U.S. patent application number 17/570090 was filed with the patent office on 2022-08-11 for wing-in-ground effect vehicle.
The applicant listed for this patent is REGENT Craft Inc.. Invention is credited to Christian Bailey, William Bryan Baker, Daniel Cottrell, Michael Klinker, Edward Lester, William Thalheimer.
Application Number | 20220250743 17/570090 |
Document ID | / |
Family ID | |
Filed Date | 2022-08-11 |
United States Patent
Application |
20220250743 |
Kind Code |
A1 |
Thalheimer; William ; et
al. |
August 11, 2022 |
Wing-In-Ground Effect Vehicle
Abstract
An example wing-in-ground effect vehicle includes (i) a main
wing having main wing control surfaces; (ii) a tail having tail
control surfaces; (iii) a blown-wing propulsion system arranged
along the main wing or the tail; (iv) a retractable hydrofoil
configured to operate in: (a) an extended configuration in which
the retractable hydrofoil extends below a hull of the vehicle for
submersion below a water surface and (b) a retracted configuration
in which the retractable hydrofoil is retracted at least partially
into the hull of the vehicle; and (v) a control system configured
to maneuver the vehicle by (i) causing a change in orientation of
the retractable hydrofoil when the retractable hydrofoil is
operating in the extended configuration, and (ii) causing a change
in orientation of the main wing control surfaces and tail control
surfaces when the retractable hydrofoil is operating in the
retracted configuration.
Inventors: |
Thalheimer; William;
(Waltham, MA) ; Klinker; Michael; (Hollis, NH)
; Baker; William Bryan; (Cohasset, MA) ; Lester;
Edward; (Somerville, MA) ; Cottrell; Daniel;
(Centreville, VA) ; Bailey; Christian; (Palo Alto,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
REGENT Craft Inc. |
Burlington |
MA |
US |
|
|
Appl. No.: |
17/570090 |
Filed: |
January 6, 2022 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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63281594 |
Nov 19, 2021 |
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63148565 |
Feb 11, 2021 |
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International
Class: |
B64C 35/00 20060101
B64C035/00; B63B 1/30 20060101 B63B001/30 |
Claims
1. A wing-in-ground effect vehicle comprising: a main wing
comprising one or more main wing control surfaces; a tail
comprising one or more tail control surfaces; a blown-wing
propulsion system comprising an array of electric motors arranged
along at least one of the main wing or the tail; a retractable
hydrofoil system comprising a retractable hydrofoil, wherein the
retractable hydrofoil system is configured to operate in: (i) an
extended configuration in which the retractable hydrofoil extends
below a hull of the wing-in-ground effect vehicle for submersion
below a water surface and (ii) a retracted configuration in which
the retractable hydrofoil is retracted at least partially into the
hull of the wing-in-ground effect vehicle; and a control system
configured to (i) determine a position, orientation, and velocity
of the wing-in-ground effect vehicle and (ii) maneuver the
wing-in-ground effect vehicle based on the determined position,
orientation, and velocity, wherein maneuvering the wing-in-ground
effect vehicle comprises (i) causing one or more actuators of the
retractable hydrofoil system to change an orientation of the
retractable hydrofoil when the retractable hydrofoil system is
operating in the extended configuration, (ii) causing one or more
actuators of the main wing and the tail to change an orientation of
the main wing control surfaces and tail control surfaces when the
retractable hydrofoil system is operating in the retracted
configuration and (iii) causing one or more of the electric motors
of the blown-wing propulsion system to change speed.
2. The wing-in-ground effect vehicle of claim 1, wherein the
wing-in-ground effect vehicle is capable of sustained operation in
each of the following operational modes: a hull-borne mode in which
the hull of the vehicle contacts the water surface; a
hydrofoil-borne mode in which the retractable hydrofoil is at least
partially submerged below the water surface and the hull of the
vehicle is entirely above the water surface; and a wing-borne mode
in which the wing-in-ground effect vehicle is entirely above the
water surface.
3. The wing-in-ground effect vehicle of claim 2, wherein the
control system is further configured to: while the wing-in-ground
effect vehicle is operating in the hull-borne mode, (i) cause the
retractable hydrofoil system to transition from operating in the
retracted configuration to operating in the extended configuration,
and (ii) cause the blown-wing propulsion system to accelerate the
wing-in-ground effect vehicle until the wing-in-ground effect
vehicle transitions from operating in the hull-borne mode to
operating in the hydrofoil-borne mode.
4. The wing-in-ground effect vehicle of claim 2, wherein the
control system is further configured to: determine that the
wing-in-ground effect vehicle has transitioned from operating in
the hydrofoil-borne mode to operating in the wing-borne mode; and
based on determining that the wing-in-ground effect vehicle has
transitioned from operating in the hydrofoil-borne mode to
operating in the wing-borne mode, cause the retractable hydrofoil
system to transition from operating in the extended configuration
to operating in the retracted configuration.
5. The wing-in-ground effect vehicle of claim 2, wherein the
control system is further configured to: determine that the
wing-in-ground effect vehicle has transitioned from operating in
the wing-borne mode to operating in the hull-borne mode; and based
on determining that the wing-in-ground effect vehicle has
transitioned from operating in the wing-borne mode to operating in
the hull-borne mode, cause the retractable hydrofoil system to
transition from operating in the retracted configuration to
operating in the extended configuration.
6. The wing-in-ground effect vehicle of claim 2, wherein the
retractable hydrofoil system is a first retractable hydrofoil
system, the retractable hydrofoil is a first retractable hydrofoil,
the extended configuration is a first extended configuration, and
the retracted configuration is a first retracted configuration, and
wherein the wing-in-ground effect vehicle further comprises: a
second retractable hydrofoil system comprising a second retractable
hydrofoil, wherein the second retractable hydrofoil system is
configured to operate in: (i) a second extended configuration in
which the second retractable hydrofoil extends below the hull of
the wing-in-ground effect vehicle for submersion below the water
surface and (ii) a second retracted configuration in which the
second retractable hydrofoil is retracted at least partially into
or toward the hull of the wing-in-ground effect vehicle.
7. The wing-in-ground effect vehicle of claim 6, wherein the
control system is further configured to: while the wing-in-ground
effect vehicle is operating in the hull-borne mode, (i) cause the
first retractable hydrofoil system to transition from operating in
the first retracted configuration to operating in the first
extended configuration, (ii) cause the second retractable hydrofoil
system to transition from operating in the second retracted
configuration to operating in the second extended configuration,
and (iii) cause the blown-wing propulsion system to accelerate the
wing-in-ground effect vehicle until the wing-in-ground effect
vehicle transitions from operating in the hull-borne mode to
operating in the hydrofoil-borne mode.
8. The wing-in-ground effect vehicle of claim 6, wherein the
control system is further configured to: determine that the
wing-in-ground effect vehicle has transitioned from operating in
the hydrofoil-borne mode to operating in the wing-borne mode; and
based on determining that the wing-in-ground effect vehicle has
transitioned from operating in the hydrofoil-borne mode to
operating in the wing-borne mode, (i) cause the first retractable
hydrofoil system to transition from operating in the first extended
configuration to operating in the first retracted configuration and
(ii) cause the second retractable hydrofoil system to transition
from operating in the second extended configuration to operating in
the second retracted configuration.
9. The wing-in-ground effect vehicle of claim 6, wherein the
control system is further configured to: determine that the
wing-in-ground effect vehicle has transitioned from operating in
the wing-borne mode to operating in the hull-borne mode; and based
on determining that the wing-in-ground effect vehicle has
transitioned from operating in the wing-borne mode to operating in
the hull-borne mode, (i) cause the first retractable hydrofoil
system to transition from operating in the first retracted
configuration to operating in the first extended configuration and
(ii) cause the second retractable hydrofoil system to transition
from operating in the second retracted configuration to operating
in the second extended configuration.
10. The wing-in-ground effect vehicle of claim 6, wherein: the
first retractable hydrofoil system is positioned between (i) a bow
of the wing-in-ground effect vehicle and (ii) a midpoint between
the bow and a stern of the wing-in-ground-effect vehicle; and the
second retractable hydrofoil system is positioned below the tail of
the wing-in-ground effect vehicle.
11. The wing-in-ground effect vehicle of claim 10, wherein the tail
further comprises a rudder, and wherein, when the second
retractable hydrofoil system is operating in the second retracted
configuration, the second retractable hydrofoil is retracted at
least partially into the rudder.
12. The wing-in-ground effect vehicle of claim 1, wherein an aspect
ratio of the main wing is greater than or equal to five.
13. The wing-in-ground effect vehicle of claim 1, wherein causing
one or more actuators of the retractable hydrofoil system to change
the orientation of the retractable hydrofoil when the retractable
hydrofoil system is operating in the extended configuration
comprises causing one or more actuators of the retractable
hydrofoil system to change an angle of attack of the retractable
hydrofoil when the retractable hydrofoil system is operating in the
extended configuration.
14. The wing-in-ground effect vehicle of claim 1, wherein the
retractable hydrofoil includes one or more hydrofoil control
surfaces, and wherein the control system is further configured to
cause one or more actuators of the retractable hydrofoil system to
change an orientation of the one or more hydrofoil control surfaces
when the retractable hydrofoil system is operating in the extended
configuration.
15. The wing-in-ground effect vehicle of claim 14, wherein the one
or more hydrofoil control surfaces include at least one of a
hydrodynamic elevator, a hydrodynamic flap, or a hydrodynamic
rudder.
16. The wing-in-ground effect vehicle of claim 1, wherein: the
retractable hydrofoil comprises a foil and at least one strut
coupling the foil to the hull of the wing-in-ground effect vehicle,
and when the retractable hydrofoil system is operating in the
retracted configuration, the at least one strut is at least
partially retracted into the hull of the wing-in-ground effect
vehicle.
17. The wing-in-ground effect vehicle of claim 16, wherein the foil
comprises: a horizontal center portion; and two end portions
extending diagonally upward from respective ends of the horizontal
center portion.
18. The wing-in-ground effect vehicle of claim 1, wherein the
control system is further configured to: determine a location of an
obstacle based on data received from at least one sensor of the
wing-in-ground effect vehicle, wherein maneuvering the
wing-in-ground effect vehicle comprises maneuvering the
wing-in-ground effect vehicle based on both (i) the determined
position, orientation, and velocity of the wing-in-ground effect
vehicle and (ii) the determined location of the obstacle.
19. A control system for controlling a wing-in-ground effect
vehicle that includes (i) a main wing comprising one or more main
wing control surfaces, (ii) a tail comprising one or more tail
control surfaces, (iii) a blown-wing propulsion system comprising
an array of electric motors arranged along at least one of the main
wing or the tail, and (iv) a retractable hydrofoil system
comprising a retractable hydrofoil, the control system comprising:
at least one processor; non-transitory computer-readable medium;
and program instructions stored on the non-transitory
computer-readable medium that are executable by the at least one
processor such that the control system is configured to: cause the
retractable hydrofoil system to operate in an extended
configuration in which the retractable hydrofoil extends below a
hull of the wing-in-ground effect vehicle for submersion below a
water surface; while the retractable hydrofoil system is in the
extended configuration, (i) determine a first position,
orientation, and velocity of the wing-in-ground effect vehicle and
(ii) based on the determined first position, orientation, and
velocity of the wing-in-ground effect vehicle, maneuver the
wing-in-ground effect vehicle by causing one or more actuators of
the retractable hydrofoil system to change an orientation of the
retractable hydrofoil; cause the retractable hydrofoil system to
operate in a retracted configuration in which the retractable
hydrofoil is retracted at least partially into the hull of the
wing-in-ground effect vehicle; and while the retractable hydrofoil
system is in the retracted configuration, (i) determine a second
position, orientation, and velocity of the wing-in-ground effect
vehicle and (ii) based on the determined second position,
orientation, and velocity of the wing-in-ground effect vehicle,
maneuver the wing-in-ground effect vehicle by causing one or more
actuators of the main wing and the tail to change an orientation of
the main wing control surfaces and tail control surfaces.
20. A method for controlling a wing-in-ground effect vehicle that
includes (i) a main wing comprising one or more main wing control
surfaces, (ii) a tail comprising one or more tail control surfaces,
(iii) a blown-wing propulsion system comprising an array of
electric motors arranged along at least one of the main wing or the
tail, and (iv) a retractable hydrofoil system comprising a
retractable hydrofoil, the method comprising: causing the
retractable hydrofoil system to operate in an extended
configuration in which the retractable hydrofoil extends below a
hull of the wing-in-ground effect vehicle for submersion below a
water surface; while the retractable hydrofoil system is in the
extended configuration, (i) determining a first position,
orientation, and velocity of the wing-in-ground effect vehicle and
(ii) based on the determined first position, orientation, and
velocity of the wing-in-ground effect vehicle, maneuver the
wing-in-ground effect vehicle by causing one or more actuators of
the retractable hydrofoil system to change an orientation of the
retractable hydrofoil; causing the retractable hydrofoil system to
operate in a retracted configuration in which the retractable
hydrofoil is retracted at least partially into the hull of the
wing-in-ground effect vehicle; and while the retractable hydrofoil
system is in the retracted configuration, (i) determining a second
position, orientation, and velocity of the wing-in-ground effect
vehicle and (ii) based on the determined second position,
orientation, and velocity of the wing-in-ground effect vehicle,
maneuver the wing-in-ground effect vehicle by causing one or more
actuators of the main wing and the tail to change an orientation of
the main wing control surfaces and tail control surfaces.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of priority under 35
U.S.C. .sctn. 119 to U.S. Provisional Patent App. No. 63/148,565,
filed on Feb. 11, 2021, and U.S. Provisional Patent App. No.
63/281,594, filed on Nov. 19, 2021, each of which is incorporated
herein by reference in its entirety.
FIELD OF THE DISCLOSURE
[0002] This disclosure is related to wing-in-ground effect vehicles
(WIGs) and, more particularly, to systems and methods directed
toward WIGs designed to operate for significant distances in water
before takeoff and after landing.
BACKGROUND
[0003] WIGs can include a propulsion source and an aerodynamic
surface which is designed to operate close to the ground or water
surface in aerodynamic ground-effect. The primary reason for
operation in aerodynamic ground-effect is the increase in flight
efficiency resulting from the decrease in the induced drag of the
wing.
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] Features, aspects, and advantages of the presently disclosed
technology may be better understood with regard to the following
description, appended claims, and accompanying drawings where:
[0005] FIG. 1A depicts a perspective view of an example WIG,
according to an example embodiment;
[0006] FIG. 1B depicts a top view of an example WIG;
[0007] FIG. 1C depicts a side view of the example WIG;
[0008] FIG. 1D depicts a front view of the example WIG;
[0009] FIG. 2 depicts a battery system of the example WIG;
[0010] FIG. 3 depicts a main hydrofoil deployment system of the
example WIG;
[0011] FIG. 4A depicts a rear hydrofoil deployment system of the
example WIG;
[0012] FIG. 4B depicts the rear hydrofoil deployment system of the
example WIG;
[0013] FIG. 5 depicts a control system of the example WIG; and
[0014] FIG. 6 depicts various operational modes of the example
WIG.
[0015] The drawings are for the purpose of illustrating example
embodiments, and it is to be understood that the present disclosure
is not limited to the arrangements and instrumentalities shown in
the drawings.
DETAILED DESCRIPTION
I. Overview
[0016] The example WIGs described herein include features designed
to create a more comfortable passenger experience and wider
environmental operating range compared to existing WIGs. Advantages
may include, but are not limited to, more comfortable takeoff and
landing maneuvers, a smaller turning radius, a higher cruise
efficiency, increased flight stability and safety, decreased
operating costs, and the ability to operate comfortably in high
seas and at low speeds in crowded harbors. The WIGs described
herein are designed to fly over bodies of water and can therefore
be used for transporting people and/or cargo between coastal
destinations or between shore and offshore infrastructure. The WIGs
can emit zero emissions during operation by utilizing an
all-electric drivetrain that sources energy from a battery or
hydrogen fuel cell system.
[0017] The WIGs described herein are configured to operate in at
least three different operational modes including a first
waterborne mode in which the hull of the WIG is at least partially
submerged in water, a second waterborne mode in which the hull of
the WIG is elevated above the water while one or more hydrofoils of
the WIG are at least partially submerged in water, and an airborne
mode in which the entire WIG is elevated above the water in
ground-effect flight. Unlike existing vehicles, the WIGs described
herein may operate in each of these three modes over extended
distances and times.
[0018] In order to provide such improvements over existing
vehicles, the WIGs described herein can combine multiple different
technologies including (i) an electric powertrain in a distributed
blown-wing configuration, (ii) a retractable hydrofoil system,
(iii) digital flight control systems for stabilizing the WIG and
controlling an altitude of the WIG near a water surface, and (iv)
control systems for detecting and avoiding maritime traffic and
obstacles. These technologies are explained in further detail
below.
II. Example Wing-In-Ground Effect Vehicles
[0019] FIGS. 1A-1D depict different views of an example WIG 100,
including a perspective view in FIG. 1A, a top view in FIG. 1B, a
side view in FIG. 1C, and a front view in FIG. 1D. As shown in
these various views, the WIG 100 includes a hull 102, a main wing
104, a tail 106, a main hydrofoil assembly 108, and a rear
hydrofoil assembly 110.
[0020] A. Hull
[0021] In line with the discussion above and as further described
below, the WIG 100 is capable of operating in a first waterborne
mode for extended periods of time, during which the hull 102 is at
least partially submerged in water. As such, the hull 102 may be
designed to be watertight, particularly for surfaces of the hull
that contact the water during this first waterborne operational
mode. Further, the hull 102, as well as the entirety of the WIG
100, is configured to be passively stable on all axes when floating
in water. To help achieve this, the hull 102 may include a keel (or
centerline) 112 which may provide improved stability and other
benefits described below. And in some examples, the WIG 100 may
include various mechanisms for adjusting the center of mass of the
WIG 100 so that the center of mass aligns with the center of
buoyancy of the WIG 100. One way to achieve this is to couple a
battery system (described in further detail below in connection
with FIG. 2) of the WIG 100 to one or more moveable mounts that may
be moved by one or more servo motors or the like. A control system
of the WIG 100 may detect a change in its center of buoyancy, for
instance by detecting a rotational change via an onboard gyroscope,
and the control system may responsively operate the servo motors to
move the battery system until the gyroscope indicates that the WIG
100 has stabilized. Another way to adjust the center of mass of the
WIG 100 so that the center of mass aligns with the center of
buoyancy of the WIG 100 is to include a ballast system for pumping
water or air to various tanks distributed throughout the hull 102
of the WIG 100, which may allow for adjusting the center of mass of
the WIG 100 in a similar manner as moving the battery system. Other
example systems may be used to control the center of mass of the
WIG 100 as well.
[0022] Additionally, the hull 102 may be designed to reduce drag
forces when both waterborne and airborne. For instance, the hull
102 may have a high length-to-beam ratio (e.g., greater than or
equal to 8), which may help reduce hydrostatic drag forces when the
WIG 100 is under forward waterborne motion. In some examples, the
keel 112 may be curved or rockered to improve maneuverability when
waterborne. Further, the hull 102 may be designed to pierce the
surface of waves (e.g., to increase passenger and crew comfort) by
including a narrow, low-buoyancy bow portion of the hull 102.
[0023] B. Wing and Distributed Propulsion System
[0024] The main wing 104 may also include features to improve
stability of the WIG 100 during waterborne operation. For instance,
as shown in FIGS. 1A-1D, the main wing 104 may include an outrigger
114 at each end of the main wing 104. The outriggers 114 (which are
sometimes referred to as "wing-tip pontoons") are configured to
provide a buoyant force to the main wing 104 when submerged or when
otherwise in contact with the water. As depicted in the front view
of the WIG 100 in FIG. 1D, the main wing 104 may be designed to
have a gull wing shape such that the outriggers 114 at the ends of
the main wing 104 are at the lowest point of the main wing 104 and
are positioned approximately level with (or slightly above) a
waterline of the hull 102 when the hull 102 is waterborne.
[0025] As best shown in the top view of the WIG 100 in FIG. 1B, the
main wing 104 is designed to have a high aspect ratio, which
represents the ratio of the span of the main wing 104 to the mean
chord of the main wing 104. In some examples, the aspect ratio of
the main wing 104 is greater than or equal to five, or greater than
or equal to six, but other example aspect ratios are possible as
well.
[0026] High aspect ratio wings may provide certain drawbacks when
compared to low aspect ratio wings, including reduced pitch
stability due to a shorter mean chord. Previous WIGs have opted for
low aspect ratio wings to address these instability issues. For
instance, when a WIG is flying in ground-effect, there is an
increase in static pressure underneath the wings, which shifts the
aerodynamic center of the WIG backward and causes aerodynamic
instability in the WIG's pitch axis. Low aspect ratio wings focus
the lift force on the leading edge of the wing, and when the WIG
pitches upward the leading edge also pitches upward, causing the
WIG to leave ground-effect, lose lift, and settle back down.
However, while this low aspect ratio wing design addressed
instability issues, it significantly reduced the aerodynamic
efficiency of these previous WIG designs.
[0027] Another drawback of high aspect ratio wings, generally, is
their reduced maneuverability due to a lower roll angular
acceleration. And the maneuverability of high aspect ratio wings
may be further reduced for WIGs. For instance, when operating in a
ground-effect flight mode over a water surface, a WIG with a high
aspect ratio wing may be close enough to the water surface that too
much roll could cause the wing to collide with the water surface.
To address these and other issues, the WIG 100 disclosed herein may
include various additional mechanisms, as described in further
detail below, for improving its maneuverability to compensate for
the reduced maneuverability resulting from the high aspect ratio of
the main wing 104.
[0028] While high aspect ratio wings may provide various drawbacks,
such as those identified above, high aspect ratio wings may also
provide a number of improvements over low aspect ratio wings,
including increased roll stability and increased efficiency
resulting from higher lift-to-drag ratios. Further, another benefit
of a high aspect ratio wing is that it provides a longer leading
edge for mounting a distributed propulsion system along the wing.
Arranging propulsion systems in this distributed manner along the
wing provides a "blown-wing" propulsion system in which the
propulsion systems can increase the velocity of air moving over the
wing, and the increased air velocity over the main wing increases
the lift generated by the main wing. This increase in lift can
enable the WIG to takeoff and become airborne at slower speeds,
which can be especially advantageous for takeoff of waterborne
WIGs. For instance, waterborne WIGs may be subjected to various
forces that limit their takeoff speed, such as water resistance and
reduced lift caused by cavitation when operating on one or more
hydrofoils, as explained in further detail below.
[0029] Previous WIG designs have typically incorporated low aspect
ratio wing designs, such as inverse-delta wing designs. Such low
aspect ratio wings have been used to increase the pitch stability
of the WIG when flying in ground effect. In connection with low
aspect ratio wings, previous WIG designs have also incorporated
various ram-air methods that involve using the primary propulsion
system to push air under the WIG between the wing and the water
surface to artificially create additional lift.
[0030] Unlike previous designs that have used ram-air methods to
assist with takeoff, the WIG 100 disclosed herein incorporates a
distributed blown-wing propulsion system that assists with takeoff
by allowing for slower takeoff speeds. As shown in FIGS. 1A-1D, the
main wing 104 includes a number of electric motor propeller
assemblies 116 distributed across a leading edge of the main wing
104. Arranging the propeller assemblies 116 in this manner can
increase the velocity of air moving over the main wing 104, and the
increased air velocity over the main wing 104 increases the lift
generated by the main wing 104. This increase in lift can enable
the WIG 100 to take off and become airborne at slower vehicle
speeds.
[0031] The distributed blown-wing arrangement of the electric motor
propeller assemblies 116 improves upon arrangements in existing
WIGs, which have relied on one or more liquid-fueled engines as the
primary propulsion source during operation. Liquid-fueled engines
are typically much heavier, more complex, and larger than electric
motors, so any benefits of additional lift provided by a
distributed blown-wing arrangement of liquid-fueled engines may be
outweighed by the additional weight and complexity of multiple
engines. Further, coupling an array of propellers to the
liquid-fueled engines may require multiple rotating shafts and
gearboxes, thereby increasing the mechanical complexity and
resultant maintenance costs to the point of unfeasibility. Using
the electric motor propeller assemblies 116, however, alleviates
such issues. Each individual electric motor propeller assembly 116
can be controlled by an electronic speed controller and powered by
an onboard battery system, such as, for example, a lithium-ion,
magnesium-ion, or lithium-sulfur system, or by some other onboard
electrical supply system, such as a fuel cell or a centralized
liquid-fueled electricity generator. In some examples, the onboard
electrical supply system may include multiple systems for supplying
power during different operational modes, such as a first battery
system configured to deliver large amounts of power during takeoff
and a second system with a higher energy density but lower peak
power capability for delivering sustained lower power during cruise
operation (e.g., during hydrofoil waterborne operation or during
airborne operation, each of which are described in further detail
below).
[0032] An example onboard battery system 200 is depicted in FIG. 2.
As shown, the battery system 200 may be arranged in a protected
area 202 of the hull 102 below a passenger seating area 204. The
battery system 200 may be separated from the passenger seating area
204 by a firewall 206 to protect the passengers from harm if a
thermal runaway occurs. In some examples, additional or alternative
protective measures may be taken as well. For instance, the WIG 100
may include one or more mechanisms for flooding the battery system
200 upon detecting a thermal runaway or a fire in the protected
area 202. In order to flood the battery system 200, the WIG 100 may
include a battery management system comprising voltage and/or
thermal sensors for detecting thermal runaway or some other fire
detection system for detecting a fire in the protected area 202.
Further, the hull 102 may include one or more valves or other
controllable openings in the hull 102. Responsive to detecting a
fire in the protected area 202 or thermal runaway in the battery
system 200, a control system of the WIG 100 may open the valves or
other controllable openings in the hull 102 to expose the protected
area 202 and the battery system 200 to the water in which the WIG
is floating.
[0033] A water-based flooding system as described above would only
work while the WIG 100 is waterborne, so other measures may be
taken to account for fires or thermal runaway during airborne
operation. As one example, any controllable openings in the hull
102 may be configured to be large enough to jettison the battery
system 200 out of the hull 102 through the openings. The battery
system 200 may be configured such that the weight of the battery
system 200 provides sufficient force to jettison the battery system
200 out of the hull 102 when the hull 102 is opened, or the WIG 100
may include an actuator or some other mechanism to jettison the
battery system 200 out of the hull 102. As another example, the WIG
100 may include an inert gas fire suppression system for reducing
the amount of oxygen in the protected area 202 and suppressing any
fires in response to detecting a fire in the protected area 202 or
thermal runaway in the battery system 200. Other examples are
possible as well.
[0034] In other examples, the WIG 100 may take measures to become
waterborne in response to detecting a fire in the protected area
202 or thermal runaway in the battery system 200. For instance,
responsive to making such a detection, the control system of the
WIG 100 may determine an operational state of the WIG 100,
including whether the WIG 100 is operating in a hull-borne mode, a
hydrofoil-borne mode, or a wing-borne mode (each of which are
described in further detail below). In response to determining that
the WIG 100 is operating in a hull-borne mode, the control system
may flood the battery system 200 upon detecting a thermal runaway
or a fire in the protected area 202 as described above. If,
however, the control system determines that the WIG 100 is
operating in a hydrofoil-borne mode or a wing-borne mode, the
control system may cause the WIG 100 to transition to the
hull-borne mode upon detecting a thermal runaway or a fire in the
protected area 202 and then flood the battery system 200.
Techniques for transitioning between operational modes are
described in further detail below in connection with FIG. 6.
[0035] The positioning of the electric motor propeller assemblies
116 along the leading edge of the main wing 104 may be determined
based on a variety of factors including, but not limited to, (i)
the required total thrust for all modes of operation of the WIG
100, (ii) the thrust generated by each individual propeller
assembly 116, (iii) the radius of each propeller in the respective
propeller assemblies 116, (iv) the required tip clearance between
each propeller and the surface of the water, and (v) the additional
freestream velocity over the main wing 104 required for operation.
As shown in FIGS. 1A-1D, the number of propeller assemblies 116 is
symmetrical across both sides of the hull 102. The propeller
assemblies 116 may all be identical, or they may have different
propeller radii or blade configurations along the span so long as
the configuration is symmetrical across the hull 102. One advantage
for having different propeller assembly 116 radii is allowing
adequate propeller tip clearance from the water or vehicle
structure. An advantage of having different blade configurations on
the propeller assemblies 116 is to allow some propellers to be
optimized for different operational conditions, such as airborne
cruise. The propeller placement and configuration may vary to
increase the airflow over the main wing 104 or tail system 106 to
improve controllability or stability. While FIGS. 1A-1D depict an
example WIG 100 having eight total propeller assemblies 116, the
actual number of propeller assemblies 116 can vary based on the
requirements of the WIG 100.
[0036] In some examples, the respective propeller assemblies 116
may have different pitch settings or variable pitch capabilities
based on their position on the main wing 104. For instance, a
subset of the propeller assemblies 116 may have fixed-pitch
propellers sized for cruise speeds, while the remainder of the
propeller assemblies 116 can have fixed-pitch propellers configured
for takeoff, or can allow for varying of the propeller's pitch.
Additionally, different propeller assemblies 116 may be turned off
or have reduced rotational speeds during different modes of
operation. For instance, during waterborne operation, one or more
of the propeller assemblies 116 may be turned off or have reduced
rotational speeds in a manner that generates asymmetrical thrust.
This may create a yawing moment on the WIG 100, allowing the WIG
100 to turn without large bank angles and increasing the turning
maneuverability of the WIG 100. For instance, in order to yaw
right, the WIG 100 may increase the rotational speeds of the
propellers of one or more of propeller assemblies 116e-h while
decreasing the rotational speeds of the propellers of one or more
of propeller assemblies 116a-d. Similarly, in order to yaw left,
the WIG 100 may increase the rotational speeds of the propellers of
one or more of propeller assemblies 116a-d while decreasing the
rotational speeds of the propellers of one or more of propeller
assemblies 116e-h.
[0037] The main wing 104 may further include one or more
aerodynamic control surfaces, such as flaps 118 and ailerons 120,
which may comprise movable hinged surfaces on the trailing or
leading edges of the main wing 104 for changing the aerodynamic
shape of the main wing 104. The flaps 118 may be configured to
extend downward below the main wing 104 in order to reduce stall
speed and create additional lift at low airspeeds, while the
ailerons 120 may be configured to extend upward above the main wing
104 in order to decrease lift on one side of the main wing 104 and
induce a roll moment in the WIG 100. In some examples, the ailerons
120 may be additionally configured to extend downward below the
main wing 104 in a flaperon configuration to help the flaps 118
generate additional lift on the main wing 104, which may be used to
either create a rolling moment or additional balanced lift
depending on coordinated movement of both ailerons. The flaps 118
and ailerons 120 may each include one or more actuators for raising
and lowering the flaps 118 and ailerons 120. The flaps 118 may
include, for example, one or more of plain flaps, split flaps,
slotted flaps, Fowler flaps, slotted Fowler flaps, Gouge flaps,
Junkers flaps, or Zap flaps. Further, the flaps 118 (and the
ailerons 120 when configured as flaperons) should be positioned so
that they are in the wake of one or more of the propeller
assemblies 116. The ailerons 120 may be positioned so that they are
in the wake of one or more of the propeller assemblies 116 in order
to increase the effectiveness of the ailerons at low forward
velocities. Some of the propeller assemblies 116 may be positioned
so that no ailerons 120 are in their wake to increase thrust on the
outboard wing during a turn without inducing adverse yaw. For
example, in a left turn, a normal airplane would have adverse yaw
to the right as the right aileron is deflected down, increasing
drag. In the present disclosure, however, the right propeller
assembly outboard of the right aileron may have its thrust
increased relative to the respective left propeller assembly,
initiating a turn without adverse yaw.
[0038] C. Tail System
[0039] The tail 106 includes a vertical stabilizer 122, a
horizontal stabilizer 124, and one or more control surfaces, such
as elevators 126. Similar to the flaps 118 and ailerons 120, the
elevators 126 may comprise movable hinged surfaces on the trailing
or leading edges of the horizontal stabilizer 124 for changing the
aerodynamic shape of the horizontal stabilizer 124 to control a
pitch of the WIG 100. The horizontal stabilizer 124 may be combined
with the elevator 126, creating a fully articulating horizontal
stabilizer. Raising the elevators 126 above the hinge point creates
a net downward force on the tail system and causes the WIG 100 to
pitch upward. Lowering the elevators 126 below the hinge point
creates a net upward force on the horizontal stabilizer 124 and
causes the WIG 100 to pitch downward. The elevators 126 may include
actuators, which may be operated by a control system of the WIG 100
in order to raise and lower the elevators 126.
[0040] The tail 106 may further include a rudder 128. The rudder
128 may comprise a movable hinged surface on the trailing edge of
the vertical stabilizer 122 for changing the aerodynamic shape of
the vertical stabilizer 122 to control the yaw of the WIG 100 when
operating in an airborne mode. In some examples, the rudder 128 may
additionally change a hydrodynamic shape of the hull 102 to control
the yaw of the WIG 100 when operating in a waterborne mode. In
order to facilitate such hydrodynamic control, the rudder 128 may
be positioned low enough on the tail 106 that the rudder 128 is
partially or entirely submerged when the hull 102 is floating in
water. Namely, the rudder 128 may be positioned partially or
entirely below a waterline of the hull 102. The rudder 128 may
include one or more actuators, which may be operated by a control
system of the WIG 100 in order to rotate the hinged surface of the
rudder 128 to the left or right of the vertical stabilizer 122.
Actuating the rudder 128 to the left (relative to the direction of
travel) causes the WIG 100 to yaw left. Actuating the rudder 128 to
the right (relative to the direction of travel) causes the WIG 100
to yaw right. As such, the rudder 128 may be used in combination
with any of the other mechanisms disclosed herein for controlling
the yaw of the WIG 100, including in combination with the ailerons
120 during airborne operation and in combination with varying the
rotational speeds of different ones of the propeller assemblies 116
to help improve maneuverability of the WIG 100 during waterborne
operation.
[0041] While not shown in FIGS. 1A-1D, the WIG 100 may also include
a distributed propulsion system on the tail 106, which may be
similar to the distributed propulsion system of propeller
assemblies 116 on the main wing 104. Such a distributed propulsion
system may provide similar benefits of increasing the freestream
velocity over the control surfaces (e.g., the elevators 126 and/or
the rudder 128) to allow for increased pitch and yaw control of the
WIG 100 at lower travel speeds. When determining the number and
size of propeller assemblies to include on the tail 106, one may
apply the same factors described above when determining the number
and size of propeller assemblies to include on the main wing
104.
[0042] D. Hydrofoil Systems
[0043] As further shown in FIGS. 1A-1D, the WIG 100 may include one
or more hydrofoil assemblies, such as the main hydrofoil assembly
108, which is positioned closer to the middle or bow of the WIG
100, and the rear hydrofoil assembly 110, which is positioned
closer to the stern of the WIG 100. For instance, the main
hydrofoil assembly 108 may be positioned between the bow and a
midpoint (between the bow and stern) of the WIG 100, and the rear
hydrofoil assembly 110 may be positioned below the tail 106 of the
WIG 100. The main hydrofoil assembly 108 and the rear hydrofoil
assembly 110 may help address a common challenge faced by
waterborne WIGs, which is the process of breaking contact between
the hull of the WIG and the water surface during takeoff. Prior to
becoming airborne, WIGs experience a peak hydrodynamic drag, which
is also known as the "hump drag." This can be problematic for WIGs,
as a large amount of power may be required to overcome this hump
drag, which is required to further increase forward velocity and
transition to airborne flight.
[0044] Previous design attempts for reducing the hump drag include
both aerodynamic and hydrodynamic design approaches. As noted above
in connection with the discussion of previous WIG designs having
low aspect ratio wings, one example of an aerodynamic design
approach is through the use of a power augmented ram (PAR), which
uses forward-mounted propulsors to blow air under the wing, thereby
creating a high-pressure zone under the WIG and lifting the WIG out
of the water. These PAR designs are not well-suited for WIGs with
high aspect ratio wings but instead are more effective with low
aspect ratio wings very close to the water where the high pressure
air can be better concentrated under the WIG. However, as noted
above, low aspect ratio wings suffer significantly in aerodynamic
efficiency and do not allow for a distributed blown-wing propulsion
system.
[0045] Another example aerodynamic approach to reducing the hump
drag is the use of catamaran hulls with textile skirts at the bow
and stern to form an entrapped volume of air between the catamaran
hulls. This volume of air can be inflated with high pressure air
using the vehicle's aft propellers, allowing the vehicle to act as
a quasi-hovercraft upon takeoff. However, this solution is less
efficient than the PAR designs due to losses in the air tunnel, and
presents additional challenges in the presence of waves on the
water's surface.
[0046] Examples of hydrodynamic design approaches for reducing the
hump drag include ski gear and fixed hydrofoils. Some WIGs have
included ski gear, or deflecting planing tabs, to overcome the
water suction and lift the WIG out of the water during takeoff.
However, these designs have very high hydrodynamic drag, which may
lead to reduced aerodynamic efficiency during flight. Other WIGs
have included fixed hydrofoils that create an additional lift force
while the WIG is waterborne in order to reduce the wetted surface
area on the vehicle's hull at intermediate speeds prior to takeoff.
However, because WIGs need to fly at very low altitudes when
airborne, the fixed hydrofoils needed to be very short to avoid
colliding with the water during flight. As a result, the fixed
hydrofoils in these WIGs cannot lift the hull of the vehicle above
the water waves during waterborne operation, which means the
vehicles cannot (a) operate in high sea states or (b) operate at
medium speeds (e.g., between the low speeds of a hull-borne
operational mode and the high speeds of a wing-borne flight mode)
in crowded harbors.
[0047] To improve upon and help address the issues of the previous
WIG design described above, the main hydrofoil 108 and the rear
hydrofoil 110 of the WIG 100 disclosed herein are configured to be
retractable, large enough to lift the entire WIG out of the water
and not impact the water surface, and to enable sustained operation
in the hyrdrofoil-borne mode (where the entire weight of the craft
is supported by the hydrofoil). The main hydrofoil assembly 108 may
include a main foil 130, one or more main foil struts 132 that
couple the main foil 130 to the hull 102, and one or more main foil
control surfaces 134. Similarly, the rear hydrofoil assembly 110
may include a rear foil 136, one or more rear foil struts 138 that
couple the rear foil 136 to the hull 102, and one or more rear foil
control surfaces 140.
[0048] The main foil 130 and the rear foil 136 may each take the
form of one or more hydrodynamic lifting surfaces (also referred to
as "foils") designed to be operated submerged underwater while the
hull 102 of the WIG 100 remains above and clear of the water's
surface. In operation, as the WIG 100 moves through water with the
main foil 130 and the rear foil 136 submerged, the foils generate a
lifting force that causes the hull 102 to rise above the surface of
the water. In order to cause the hull 102 to rise above the surface
of the water, the lifting force generated by the foils must be at
least equal to the weight of the WIG 100. The lifting force of the
foils depends on the speed and angle of attack at which the foils
move through the water, as well as their various physical
dimensions, including the aspect ratio, the surface area, the span,
and the chord of the foils.
[0049] The height at which the hull 102 is elevated above the
surface of the water during hydrofoil-borne operation is limited by
the length of the one or more main foil struts 132 that couple the
main foil 130 to the hull 102 and the length of the one or more
rear foil struts 138 that couple the rear foil 136 to the hull 102.
In some examples, the main foil struts 132 and the rear foil struts
138 may be long enough to lift the hull 102 at least five feet
above the surface of the water during hydrofoil-borne operation,
which may allow for operation in substantially choppy waters.
However, struts of other lengths may be used as well with the
understanding that longer struts will allow for better
wave-isolation of the hull 102 (but at the expense of stability of
the WIG 100 and increasing complexity of the retraction
system).
[0050] In practice, hydrofoils have a limited top speed before
cavitation occurs, which results in vapor bubbles forming and
imploding on the surface of the hydrofoil. Cavitation not only may
cause damage to a hydrofoil, but also significantly reduces the
amount of lift force generated by the hydrofoil and increases drag.
Therefore, it is desirable to reduce the onset of cavitation by
designing the main foil 130 and the rear foil 136 in a way that
allows the foils to operate at higher speeds (e.g., .about.20-45
mph) and across the entire required hydrofoil-borne speed envelope
before cavitation occurs. For instance, the onset of cavitation may
be controlled based on the geometric design of the main foil 130
and the rear foil 136. Additionally, the structural design of the
main foil 130 and the rear foil 136 may allow the surfaces of the
foils to flex and twist at higher speeds, which may reduce loading
on the foils and delay the onset of cavitation.
[0051] Further, the distributed blown-wing propulsion system may
help further delay the onset of cavitation on the main foil 130 and
the rear foil 136. Cavitation is caused by both (i) the amount of
lift force generated by a hydrofoil and (ii) the profile of the
hydrofoil (which is affected by both the hydrofoil's angle of
attack and its vertical thickness) as it moves through water.
Reducing the amount of lift force generated by the hydrofoil delays
the onset of cavitation. Because the blown-wing propulsion system
creates additional lift on the main wing 104, the amount of lift
force exerted on the main foil 130 and the rear foil 136 to lift
the hull 102 out of the water is reduced. Further, because the main
foil 130 and the rear foil 136 do not need to generate as much lift
force to raise the hull 102 out of the water, their angles of
attack may be reduced as well, which further reduces the onset of
cavitation. By combining the blown-wing propulsion system with the
hydrofoil designs described herein, the WIG 100 may operate in a
hydrofoil-borne mode at speeds above 35 knots before cavitation
occurs.
[0052] As shown in FIGS. 1A-1D, the main foil 130 may have a
flattened V-shaped design in which a center portion of the main
foil 130 is substantially flat and the ends of the main foil 130
extend upward toward the hull 102 of the WIG 100. This flattened
V-shape design may allow for passive regulation of the distance
between the hull 102 and the surface of the water (also referred to
as "ride height") while also allowing for passive roll-moment
control. The passive regulation of ride height is achieved by
having the tips of the V-shaped hydrofoil breach the surface of the
water, reducing the lifting surface that is underwater. If the ride
height is too low, the increased hydrofoil surface area under the
surface of the water will create a net force greater than the
weight of the WIG 100, causing it to rise higher. If the ride
height is too high, there will not be enough hydrofoil lifting area
under the surface of the water, causing the WIG 100 to descend into
the water. The passive roll stability is due to one side of the
V-shaped hydrofoil breaching further out of the water than the
other side. This creates a stabilizing roll moment when the WIG 100
is rolled to (for example) the left, because the left side of the
V-shaped hydrofoil will have more surface under the water surface,
allowing it to generate more lift than the right side.
[0053] As noted above, the main hydrofoil assembly 108 may include
one or more main foil control surfaces 134, and the rear hydrofoil
assembly 110 may include one or more rear foil control surfaces
140. The main foil control surfaces 134 may include one or more
hinged surfaces on a trailing or leading edge of the main foil 130
as well as one or more actuators, which may be operated by a
control system of the WIG 100 in order to rotate the hinged
surfaces so that they extend above or below the main foil 130. The
main foil control surfaces 134 on the main foil 130 may be operated
in a similar manner as the flaps 118 and ailerons 120 on the wing
104 of the WIG 100. As one example, lowering the control surfaces
134 to extend below the main foil 130 may change a hydrodynamic
shape of the main foil 130 in a manner that generates additional
lift on the main foil 130, similar to the aerodynamic effect of
lowering the flaps 118. As another example, asymmetrically raising
one or more of the control surfaces 134 (e.g., raising a control
surface 134 on only one side of the main foil 130) may change a
hydrodynamic shape of the main foil 130 in a manner that generates
a roll force on the main foil 130, similar to the aerodynamic
effect of raising one of the ailerons 120.
[0054] Likewise, the rear foil control surfaces 140 may include one
or more hinged surfaces on a trailing or leading edge of the rear
foil 136 as well as one or more actuators, which may be operated by
a control system of the WIG 100 in order to rotate the hinged
surfaces so that they extend above or below the rear foil 136. The
rear foil control surfaces 140 on the rear foil 136 may be operated
in a similar manner as the elevators 126 on the tail 106 of the WIG
100. As one example, lowering the control surfaces 140 to extend
below the rear foil 136 may change a hydrodynamic shape of the rear
foil 136 in a manner that causes the WIG 100 to pitch downwards,
similar to the aerodynamic effect of lowering the elevators 126. As
another example, raising the control surfaces 140 to extend above
the rear foil 136 may change a hydrodynamic shape of the rear foil
136 in a manner that causes the WIG 100 to pitch upwards, similar
to the aerodynamic effect of raising the elevators 126.
[0055] In some examples, one or both of the main foil control
surfaces 134 or the rear foil control surfaces 140 may include
rudder-like control surfaces similar to the rudder 128 on that tail
106 of the WIG 100. For instance, the main foil control surfaces
134 may include one or more hinged surfaces on a trailing edge of
the main foil strut 132 as well as one or more actuators, which may
be operated by a control system of the WIG 100 in order to rotate
the hinged surfaces so that they extend to the left or right of the
main foil strut 132. Similarly, the rear foil control surfaces 140
may include one or more hinged surfaces on a trailing edge of the
rear foil strut 138 as well as one or more actuators, which may be
operated by a control system of the WIG 100 in order to rotate the
hinged surfaces so that they extend to the left or right of the
rear foil strut 138. Actuating the main foil control surfaces 134
or the rear foil control surfaces 140 in this manner may
respectively change a hydrodynamic shape of the main foil strut 132
or the rear foil strut 138, which may allow for controlling the yaw
of the WIG 100 when operating in a waterborne or hyrdofoil-borne
mode, similar to the effect of actuating the rudder 128 of the WIG
100 as described above.
[0056] In some examples, instead of (or in addition to) actuating
hinged control surfaces on the main foil 130 and/or the rear foil
136, a control system of the WIG 100 may actuate the entire main
foil 130 and/or the entire rear foil 136 themselves. As one
example, the WIG 100 may include one or more actuators for rotating
the main foil 130 and/or the rear foil 136 around the yaw axis. As
another example, the WIG 100 may include one or more actuators for
controlling an angle of attack of the main foil 130 and/or the rear
foil 136 (i.e., rotating the main foil 130 and/or the rear foil 136
around the pitch axis). As another example, the WIG 100 may include
one or more actuators for rotating the main foil 130 and/or the
rear foil 136 around the roll axis. As another example, the WIG 100
may include one or more actuators for changing a camber or shape of
the main foil 130 and/or the rear foil 136. As yet another example,
the WIG 100 may include one or more actuators for flapping the main
foil 130 and/or the rear foil 136 to help propel the WIG 100
forward or backwards. Other examples are possible as well.
[0057] Further, in some examples, the WIG 100 may dynamically
control an extent to which the main foil 130 and/or the rear foil
136 are deployed based on an operational mode (e.g., hull-borne,
hydrofoil-borne, or wing-borne modes) of the WIG 100. For instance,
during hull-borne mode, the rear foil 110 may be partially deployed
or retracted to increase turning authority. The amount of partial
deployment or retraction may be a function of the desired overall
vehicle draft when operating in a shallow water environment. During
hydrofoil-borne mode, the main hydrofoil 108 may be partially
retracted in order to reduce the distance between the hull of the
vehicle and the water's surface. This may increase the amount of
lift generated by the main wing 104 by operating the wing closer to
the surface of the water, increasing the effects of aerodynamic
ground effect.
[0058] As noted above, one or both of the main hydrofoil assembly
108 or the rear hydrofoil assembly 110 may interface with a
deployment system that allows for retracting the main hydrofoil
assembly 108 and/or the rear hydrofoil assembly 110 into or toward
the hull 102 for hull-borne or wing-borne operation and extending
the main hydrofoil assembly 108 and/or the rear hydrofoil assembly
110 below the hull 102 for hydrofoil-borne operation.
[0059] FIG. 3 depicts an example main hydrofoil deployment system
300 that allows for retracting and extending the main hydrofoil
assembly 108. As shown, the main hydrofoil deployment system 300
may take the form of a linear actuator that includes one or more
brackets 302 coupling the main hydrofoil assembly 108 (by way of
the main foil struts 132) to one or more vertical tracks 304. The
brackets 302 may be configured to move vertically along the tracks
304, such that when the brackets 302 move vertically along the
tracks 304, the main hydrofoil assembly 108 likewise moves
vertically. The brackets 302 may be coupled to a leadscrew 306
that, when rotated, causes vertical movement of the brackets 302.
The leadscrew 306 may be rotated by any of various sources of
torque, such as an electric motor coupled to the leadscrew 306 by a
gearbox 308.
[0060] The main hydrofoil deployment system 300 may further include
one or more sensors 310 configured to detect a vertical position of
the main hydrofoil assembly 108. As shown, the sensors 310 include
a first sensor 310a that senses when the main hydrofoil assembly
108 has reached a fully retracted position and a second sensor 310b
that senses when the main hydrofoil assembly 108 has reached a
fully extended position. However, the main hydrofoil deployment
system 300 may include additional sensors for detecting additional
discrete positions or continuous positions of the main hydrofoil
assembly 108. The sensors 310 may be included as part of, or
otherwise configured to communicate with, the control system of the
WIG 100 to provide the control system with data indicating the
position of the main hydrofoil assembly 108. The control system may
then use the data from the sensors 310 to determine whether to
operate the electric motor to retract or extend the main hydrofoil
assembly 108.
[0061] In some examples, such as examples where the linear actuator
is not a self-locking linear actuator, the main foil deployment
system 300 may include a locking or braking mechanism for holding
the main foil struts 132 in a fixed position (e.g., in a fully
retracted or fully extended position). The locking mechanism may
be, for example, a dual-action mechanical brake coupled to the
electric motor, the leadscrew 306, or the gearbox 308.
[0062] While the above description provides various details of an
example main foil deployment system 300, it should be understood
that the main foil deployment system 300 depicted in FIG. 3 is for
illustrative purposes and is not meant to be limiting. For
instance, the main foil deployment system 300 may include any of
various linear actuators now known or later developed that are
capable of retracting and extending the main hydrofoil assembly
108.
[0063] FIGS. 4A and 4B depict an example rear foil deployment
system 400 that allows for retracting and extending the rear foil
136. As shown, the rear foil deployment system 400 may include a
pulley system 403 that couples an actuator 405 to the rear foil
strut 138. When actuated, the actuator 405 causes the pulley system
403 to raise or lower the rear foil strut 138 by causing the rear
foil strut 138 to slide vertically along a shaft 407. While not
depicted in FIGS. 4A and 4B, the rudder 128 may also be mounted to
the shaft 407 such that, when the actuator 405 raises the rear foil
strut 138, the rear foil strut 138 retracts at least partially into
the rudder 128. Additionally, the rear foil deployment system 400
may include one or more servo motors for rotating the rear foil
strut 138 around the shaft. In this respect, the rear foil strut
138 may be rotated around the shaft to act as a hydro-rudder when
submerged in water or to act as an aero-rudder when out of the
water. Further, because the rudder 128 is mounted to the same shaft
407 as the rear foil strut 138 and the rear foil strut 138 can be
retracted into the rudder 128, the same servo motor can also be
used to control rotation of the rudder 128.
[0064] The actuator 405 of the rear foil deployment system 400 may
take various forms and may, for instance, include any of various
linear actuators now known or later developed that are capable of
retracting and extending the rear hydrofoil assembly 110. Further,
in some examples, the actuator 405 may have a non-unitary actuation
ratio such that a given movement of the actuator 405 causes a
larger corresponding induced movement of the rear hydrofoil
assembly 110. This can help allow for faster retractions of the
rear hydrofoil assembly 110, which may be beneficial during
takeoff, as described in further detail below.
[0065] The main hydrofoil assembly 108 and/or the rear hydrofoil
assembly 110 may be designed such that, when fully retracted, the
hydrofoil assembly is flush, conformal, or tangent to the hull 102.
For instance, in some examples, the hull 102 may include one or
more recesses configured to receive the main hydrofoil assembly 108
and/or the rear hydrofoil assembly 110, and the main hydrofoil
assembly 108 and/or the rear hydrofoil assembly 110 may be shaped
such that when the main hydrofoil assembly 108 and/or the rear
hydrofoil assembly 110 are fully retracted into the one or more
recesses of the hull 102, the outer contour of the hull 102 forms a
substantially smooth transition at the intersection of the hull 102
and the main hydrofoil assembly 108 and/or the rear hydrofoil
assembly 110.
[0066] In other examples, the main hydrofoil assembly 108 and/or
the rear hydrofoil assembly 110 may not conform to the shape of the
hull 102 when fully retracted but instead may protrude slightly
below the hull 102. In these examples, the main hydrofoil assembly
108 and/or the rear hydrofoil assembly 110 may have a
non-negligible effect on the aerodynamics of the WIG 100, and the
WIG 100 may be configured to leverage these effects to provide
additional control of the WIG 100. For instance, when the main
hydrofoil assembly 108 and/or the rear hydrofoil assembly 110 are
retracted but still exposed, the exposed hydrofoil may be
manipulated in flight to impart forces and moments on the WIG 100
similar to an aero-control surface. Traditional hydrofoils have
control surfaces (such as flaps attached at the rear) that are
sized to displace water and would not be effective in
much-lighter-than-water air. One or both of the main hydrofoil
assembly 108 and/or the rear hydrofoil assembly 110 of the WIG 100
disclosed herein, however, may be mounted on a pivot which is
locked underwater but may be unlocked to allow the hydrofoil to
move around the pivot in the air. At that point, the control
surfaces act like trim tabs and are able to effect movement of the
entire unlocked, pivoting hydrofoil which would otherwise
impractically large and heavy servo motors. An additional benefit
of this design is that the hydrofoil may be unlocked and moved
through a slow servo and/or a combination of control surface
movement combined with forward movement through water, and then
re-locked such that the hydrofoil is at a selected angle of
incidence.
[0067] Because the main hydrofoil assembly 108 is configured to be
retractable, the hull 102 may include openings through which the
struts 132 of the main hydrofoil assembly 108 may be retracted and
extended. However, when the hull 102 contacts the water surface,
water may seep into the hull 102 through these openings. To account
for this, the hull 102 may be designed to isolate any water that
enters the hull 102 and allow for the water to drain from the hull
102 when the hull 102 is lifted out of the water. For instance, the
hull 102 may include pockets 142 on each side of the hull 102
aligned above the struts 132. The pockets 142 may be isolated from
the remainder of the interior of the hull 102 so that when water
accumulates in the pockets 142, the water does not reach any
undesired areas, like the cockpit, passenger seating area, or any
areas that house the battery system 200 or components of the
control system of the WIG 100. Further, the pockets 142 may include
venting holes or other openings located at or near the bottom of
the pockets 142. While such venting openings may allow water to
enter the pockets 142, they may likewise allow any accumulated
water to vent out of the pockets 142 when the hull 102 is lifted
out of the water.
[0068] While not shown in the figures, the main hydrofoil assembly
108 and/or the rear hydrofoil assembly 110 may further include one
or more propellers for additional propulsion when submerged
underwater. For instance, one or more propellers may be mounted to
the main foil 130 and/or the rear foil 136. Such propellers may
provide additional propulsion force to the WIG 100 during
hydrofoil-borne or hull-borne operation. In some examples, the one
or more propellers may additionally or alternatively be mounted to
the hull 102 such that the propellers are submerged during
hull-borne operation and may be used to provide additional
propulsion force to the WIG 100 during hull-borne operation.
[0069] The main hydrofoil assembly 108 and/or the rear hydrofoil
assembly 110 may further include various failsafe mechanisms in
case of malfunction. For instance, if the main hydrofoil deployment
system 300 or the rear hydrofoil deployment system 400 malfunctions
and cannot retract the main hydrofoil assembly 108 and/or the rear
hydrofoil assembly 110, then the WIG 100 may be configured to
jettison the assembly that is unable to be retracted. The main
hydrofoil assembly 108 and/or the rear hydrofoil assembly 110 may
be coupled to the hull 102 by a releasable latch. The control
system of the WIG 100 may identify a retraction malfunction, for
instance based on data received from the positional sensors 310,
and the control system may responsively open the latch to release
the connection between the hull 102 and the malfunctioning
hydrofoil assembly. In some examples, the weight of the
malfunctioning hydrofoil assembly may provide sufficient force to
jettison the malfunctioning hydrofoil assembly out of the hull 102
when the latch is opened, or the WIG 100 may include an actuator or
some other mechanism to jettison the malfunctioning hydrofoil
assembly out of the hull 102. In other examples, instead of
jettisoning a malfunctioning hydrofoil assembly, the main hydrofoil
assembly 108 and/or the rear hydrofoil assembly 110 may be designed
to break in a controlled manner upon impact with a water surface.
For instance, a joint between the main foil struts 132 and the hull
102 and/or a joint between the rear foil struts 138 and the hull
102 may be configured to disconnect when subjected to a torque
significantly larger than standard operational torques at the
joints. Other designs for providing controlled breaks are possible
as well.
[0070] E. Control System
[0071] FIG. 5 depicts a simplified block diagram illustrating
various components that may be included in an example control
system 500 of the WIG 100. The components of the control system 500
may include one or more processors 502, data storage 504, a
communication interface 506, a propulsion system 508, actuators
510, a Global Navigation Satellite System (GNSS) 512, an inertial
navigation system (INS) 514, a radar system 516, a lidar system
518, an imaging system 520, various sensors 522, a flight
instrument system 524, and control effectors 526, some or all of
which may be communicatively linked by one or more communication
links 528 that may take the form of a system bus, a communication
network such as a public, private, or hybrid cloud, or some other
connection mechanism.
[0072] The one or more processors 502 may comprise one or more
processing components, such as general-purpose processors (e.g., a
single- or multi-core microprocessor), special-purpose processors
(e.g., an application-specific integrated circuit or digital-signal
processor), programmable logic devices (e.g., a field programmable
gate array), controllers (e.g., microcontrollers), and/or any other
processor components now known or later developed. Further, while
the one or more processors 502 are depicted as a separate
stand-alone component of the control system 500, it should also be
understood that the one or more processors 502 could comprise
processing components that are distributed across one or more of
the other components of the control system 500.
[0073] The data storage 504 may comprise one or more non-transitory
computer-readable storage mediums that are collectively configured
to store (i) program instructions that are executable by the one or
more processors 502 such that the control system 500 is configured
to perform some or all of the functions disclosed herein, and (ii)
data that may be received, derived, or otherwise stored, for
example, in one or more databases, file systems, or the like, by
the control system 500 in connection with the functions disclosed
herein. In this respect, the one or more non-transitory
computer-readable storage mediums of data storage 504 may take
various forms, examples of which may include volatile storage
mediums such as random-access memory, registers, cache, etc. and
non-volatile storage mediums such as read-only memory, a hard-disk
drive, a solid-state drive, flash memory, an optical-storage
device, etc. Further, while the data storage 504 is depicted as a
separate stand-alone component of the control system 500, it should
also be understood that the data storage 504 may comprise
computer-readable storage mediums that are distributed across one
or more of the other components of the control system 500.
[0074] The communication interface 506 may include one or more
wireless interfaces and/or one or more wireline interfaces, which
allow the control system 500 to communicate via one or more
networks. Example wireless interfaces may provide for communication
under one or more wireless communication protocols, such as
Bluetooth, WiFi (e.g., an IEEE 802.11 protocol), Long-Term
Evolution (LTE), WiMAX (e.g., an IEEE 802.16 standard), a
radio-frequency ID (RFID) protocol, near-field communication (NFC),
and/or other wireless communication protocols. Example wireline
interfaces may include an Ethernet interface, a Universal Serial
Bus (USB) interface, CAN Bus, RS-485, or similar interface to
communicate via a wire, a twisted pair of wires, a coaxial cable,
an optical link, a fiber-optic link, or other physical connection
to a wireline network.
[0075] The propulsion system 508 may include one or more electronic
speed controllers (ESCs) for controlling the electric motor
propeller assemblies 116 distributed across the main wing 104 and,
in some examples, across the horizontal stabilizer 124. In some
examples, the propulsion system 508 may include a separate ESC for
each respective propeller assembly 116, such that the control
system 500 may individually control the rotational speeds of the
electric motor propeller assemblies 116.
[0076] The actuators 510 may include any of the actuators described
herein, including (i) actuators for raising and lowering the flaps
118, ailerons 120, elevators 126, main foil control surfaces 134,
and rear foil control surfaces 140, (ii) actuators for turning the
rudder 128, the main foil control surfaces 134 positioned on the
main foil struts 132, and the rear foil control surfaces 140
positioned on the rear foil strut 138, (iii) actuators for
retracting and extending the main hydrofoil assembly 108 and the
rear hydrofoil assembly 110, and/or (iv) actuators for performing
the various other disclosed actuations of the main hydrofoil
assembly 108 and the rear hydrofoil assembly 110. Each of the
actuators described herein may include any actuators now known or
later developed capable of performing the disclosed actuation.
Examples of different types of actuators may include linear
actuators, rotary actuators, hydraulic actuators, pneumatic
actuators, electric actuators, electro-hydraulic actuators, and
mechanical actuators. Further, more specific examples of actuators
may include electric motors, stepper motors, and hydraulic
cylinders. Other examples are contemplated herein as well.
[0077] The GNSS system 512 may be configured to provide measurement
of the location, speed, altitude, and heading of the WIG 100. The
GNSS system 512 includes one or more radio antennas paired with
signal processing equipment. Data from the GNSS system 512 may
allow the control system 500 to estimate the position and velocity
of the WIG 100 in a global reference frame, which can be used for
route planning, operational envelope protection, and vehicle
traffic deconfliction by both understanding where the WIG 100 is
located and comparing the location with known traffic.
[0078] The INS 514 may include various sensors that are configured
to provide data that is typical of well-known INS systems. For
example, the INS 514 may include motion sensors, such as angular
and/or linear accelerometers, and rotational sensors, such as
gyroscopes, to calculate the position, orientation, and velocity of
the WIG 100 using dead reckoning techniques. One or more INS
systems may be used by the control system to calculate actuator
outputs to stabilize or otherwise control the vehicle during all
modes of operation.
[0079] The radar system 516 may be configured to provide data that
is typical of well-known radar systems. For example, the radar
system 516 may include a transmitter and a receiver. The
transmitter may transmit radio waves via a transmitting antenna.
The radio waves reflect off an object and return to the receiver.
The receiver receives the reflected radio waves via a receiving
antenna, which may be the same antenna as the transmitting antenna,
and the radar system 516 processes the received radio waves to
determine information about the object's location and speed
relative to the WIG 100. This radar system 516 may be utilized to
detect, for example, the water surface, maritime or airborne
vehicle traffic, wildlife, or weather.
[0080] The lidar system 518 may be configured to provide data that
is typical of well-known lidar systems. For example, the lidar
system 518 may include a light source and an optical receiver. The
light source emits a laser that reflects off an object and returns
to the optical receiver. The lidar system 518 measures the time for
the reflected light to return to the receiver to determine a
distance between the WIG 100 and the object. This lidar system 518
may be utilized by the flight control system to measure the
distance from the WIG 100 to the surface of the water in various
spatial measurements.
[0081] The imaging system 520 may include one or more still and/or
video cameras configured to capture image data from the environment
of the WIG 100. In some examples, the cameras may include
charge-coupled device (CCD) cameras, complementary
metal-oxide-semiconductor (CMOS) cameras, short-wave infrared
(SWIR) cameras, mid-wave infrared (MWIR) cameras, or long-wave
infrared (LWIR) cameras. The imaging system 520 may provide any of
various possible applications, such as obstacle avoidance,
localization techniques, water surface tracking for more accurate
navigation (e.g., by applying optical flow techniques to images),
video feedback, and/or image recognition and processing, among
other possibilities.
[0082] As noted above, the control system 500 may further include
various other sensors 522 for use in controlling the WIG 100. In
line with the discussion above, examples of such sensors 522 may
include thermal sensors or other fire detection sensors for
detecting a fire in the hull 102 or for detecting thermal runaway
in the battery system 200. As further described above, the sensors
522 may include position sensors for sensing a position of the main
hydrofoil assembly 108 and/or the rear hydrofoil assembly 110
(e.g., sensing whether the assemblies are in a retracted or
extended position). Examples of position sensors may include
photodiode sensors, capacitive displacement sensors, eddy-current
sensors, Hall effect sensors, inductive sensors, or any other
position sensors now known or later developed.
[0083] In some examples, the sensors 522 may include any of various
altimeter sensors. As one example, the sensors 522 may include an
ultrasonic altimeter configured to emit and receive ultrasonic
waves. The emitted ultrasonic waves reflect off the water surface
below the WIG 100 and return to the altimeter. The ultrasonic
altimeter measures the time for the reflected ultrasonic wave to
return to the altimeter to determine a distance between the WIG 100
and the water surface. As another example, the sensor 522 may
include a barometer for use as a pressure altimeter. The barometer
measures the atmospheric pressure in the environment of the WIG 100
and determines the altitude of the WIG 100 based on the measured
pressure. As another example, the sensor 522 may include a radar
altimeter to emit and receive radio waves. The radar altimeter
measures the time for the radio wave to reflect off of the surface
of the water below the WIG 100 to determine a distance between the
WIG 100 and the water surface. These various sensors may be placed
on different locations on the WIG 100 in order to reduce the impact
of sensor constraints, such as sensor deadband or sensitivity to
splashing water.
[0084] Further, the control system 500 may be configured to use
various ones of the sensors 522 or other components of the control
system 500 to help navigate the WIG 100 through maritime traffic or
to avoid any other type of obstacle. For example, the control
system 500 may determine a position, orientation, and velocity of
the WIG 100 based on data from the INS 514 and/or the GNSS 512, and
the control system 500 may determine the location of an obstacle,
such as a maritime vessel, a dock, or various other obstacles,
based on data from the radar system 516, the lidar system 518,
and/or the imaging system 520. In some examples, the control system
500 may determine the location of an obstacle using the Automatic
Identification System (AIS). In any case, based on the determined
position, orientation, and velocity of the WIG 100 and the
determined location of the obstacle, the control system 500 may
maneuver the WIG 100 to avoid collision with the obstacle by
actuating various control surfaces of the WIG 100 in any of the
manners described herein.
[0085] The flight instrument system 524 may include various
instruments for providing a pilot of the WIG 100 with data about
the flight situation of the WIG 100. Example instruments may
include instruments for providing data about the altitude,
velocity, heading, orientation (e.g., yaw, pitch, and roll),
battery levels, or any other information provided by the various
other components of the control system 500.
[0086] The control effectors 526 may include various input devices
that may allow an operator to interact with and input signals to
the control system 500. Example control effectors 526 may include
one or more joysticks, thrust control levers, buttons, switches,
dials, levers, or touch screen displays, to name a few. In
operation, a pilot may use the control effectors 526 to operate one
or more control surfaces of the WIG 100. For instance, as one
example, when the pilot moves the joystick in a particular
direction, the control system 500 may actuate one or more control
surfaces of the WIG 100 to cause the WIG 100 to move in the
direction corresponding to the joystick movement. As another
example, when the pilot actuates (or increases actuation of) the
throttle, the control system 500 may cause a propulsion control
surface of the WIG 100 (e.g., the propeller assemblies 116) to
increase the propulsion force exerted on the WIG 100, and when the
pilot reduces actuation of the throttle, the control system 500 may
cause a propulsion control surface of the WIG 100 to decrease the
propulsion force exerted on the WIG 100. Other examples of control
effectors 526 may be implemented for actuating various control
surfaces of the WIG 100 as well.
[0087] The control surfaces on the WIG 100 may be utilized by the
control system 500 in different modes of operation. The amount of
deflection of each control surface may be calculated by the control
system 500 based on a number of input variables, including but not
limited to vehicle position, velocity, attitude, acceleration,
rotational rates, and/or altitude above water. Table 1 below
identifies, for each control surface of the WIG 100, example
operational modes in which the control surface may be used to
control movement of the WIG 100. In the tables below, the
propulsion control surfaces may include the propeller assembly 116
as well as any propellers mounted to the hull 102, main hydrofoil
assembly 108, or rear hydrofoil assembly 110. The aerodynamic
elevator control surfaces may include elevator 126, the aerodynamic
ailerons may include ailerons 120, the aerodynamic rudder may
include rudder 128 (when not submerged), the aerodynamic flaps may
include flaps 118, the hydrodynamic elevator may include rear foil
control surfaces 140, the hydrodynamic flaps may include main foil
control surfaces 134, and the hydrodynamic rudder may include
rudder 128 (when submerged).
TABLE-US-00001 TABLE 1 Example operational modes (Hull-borne,
Hydrofoil-borne, Wing-borne) supported by control surfaces of the
WIG 100. Control Surface Hull-borne Hydrofoil-borne Wing-borne
Propulsion Y Y Y Aerodynamic N Y Y Elevator Aerodynamic N Y Y
Ailerons Aerodynamic Rudder Y Y Y Aerodynamic Flaps N Y Y
Hydrodynamic Y Y N Elevator Hydrodynamic Flaps Y Y N Hydrodynamic Y
Y N Rudder
[0088] When actuating the control surfaces in the various example
operational modes identified in Table 1 above, the control system
500 may execute different levels of stabilization along the various
vehicle axes during different modes of operation. Table 2 below
identifies example stabilization controls that the control system
500 may apply during the various modes of operation for each axis
of the WIG 100. Closed loop control may comprise feedback and/or
feed forward control.
TABLE-US-00002 TABLE 2 Example stabilization control techniques
applied to different axes of the WIG 100 for each operational mode.
Vehicle Axis Hull-borne Hydrofoil-borne Wing-borne Pitch None
Closed loop Closed loop Axis control on control on vehicle ride
height vehicle altitude Roll None Closed loop Stabilization Axis
control around and closed loop vehicle bank control on angle = 0
heading Yaw Rate Closed loop Closed loop Axis stabilization control
on control on vehicle heading vehicle heading Speed Closed loop
Closed loop Closed loop Control control on control on control on
vehicle GPS Speed vehicle GPS Speed vehicle airspeed
[0089] Further, the control system 500 may be configured to actuate
different control surfaces to control movement of the WIG 100 about
its different axes. Table 3 below identifies example axial motions
that are affected by the various control surfaces of the WIG
100.
TABLE-US-00003 TABLE 3 Example axial motions affected by various
control surfaces of the WIG 100. Control Surface Axis Control
Function Propulsion (a) accelerate and decelerate the vehicle (b)
turn the vehicle about yaw axis (c) create a rolling moment
Aerodynamic Elevator (a) create a pitch up or pitch down moment
Aerodynamic Ailerons (a) create a rolling moment (b) increase lift
on aerodynamic wing (c) create a pitch down moment Aerodynamic
Rudder (a) create a yawing moment Aerodynamic Flaps (a) increase
lift on aerodynamic wing (b) create a pitch down moment
Hydrodynamic Elevator (a) create a pitch moment (b) generate heave
force on rear hydrofoil Hydrodynamic Flaps (a) generate heave force
on main hydrofoil Hydrodynamic Rudder (a) create a yaw moment
III. Example Modes of Operation
[0090] FIG. 6 depicts various example modes of operation of the WIG
100, separated into six numbered stages, each of which are
described in further detail below.
[0091] A. Hull-Borne Operation
[0092] At stage one, the WIG 100 is docked and floating on the hull
102 (i.e., in a hull-borne mode) with the buoyancy of the
outriggers 114 providing for roll stabilization of the WIG 100.
While docked, the battery system 200 of the WIG 100 may be charged.
Rapid charging may be aided with water-based cooling systems, which
may be open- or closed-loop systems. The surrounding body of water
may be used in the loop or as a heat sink. In some examples, the
WIG 100 may include a heat sink integrated into the hull 102 for
exchanging heat from the battery system 200 to the surrounding body
of water. In other examples, the heat sink may be located offboard
in order to reduce the mass of the WIG 100.
[0093] Additionally, while the WIG 100 is docked, the propeller
assemblies 116 may be folded in a direction away from the dock to
help avoid collision with nearby structures or people. This folding
may be actuated in various ways, such as by metal spring force,
hydraulic pressure, electromechanical actuation, or centrifugal
force due to propeller rotation. Other examples are possible as
well. Further, the main hydrofoil assembly 108 and the rear
hydrofoil assembly 110 may be retracted (or partially retracted) to
avoid collisions with nearby underwater structures.
[0094] Once any passengers or cargo have been loaded onto the WIG
100 and the WIG 100 is ready to depart, the WIG 100 can use its
propulsion systems, including the propeller assemblies 116 and/or
the underwater propulsion system (e.g., one or more propellers
mounted to the hull 102, the main foil 130, and/or the rear foil
136), to maneuver away from the dock while remaining hull-borne. In
some examples, the main hydrofoil assembly 108 and the rear
hydrofoil assembly 110 may remain retracted (or partially
retracted) during this maneuvering to reduce the risk of hitting
underwater obstacles near docks or in shallow waterways. However,
when there is limited risk of hitting underwater obstacles, the WIG
100 may partially or fully extend the main hydrofoil assembly 108
and/or the rear hydrofoil assembly 110. With the main hydrofoil
assembly 108 and/or the rear hydrofoil assembly 110 extended, the
WIG 100 may actuate the main foil control surfaces 134 and/or the
rear foil control surfaces 140 to improve maneuverability as
described above.
[0095] At low speeds during hull-borne operation, the control
system 500 may control a position and/or rotation of the WIG 100 by
causing all of the propeller assemblies 116 to spin at the same
idle speed, but with a first subset spinning in a forward direction
and a second subset spinning in a reverse direction. For example,
the control system 500 may cause propeller assemblies 116a, 116c,
116f, and 116h to idle in reverse and propeller assemblies 116b,
116d, 116e, and 116g to idle forward. In this arrangement, the
control system 500 may cause the WIG 100 to make various maneuvers
without having to change the direction of rotation of any of the
propeller assemblies 116. For instance, in order to induce a yaw on
the WIG 100, the control system 500 may increase the speed of the
reverse propeller assemblies on one side of the wing 104 while
increasing the speed of the forward propeller assemblies on the
other side of the wing 104 and without causing any of the propeller
assemblies to transition from forward to reverse or from reverse to
forward. For example, idling the propellers at a nominal RPM may
allow for faster response in generating a yaw moment on the WIG
100, because the propellers required for generating the yaw moment
do not have to increase from zero RPM to the desired RPM value,
they can spin from the idle RPM to the desired RPM value.
[0096] B. Hydrofoil-Borne Operation
[0097] In order to transition to stage two, the WIG 100 can fully
extend the main hydrofoil assembly 108 and the rear hydrofoil
assembly 110 (if not already extended) and accelerate using the
propulsion system as previously described. The WIG 100 accelerates
to a speed at which the main hydrofoil assembly 108 and the rear
hydrofoil assembly 110 alone support the weight of the WIG 100, and
the hull 102 is lifted above the surface of the water and clear of
any surface waves (e.g., example embodiments may support a maximum
wave height of .about.3-5 ft).
[0098] While transitioning to this hydrofoil-borne mode, the
control system 500 may actuate the main foil control surfaces 134
and/or the rear foil control surfaces 140 and/or the propulsion
system to stabilize the attitude of the WIG 100 in order to
maintain the desired height above the surface of the water, vehicle
heading, and vehicle forward velocity. For instance, the control
system 500 may detect various changes in the yaw, pitch, or roll of
the WIG 100 based on data provided by the INS 514, and the control
system 500 may make calculated actuations of the main foil control
surfaces 134 and/or the rear foil control surfaces 140 to
counteract the detected changes.
[0099] Once the WIG 100 has fully transitioned to hydrofoil-borne
operation and the hull 102 leaves the surface of the water, the
drag forces exerted on the WIG 100 drop significantly due to the
hull 102 no longer contributing to the water-based drag. As such,
the control system 500 may reduce the speeds of the propeller
assemblies 116 to lower the thrust of the WIG 100. The control
system 500 can sustain this operational mode by actively
controlling the pitch and speed of the WIG 100 so that the main
hydrofoil assembly 108 and the rear hydrofoil assembly 110 continue
to entirely support the weight of the WIG 100.
[0100] C. Wing-Borne Operation
[0101] In order to transition to wing-borne operation in stage
three, the control system 500 may accelerate the WIG 100 by
increasing the speeds of the propeller assemblies 116. The control
system 500 may accelerate the WIG 100 to a desired takeoff speed.
Because the WIG 100 is operating in a hydrofoil-borne mode at this
point, the desired takeoff speed must be below the hydrofoil
cavitation speed and is therefore significantly limited. In some
examples, the desired takeoff speed is approximately 40 knots.
However, as described above, by arranging the propeller assemblies
116 in a blown-wing configuration, the WIG 100 may generate
additional lift that allows for takeoff at such low speeds.
[0102] Once the control system 500 determines that the WIG 100 has
reached the desired takeoff speed, the control system 500 may
deploy the flaps 118 (and the ailerons 120 if configured as
flaperons), causing the wing 104 to generate additional lift. The
control system 500 additionally actuates the rear foil control
surfaces 140 and/or the elevators 126 in order to pitch the WIG 100
upward and increase the angle of attack of the wing 104 and the
hydrofoil assemblies 108, 110. In this configuration, the wing 104
and hydrofoil assemblies 108, 110 create enough lift force to
accelerate the WIG 100 upwards until the hydrofoil assemblies 108,
110 breach the surface of the water and the entire weight of the
WIG 100 is supported by the lift of the wing 104.
[0103] In some examples, when performing this transition from
hydrofoil-borne operation to wing-borne operation, the control
system 500 may quickly deploy the flaps 118 (and the ailerons 120
if configured as flaperons) over a very short period of time (e.g.,
in less than 1 second, less than 0.5 seconds, or less than 0.1
seconds). Quickly deploying the flaps 118 (and ailerons 120) in
this manner creates even further additional lift forces on the wing
104 that may help "pop" the WIG 100 out of the water and into
wing-borne operation.
[0104] Additionally, during the transition from hydrofoil-borne
operation to wing-borne operation, the control system 500 may
actuate various control surfaces of the WIG 100 to balance moments
along the pitch axis. For instance, the propeller assemblies 116,
the flaps 118, and the drag from the hydrofoil assemblies 108, 110
all generate nose-down moments around the center of gravity about
the pitch axis during transition. To counteract these forces, the
control system 500 may deploy the elevator 126 and the rear foil
control surfaces 140 to generate a nose-up moment and stabilize the
WIG 100.
[0105] Once the transition from hydrofoil-borne operation to
wing-borne operation is complete at stage three, the control system
500 may cause the main hydrofoil deployment system 300 and the rear
hydrofoil deployment system 400 to respectively retract the main
hydrofoil assembly 108 and the rear hydrofoil assembly 110. In
practice, the control system 500 may initiate this retraction as
soon as the hydrofoil assemblies 108, 110 are clear of the water in
order to reduce the chance of the hydrofoil assemblies 108, 110
reentering the water. The control system 500 may determine that the
hydrofoil assemblies 108, 110 are clear of the water in various
ways. As one example, the control system 500 may make such a
determination based on a measured altitude of the WIG 100 (e.g.,
based on data provided by the radar system 516, the lidar system
518, or the other sensors 522 described above for measuring an
altitude of the WIG 100). As another example, the sensors 522 may
further include one or more conductivity sensors, temperature
sensors, pressure sensors, strain gauge sensors, or load cell
sensors arranged on the hydrofoil assemblies 108, 110, and the
control system 500 may determine that the hydrofoil assemblies 108,
110 are clear of the water based on data from these sensors.
[0106] Once the WIG 100 is clear of the water, the control system
500 can continue to accelerate the WIG 100 to a desired cruise
velocity by controlling the speed of the propeller systems 116. The
control system 500 may retract the flap systems when the WIG 100
has achieved sufficient airspeed to generate enough lift to sustain
altitude without them. Additionally, the control system 500 can
actuate the various control surfaces of the WIG 100 and/or apply
differential thrust to the propeller systems 116 to perform any
desired maneuvers, such as turning, climbing, or descending, and to
provide efficient lift distribution. While in wing-borne mode, the
WIG 100 can fly both low over the water's surface in ground-effect,
or above ground-effect depending on operational conditions and
considerations.
[0107] D. Return to Hull-Borne Operation
[0108] In order to transition to stage four, the control system 500
determines that the hydrofoil assemblies 108, 110 are fully
retracted so that the WIG 100 may safely land on its hull 102. The
control system 500 may additionally determine and suggest a desired
landing direction and/or location based on observed, estimated, or
expected water surface conditions (e.g., based on data from the
radar system 516, the lidar system 518, the imaging system 520, or
other sensors 522).
[0109] The control system 500 initiates deceleration of the WIG
100, for instance by reducing the speeds of the propeller systems
116, until the WIG 100 reaches a desired landing airspeed. During
the deceleration, the control system 500 may deploy the flaps 118
to increase lift at low airspeeds and/or to reduce the stall speed.
Once the WIG 100 reaches the desired landing airspeed (e.g.,
approximately 50 knots), the control system 500 reduces the descent
rate (e.g., to be less than approximately 200 ft/min). As the WIG
100 approaches the surface of the water (e.g., once the control
system 500 determines that the WIG 100 is within 5 feet of the
water surface), the control system 500 further slows the descent
rate to cushion the landing (e.g., to be less than approximately 50
ft/min). As the hull 102 of the WIG 100 impacts the surface of the
water, the control system 500 reduces thrust, and the WIG 100
rapidly decelerates due to the presence of hydrodynamic drag, the
reduction in forward thrust, and the reduction or elimination of
blowing air over the wing which significantly reduces lift causing
the vehicle to settle into the water. The hull 102 settles into the
water as the speed is further reduced until the WIG 100 is
stationary.
[0110] Once the WIG 100 is settled in the water, the WIG 100 may
transition to stage five by extending the hydrofoil assemblies 108,
110 in order to transition from hull-borne operation to
hydrofoil-borne operation in the same manner as described above.
The control system 500 may then sustain the hydrofoil-borne mode at
stage five and maneuver the WIG 100 into port while keeping the
hull 102 insulated from surface waves. The WIG 100 may then
transition to back to hull-borne operation in stage six when the
control system 500 reduces the thrust generated by the propeller
assemblies 116 to lower the speed of the WIG 100 until the hull 102
settles into the water. The control system 500 may then retract the
hydrofoil assemblies 108, 110 and engage in hull-borne operation as
described above to maneuver the WIG 100 into a dock for
disembarking passengers or goods and recharging the battery system
200.
IV. CONCLUSION
[0111] The above detailed description describes various features
and functions of the disclosed WIGs and methods of operation with
reference to the accompanying figures. While various aspects and
embodiments have been disclosed herein, other aspects and
embodiments will be apparent to those skilled in the art. The
various aspects and embodiments disclosed herein are for purposes
of illustration and are not intended to be limiting, with the true
scope being indicated by the following claims.
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