 -Jet 2
[0065] To achieve translations in the y direction, jets 1 and 2 are
angled and then the high speed nature of the Coanda effect valve is
used. By switching Jet 1 between positive and negative in a fast
but symmetric manner, pure translation in the +y direction can be
achieved because the x translations cancel out. This high speed
switching is enabled by the use of the Coanda effect valve which
has a response time that is much faster than the response time of
the vehicle. Slower valves would cause the vehicle to wobble or
oscillate. The use of the angled jets is one of the very unique
features of this robot design.
[0066] Due to the Munk moment effect described in the background
above, the yaw and pitch directions of the robot are unstable.
Traditionally, these directions are stabilized using fins placed in
the rear of the vehicle.
[0067] In a specific embodiment, stabilizing yaw is achieved
without the use of external fins. In this specific embodiment, the
use of external fins is avoided by using a combination of novel
design and feedback control. Nonlinear and linearized models for
these dynamics are provided in Appendix B. One thing to immediately
note from the state space model is the coupling between the sway
velocity "v" and the yaw angle ".phi.." This unusual coupling is a
result of the sideslip angle. Note that if the jets were not angled
to produce forces along the "y" direction, the system would be
theoretically uncontrollable.
[0068] Stabilizing the pitch direction is achieved by placing the
center of mass below the geometric center of the robot. Errors in
the pitch direction will be eventually balanced by gravitational
forces and will therefore not grow unbounded. This solution allows
the maintenance of the smooth external shape.
[0069] As discussed above, the full design has been realized and
tested. FIG. 10 shows drawing of the physical prototype components.
In addition, videos have been made of the robot performing several
unique maneuvers. Two such maneuvers are illustrated in FIGS. 11A
and 11B. FIG. 11A illustrates a "forward and reverse" test where
the robot is commanded to go straight forward and then straight in
reverse. This type of maneuver would be difficult if not impossible
for a robot that used fins to stabilize it. FIG. 11B illustrates
the "sway translation" test. Essentially the robot moves sideways.
Many robots are not capable of this motion. These figures have been
included in this patent application to highlight how the angled
jets can be used to achieve motions in both surge and sway
separately.
[0070] Some advantages of the robot include an outer surface that
is entirely or substantially smooth, being capable of 5 degrees of
freedom, and a 90 degree pump or a retrofitted pump to achieve
large forces in 2 directions using a centrifugal pump. A specific
embodiment of the robot is a robot that uses an entirely or
substantially smooth shape without external propellers or fins.
Other advantages of the robot include water jets manipulated by
valves instead of servo motors, a lack of external stabilizes, more
than 3 outlet directions for jets that provide the ability to
translate in the sway direction, discrete jets for steering rather
than vectored thrust, two pumps, angled jets, pumps with 90 degree
outlets (which provide an increase in performance over pumps with
180 degree outlets), and others.
[0071] There many commercial applications for a robot as described
in this patent application. One application includes the inspection
of large water filled piping systems such as those inside nuclear
power plants. The robot can be equipped to carry cameras that can
take pictures and video of various inaccessible areas. In addition,
water transport and sewage systems also require inspection and
could make use of this robot or aspects of the robot for some of
their larger piping systems. Further, this robot is very quiet and
highly maneuverable. Therefore it could be relevant for underwater
surveillance or other naval applications.
[0072] As discussed above, a prototype of the robot has been fully
built and tested. Appendix A includes some photos of a prototype.
FIG. A1 shows a top view of the robot. FIG. A2 shows an end view.
FIG. A3 shows a top view. FIG. A4 shows a bottom view. FIG. A5
shows a front or first end view. FIG. A6 shows a back or second end
view. FIG. A7 shows a perspective view of a valve. This view shows
an intake port of the valve. Also shown is a winged flapper piece
(shown in black) that pivots back and forth to control the opening
and closing of the valve control ports. FIG. A8 shows a top view of
the valve. A coin has been included in the photograph to show the
relative size of the valve. FIG. A9 shows an example of an
actuation unit. The actuation unit includes a pump and two valves
attached to the pump. FIG. A10 shows a diagram of the inside of the
robot. Various components of the robot are shown in color for
clarity. FIGS. A11-A12 show diagrams illustrating the direction of
the jets. A coordinate system has been shown for orientation. As
discussed above, Jets 1 and 2 are angled at their outputs (FIG.
A11).
[0073] FIG. A12 shows a photograph of the inside of the robot
prototype. FIGS. A14-A15 show the robot having been placed in a
body of liquid (e.g., water). A movement trace has been
superimposed on the photos to show the movement of the robot
through the water. FIGS. A16-A17 shows a photo of forward and
backward trajectory and an accompanying time graph. FIGS. A18-A19
shows another photo of movement accompanying time graph. FIGS.
A20-A21 shows another photo of movement accompanying time graph.
FIGS. A22-A23 shows another photo of movement accompanying time
graph.
[0074] In a specific implementation, a submersible mini-robot is
provided that targets inspection of nuclear reactor internals and
other critical components. The robot is designed to function
wirelessly and without tethers, and has the ability to move in all
directions to access difficult locations. Remote-operated vehicles
developed for marine applications have proven successful for the
visual inspection of submerged components in nuclear reactor
vessels and spent fuel pools, but commercially available
technologies have several limitations. The robot, as provided in
this patent application represents a step-change improvement in the
nuclear power industry's underwater inspection capabilities.
[0075] The robot is designed to allow safe, reliable, and
non-intrusive operation while providing high-fidelity visual
inspection across a broad range of components, configurations, and
locations. A prototype robot has been built and tested. This robot
features a compact and appendage-free design, a high degree of
maneuverability, and wireless operation. In this specific
embodiment, its ovoid form measures about 4 inches by 6 inches,
allowing it to nestle comfortably in the palm of a hand. Its
innovative propulsion and navigation system applies centrifugal
pumps, high-speed valves, and maneuvering jets for precisely
controlled motion.
[0076] The robot's shape and umbilical-free operation allow for
successful in-plant applications. Many existing technologies employ
propellers, rudders, and other appendages and attachments that
limit access to some component locations and preclude certain types
of motion. These appendages also may break off during collisions or
snag on obstacles, creating the potential for contamination of
carefully controlled reactor environments or other operational
issues. The robot as provided in this patent application has
demonstrated the ability to navigate through intricate and tight
geometries and to conduct inspection-type passes over surfaces.
[0077] For example, under joystick control, it can dive and rise,
turn in place, and move forward, backward, and sideways. The robot
is capable of carrying cameras and includes a wireless
communications system. In a specific embodiment, the payload
includes two cameras. The first camera supports real-time
navigation and visual examination by the robot operator, and the
second camera captures higher-resolution imaging data for
subsequent inspection, nondestructive evaluation, and asset
management applications.
[0078] Improving wireless communications for submersed usage poses
challenges. Water attenuates most frequencies, and systems and
components pose complex configurations. Features of the robot
combine optical communication capable of high data rates at a
distance with radio communication capable of two-way data exchange
when line of sight is lost between the mini-robot and its
controller.
[0079] In the description above and throughout, numerous specific
details are set forth in order to provide a thorough understanding
of an embodiment of this disclosure. It will be evident, however,
to one of ordinary skill in the art, that an embodiment may be
practiced without these specific details. In other instances,
well-known structures and devices are shown in block diagram form
to facilitate explanation. The description of the preferred
embodiments is not intended to limit the scope of the claims
appended hereto. Further, in the methods disclosed herein, various
steps are disclosed illustrating some of the functions of an
embodiment. These steps are merely examples, and are not meant to
be limiting in any way. Other steps and functions may be
contemplated without departing from this disclosure or the scope of
an embodiment.
* * * * *