U.S. patent application number 12/426162 was filed with the patent office on 2010-01-21 for gyro-stabilized air vehicle.
Invention is credited to Nicolae Bostan.
Application Number | 20100012790 12/426162 |
Document ID | / |
Family ID | 37107575 |
Filed Date | 2010-01-21 |
United States Patent
Application |
20100012790 |
Kind Code |
A1 |
Bostan; Nicolae |
January 21, 2010 |
GYRO-STABILIZED AIR VEHICLE
Abstract
A vertical takeoff and landing (VTOL) air vehicle disclosed. The
air vehicle can be manned or unmanned. In one embodiment, the air
vehicle includes two shrouded propellers, a fuselage and a
gyroscopic stabilization disk installed in the fuselage. The
gyroscopic stabilization disk can be configured to provide
sufficient angular momentum, by sufficient mass and/or sufficient
angular velocity, such that the air vehicle is gyroscopically
stabilized during various phases of flight. In one embodiment the
fuselage is fixedly attached to the shrouded propellers. In another
embodiment, the shrouded propellers are pivotably mounted to the
fuselage.
Inventors: |
Bostan; Nicolae; (Ontario,
CA) |
Correspondence
Address: |
KNOBBE MARTENS OLSON & BEAR LLP
2040 MAIN STREET, FOURTEENTH FLOOR
IRVINE
CA
92614
US
|
Family ID: |
37107575 |
Appl. No.: |
12/426162 |
Filed: |
April 17, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11384167 |
Mar 17, 2006 |
7520466 |
|
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12426162 |
|
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|
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60662999 |
Mar 17, 2005 |
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Current U.S.
Class: |
244/23A |
Current CPC
Class: |
B64C 29/02 20130101;
B64C 2201/088 20130101; B64C 2201/042 20130101; B64C 2201/104
20130101; B64C 2201/108 20130101; B64C 2201/146 20130101; B64C
3/385 20130101; B64C 2201/048 20130101; Y02T 50/14 20130101; B64C
2201/162 20130101; B64C 2201/165 20130101; B64C 39/024 20130101;
B64C 17/06 20130101; B64C 27/20 20130101; B64C 29/0033 20130101;
B64C 2201/127 20130101; B64C 2201/027 20130101; B64C 2201/044
20130101; Y02T 50/10 20130101 |
Class at
Publication: |
244/23.A |
International
Class: |
B64C 29/04 20060101
B64C029/04 |
Claims
1. An aircraft for vertical, horizontal or stationary flight,
comprising: a fuselage; two shrouded propulsion assemblies; a
plurality of control surfaces attached to the shrouded propulsion
assemblies for controlling the flight of the aircraft; an engine
mounted to the fuselage having an engine shaft arranged to rotate
about a longitudinal axis of the aircraft; two propellers one in
each shrouded propulsion assembly that produces thrust such that
the aircraft is in flight and such that air flow is created over
the plurality of control surfaces; a gyroscopic stabilization
member attached to the engine shaft via a gear box such that the
gyroscopic stabilization member rotates with an angular momentum
that is selected, with respect to the moment of inertia of the
aircraft about the axis of rotation of the gyroscopic stabilization
member, such that the aircraft is gyroscopically stabilized during
flight.
Description
PRIORITY CLAIM
[0001] This application is a continuation of U.S. application Ser.
No. 11/384,167 filed Mar. 17, 2006, which claims the benefit of
U.S. Provisional Patent Application No. 60/662,999, filed on Mar.
17, 2005, entitled "Vertical Takeoff and Landing Air Vehicle with
Tilt Shrouded Propellers Gyro Stabilized by a Rotating Disk," which
are hereby incorporated by reference in their entirety.
BACKGROUND
[0002] 1. Field
[0003] The present disclosure generally relates to aircraft
technology, and in particular, relates to a manned or unmanned
vertical takeoff and landing (VTOL) air vehicle that is
gyroscopically stabilized to enhance controllability of flight
operations.
[0004] 2. Description of the Related Art
[0005] Unmanned air vehicles (UAV) are vehicles that provide
tremendous utility in numerous applications. For example, UAVs are
commonly used by the military to provide mobile aerial observation
platforms that allow for observation of ground sites at reduced
risk to ground personnel. A typical UAV used in military
applications, and also in other civilian type applications, usually
includes an aircraft that has the general configuration of fixed
wing aircrafts known in the art. In particular, the typical UAV
that is used today has a fuselage with wings extending outward
therefrom, control surfaces mounted on the wings, a rudder and an
engine that propels the UAV in a generally forward flight. Such
UAVs can fly autonomously and/or can be controlled by an operator
from a remote location. UAVs of the prior art can thus be used for
obtaining photographic images without the risks to a pilot.
[0006] A typical UAV takes off and lands like an ordinary airplane.
For example, such typical UAV takes off from and lands on a runway,
much like a fixed-wing aircraft. In many situations, however,
runways may not be available, or their use may be impractical. For
example, for military applications, land based runways are often
unavailable adjacent to the operational military zone or the
available runways will be occupied by larger manned fixed-wing
aircraft. Similarly, ship borne UAVs can be even further restricted
in available runway space since most military ships are not
equipped with sufficient deck space to constitute a runway.
Consequently, UAVs are often forced to be launched with expensive
catapult equipment and then recaptured using expensive net systems.
Such launching and landing can result in damage to the UAV.
[0007] A further difficulty faced by airplane-type UAVs is that the
UAVs are often insufficiently mobile effective operation in
confined airspace. It is often desirable to be able to move the UAV
in a confined airspace, such as in an urban setting, at relatively
low elevations. Airplane-type UAVs typically travel too fast to
operate effectively in these types of environments.
SUMMARY
[0008] The foregoing needs can be addressed by various embodiments
of a vertical takeoff and landing (VTOL) air vehicle. The air
vehicle can be manned or unmanned. In one embodiment, the air
vehicle includes two shrouded propulsion assemblies, a fuselage and
a gyroscopic stabilization disk installed in the fuselage. The
gyroscopic stabilization disk can be configured to provide
sufficient angular momentum, by sufficient mass and/or sufficient
angular velocity, such that the air vehicle is gyroscopically
stabilized during various phases of flight. In one embodiment the
fuselage is fixedly attached to the shrouded propulsion assemblies.
In another embodiment, the shrouded propulsion assemblies are
pivotably mounted to the fuselage. Other configurations are
possible.
[0009] One embodiment of the present disclosure relates to a
manned/unmanned air vehicle which includes a fuselage and two
shrouded propulsion assemblies. An engine mounted in the fuselage
can transmit its power via gear boxes and interconnecting shafts to
the two shrouded propulsion assemblies to thereby provide thrust
for the air vehicle. The air vehicle can also include a gyroscopic
stabilization member coupled to an electric motor shaft or an
engine shaft via a gear box, such that rotation of the shaft
results in rotation of the gyroscopic member. The moment of inertia
and the rate of rotation of the gyroscopic member can be selected
such that the angular momentum of the gyroscopic member is
significantly larger than the moment of inertia of the aircraft (in
one embodiment, at least 20 times larger), so that the air vehicle
is substantially gyroscopically stabilized throughout the
substantially entire flight envelope.
[0010] In one embodiment, the air vehicle includes a flight control
system that is configured to allow control of the flight of the air
vehicle during flight. The control system can be configured to
permit vertical take-off and landing of the air vehicle via a
transition of the orientation of the plane of the shrouded
propulsion assemblies with respect to the plane of the ground. When
the plane of the shrouded propulsion assemblies is substantially
parallel to the plane of the ground, horizontal flight can occur.
When the plane of the shrouded propulsion assemblies is
substantially perpendicular to the plane of the ground, the air
vehicle can take-off from or land on the ground. In one embodiment,
gyroscopic stabilization can be provided during such
transition.
[0011] In one embodiment, the use of a gyroscopic stabilization
member in the air vehicle can result in the air vehicle being more
stable during the entire flight envelope, as the effects of
external and internal moments (such as changes in moments due to
fuel consumption or wind gust) result in gyroscopic precession of
the air vehicle. As a result of the gyroscopic precession, the
changes in direction of flight of the air vehicle can occur
approximately 90 degrees in the direction of rotation from the
point where the resulting moment is applied. Preferably, the
angular momentum of the gyroscopic member is large enough such that
possible variations of the vehicle orientation due to wind gust
(and/or other effects) can be rapidly suppressed without affecting
the air vehicle's position in space.
[0012] In one embodiment, the gyroscopic member that rotates as a
result of rotation of the electric motor shaft or the engine shaft,
includes a disk that is coupled to the drive shaft via a gear
assembly such that the disk can be rotated at an angular velocity
selected to provide the gyroscopic stabilization for the air
vehicle. In one embodiment, the gyroscopic stabilization member is
mounted inside the fuselage.
[0013] In one embodiment, the flight control system includes a
plurality of movable flight control surfaces that can be
independently moved so as to provide directional control about the
pitch, yaw and roll axes. In one Class II embodiment, in
substantially all orientation of flight the gyroscopic
stabilization member tilts together with the shrouded propulsion
assemblies and provides gyroscopic stabilization about the pitch
and yaw axes of the air vehicle. In one Class III embodiment, where
the gyroscopic member is substantially solidly attached to the
fuselage the gyroscopic member provides gyroscopic stabilization
about the pitch and roll axes. The flight control system can be
configured to allow the air vehicle to take-off and land, where the
plane of rotation of the shrouded propulsion assemblies is
substantially parallel to the landing surface.
[0014] In one embodiment, the shrouded propulsion assemblies of the
air vehicle are further configured such that, following vertical
take-off, the plane of the shrouded propulsion assemblies can be
oriented so as to have an approximately 5-10 degrees offset from
the plane of the ground so as to propel the vehicle in a direction
parallel to the plane of the ground at a relatively low speed. The
flight control system is further configured to allow the shrouded
propulsion assemblies to orient themselves such that the plane of
the propellers is substantially perpendicular to the plane of the
ground to allow for horizontal flight at high speed. During each of
the three general zones of the flight envelope the Class III
fuselage can be parallel to the ground. In the first embodiment
when gyroscopic stabilization member provides gyroscopic
stabilization about the pitch axis and yaw axes which are
perpendicular to each other and also perpendicular to the roll axis
which comprises the longitudinal axis of the fuselage and the air
vehicle.
[0015] In one embodiment, the air vehicle can be considerably more
stable in operation due to the operation of the gyroscopic
stabilization member. Further, the addition of the gyroscopic
stabilization member can be an inexpensive way to design an
aircraft that is capable of vertical flight, unusual
maneuverability and horizontal flight at high speed. The use of
shrouded propeller type design provides a vehicle that can be
suitable for take-off and landing on confined spaces and surfaces
with little preparation, without posing undue risk to the operating
personnel standing nearby.
[0016] One embodiment of the present disclosure relates to an
aircraft for vertical, horizontal or stationary flight. The
aircraft includes a fuselage, and two shrouded propulsion
assemblies. The aircraft further includes a plurality of control
surfaces attached to the shrouded propulsion assemblies for
controlling the flight of the aircraft. The aircraft further
includes an engine mounted to the fuselage having an engine shaft
arranged to rotate about a longitudinal axis of the aircraft. The
aircraft further includes two propellers one in each shroud that
produces thrust such that the aircraft is in flight and such that
air flow is created over the plurality of control surfaces. The
aircraft further includes a gyroscopic stabilization member
attached to the engine shaft via a gear box such that the
gyroscopic stabilization member rotates with an angular momentum
that is selected, with respect to the moment of inertia of the
aircraft about the axis of rotation of the gyroscopic stabilization
member, such that the aircraft is gyroscopically stabilized during
flight.
[0017] In one embodiment, the gyroscopic stabilization member is a
disk rotating about longitudinal axis of the aircraft. In one
embodiment, the fuselage housing the gyroscopic stabilization
member is solidly attached to the shrouds.
[0018] In one embodiment, the gyroscopic stabilization member is a
disk rotating about the yaw axis of the aircraft. In one
embodiment, the fuselage housing the gyroscopic stabilization
member is pivotably attached between the shrouds.
[0019] Another embodiment of the present disclosure relates to an
aircraft that includes a fuselage and two shrouded propulsion
assemblies defining flight surfaces. The fuselage is mounted
solidly between the shrouds. The aircraft further includes a
plurality of control surfaces attached to the shrouds for
controlling the flight of the aircraft. The aircraft further
includes an engine mounted in the fuselage. The aircraft further
includes two propellers, one mounted in each shroud actuated by the
engine via belt drives or gear boxes, that produce thrust such that
the aircraft is in flight and such that the airflow is created over
the plurality of control surfaces. The engine provides sufficient
thrust via the propellers so as to power the aircraft. The engine
provides sufficient thrust via the propellers so as to power the
aircraft through a flight envelope that includes vertical take off
and landing and horizontal flight and transitions therebetween. The
aircraft further includes a gyroscopic stabilization member
comprising a disk structure actuated via a gear box by the engine,
the disk structure situated in the fuselage in between the two
shrouded propulsion assemblies.
[0020] In one embodiment, the disk has a relatively small cross
section, and no portion of the disk extends into the opening of the
two shrouds.
[0021] Yet another embodiment of the present disclosure relates to
an aircraft that includes a fuselage and two shrouded propulsion
assemblies defining flight surfaces. The fuselage is mounted
pivotably between the shrouds. The aircraft further includes a
plurality of control surfaces attached to the shrouds for
controlling the flight of the aircraft. The aircraft further
includes an engine mounted in the fuselage. The aircraft further
includes two propellers, one mounted in each shroud actuated by the
engine via interconnecting shafts and gear boxes that produce
thrust such that the aircraft is in flight and such that the
airflow is created over the plurality of control surfaces. The
engine provides sufficient thrust via the propellers so as to power
the aircraft. The engine provides sufficient thrust via the
propellers so as to power the aircraft through a flight envelope
that includes vertical take off and landing and horizontal flight
and transitions there between. The aircraft further includes a
gyroscopic stabilization member comprising a disk structure
actuated via a gear box by the engine, the disk structure situated
in the fuselage in between the two shrouded propulsion
assemblies.
[0022] In one embodiment, the disk has a relatively small cross
section, and no portion of the disk extends into the opening of the
two shrouds.
[0023] Yet another embodiment of the present disclosure relates to
an aircraft having a fuselage having a longitudinal axis, and two
shrouded propeller assemblies coupled to the fuselage. Each
shrouded propeller assembly is spaced laterally from the fuselage
and provides thrust, and has one or more control surfaces that
direct at least a portion of air flow of the thrust so as to
provide flight control of the aircraft. The aircraft further
includes an engine positioned within the fuselage and coupled to
and providing power to the two shrouded propeller assemblies by a
power transfer mechanism. The aircraft further includes a
gyroscopic stabilization member positioned within the fuselage and
coupled to the power transfer mechanism such that the gyroscopic
stabilization member rotates about a rotational axis so as to yield
a selected angular momentum with respect to the longitudinal axis
and a moment of inertia of the aircraft, and thereby provide
gyroscopic stabilization of the aircraft during flight.
[0024] In one embodiment, each of the two shrouded propulsion
assemblies are mounted to the fuselage in a fixed manner such that
axes of rotation of the propellers are substantially fixed with
respect to the longitudinal axis of the fuselage. In one
embodiment, the aircraft is a Class II UAV. In one embodiment, the
aircraft further includes wings that extend laterally from the two
shrouded propulsion assemblies so as to provide additional lifting
surface during horizontal fight of the aircraft.
[0025] In one embodiment, each of the two shrouded propulsion
assemblies are mounted to the fuselage in a pivotable manner such
that axes of rotation of the propellers can vary with respect to
the longitudinal axis of the fuselage. In one embodiment, the
aircraft is a Class III UAV. In one embodiment, the aircraft
further includes wings that extend laterally from the two shrouded
propulsion assemblies so as to provide additional lifting surface
during horizontal fight of the aircraft.
[0026] In one embodiment, the power transfer mechanism includes an
engine shaft, and the gyroscopic stabilization member is driven by
the engine shaft via a gear box.
[0027] In one embodiment, the rotational axis of the gyroscopic
stabilization member is substantially parallel to the longitudinal
axis of the fuselage. In one embodiment, the rotational axis of the
gyroscopic stabilization member is substantially perpendicular to
the longitudinal axis of the fuselage.
[0028] In one embodiment, the gyroscopic stabilization member
comprises a disk. In one embodiment, the disk has a mass
distribution that varies with radial distance from its rotational
axis. In one embodiment, the disk spinning at an operational
rotational rate has an angular momentum that is about 10 to 20
times or greater than the static moment of inertia of the aircraft
about the rotational axis of the disk.
[0029] In one embodiment, the aircraft further includes a flight
control component configured to receive an input signal indicative
of a need or a desire to change an attitude of the aircraft, and
generate an output signal for effectuating movement of the one or
more control surfaces. In one embodiment, the movement of the one
or more control surfaces induces a precession of the selected
angular momentum of the gyroscopic stabilization member.
[0030] In one embodiment, the fuselage between the two propulsion
units provides a space suitable for a payload. In one embodiment,
the total thrust provided by the two propulsion devices is
substantially greater than a thrust from a single propulsion device
that is substantially similar to each of the two propulsion
devices, such that use of two propulsion devices and the fuselage
allows for improved payload of the aircraft.
[0031] Yet another embodiment of the present disclosure relates to
an aircraft that includes a fuselage having a longitudinal axis,
and two propulsion devices coupled to the fuselage. Each propulsion
device provides thrust and has one or more control surfaces that
direct at least a portion of air flow of the thrust so as to
provide flight control of the aircraft. The aircraft further
includes a gyroscopic stabilization member coupled to a power
source such that the gyroscopic stabilization member rotates about
a rotational axis so as to yield a selected angular momentum with
respect to the longitudinal axis and a moment of inertia of the
aircraft, and thereby provide gyroscopic stabilization of the
aircraft during flight.
BRIEF DESCRIPTION OF THE DRAWINGS
[0032] FIG. 1 shows a perspective view of one embodiment of an air
vehicle that can be classified as a Class II air vehicle;
[0033] FIG. 2 shows a cross-sectional view of the air vehicle of
FIG. 1;
[0034] FIG. 3 shows a bottom view of the air vehicle of FIG. 1;
[0035] FIG. 4 shows a front view of the air vehicle of FIG. 1;
[0036] FIG. 5 shows a top view of the air vehicle of FIG. 1;
[0037] FIG. 6 shows a side view of the air vehicle of FIG. 1;
[0038] FIGS. 7A-7D show one embodiment of control surfaces that can
provide pitch, yaw, and roll controls for the air vehicle of FIG.
1;
[0039] FIGS. 8A-8C show an example transition between forward
flight and vertical takeoff and landing for one embodiment of the
air vehicle;
[0040] FIGS. 9A-9C show an example transition between forward
flight and vertical takeoff and landing for another embodiment of
the air vehicle;
[0041] FIG. 10 shows a perspective view of one embodiment of an air
vehicle that can be classified as a Class III air vehicle, where
the air vehicle is configured for vertical takeoff and landing;
[0042] FIG. 11 shows a perspective view of the air vehicle of FIG.
10, where the air vehicle is configured for forward flight;
[0043] FIG. 12 shows a front view of one embodiment of the air
vehicle of FIG. 11;
[0044] FIG. 13 shows a top view of one embodiment of the air
vehicle of FIG. 10;
[0045] FIG. 14 shows a front view of another embodiment of the air
vehicle of FIG. 11;
[0046] FIG. 15 shows a top view of another embodiment of the air
vehicle of FIG. 10;
[0047] FIG. 16 shows a sectional side view of the air vehicle of
FIG. 12 or 14;
[0048] FIGS. 17A-17D show various views of one embodiment of the
air vehicle in the vertical flight configuration;
[0049] FIGS. 18A-18D show various views of one embodiment of the
air vehicle in the forward flight configuration;
[0050] FIGS. 19A-19D show one embodiment of control surfaces that
can provide pitch, yaw, and roll controls for the air vehicle in
the vertical flight configuration;
[0051] FIGS. 19E-19H show one embodiment of control surfaces that
can provide pitch, yaw, and roll controls for the air vehicle in
the forward flight configuration;
[0052] FIGS. 20A-20C show an example transition between forward
flight and vertical takeoff and landing for one embodiment of a
Class III air vehicle;
[0053] FIGS. 21A-21C show an example transition between forward
flight and vertical takeoff and landing for another embodiment of a
Class III air vehicle;
[0054] FIG. 22 shows a block diagram of one embodiment of a flight
control system configured to provide flight control for some
embodiments of the gyroscopically stabilized air vehicles of the
present disclosure;
[0055] FIG. 23 shows one embodiment of a process for providing
flight control for some embodiments of the gyroscopically
stabilized air vehicles of the present disclosure; and
[0056] FIGS. 24A and 24B show different views of one example
embodiment of a disk member that can be used to provide gyroscopic
stabilization.
[0057] These and other aspects, advantages, and novel features of
the present teachings will become apparent upon reading the
following detailed description and upon reference to the
accompanying drawings. In the drawings, similar elements have
similar reference numerals.
DETAILED DESCRIPTION OF SOME EMBODIMENTS
[0058] The present disclosure generally relates to air vehicles
capable of vertical takeoff and landing (VTOL). It will be
understood that various features of the present disclosure can also
be implemented in other air vehicles such as vertical short takeoff
and landing (VSTOL). Thus, although VTOLs are described herein,
similar features can also be incorporated into VSTOL and any other
air vehicles where stability can be a concern during transition
between forward flight and takeoff/landing. It will also be
understood that in some embodiments, the air vehicle can be manned;
while other embodiments the air vehicle can be an unmanned air
vehicle (UAV).
[0059] As described herein, various embodiments of the air vehicle
includes a fuselage and two or more propulsion units that are
spaced laterally from the fuselage. In some embodiments the
fuselage houses an engine, and two propulsion units are in the form
of shrouded propeller assemblies. Propellers in such shroud
assemblies are mechanically coupled to the engine via a power
transmission mechanism so as to provide thrust. In such
embodiments, the fuselage also houses a gyroscopic stabilization
member such as a disk. Such a disk can be spun at a selected rate
by, for example, coupling it to the power transmission
mechanism.
[0060] An air vehicle having such features can provide a number of
advantageous performance characteristics. Some non-limiting
examples of such advantages are as follows. First, when compared to
an aircraft having a single shroud with a given diameter (for
example, an aircraft disclosed in U.S. Pat. No. 6,604,706), two
shrouds (with each having a similar diameter) can produce
significantly greater thrust for various reasons. A static thrust
"T" from a shrouded propeller unit can be estimated as
T=(13.13)(M.times.P.times.D).sup.2/3, where T is in lb, M is an
efficiency factor that takes into account the various effects of
viscosity and flow turbulence inside the shroud, P is the engine
power in HP, and D is the exit diameter of the exit shroud. Thus,
one can see that for a given engine power, the effective exit
diameter of two shrouds is greater than one shroud. Moreover, the
efficiency M of each of the two shrouds can be significantly
greater than that of a single shroud that also encloses an engine.
In such single shroud (with engine) configuration, the flow
disturbance around the engine, even if streamlined, can be a major
factor that decreases the efficiency of thrust generation.
[0061] In contrast, various embodiments of the shrouded propeller
units of the present disclosures do not have an engine within the
shrouds. Thus, thrust-generating efficiency is increased. In one
estimation, this increased efficiency (combined with the increased
exit diameter) have been shown to increase the static thrust of the
two-shroud aircraft by about 70% over a single-shroud (with an
engine in the shroud) aircraft having similar sized shroud.
[0062] Second, the increased thrust generally allows for greater
payload of an aircraft. In various embodiments of the present
disclosure, a fuselage is provided between the two shrouds, thereby
providing space for such payload. In some embodiments, the payload
can be carried within the fuselage.
[0063] Third, the fuselage also allows for greater flexibility in
the configuration of the gyroscopic stabilization member. As
described herein, the angular momentum axis of the gyroscopic
stabilization member can be directed in different directions (for
example, parallel or perpendicular to the longitudinal axis of the
fuselage). Such differences in the orientation of the disks can
provide flexibility in configuration of flight controls.
[0064] Fourth, as described herein, use of two spaced thrust units
(e.g., two shrouded propeller units) also allows for additional
flexibility in flight control that is not present in a
single-thrust aircraft. For example, one side of the aircraft can
be provided with greater thrust, and such thrust imbalance can be
used to induce gyroscopic precession for flight control of the
aircraft.
[0065] In the description herein, a term "shrouded propeller" is
sometimes used interchangeably with a term "shrouded propulsion
unit."
Class II or Class II Type Example Embodiment
[0066] FIGS. 1 to 6 show one embodiment of an unmanned air vehicle
(UAV) that can be designated Class II UAV. The UAV can be
gyroscopically stabilized in a manner that will be described in
greater detail below. Class II UAV in this embodiment has a
shrouded propeller configuration that includes a fuselage 101 and
two shrouded propellers 102. In this embodiment the fuselage 101
has an aerodynamic shape and is substantially centrally and solidly
mounted between the two shrouded propellers 102. In one embodiment,
the fuselage 101 can be generally symmetrical about the air
vehicle's longitudinal axis 115 that extends longitudinally so as
to coincide with the axis of spin associated with a gyroscopic
stabilization (GS) member 107. In one embodiment, the GS member 107
is a disk.
[0067] In one embodiment, the shrouded propellers 102 are installed
at substantially equal distances from the air vehicle's
longitudinal axis 115. The shrouded propellers 102 have
longitudinal axes 118 and 119 that can be substantially parallel
with the air vehicle's longitudinal axis 115, and located in the
substantially same plane created by the air vehicle's longitudinal
115 and pitch 116 (see FIG. 7A) axes. In one embodiment, the
propeller shroud can be generally circular and provides an opening
in which the propulsion mechanism 103 is mounted. The shroud can be
substantially symmetrical about its longitudinal axis 118 (119)
that extends through the shroud opening so as to be substantially
coincident with the propeller 103 shaft. In this embodiment the
propeller 103 can incorporate a plurality of blades that are
preferably variable pitch blades such that the pitch of the blades
can be changed to alter the propulsion force provided by the
propeller 103. As shown in FIG. 1, the forward edge of the shroud
can be generally rounded so as to permit smooth flow into the
shroud opening and also over the outer surfaces. The forward edge
of the shroud can be designed to significantly increase the
propeller thrust.
[0068] As is also shown in FIGS. 1 through 6, each shroud can be
adapted to have a plurality of landing legs 110 attached to a
landing ring 111 so as to enable the air vehicle to land and
takeoff in a vertical takeoff and landing (VTOL) profile. In
particular, two example landing assemblies, where each assembly
includes four landing legs and a ring attached thereto, allow the
air vehicle to takeoff from a surface with the plane of propeller
103 being substantially parallel to the plane of the ground and
further allowing the air vehicle to land in a similar manner.
[0069] As is also shown in FIGS. 1 through 6, the air vehicle can
also be equipped with optional wings 109 that can either be fixably
mounted to the shroud 102 or can be pivotably mounted in a manner
known to the art. The wings 109 can be optional in that they can
provide additional flight surfaces to facilitate horizontal flight
of the air vehicle. In such horizontal flight, the plane of the
propeller 103 can be substantially perpendicular to the plane of
the ground. It will, however, be appreciated that in some
embodiments, the shroud 102 surfaces can provide sufficient lift to
allow for horizontal flight of the air vehicle, and that the wings
109 can thus be optional to provide better flight characteristics
for the desired UAV mission.
[0070] In one embodiment, the Class II UAV can be specifically
configured as a reconnaissance vehicle for use in aerial
reconnaissance, such as the type of reconnaissance conducted during
military operations. Thus in one embodiment, a rotatable gimbaled
camera 114 can be mounted on the bottom outer section of the
fuselage 101 in a manner shown in FIGS. 1 through 6. The camera 114
can be one of a number of well known reconnaissance cameras that
can be controllable by the flight control system or a remote
operator in a manner that is generally known in the art.
Class III or Class III Type Example Embodiment
[0071] In some embodiments, gyro stabilization can be implemented
in air vehicles that can be classified as Class III VTOL UAV. In
one embodiment, gyro stabilization can be provided by a rotating
disk. Three non-limiting example embodiments of Class III UAVs are
described.
[0072] The following description can be common to the three example
embodiments. FIGS. 10, 11, 17, and 18 show one embodiment of an
unmanned air vehicle (UAV) designated Class III UAV that can be
configured to be gyroscopically stabilized in a manner that will be
described in greater detail below. Class III UAV in this example
embodiment has a shrouded propeller configuration having a fuselage
201 and the two shrouded propellers 202. In this embodiment, the
fuselage 201 has an aerodynamic shape and is centrally mounted
between the two shrouded propellers 202. The shrouded propellers
202 can tilt about the fuselage 201 from a vertical position for
vertical flight to a horizontal position for forward flight. The
fuselage 201 can be generally symmetrical about the air vehicle's
longitudinal axis 217 (see FIG. 13, for example) that extends
longitudinally. In one embodiment, the longitudinal axis 217 of the
air vehicle is substantially perpendicular to the axis of spin of a
GS member 225 (see FIG. 13).
[0073] In one embodiment, the shrouded propellers 202 are installed
at substantially equal distances from the air vehicle's
longitudinal axis 217 and yaw axis 219. The shrouded propellers
longitudinal axes 220 and 221 are substantially parallel with the
plane created by the air vehicle's longitudinal axis 217 and yaw
axis 219 (see FIG. 19C). In this embodiment the propeller shroud is
generally circular and provides an opening in which the propulsion
mechanism 203 is mounted. The shroud is substantially symmetrical
about its longitudinal axis 220 (221) that extends through the
shroud opening so as to be substantially coincident with the
propeller shaft. In this example embodiment, the propeller 203
incorporates a plurality of blades that are preferably variable
pitch blades such that the pitch of the blades can be changed to
alter the propulsion force provided by the propeller 203. As shown
in FIGS. 10 and 11, the forward edge of the shroud can be generally
rounded so as to permit smooth flow into the shroud opening and
also over the outer surfaces. The forward edge of the shroud can be
designed to significantly increase the propeller thrust.
[0074] As shown in FIGS. 10 to 16, the fuselage 201 can be
configured to have an example tricycle landing gear 210 and 211 so
as to enable the Class III UAV to land and takeoff in a vertical
takeoff and landing (VTOL) profile, short takeoff and landing
(STOL) profile or conventional takeoff and landing (CTOL) profile.
In all these landing modes the fuselage can generally maintain a
horizontal orientation. The shrouded propellers 202 can tilt about
the fuselage 201. For VTOL profile the air vehicle can takeoff from
a surface with the plane of propeller 203 being substantially
parallel to the plane of the ground and further allowing the UAV to
land in a similar manner. During a STOL profile the plane of
propeller is at a high angle of attack (in one embodiment,
approximately 75 to 80 degrees) to the plane of the ground for
takeoff and landing. For a CTOL profile the air vehicle can takeoff
from a surface with the plane of propeller 203 being substantially
perpendicular to the plane of the ground and further allowing the
UAV to land in a similar manner.
[0075] As is also shown in FIGS. 10 to 18, the Class III UAV can
also be equipped with optional wings 209 that can either be fixably
mounted to the shroud 202 or be pivotably mounted in a manner known
to the art. The wings 209 can be optional in that they can provide
additional flight surfaces to facilitate horizontal flight of the
Class III UAV. It will, however, be appreciated that, by the
following description, the shroud 202 surfaces can provide
sufficient lift to allow for horizontal flight of the Class III UAV
and that the wings 209 can thus be optional to provide better
flight characteristics for the desired UAV mission.
[0076] Three non-limiting example embodiments of the Class III UAV
are now described.
Class III-A Example Embodiment
[0077] One embodiment of a Class III-A UAV, as shown in FIGS. 12
and 13, includes one 222 (223) engine installed in each of the
shrouded propellers 202. The engine shaft axis substantially
coincides with the shrouded propeller axis 220 (221). The GS disk
225 is depicted as being actuated by a third engine 224 via a gear
box 205 (see FIG. 16).
Class III-B Example Embodiment
[0078] One embodiment of a Class III-B, as shown in FIGS. 14-16,
includes two engines 204 and 215 installed in the fuselage 201. The
GS disk includes two disks 207 and 216. In one embodiment, the
disks 207 and 216 can rotate at a substantially same angular
velocity and in the same direction. Engines 204 and 215 can actuate
the shrouded propellers 203 and the GS disks 207 and 216 via gear
boxes 205 and 206. During vertical takeoff and landing both engines
204 and 215 can provide power to the propellers 203 and the GS
disks 207, 216. In forward flight the power requirements can be
considerably lower, and accordingly, one of the engines can be
stopped.
Class III-C Example Embodiment
[0079] One embodiment of a Class III-C can be similar to Class
III-B except that the air vehicle has only one engine installed in
the fuselage and one GS disk.
Control System and Stabilization
[0080] As is shown in FIGS. 1-6 and 11-18, at the rear of each
shrouded propeller there can be installed two sets of control
surfaces, 112 and 113 for Class II and 212 and 213 for Class III
air vehicle. Preferably there are two or more control surfaces in
each set. The control surfaces are pivotally mounted and are
controlled by a flight control system such that by pivoting the
control surfaces 112 and 113 (212 and 213) of either or both
shrouds the flight operation of the air vehicles can be controlled
about the pitch, yaw and roll axes. Examples of operations of the
control surfaces 112 and 113 are described in greater detail below
for Class II and Class III air vehicles.
[0081] As discussed above, various embodiments of the UAV
incorporates a gyroscopic stabilization (GS) disk 107 (207) that
provides gyroscopic stabilization of the UAV. As it will be
described in greater detail below, the gyroscopic stabilization
disk 107 (207) gyroscopically stabilizes the air vehicle such that
an external or internal force on the air vehicle results in the air
vehicle experiencing gyroscopic precession motion. Gyroscopic
precession is manifested ahead approximately 90 degrees in the
direction of rotation of the gyro stabilizing disk 107 (207). In
other words, the air vehicle is stabilized by the disk 107 (207)
such that when an external torque (having a component perpendicular
to the axis of rotation) acts upon the air vehicle, this results in
a change in the direction of the angular momentum of the UAV. Due
to the gyroscopic stabilization disk 107 (207), the external torque
is manifested as a change in the direction of the angular momentum
of the disk 107 (207). This results in the axis about which the
disk 107 (207) is rotating (in this case the axis 115 (219)
precessing or changing its orientation.
[0082] The angular momentum of the gyroscopic member 107 (207) can
depend on factors such as the weight of the disk 107 (207), the
weight distribution, and also the rate at which it is rotated. In
some embodiments, the weight distribution of the disk 107 (207) is
selected so that the weight is concentrated at the outer perimeter
so as to increase the moment of inertia of the disk (and thus the
angular momentum of the disk at a given rotational rate). In one
embodiment, as it will be described in greater detail below, the
angular momentum of the disk 107 (207) is significantly greater
than the moment of inertia of the rest of the air vehicle about the
axis of the disk rotation 115 (219) so that the air vehicle is
gyroscopically stabilized. As it will be apparent, the weight of
the components comprising the air vehicle are preferably positioned
such that the center of gravity and the aerodynamic center of the
air vehicle are substantially coincident with the center of
rotation of the disk such that the stability of the air vehicle is
enhanced.
[0083] In some embodiments, an electrical starter and an electrical
generator could be attached to the air vehicle engine 104 (204)
such that the electrical starter can start the engine from a remote
command and the electrical generator can produce electrical power
for the electrical system of the air vehicle. As discussed above,
the propellers 103 (203) are preferably variable pitch propellers
and a variable pitch mechanism of a type known in the art is used
to control the pitch of the propellers so as to control the thrust
produced by the aircraft and, consequently, the speed of operation
of the air vehicle.
[0084] By gyroscopically stabilizing the UAV, internal and external
torque(s) exerted upon the air vehicle during flight can result in
the precession of the air vehicle. Moreover, the gyroscopic
stabilization of the air vehicle results in a slower rate of change
in the orientation of the air vehicle in response to changes in
internal and external torque(s), such as changing due to fuel
consumption, change in propeller pitch, wind and other disruptive
forces. This decrease in the rate of change of the orientation of
the air vehicle gives ample time to flight control system and/or
the pilot to respond and control the air vehicle.
[0085] In particular, it will be appreciated that the gyroscopic
disk enables the attitude or orientation of the air vehicle to be
changed in a predictable manner. In particular, since the angular
momentum of the gyroscopic disk is relatively large when compared
with the rotational inertia of the air vehicle along an axis
perpendicular to the rotational axis of the gyroscopic disk as it
will be described in greater detail below, the rotational dynamics
of the air vehicle are substantially influenced by the rotational
dynamics of the gyroscopic disk. Specifically, instead of changing
the magnitude of the angular momentum of the air vehicle an
external torque acting on the air vehicle which is substantially
perpendicular to the rotational axis of the gyroscopic disk induces
the angular momentum of the gyroscopic disk to change direction.
Thus, when the air vehicle is exposed to such external torque(s),
the air vehicle will tend to rotate in a manner that eventually
results in a substantially slow precession of the gyroscopic disk.
Furthermore, since the rotational axis of the gyroscopic disk
changes in the direction of the applied torque, the gyroscopic disk
can be induced into precession within a first plane simple by
exposing the air vehicle to at least one external force which is
substantially perpendicular to the first plane as it will be
describe in greater detail below.
[0086] It will also be appreciated that the relatively large
angular momentum of the gyroscopic disk provides the air vehicle
with improved stability. Furthermore, since the rate of precession
of any spinning object is inversely proportional to the magnitude
of its angular momentum, the relatively large angular momentum of
the gyroscopic disk ensures that the air vehicle will most likely
experience a relatively small rotational velocity.
[0087] Thus, when an uncontrollable external torque is applied onto
the air vehicle, such as that caused by turbulent airflow over the
exposed surfaces of the air vehicle, the air vehicle can react in a
relatively slow manner. Consequently, since such torques are
usually exerted over short periods of time, the air vehicle is less
likely to experience a change in attitude that is beyond an
uncorrectable threshold level. Moreover, since the average value of
such torques over extended periods of time is substantially small,
less attitude adjustment is demanded of the control system.
Furthermore, since the control system is provided a relatively
large reaction time period, the control system is better able to
provide attitude correction so that the attitude of the air vehicle
is more likely to remain within an acceptable range so as to reduce
the likelihood that the air vehicle will likely undergo
uncontrollable rolling motion along either of its gyro stabilized
axes.
[0088] In some embodiments, the UAV can incorporate a control
system that is configured to control the air vehicle during flight.
In one embodiment, the control system can include an on-board
computer that maintains the UAV desired orientation and heading in
accordance with a programmed flight path and it will also be
responsive to external commands from a remote location so as to
change the orientation and heading of the aircraft. Further, since
the UAVs are usually adapted to provide reconnaissance, the control
system can also be configured to accommodate equipments such as the
video/IR sensor 114 (214) in order to obtain reconnaissance
data.
[0089] In one embodiment, the UAV control system can be in
communication with a ground control station (GCS) and include a
data link for the reconnaissance signal and telemetry signals.
Thus, the flight control system can include a flight controller
which is receiving information from onboard sensors indicating the
current orientation and flight characteristics of the UAV. The
control system can be further capable of receiving and sending
information to the GCS via telemetry system. The flight controller
receives heading information from the GCS, but has onboard control
suitable for maintaining a desired orientation or attitude of the
aircraft. The flight controller can be capable of sending output
signals to control surface actuators and the propulsion control
actuators. The flight controller is also capable of receiving and
sending output signals to control the reconnaissance sensor
orientation. It is contemplated that the aircraft can be operated
in either an auto pilot mode or in a manual mode.
[0090] As discussed above, the UAV can include four sets of control
surfaces 112, 113 (212, 213) capable of controlling the orientation
of the aircraft about the yaw, pitch and roll axes. Moreover, the
propulsion unit can be controlled either by increasing the speed of
operation of the engine 104 (204) or, in the embodiments where the
speed of operation of the engine is fixed, by varying the pitch
angle of the propellers 103 (203) to increase or decrease the
degree of thrust produced by each individual propeller of the
vehicle. Each variable pitch propeller 103 (203) can be controlled
independently.
[0091] In some embodiments, effectuating the foregoing actuations
of the control surfaces and/or the propeller pitch can be achieved
in a known manner. In some embodiments, the flight controller can
be programmed to sense when the orientation of the aircraft about
the pitch roll or yaw axes has moved from a desired orientation as
a result of either internal or external forces acting upon the air
vehicle. Due to the fact that the air vehicle is gyroscopically
stabilized, the speed at which an internal or external force will
create a substantial change in the heading of the aircraft is
slowed down by the considerably higher value of the disk angular
momentum when compared to the air vehicle moments of inertia. The
flight control system thus can have considerably more time to take
corrective action to maintain the desired orientation of the
aircraft. Thus, the aircraft is more stable in operation and the
necessity of applying sudden corrections and sudden movements of
the control surfaces can be reduced as the rate of change of
orientation of the aircraft as a result of external forces is
decreased.
[0092] FIGS. 7A-7D show examples of the positioning of the control
surfaces 112 and 113 (FIGS. 19A-19H for 212 and 213) in order to
effectuate movement about the three axes of the aircraft. In
particular, it should be appreciated that, due to the precession of
the aircraft as a result of the gyroscopic stabilization, an
external or internal force applied to the aircraft, such as the
force resulting from changing the profile of the flight control
surfaces 112 and 113 (212 and 213) and the thrust exhaust of the
variable pitch propellers 103 (203) is manifested ahead
approximately 90 degrees in the direction of rotation. Thus, the
orientation of the control surfaces 112 and 113 (212 and 213) can
be similarly adjusted to achieve a desired movement about the pitch
and yaw axes. Hence, the control system can be configured such that
a change in a desired direction takes into account the gyroscopic
stabilization and the resulting precession of the aircraft.
[0093] In some embodiments, there can be significant differences
between the Class II UAV flight control system and Class III UAV
flight control systems and as result, examples of their operations
are described separately.
Control System Operation for Class II or Class II Type Air
Vehicle
[0094] For Class II UAV or similar vehicles, control surfaces can
maintain their function substantially throughout the flight
envelope. In one embodiment where the gyroscopic spin axis is
generally coaxial with the longitudinal axis of the air vehicle,
the air vehicle can be gyro stabilized in yaw and pitch. In one
embodiment, as shown in FIGS. 2 and 6 (for example), the air
vehicle can include control surfaces 112 and 113 that can provide
various attitude of the air vehicle relative to various axes.
Examples of such controls are now described in reference to FIGS.
7A-7D.
[0095] FIG. 7A shows an example where the orientations of the
control surfaces 112 and 113 for the left and right shrouded
propellers can change in order to effectuate the stability of the
air vehicle about the roll axis which, in one embodiment, is
substantially coincident with the longitudinal axis 115 of the
fuselage 101. In order to counteract the tendency of the air
vehicle to rotate in a counterclockwise direction as a result of
the example clockwise rotation (when facing forward) of the GS disk
107, each of the left and right shrouded propeller 113 control
surfaces can be pivoted in the directions of the arrows 180 so that
a greater surface area is exposed to the thrust from the shrouded
propellers 102 so as to counteract the tendency of the fuselage 101
(see FIGS. 1 to 6) to rotate in the counterclockwise direction in
response to the clockwise torque of the GS disk 107. It will he
appreciated that increasing the angle of the left and right control
surfaces 113 in the direction of the arrows 180 can result in a
roll motion of the air vehicle in the clockwise direction.
Similarly, having the left and right control surfaces 113 to be
pivoted in the opposite direction, i.e. in the direction of the
arrows 181, can result in the air vehicle to roll in a
counterclockwise direction.
[0096] FIG. 7B shows an example of the orientation of the left and
right control surfaces 112 to effectuate the pitch of the air
vehicle. Pitch is the longitudinal change of the air vehicle about
the pitch axis 116 that is perpendicular to the longitudinal axis
115 and yaw axis 117. In effect, the forward edge of the fuselage
is moving either up or down with respect to the rear edge. Due to
the gyroscopic precession, the left and right control surfaces 112,
i.e. the vertical control surfaces in this particular example
orientation of the aircraft, can be both moved either left or right
in order to effectuate a change in pitch of the aircraft. In
particular, moving the control surfaces 112 in a direction 190 such
that a larger surface area of the control surfaces 112 are exposed
to the thrust emanating from the left and right propellers 103
which thereby imparts a force on the rear of the aircraft which, in
the absence of precession, would result in the aircraft yawing from
left to right. However, due to the precession of the aircraft, this
results in the forward edge of the fuselage 101 moving up with
respect to the rear edge. Similarly, moving the left and right
control surfaces 112 in the direction 191 can result in the forward
edge of the fuselage 101 dipping downward with respect to the rear
edge.
[0097] Another way of controlling the air vehicle pitch, as shown
in FIG. 7C, is by adjusting the left or right shrouded propeller
103 blade angle of attack. By reducing or increasing blades angle
of attack the shrouded propeller thrust is reduced or increased
accordingly. When the left shrouded propeller thrust is reduced and
the right shrouded propeller thrust is maintained substantially
constant or increased the fuselage nose can pitch down. Similarly,
when the left shrouded propeller thrust is increased and the right
propeller thrust is reduced or maintained substantially constant
the nose can pitch up.
[0098] Lastly, FIG. 7D shows an example of the orientation of the
left and right control surfaces 113 that can effectuate a yaw, i.e.
a change in orientation about the yaw axis 117 which is
substantially perpendicular to the longitudinal axis 115 and pitch
axis 116. In particular, in order to induce a yaw from left to
right, both left and right control surfaces 113 can be moved in the
direction 184 so that a greater surface area of the control surface
is exposed to the thrust in the direction of the arrows 184 so as
to exert a downward force in the rear of the air vehicle.
Similarly, to get the air vehicle to yaw from right to left, both
left and right control surfaces 113 can be moved in the opposite
direction, i.e. in the direction of the arrows 185.
[0099] Thus as describe above by way of examples, the stability of
the air vehicle can enhanced by having a gyroscopic stabilization
member that translates any force exerted against the air vehicle
into a gyroscopic precession, i.e. a change in the angular
orientation of the air vehicle. The relatively slow rate of change
in the orientation of the air vehicle can allow for greater
stability which thereby allows the air vehicle to more successfully
transition between vertical flight and substantially horizontal
flight.
[0100] In one embodiment, a Class II UAV is designed to take off
and land in a generally vertical orientation off of the landing
gear comprised of the landing legs 110 and landing ring 111. After
leaving the ground (as depicted in FIG. 8C), the air vehicle can
tilt forward (as depicted in FIG. 8B) in a particular direction. In
one example, the forward tilt of the longitudinal axis 115 is
approximately 10 to 15 degrees from a perpendicular axis. As the
air vehicle gains forward speed the shrouded propellers can tilt
forward to a forward flight angle of attack of approximately 8-10
degrees or as required by the flight mission (as depicted in FIG.
8A).
[0101] As described herein some embodiments of the Class II UAV can
have wings, while some do not. For example, the air vehicle
depicted in FIGS. 8A-8C includes wings. FIGS. 9A-9C show a Class II
UAV without wings in a transition from a vertical takeoff to a
horizontal flight, in a manner generally similar to that shown in
FIGS. 8A-8C.
Control System Operation for Class III or Class III Type Air
Vehicle
[0102] In some embodiments, Class III UAV control surfaces can
change their function from vertical flight to horizontal flight.
The air vehicle can be gyro stabilized in roll and pitch.
[0103] FIG. 19A shows the direction at which the control surfaces
212 and 213 for the left and right shrouded propellers can change
in order to effectuate the stability of aircraft about the aircraft
yaw axis 219 (in and out of page in FIG. 19A) which can be
substantially coincident with the GS disk 207 spin axis in vertical
flight and in forward flight. In order to counteract the tendency
of the aircraft to rotate in a counterclockwise direction as a
result of the example clockwise (when viewed from the top) rotation
of the GS disk 207, in vertical flight each of the left and right
shrouded propeller control surfaces 213 can be pivoted in the
directions of the arrows 284.
[0104] During forward flight, as shown in FIG. 19E, the tendency of
the aircraft to rotate counterclockwise in response to the
clockwise torque of the GS disk 207, is taken over by the left and
right 212 control surfaces which can be pivoted in the direction of
the arrows 284.
[0105] It will be appreciated that increasing the angle of the left
and right control surfaces 213 in the direction of the arrows 284
for vertical flight and of the left and right 212 control surfaces
in forward flight can result in a yaw right motion of the air
vehicle. Similarly, having the left and right control surfaces 213
to be pivoted in the opposite direction for vertical flight and
left and right control surfaces 212 for forward flight, i.e. in the
direction of the arrows 285, can result in the air vehicle to yaw
left.
[0106] FIG. 19B shows an example orientation of the left and right
control surfaces 212 that can effectuate the pitch of the air
vehicle in vertical flight. In forward flight the air vehicle's
pitch motion can be controlled by differential deflection of left
and right control surfaces 213 as illustrated in FIG. 19F.
[0107] Pitch is the longitudinal change of the aircraft about the
pitch axis 218 that is substantially perpendicular to the
longitudinal axis 217 and yaw axis 219. In effect, the forward edge
of the fuselage is moving either up or down with respect to the
rear edge. Due to the gyroscopic precession, the left and right
control surfaces 212 can be both moved either left or right in
order to effectuate a change in pitch of the aircraft for vertical
flight and control surfaces 213 can be moved differentially (one
up, and the other down) in order to effectuate a change in pitch in
forward flight. In particular, moving the control surfaces 212 in a
direction 290 for vertical flight (FIG. 19B) and control surfaces
213 in a direction 290 for forward flight (FIG. 19F), imparts a
force on the rear of the aircraft which due to the precession of
the aircraft, results in the forward edge of the fuselage 201
moving up with respect to the rear edge. Similarly, moving the left
and right control surfaces 212 in the direction 291 for vertical
flight (FIG. 19B) and control surfaces 213 in a direction 291 for
forward flight (FIG. 19F) can result in the forward edge of the
fuselage 201 dipping downward with respect to the rear edge.
[0108] Another way of controlling the aircraft pitch in vertical
flight is by adjusting, for the left or right shrouded propeller
203, blade angle of attack as shown in FIG. 19C. By reducing or
increasing blades angle of attack the shrouded propeller thrust is
reduced or increased accordingly. When the left shrouded propeller
thrust is reduced and the right shrouded propeller thrust is
maintained substantially constant or increased (depicted as arrows
291) the fuselage nose can pitch down. Similarly, when the left
shrouded propeller thrust is increased and the right propeller
thrust is reduced or maintained substantially constant (depicted as
arrows 290) the aircraft nose can pitch up.
[0109] In forward flight, as shown in FIG. 19G, when the left
shrouded propeller thrust is reduced and the right shrouded
propeller thrust is maintained substantially constant or increased
(depicted as arrows 285) the aircraft can yaw left. Similarly, when
the left shrouded propeller thrust is increased and the right
propeller thrust is reduced or maintained substantially constant
(depicted as arrows 284) the aircraft can yaw right.
[0110] FIGS. 19D and 19H show the orientation of the left and right
control surfaces 213 that can effectuate a roll in vertical flight
(FIG. 19D) and forward flight (FIG. 19H), i.e. a change in
orientation about the longitudinal axis 217. In particular, in
order to induce a left roll, both left and right control surfaces
213 can be moved together in the direction 280 so that a greater
surface area of the control surface is exposed to the thrust in the
direction of the arrows 280 so as to exert a downward force on the
left wing of the aircraft. Similarly, to get the aircraft to roll
right, both left and right control surfaces 213 can be moved in the
opposite direction, i.e. in the direction of the arrows 281. In one
embodiment, Class III air vehicle roll control surfaces and
functions can remain substantially the same throughout the flight
envelope.
[0111] Hence, the stability of the aircraft can be enhanced as a
result of having a gyroscopic stabilization member that translates
one more forces exerted against the aircraft into gyroscopic
precession, i.e. a change in the angular orientation of the
aircraft. The relatively slow rate of change in the orientation of
the aircraft allows for greater stability which thereby allows the
aircraft to more successfully transition between vertical flight
and substantially horizontal flight (for example, from vertical
flight to substantially horizontal flight).
[0112] In some embodiments, Class III UAVs can be designed to
operate in vertical takeoff and landing (VTOL) mode, short takeoff
and landing (STOL) mode and conventional takeoff and landing (CTOL)
mode. In one embodiment, to takeoff and land on the vertical the
shrouded propellers 202 can have a generally vertical orientation
and the fuselage 201 a generally horizontal orientation. The
landing gear such as a tricycle type landing gear 210 and 211, can
be attached to the fuselage. An example of a vertical takeoff is
depicted in FIG. 20C. After leaving the ground the shrouded
propellers 202 can then tilt forward in a particular direction with
respect to their longitudinal axes 220 and 221. An example of such
a transition configuration is depicted in FIG. 20B. In one
embodiment, such a tilt can be approximately 10 to 15 degrees from
the perpendicular axis. As the aircraft gains forward speed, the
shrouded propellers can tilt forward to a forward flight angle of
attack. An example of such forward flight configuration is depicted
in FIG. 20A. In on embodiment, the forward flight angle of attach
can be approximately 8-10 degrees or as required by the flight
mission. In one embodiment, the fuselage 201 maintains its
generally horizontal orientation.
[0113] As described herein some embodiments of the Class II UAV can
have wings, while some do not. For example, the air vehicle
depicted in FIGS. 20A-20C includes wings. FIGS. 21A-21C show a
Class III UAV without wings in a transition from a vertical takeoff
to a horizontal flight, in a manner generally similar to that shown
in FIGS. 20A-20C.
[0114] In some embodiments, for a short takeoff the shrouded
propellers 202 can be tilted forward at an angle of approximately
15-20 degrees from the perpendicular axis. For a conventional
takeoff the shrouded propellers can be tilted at an angle of
approximately 70-75 degrees from the perpendicular axis. As the
aircraft rolls forward at a certain forward speed it will lift off
the ground and become airborne. The shrouded propellers can then be
tilted forward to a forward flight angle of attack of approximately
8-10 degrees or as required by the flight mission. On landing the
aircraft can land on the vertical, short landing with the shrouds
tilted at approximately 15-20 degrees and conventional landing with
the shrouds tilted at approximately 70-75 degrees from the
perpendicular axis. The short and conventional takeoff could be
used to increase the aircraft payload capability.
[0115] Flying forward with the shrouds at a very high angle of
attack is limited by the forward speed. Flying forward the inner
surfaces of the shroud 102, the fuselage 101 and the wings 109 are
forming the flight surfaces in a well-known manner. It will,
however, be appreciated that, as the speed of the aircraft is
increased in the transition mode, turbulence can result in the
shrouded propellers that could reduce the shrouded propeller thrust
and stress the propeller blades.
[0116] Consequently, ducted fan aircrafts have a relatively low
maximum horizontal flight speed in the hover mode. Moreover, due to
the instability associated with these particular aircraft, ducted
fan aircraft have been unable to make the transition to full
horizontal flight wherein the longitudinal axis 115 is
substantially parallel to the plane of the earth or, alternatively,
the plane of rotation of the propellers 102 is substantially
perpendicular to the plane of the earth.
[0117] It will be appreciated that the inability of ducted fan
aircraft to travel in a horizontal mode limits the upper speed of
the aircraft which, in combat environments, can be too slow to
protect the aircraft. By gyroscopically stabilizing the aircraft,
the Applicant is capable of producing an aircraft that can make the
transition from vertical flight or hover flight into substantially
horizontal flight. This is due to the increase in the angular
momentum of the aircraft and the fact that the rate of change in
the angular orientation of the aircraft due to external forces is
decreased approximately by the ratio of the angular momentum to the
moment of inertia of the aircraft. Hence, due to the increased
stability, the Applicant can fly a shrouded propeller configuration
of aircraft in a vertical mode, a hover mode and a horizontal
mode.
[0118] The shrouded propeller air vehicle has a much lower disk
loading (ratio between the propeller disk area and the air
vehicle's weight) than the disk loading of a ducted fan air
vehicle. The lower disk loading can enable a shrouded propeller air
vehicle to carry significantly more payload and have a much longer
endurance in hover and forward flight.
[0119] Class III air vehicle has a significant advantage over the
ducted fan when landing in adverse weather conditions. When landing
on the vertical in windy conditions a ducted fan has to tilt into
the wind and land at an angle to the ground surface. This situation
may lead to the possibility of the air vehicle flipping over and
rolling on the landing surface. Landing in cross winds becomes more
critical when the ducted fan has to land on a rolling and pitching
landing platform of a Navy vessel. In one embodiment, Class III
fuselage remains generally parallel to the landing surface. As the
air vehicle approaches the landing surface only the shrouded
propellers tilt into the wind. The air vehicle can land on the
vertical and can even roll forward a few feet before coming to a
complete stop.
Example Configuration for One Embodiment of a Class II UAV
[0120] Table 1 provides a list of estimated performance
characteristics for one example embodiment of a Class II UAV. Other
configurations are possible.
TABLE-US-00001 TABLE 1 Description Characteristic Power plant 1
.times. 372 cc Power available for VTOL thrust 30 HP Shrouded prop
inside diameter 21 in Shrouded prop exit diameter 22 in Shrouded
prop outside diameter 27 in Air vehicle height (VTOL) 30 in Span
(without wings) 60 in Span (with wings) 13 ft Empty weight (without
wings) 102 lb Wings weight 8 lb Fuel weight (without wings) 48 lb
Fuel weight (with wings) 30 lb Payload weight 20 lb Maximum
vertical takeoff weight 170 lb Air speed for optimized endurance 60
kts Air speed for optimized range 80 kts Endurance - hover at range
3.2 hrs Endurance - loiter (with wings) 7 hrs Altitude 25,000 ft
Range 16 km
Example Configuration for One Embodiment of a Class III UAV
[0121] Table 2 provides a list of estimated performance
characteristics for one embodiment of a Class III UAV. Other
configurations are possible.
TABLE-US-00002 TABLE 2 Description Characteristic Power plant 2
.times. 280 cc Power available for VTOL thrust 2 .times. 25 HP = 50
HP Shrouded prop inside diameter 21 in Shrouded prop exit diameter
22 in Shrouded prop outside diameter 27 in Air vehicle height
(VTOL) 30 in Air vehicle length 60 in Span (without wings) 72 in
Span (with wings) 14 ft Empty weight (without wings) 120 lb Wings
weight 10 lb Fuel weight (without wings) 68 lb Fuel weight (with
wings) 58 lb Payload weight 20 lb Maximum vertical takeoff weight
190 lb Air speed for optimized endurance 60 kts Air speed for
optimized range 100 kts Endurance - hover at range 1.5 hrs
Endurance - loiter (with wings) 4 hrs Altitude 25,000 ft Range 125
km
Example Configuration of Flight Control System
[0122] FIG. 22 shows a block diagram of one embodiment of a flight
control system 700 that includes a flight control component 702.
The flight control component 702 is depicted as receiving one or
more input signals from a user control 704 and/or one or more
sensors 706. A dashed line 708 indicates that the input from the
user control 704 can be wireless (for example, when remotely
controlled) or wire-based. In one embodiment, an input from the
user control 704 may include a control instruction indicative of
the user's desire to change the existing flight parameter(s) (for
example, direction of flight or transition between vertical and
horizontal flight). For the purpose of description of FIG. 22 (and
FIG. 23), a "user" can include a human operator or a set of
programmed instructions.
[0123] In one embodiment, an input from the sensor 706 can include
one or more signals indicative of changes or sudden perturbations
of the existing flight parameter(s). For example, as described
above, effects such as sudden wind gusts or consumption of fuel can
result in relatively sudden or relatively gradual changes that can
affect the direction and/or attitude of the air vehicle.
[0124] As shown in FIG. 22, the flight control component 702 can
receive such inputs and generate one or more output signals for
effectuating the adjustments of the flight control surface(s). In
some embodiments, such adjustments of the flight control surface(s)
induce a precession of the angular momentum of the gyroscopic
stabilization member. Examples of such examples have been described
above.
[0125] FIG. 23 shows one embodiment of a process that can be
performed by the flight control component 702 of FIG. 22. In a
process block 722, input signal is received from a user control
and/or a sensor. In one embodiment, the input signal is indicative
of a need or a desire to change at least one of the air vehicle's
pitch, yaw, and roll orientation. In a process block 724, the
process 720 determines an adjustment of one or more flight control
surfaces to induce gyroscopic precession in a desired direction. In
a process block 726, one or more output signals are transmitted to
effectuate the adjustment of the one or more flight control
surfaces.
Example Configuration of Gyroscopic Stabilization Member
[0126] In some embodiments, the gyroscopic stabilization (GS)
member can be configured to accommodate different flight
requirements or characteristics. Dimensions, total mass,
mass-distribution, or any combination thereof, can be adjusted to
provide a desired angular momentum of the GS member.
[0127] In some embodiments, the desired angular momentum can be
chosen depending on various factors. For example, having a
relatively large angular momentum can provide more GS
stabilization. In some situations, such stabilization can be at the
expense of maneuverability, which may or may not be desirable. In
some embodiments, such conflicting flight characteristics can be
accommodated by allowing for adjustments to the GS member--by
changing the moment of inertia of the GS member (by replacement,
for example) and/or by changing the rotational speed of the GS
member. For example, an initial GS configuration may provide a
relatively large angular momentum, thereby providing a very stable
and steady air vehicle for a pilot to become familiar with the air
vehicle's flight characteristics. As the pilot's expertise in
flying the air vehicle increases, the angular momentum of the GS
member may be reduced, thereby providing greater maneuverability.
In some embodiments, the angular momentum may further be reduced
when the air vehicle is controlled by an airborne computer.
[0128] FIGS. 24A and 24B show different views of one embodiment of
a disk member 750 that can be used as a gyroscopic stabilization
(GS) member. As shown, the disk member 750 can include a disk 752
mounted to a shaft 754. In one embodiment, the disk 752 can be spun
by coupling the shaft to a power source (for example, coupling an
engine shaft via a gear box) in various known manners.
[0129] For the example embodiments described above in reference to
Tables 1 and 2, one embodiment of the disk member 750 can include a
precision machined steel shaft 754, a middle (radial) section 756
and an outer section 758. The middle section 756 and the outer
section 758 can be fabricated from high strength carbon fiber. The
disk's angular momentum varies substantially directly with its
rotational velocity and its moment of inertia. In one embodiment,
as shown in FIGS. 24A and 24B, mass can be distributed more towards
the periphery of the disk to provide a greater moment of inertia
(and thereby greater angular momentum for a given rotational rate)
for a given total mass and overall dimension of the disk 752.
[0130] In one example embodiment, the radial middle section
includes unidirectional carbon fibers having a radial orientation.
Multiple layers of fibers and the steel shaft are placed in an
aluminum mold and cured at high temperature. After the radial
middle section is cured the outer diameter is machined to the
designed dimensions and the assembly is placed in the ring mold.
The ring is fabricated of a continuous carbon fiber tow. As the
disk mold assembly is rotated on an assembly fixture the continuous
fiber, subjected to a pull force, is placed in the mold. The entire
assembly is placed in a vacuum bag to substantially eliminate
possible air bubbles and cured at high temperature. After the
curing process, the outer ring surface layer is machined for
uniformity. The disk is then dynamically balanced and become ready
for installation. Should it be necessary, the mass of the outer
section can be increased by weaving in one or more very thin
continuous steel wire.
[0131] For the example Class II UAV described above in reference to
Table 1, the above-described GS disk 750 can be spun at, for
example, about 30,000 to 32,000 RPM. For the example Class III UAV
described above in reference to Table 2, the above-described GS
disk 750 can be spun at, for example, about 24,000 RPM. As
described herein, other rotational rates are possible.
Examples of Variations of the Air Vehicle
[0132] Based on the foregoing description, it will be appreciated
that many variations of gyroscopically stabilized air vehicle can
be implemented. Some non-limiting example variations and/or
alternate embodiments include, UCAV-type aircraft such as VTOL
UCAV, MRE VTOL UCAV, and HALE VTOL UCAV; Class IV or larger UAVs
such as Class IV VTOL UAV, MRE VTOL UAV, and HALE VTOL UAV; and
manned aircraft such as One-Two seat M/U/C VTOL aircraft, Four-Six
seat M/U/C VTOL aircraft, and 20-seat M/U/C VTOL aircraft. Other
variations are possible.
[0133] For example, various features of the present disclosure can
be applied to larger VTOL UAV designed to fulfill the FCS Class IV
requirements. Due to their relatively long endurance, such air
vehicles can provide continuous 72 hours reconnaissance coverage
which could include 72 hours persistent stare.
[0134] In another example, a similar-sized aircraft as a
single-seat or a Class IV could fulfill the role of a low cost VTOL
UCAV. Its speed flexibility (0-350 mph), relatively high
maneuverability and relatively small size can make it ideal to
conduct missions in confined spaces like an urban environment or
rough mountainous terrain. The aircraft can hover, fly at low speed
and when necessary dash at high speed to escape enemy fire. Due to
its gyroscopic stability and the fact that all its moving
components are substantially entirely enclosed (in one embodiment)
the aircraft can bump into land structures without changing its
position in space. The aircrafts gyroscopic stability during such
sudden impacts has been demonstrated in testing of various
embodiments of the air vehicles of the present disclosure. The
aircraft can provide a stable and steady platform for weapons
delivery.
[0135] Other applications for larger air vehicles are also
contemplated. Larger shrouded propeller aircrafts have been
demonstrated in 1950s and 1960s. However, those programs did not
succeed due to stability and control problems in vertical and
transition to and from forward flight and also low payload
capabilities. Applying materials technology the aircrafts could be
built considerably lighter. For example, in 1950s and 1960s, such
aircrafts were built of metal (aluminum and steel); whereas now,
aircraft structures can be built using materials such as graphite
composites that are considerably lighter and stronger. Also,
today's engines have a higher power to weight ratio and better
controls then the engines produced in 1960s.
[0136] In the description herein, various embodiments of the
aircraft were described as having two propulsion units (for example
two shrouded propellers). However, it will be understood that more
than two (for example, four) propulsion units can be used.
[0137] In some embodiments, the air vehicles of the present
disclosure can have propulsion systems other than the shrouded
propellers. For example, turbofan engines or jet engines can be
used.
[0138] In one embodiment, the shrouded propeller propulsion system
can be replaced with large diameter turbofans, to provide speed and
lifting capabilities of the aircraft. The turbofans can produce a
more powerful jet blast on the take off and landing surface and as
a result the vertical takeoff and landing may be restricted to
prepared surfaces (concrete, metal, etc.). From unprepared surfaces
the air vehicle can takeoff after a very short run and on landings
rolling a short distance on the ground. A larger turbofan will
provide adequate mixing of hot and cool exhaust gasses, thus
reducing the infrared signature on landing surface and in
flight.
[0139] Such high performance VTOL aircraft can be useful for Navy
applications. The landing platforms are readily available and the
aircraft's high speed and endurance can enable it to cover large
distances. A medium to high speed VTOL air vehicle powered by
turbofans can be configured for UAV and/or UCAV missions. As a
manned aircraft it could find uses with special operations,
executive aircraft, commuter aircraft, transport aircraft, etc.
[0140] Although the above-disclosed embodiments have shown,
described, and pointed out the fundamental novel features of the
invention as applied to the above-disclosed embodiments, it should
be understood that various omissions, substitutions, and changes in
the form of the detail of the devices, systems, and/or methods
shown may be made by those skilled in the art without departing
from the scope of the invention. Consequently, the scope of the
invention should not be limited to the foregoing description, but
should be defined by the appended claims.
* * * * *