U.S. patent application number 16/163673 was filed with the patent office on 2022-02-17 for propulsion system for highly maneuverable airship.
The applicant listed for this patent is Daniel Wibbing. Invention is credited to Daniel Wibbing.
Application Number | 20220048609 16/163673 |
Document ID | / |
Family ID | 1000006122261 |
Filed Date | 2022-02-17 |
United States Patent
Application |
20220048609 |
Kind Code |
A9 |
Wibbing; Daniel |
February 17, 2022 |
Propulsion System for Highly Maneuverable Airship
Abstract
One embodiment of a propulsion system for omnidirectional
maneuverability and efficient forward flight of an airship
comprising only fixed, unidirectional engines (17, 19, 20). The
thrust vectors of the fixed engines (19, 20) are oriented in a way
that their speeds can be chosen such that all forces acting on the
airship (i.e., engine thrusts, gravity, buoyancy, wind and
potentially others) are together resulting in the desired motion.
In one embodiment these are four ducted fans (17) at the bow and
four ducted fans (19) at the stern of the aircraft. Their thrust
vectors can be decomposed into three vectors of equal length that
are each parallel to one of the three axis of a cartesian
coordinate system like defined in FIG. 8. In one embodiment
efficient forward flight is achieved by an additional engine (20)
at the stern of the airship.
Inventors: |
Wibbing; Daniel;
(Ostfildern, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Wibbing; Daniel |
Ostfildern |
|
DE |
|
|
Prior
Publication: |
|
Document Identifier |
Publication Date |
|
US 20200122813 A1 |
April 23, 2020 |
|
|
Family ID: |
1000006122261 |
Appl. No.: |
16/163673 |
Filed: |
October 18, 2018 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
62574532 |
Oct 19, 2017 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B64B 1/26 20130101; B64B
1/30 20130101; B64B 1/12 20130101 |
International
Class: |
B64B 1/26 20060101
B64B001/26; B64B 1/30 20060101 B64B001/30; B64B 1/12 20060101
B64B001/12 |
Claims
1. A propulsion system for an airship comprising at least six
engines rigidly attached to said airship and the at least six
thrust vectors of said engines fixedly oriented in a way that the
magnitude of their thrust can be chosen such that all forces acting
on the airship are together resulting in any desired motion in the
six degrees of freedom.
2. Propulsion system of claim 1 wherein the number of said engines
is eight.
3. Propulsion system of claim 2 wherein all of said eight engines
are arranged around the radial circumference of the hull of said
airship and four of said eight engines are located closer to the
bow of the airship and the other four of said eight engines are
located closer to the stern of the airship.
4. Propulsion system of claim 3 wherein the thrust vector of the
engine that is located at the upper right quarter of the bow is
pointing in the direction with the vector components x=a*1, y=b*-1,
z=c*1, the thrust vector of the engine that is located at the upper
left quarter of the bow is pointing in the direction with the
vector components x=a*1, y=b*1, z=c*1, the thrust vector of the
engine that is located at the lower right quarter of the bow is
pointing in the direction with the vector components x=a*1, y=b*-1,
z=c*-1, the thrust vector of the engine that is located at the
lower left quarter of the bow is pointing in the direction with the
vector components x=a*1, y=b*1, z=c*-1, the thrust vector of the
engine that is located at the upper right quarter of the stern is
pointing in the direction with the vector components x=d*-1,
y=e*-1, z=f*1, the thrust vector of the engine that is located at
the upper left quarter of the stern is pointing in the direction
with the vector components x=d*-1, y=e*1, z=f*1, the thrust vector
of the engine that is located at the lower right quarter of the
stern is pointing in the direction with the vector components
x=d*-1, y=e*-1, z=f*-1, the thrust vector of the engine that is
located at the lower left quarter of the bow is pointing in the
direction with the vector components x=d*-1, y=e*1, z=f*-1,
relative to a cartesian coordinate system who's x-axis is pointing
parallel to the longitudinal axis of the airship towards the stern
of the airship, who's y-axis is pointing parallel to the lateral
axis of the airship towards the right side in the direction of
forward travel and who's z-axis is pointing parallel to the
vertical axis of the airship towards the upper side of the airship,
where * is used to express an arithemtic multiplication and a, b,
c, d, e, and f are rational numbers that can be positive or
negative but not zero.
5. Propulsion system of claim 4 wherein said a, c, d, and f take
the value -1 and said b and e take the value -2.
6. Propulsion system of claim 1 wherein at least one of said
engines are ducted fans mounted inside of a streamlined
housing.
7. Propulsion system of claim 6 wherein said airship possesses four
fins and each of said streamlined housings at the stern of said
airship serves as mounting and stabilization means for one of said
four fins.
8. Propulsion system of claim 1 wherein there is at least one
engine of the said at least six engines who's thrust vector is
approximately oriented into the direction of forward flight in
order to enable an efficient flight in the forward direction.
9. Propulsion system of claim 8 wherein said at least one engine
who's thrust vector is approximately oriented into the direction of
forward flight is an engine at the stern of the airship.
10. A propulsion system for an airship comprising nine engines
rigidly attached to said airship whereof eight engines are ducted
fans and the ninth engine has a propeller with a larger diameter
than the propellers of said ducted fans.
11. Propulsion system of claim 10 wherein said ducted fans are
attached to the hull of said airship in a way that four of said
ducted fans are located closer to the bow of said airship and the
other four of said ducted fans are located closer to the stern of
said airship and in a way that all of said ducted fans are equally
distributed around the radial circumference of said hull, such that
in each quarter of the circumference of said hull there is one of
said ducted fans that is closer to the bow and one of said ducted
fans that is closer to the stern of said airship.
12. Propulsion system of claim 11 wherein said ninth engine is
mounted to the stern of said airship and its thrust vector is
approximately pointing in the direction (x, y, z)=(1, 0, 0)
relative to the cartesian coordinate system of said airship.
13. Propulsion system of claim 12 wherein the thrust vector of the
ducted fan that is located at the upper right quarter of the bow is
pointing in the direction (x, y, z)=(a*1, b*-1, c*1), the thrust
vector of the ducted fan that is located at the upper left quarter
of the bow is pointing in the direction (x, y, z)=(a*1, b*1, c*1),
the thrust vector of the ducted fan that is located at the lower
right quarter of the bow is pointing in the direction (x, y,
z)=(a*1, b*-1, c*-1), the thrust vector of the ducted fan that is
located at the lower left quarter of the bow is pointing in the
direction (x, y, z)=(a*1, b*1, c*-1), the thrust vector of the
ducted fan that is located at the upper right quarter of the stern
is pointing in the direction (x, y, z)=(d*-1, e*-1, f*1), the
thrust vector of the ducted fan that is located at the upper left
quarter of the stern is pointing in the direction (x, y, z)=(d*-1,
e*1, f*1), the thrust vector of the ducted fan that is located at
the lower right quarter of the stern is pointing in the direction
(x, y, z)=(d*-1, e*-1, f*-1), the thrust vector of the ducted fan
that is located at the lower left quarter of the bow is pointing in
the direction (x, y, z)=(d*-1, e*1, f*-1), relative to a cartesian
coordinate system of said airship, where * is the symbol for a
multiplication, a, b, c, d, e, and f are rational numbers that can
be positive or negative but not zero and the direction vectors are
meant as approximate vectors.
14. Propulsion system of claim 13 wherein said b and e each take
the value -2 and said a, c, d, and f each take the value -1.
15. Propulsion system of claim 11 wherein said ducted fans are
attached to said hull by being mounted inside of streamlined
housings and said streamlined housings being shaped in a way that
reduces their drag force in the direction of forward flight.
16. Propulsion system of claim 15 wherein said airship possesses
four fins and each of said streamlined housings at the stern of
said airship serves as mounting and stabilization means for one of
said four fins.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] The present application claims priority from provisional
patent application with Application No. 62/574,532, EFS ID
30707227, Confirmation Number 5395, filed 19 Oct. 2017 by the
present inventor, which is incorporated by reference in its
entirety.
TECHNICAL FIELD
[0002] The present invention relates to ligther-than-air vehicles,
and more particularly to their propulsion system.
BACKGROUND
Prior Art
[0003] The following is a tabulation of some prior art that
presently appears relevant:
U.S. Patents
TABLE-US-00001 [0004] Publication Pat. No. Kind Code Date Patentee
U.S. Pat. No. 5,449,129A B64B 1/26 1995 Sep. 12 Lockheed Corp. U.S.
Pat. No. 5,026,003 B64B 1/34 1991 Jun. 25 Smith U.S. Pat. No.
4,402,475 B64B 1/26 1983 Sep. 6 Airships Intl., Inc. US
020150078620A1 B64B 1/30 2015 Mar. 19 Disney Res Zurich U.S. Pat.
No. 1,457,024 B64B 1/26 1923 May 23 Franzen
Nonpatent Sources
[0005] Johannes EiBing; discussion in Facebook group "Small Airship
Union"; April 2015;
https://www.facebook.com/groups/smallairshipsunion/436456063183024/
[0006] Guy Norris, "Hybrid Hopes: An Inside Look At The Airlander
10 Airship", Aviation Week, May 15, 2015,
http://aviationweek.com/technology/hybrid-hopes-inside-look-airlander-10--
airship
[0007] The above propulsion systems and most other existing
propulsion systems for airships can be divided into three
categories: [0008] Swiveled engines [0009] Pitch-adjusted propeller
blades [0010] Fixed engines [0011] in direct air flow [0012] in
combination with thrust redirecting ducts or tubes [0013] in
combination with thrust redirecting vanes
[0014] Swiveled engines liked described by Lockheed and Disney have
two main disadvantages: [0015] Swiveling and thus changing the
direction of thrust takes some time. Immediately reacting to gusts
of wind or other fast maneuvers are hardly possible that way.
[0016] Additional actuators are necessary to cause the swivel
movement. Weight, energy consumption and complexity increase
compared to fixed engine concepts.
[0017] Pitch-adjusted propeller blades are used to reverse the
direction of thrust of a propeller. The mechanical structures
required to change the pitch of each blade of a propeller are
complex and introduce many additional parts that increase the
chance of a system failure. In order to actuate the pitch adjusting
gears and levers a separate motor is required which increases
weight and energy consumption. Finally the shape of the blades
cannot be optimized for producing thrust in the forward direction.
Instead a compromise has to be found in order to produce a
significant amount of thrust in the reversed direction as well.
[0018] The fixed engine concepts known to me, like the one
described by Smith, have the disadvantage that they do not allow
for a movement of the airship in all six degrees of freedom. Most
of these concepts lack the ability to move the airship in the
lateral direction (left/right).
[0019] The patent by Airships Intl. does describe thrusters at the
bow and stern of an airship. However, their use is only intended as
control thruster for correcting the attitude of the airship instead
of a missing empennage. Using the bow and stern thruster in order
to cause a lateral (sidewards crabbing) movement is not considered.
Vertical thrusters are described for augmentation of static lift of
the airship, but not for increasing maneuverability. Thrusters to
propel the airship forwards or backwards are not described. Like
that an omnidirectional maneuverability is not achievable by the
suggested concept.
[0020] The patent by Franzen describes the use of fixed engines
mounted inside of ducts leading throughout the entire airship body
in order to redirect the thrust of the engines. Franzen does not
describe how an omnidirectional maneuverability of the airship is
achievable by an arrangement of these ducts. The long ducts cause a
lot of friction for the air that is propelled through them, making
the propulsion very inefficient. Actuators for opening and closing
the ducts are required in order to achieve a resulting thrust in
the desired direction increasing complexity, weight and power
consumption.
[0021] The Airlander, a hybrid airship by Hybrid Air Vehicles
Limited, uses fixed engines in combination with thrust redirecting
vanes, like shown in an article by Guy Norris. However the engine
arrangement used does not allow for a lateral movement of the
airship. Tilting the vanes still takes some time, the tilting angle
is limited to less than 90.degree. and in the tilted position the
vanes are not able to redirect the complete amount of propelled air
into the desired direction, thus decreasing the efficiency of the
concept.
[0022] Johannes EiBing described in loose terms how a propulsion
concept with fixed engines could look like that would enable a
movement in almost all direction. However this concept again has
three significant drawbacks: [0023] It does not allow for a
backwards movement. [0024] It only describes the engine orientation
to be 45.degree. relative to the longitudinal and vertical axis of
the airship, which is not ideal for some applications and is not
the only orientation possible. [0025] The efficiency of a forward
flight is reduced because the thrust vectors that have to be
activated for this motion partially cancel each other out.
SUMMARY
[0026] In order to eliminate the disadvantages of the existing
propulsion concepts like those described above, embodiments of a
fixed engine concept is described here that enable
near-instantaneous movements of an airship in all directions
without having to rotate into a special direction first and without
having to reverse the thrust of any engine. This is especially new
for movements in lateral directions, i.e., for movements in the
yz-plane of the cartesian coordinate system relative to the airship
(see, e.g., illustration 1, FIG. 7). The advantages of this
near-instantaneous omnidirectional maneuverability is the ability
to closely follow a pre-defined path in any direction and to
precisely hold a position even under windy conditions. This is an
ability that has previously only been achieved by multirotor
aerodynes.
[0027] In further embodiments, high maneuverability and efficient
forward flight are both possible, as opposed to previous engine
concepts that involved a trade-off between these two objectives.
These flight characteristics are achieved for example in a first
embodiment of the propulsion system that uses eight ducted fans 17
and 19 and a stern engine 20 (see illustration 1, FIG. 7).
[0028] All embodiments have in common that the thrust vector of
each engine is pointing in one fixed direction, and at all times
engine speeds can be chosen such that all forces acting on the
airship (i.e., engine thrusts, gravity, buoyancy, wind and
potentially others) are together resulting in the desired
motion.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] I have included 6 illustrations:
[0030] Illustration 1 includes FIG. 7 which shows the engine
concept on an airship in a three dimensional perspective.
[0031] Illustration 2 includes FIG. 8 which shows the thrust vector
F of one of the eight ducted fans in its three dimensional
orientation and its projections in x, y and z direction that each
have magnitude |F/ 3|.
[0032] Illustration 3 includes FIGS. 9A, 9B, 10A and 10B which show
the following orthographic projections of the engine arrangement on
the airship: back, front, side and top.
[0033] Illustration 4 includes FIGS. 11A, 11B, 12A and 12B which
show the active engines in the top view for movements to the left,
right, back and front respectively.
[0034] Illustration 5 includes FIGS. 13A and 13B, which show the
active engines in the side view for the upwards and downwards
movement respectively. Further included are the FIGS. 14A and 14B,
which show the active engines in the top view for the yaw movement
to the left and to the right respectively.
[0035] Illustration 6 includes FIGS. 15A and 15B, which show the
active engines in the side view for the movements pitch down and
pitch up respectively. Further included are the FIGS. 16A and 16B,
which show the active engines in the front view for the roll
movements to the left and to the right respectively.
LIST OF REFERENCE NUMERALS
[0036] 17 ducted fans (in streamlined housings at bow of airship)
[0037] 17BUR ducted fan at the bow upper right position [0038]
17BUL ducted fan at the bow upper left position [0039] 17BLR ducted
fan at the bow lower right position [0040] 17BLL ducted fan at the
bow lower left position [0041] 18 duct for inlet and outlet of air
in streamlined engine housing [0042] 18BLL duct for inlet and
outlet of air at the bow lower left position [0043] 19 ducted fans
(in streamlined housings at stern of airship) [0044] 19SUR ducted
fan at the stern upper right position [0045] 19SUL ducted fan at
the stern upper left position [0046] 19SLL ducted fan at the stern
lower left position [0047] 19SLR ducted fan at the stern lower
right position [0048] 20 stern engine [0049] 21 fins [0050] 22
gondola [0051] 23 sensor [0052] 24 hull
DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS
[0053] Static Structure and Function
[0054] The figures and illustrations are given with a first
embodiment and a simple version of both model and control system
for the propulsion system in mind. The latter that is described in
the sub-subsection "Simplified Motion Control" of subsection "Hover
Mode" in section "Operation".
[0055] Illustration 1
[0056] In FIG. 7 it is shown that there are nine engines mounted to
the hull 24. These are eight ducted fans 17 and 19 and one
propeller engine 20 at the stern. There are two groups of ducted
fans, which are four ducted fans 17 near the bow and four ducted
fans 19 near the stern of the airship hull 24. One of the four
ducted fans at the stern is not numbered because it is not visible
in the three dimensional view of FIG. 7.
[0057] The ducted fans 17 and 19 each consist of a housing in the
shape of a half-drop that contains the duct for the inlet and
outlet of air (see, e.g., 18BLL) as well as rotor blades and a
motor that are both mounted inside the duct.
[0058] Each of the ducted fans has a unique three-letter name that
describes their locations on the hull 24 as seen from standing
behind the stern of the airship. The ducted fans 17 near the bow
have the following names:
[0059] BUR: Bow Upper Right
[0060] BUL: Bow Upper Left
[0061] BLR: Bow Lower Right
[0062] BLL: Bow Lower Left
[0063] The ducted fans 19 near the stern have the following
names:
[0064] SUR: Stern Upper Right
[0065] SUL: Stern Upper Left
[0066] SLR: Stern Lower Right (see Illustration 3, FIG. 9A)
[0067] SLL: Stern Lower Left
[0068] There are four identical fins 21 with rudders (not shown)
which are mounted on the streamlined housings of the ducted fans 19
near the stern. The advantage of mounting the fins 21 directly onto
the streamlined housings is, that the housings are serving the
additional purpose of supplying a rigid mounting surface with a
larger surface area resting on the hull 24 than the cross-section
of the fins 21 would supply. This way tensioning ropes between the
fins and the hull, like they are common in the prior art, can be
omitted and the drag forces that these ropes would cause in flight
do not occur.
[0069] Furthermore there is a gondola 22 attached to the bottom of
the hull 24 and a sensor 23 attached to the gondola 22.
[0070] Illustration 2
[0071] In FIG. 8 the thrust vector F of the ducted fan 17BUR is
shown as an arrow pointing from the outlet of the ducted fan
housing in the direction into which the air is blown by that ducted
fan. Each thrust vector points in one of the eight possible
directions from {-1,1}.sup.3. In other words, the thrust vector F
can be decomposed into three vectors of length |F/ 3| (F divided by
the square root of 3) that are each parallel to one of the three
axis of a cartesian coordinate system like defined in the lower
left corner of FIG. 8. As the arrangement of ducted fans 17 and 19
is symmetrical, each ducted fan is positioned and oriented
symmetrically to 17BUR. This again means that the thrust vector F
of each ducted fan 17 and 19 can be decomposed into three
components that act in the three directions of a cartesian
coordinate system and that have the same magnitude |F/ 3|.
[0072] Illustration 4
[0073] FIG. 11A shows two of the four thrust vectors that are
necessary to move the airship to the left, i.e., in the direction
-y of the cartesian coordinate system. The ducted fans activated
for this movement are 17BUL, 17BLL, 19SUL and 19SLL as seen in
FIGS. 7 and 9A.
[0074] FIG. 11B shows two of the four thrust vectors that are
necessary to move the airship to the right, i.e., in the direction
y of the cartesian coordinate system. The ducted fans activated for
this movement are 17BUR, 17BLR, 19SUR and 19SLR as seen in FIGS. 7
and 9A.
[0075] FIG. 12A shows two of the four thrust vectors that are
necessary to move the airship backwards, i.e., in the direction x
of the cartesian coordinate system. The ducted fans activated for
this movement are 19SUL, 19SUR, 19SLL and 19SLR as seen in FIGS. 7
and 9A.
[0076] FIG. 12B shows two of the four thrust vectors that are
necessary to move the airship forwards, i.e., in the direction -x
of the cartesian coordinate system. The ducted fans activated for
this movement are 17BUL, 17BUR, 17BLL and 17BLR as seen in FIGS. 7
and 9A.
[0077] Illustration 5
[0078] FIG. 13A shows two of the four thrust vectors that are
necessary to move the airship upwards, i.e., in the direction z of
the cartesian coordinate system. The ducted fans activated for this
movement are 17BLL, 17BLR, 19SLL and 19SLR as seen in FIGS. 7 and
9A.
[0079] FIG. 13B shows two of the four thrust vectors that are
necessary to move the airship downwards, i.e., in the direction -z
of the cartesian coordinate system. The ducted fans activated for
this movement are 17BUL, 17BUR, 19SUL and 19SUR as seen in FIGS. 7
and 9A.
[0080] FIG. 14A shows two of the four thrust vectors that are
necessary to yaw the airship to the left, i.e., rotate it around
the z-axis of a cartesian coordinate system, whose origin is
located near the center of the airship hull 24, in the direction of
.psi. (psi). The ducted fans activated for this movement are 17BUL,
17BLL, 19SUR and 19SLR as seen in FIGS. 7 and 9A.
[0081] FIG. 14B shows two of the four thrust vectors that are
necessary to yaw the airship to the right, i.e., rotate it around
the z-axis of a cartesian coordinate system, whose origin is
located near the center of the airship hull 24, in the direction of
-.psi. (minus psi). The ducted fans activated for this movement are
17BUR, 17BLR, 19SUL and 19SLL as seen in FIGS. 7 and 9A.
[0082] Illustration 6
[0083] FIG. 15A shows two of the four thrust vectors that are
necessary to pitch the airship down, i.e., rotate it around the
axis that is parallel to the y-axis and goes approximately through
the center of gravity of the airship, in the direction of .theta.
(theta). The ducted fans activated for this movement are 17BLL,
17BLR, 19SUL and 19SUR as seen in FIGS. 7 and 9A.
[0084] FIG. 15B shows two of the four thrust vectors that are
necessary to pitch the airship up, i.e., rotate it around the axis
that is parallel to the y-axis and goes approximately through the
center of gravity of the airship, in the direction of -.theta.
(minus theta). The ducted fans activated for this movement are
17BUL, 17BUR, 19SLL and 19SLR as seen in FIGS. 7 and 9A.
[0085] FIG. 16A shows two of the four thrust vectors that are
necessary to roll the airship left, i.e., rotate it around the axis
that is parallel to the x-axis and goes approximately through the
center of gravity of the airship, in the direction of -.PHI. (minus
phi). The ducted fans activated for this movement are 17BUL, 17BLR,
19SUL and 19SLR as seen in FIGS. 7 and 9A.
[0086] FIG. 16B shows two of the four thrust vectors that are
necessary to roll the airship right, i.e., rotate it around the
axis that is parallel to the x-axis and goes approximately through
the center of gravity of the airship, in the direction of
.PHI.(phi). The ducted fans activated for this movement are 17BUR,
17BLL, 19SUR and 19SLL as seen in FIGS. 7 and 9A.
[0087] Operation
[0088] A first embodiment of the propulsion system enables two
flight modes: a cruise mode and a hover mode, which are explained
in detail below.
[0089] Cruise Mode
[0090] In the cruise mode the airship is propelled in the forward
direction by the stern engine 20. Maneuvering is accomplished by
deflecting the rudders of the fins 21. Compared to using the ducted
fans 19, this enables a very energy efficient flight for the
following reasons: [0091] The stern propeller rotates around the
longitudinal axis (parallel to the x-axis) so that its thrust
vector is completely used for forward propulsion. [0092] The
propulsion efficiency of the stern propeller is increased by wake
effects at the stern. [0093] The stern propeller can have a rather
large diameter without having to mount it on a structure that would
have to prevent it from interfering with the hull. A large diameter
for the stern propeller is advantageous because it can rotate
slower than a smaller-diameter propeller while producing the same
amount of thrust. Motors with a lower rpm/V (revolutions per minute
per Volt) can be used at a higher voltage, which leads to a lower
current draw. The lower current draw leads to a smaller voltage
drop and to smaller heat losses across the motor wires, which
ultimately enables a more efficient operation. [0094] Maneuvering
by using the rudders is more energy efficient compared to using
propeller thrust, because comparably small servo motors are
sufficient to actuate the rudders. These only have to be actuated
from time to time to correct the flight path and do only consume
relatively little energy.
[0095] Hover Mode
[0096] In the hover mode the airship is propelled by the eight
ducted fans 17 and 19 and optionally also the stern engine 20. At
every time in this mode, all engine speeds are chosen such that all
forces acting on the airship (i.e., engine thrusts, gravity,
buoyancy, wind and potentially others) are together resulting in
the desired motion. A video of a working prototype for the hover
mode can be found on the Youtube channel of aerobotX Inc.
(https://www.youtube.com/channel/UCBQ6dG1xubKgnXz9xdFHL1A) e.g.
under the title "ObliX mini with Computer Vision":
https://youtu.be/pvzrx_ZGC54
[0097] Advanced Motion Control
[0098] In broadest terms, the propulsion system relies on two
techniques to achieve the desired motion: First, a (mathematical)
model that describes the relationship between engine thrusts and
the resulting motion. Second, a closed-loop (feedback) control
system that compensates for model inaccuracies relative to the real
world.
[0099] For illustration, two examples for both techniques are
described: [0100] 1. First, a rigid airship (but also a blimp with
a fully inflated hull) as a rigid body that behaves according to
the laws of classical mechanics may be modeled. In classical
mechanics, movement of a rigid body has six degrees of freedom:
That is, any motion can be decomposed into its translational part
(consisting of three components, for x/y/z-axis) and its rotational
part (consisting again of three components, for roll/pitch/yaw
about a fixed local axis, typically chosen as running through the
center of gravity). Translational acceleration is determined by
Newton's second law of motion ("F=ma"), and rotational acceleration
is determined by its angular analog, plus Euler's equations. Thus,
by solving a system of equations, the necessary engine thrusts can
be computed from the desired acceleration. The system of equations
is guaranteed to have a solution in all directions because there
are 8 engines, but only 6 degrees of freedom. [0101] 2. Second, a
well-known technique for a closed-loop control system is a PID
controller. There could be six PID controllers on the airship, one
each for controlling longitudinal velocity, lateral velocity,
vertical velocity, yaw velocity, roll, and pitch.
[0102] Such an implementation may be chosen if computer-supported
flight control and avionics are desired, and if there is sufficient
compute power to continuously solve systems of equations in real
time.
[0103] Simplified Motion Control
[0104] In an environment where microcontrollers are either not
feasible or not desirable, simpler implementations of both model
and control system are possible. For instance: [0105] 1. First, a
less precise model may be chosen where desirable symmetries are
just assumed to be present. For instance, one could assume that
equal thrusts in the upper stern and lower stern engines entirely
cancels out any torque. While this is clearly a simplifying
assumption, with no chance of precisely describing the real-world
behavior, it may in some use cases be sufficiently close to the
real-world behavior. [0106] 2. Second, the "control system" may as
well be embodied by a human pilot.
[0107] The figures and illustrations are given with this simple
implementation of the control system in mind.
[0108] Advantages of Ducted Fans
[0109] In the first embodiment of the propulsion system ducted fans
are used instead of big propellers because their small size does
not cause much additional air resistance and their housing guards
the fans from interference with objects or people. In addition a
vortex ring around the tip of the fan blades is avoided by the
operation in the duct, thus making propulsion more efficient.
Guarding the fans is more important than guarding the stern
propeller because the ducted fans are used when precise maneuvering
is necessary in confined spaces, close to objects or above people.
In such a situation the stern propeller can be switched off in
order to reduce the risk of damage or injury.
[0110] Operation of Ducted Fans
[0111] The maneuverability in all directions is achieved by the
orientation of the ducted fans 17 and 19. The stern engine 20 can
be helpful with station keeping or moving against the wind,
especially when the bow of the airship is pointing against the
direction of the wind.
[0112] As shown in the example for one ducted fan in FIG. 8, the
thrust vector F produced by the ducted fan is pointing in the
direction of the airflow and is oriented in such a way that it has
a component in every direction x, y and z of a cartesian coordinate
system. In this embodiment all components have the same magnitude
|F/ 3| (F divided by the square root of 3). The eight thrust
vectors F of the eight ducted fans are arranged symmetrically such
that a combination of running fans can be found in which two of the
three components x, y, z of the thrust vectors F cancel each other
out while the third components add up in a resulting thrust vector.
Illustrations 4, 5 and 6 show these combinations for every
direction x, y and z as well as for every rotation V, (I) and 0
(psi, phi and theta) as defined by the coordinate system in the
respective figures. In addition to the figure descriptions above,
one translational and one rotational movement will be explained in
detail in the following:
[0113] As shown on Illustration 4 in FIG. 11A, in order for the
airship to move left, i.e., in the direction -y, the ducted fans
17BUL, 17BLL, 19SUL and 19SLL are activated to produce a force of
magnitude |F.sub.res|. The x-components of 17BUL and 19SUL as well
as the x-components of 17BLL and 19SLL act in opposite directions
and cancel each other out. The z-components of 17BUL and 17BLL as
well as 19SUL and 19SLL also act in opposite directions and cancel
each other out. The y-components of 17BUL, 17BLL, 19SUL and 19SLL
all act in the same direction and add up to a resulting thrust of
magnitude F.sub.res=4*|F/ 3| (4 times F divided by the square root
of 3), which points in the direction parallel to the y-axis. The
symmetry of the airship design ensures that this resulting thrust
introduces only negligible rotation.
[0114] As shown on Illustration 5 in FIG. 14A, in order for the
airship to rotate around its vertical axis, i.e. in the direction
of .psi. (psi) around an axis parallel to the z-axis, the ducted
fans 17BUL, 17BLL, 19BUR and 19BLR are activated. Their thrust
vectors F can each be written as sum of three orthogonal vectors
F.sub.pll, F.sub.orth and F.sub.z where: [0115] F.sub.pll is
pointing in the direction of the dotted line that connects 17BUL
and 19SUR on the top and 17BLL and 19SLR on the bottom of the
airship respectively (not shown). [0116] F.sub.orth is pointing in
the direction that is orthogonal to F.sub.pll in the xy-plane.
[0117] F.sub.z is pointing in the direction of the z-axis (not
shown).
[0118] The thrust vectors F.sub.z of 17BUL and 17BLL as well as the
thrust vectors F.sub.z of 19BUR and 19BLR cancel each other out.
The thrust vectors F.sub.pll of 17BUL and 19SUR as well as the
thrust vectors F.sub.pll of 17BLL and 19SLR cancel each other out.
Only the thrust vectors F.sub.orth remain and add up to the
resulting momentum of rotation M.sub.res (see FIG. 14A) around an
axis that is parallel to the z-axis and goes through the center of
the airship.
[0119] The movements described above are the elementary movements
along and about the three axis of the cartesian coordinate system.
The translations in all other directions and the rotations about
all other axes are achieved by the linear combination of the
elementary movements.
[0120] For example, if the thrust vectors for the upwards movement
(see FIG. 13A) and the thrust vectors for the forward movement (see
FIG. 12B) are combined, the resulting movement will be both upward
and forward, with the airship staying level.
[0121] Symmetry Conditions
[0122] The symmetrical arrangement of ducted fans 17 at the bow and
19 at the stern (compared to only having engines at the stern or at
the bow) in the embodiment described above serves the purpose of
preventing a rotation about the center z-axis of the airship for
thrust in the y-direction as well as a rotation about the center
y-axis of the airship for thrust in the z-direction.
[0123] The symmetrical arrangement of ducted fans relative to top
and bottom of the airship (compared to only having engines at the
top or at the bottom) in the embodiment described above serves the
purpose of preventing a rotation about the center x-axis of the
airship for thrust in the y-direction as well as a rotation about
the center y-axis of the airship for thrust in the x-direction.
CONCLUSION, RAMIFICATIONS AND SCOPE
[0124] Accordingly, the reader will see that the proposed
propulsion system enables an airship to move in all six degrees of
freedom as well as hold a defined position and orientation. This is
possible even in windy conditions. The fixed direction of thrust
for every engine allows for a near-instantaneous reaction to the
control commands because only the magnitude of thrust has to be
adjusted. This is much faster than having to swivel an engine, more
energy efficient than having to redirect the direction of thrust by
mechanical means like blinds or ducts and mechanically simpler and
thus more reliable compared to swiveling an engine, blinds, ducts
or the blades of a propeller. One embodiment also enables an
efficient forward flight by an additional engine at the stern of
the airship and the use of conventional rudders. This way a so
called "Hover Mode" like known from helicopters and a so called
"Craze Mode" like known from airplanes can both be combined in
order to achieve long flight times and high maneuverability with
one aircraft.
[0125] While my above description contains many specificities,
these should not be construed as limitations on the scope, but
rather as an exemplification of one embodiment thereof. Many other
variations are possible. For example: [0126] 1. The airship can
have an arbitrary shape as long as engines can be arranged such
that combined engines thrusts can produce any required resulting
force and torque. To achieve full 6-degree-of-freedom movement this
means at least 6 engines with sufficiently different thrust vectors
(due to well-known results from linear algebra). Also see chapter
"Hover Mode". [0127] 2. A ducted stern propeller can be used for
increased efficiency and safety. [0128] 3. The thrust vectors of
the ducted fans can point into different directions, i.e.,
individually, in groups or all of them. This way different
magnitudes for the x, y and z components of the thrust vectors will
lead to different resulting forces in the directions of movement.
[0129] 3.1. For example, if the y-component of all thrust vectors
of the ducted fans 17 and 19 is increased in the same way, then the
resulting force for the movement in the y-direction will be bigger
while the resulting force in the x and/or the z directions will be
smaller. [0130] 3.2. Another example could be to increase the
y-components of the thrust vectors only for the four ducted fans 19
at the stern. This could improve movement in lateral direction by
taking into account that the lateral drag at the stern is bigger
than at the bow because of the empennage. A more balanced movement
would be the result. [0131] The direction of the thrust vector of a
ducted fan is only limited by the hull. Expelled air should not hit
the hull or flow in close proximity to it in order to avoid
surface-induced disturbances of the air flow. [0132] 3.3. As a last
example, the direction of all thrust vectors can be inverted. This
would help avoiding the Coand -Effect by leading the expelled air
away from the hull better, because the vectors would point away
from it rather than over it. [0133] 4. The eight engines 17 and 19
do not have to be ducted fans and the stern engine does not have to
be a propeller. Any other kind and size of engines can also be
used. The importance lies in the fixed direction of the thrust
vectors of all engines. [0134] 5. The stern engine 20 can be
omitted, especially when efficient forward flight is not required.
[0135] 6. The rudders on the fins 21 can be omitted and turns of
the airship can be initiated by the ducted fans 17 and 19 only. On
the one hand this would require more energy, but on the other hand
it would also reduce weight for the rudders and their actuation.
[0136] 7. The fins 21 of the airship can be omitted. In this
embodiment the ducted fans 17 and 19 have to replace the function
of the fins 21 and stabilize the airship. On the one hand this
would reduce the drag force induced by the fins 21 and safe weight.
On the other hand it would increase the energy consumption in most
practical flight situations because the passive fins can be more
efficient in stabilizing the airship in the direction of flight
than active propulsion means. [0137] 8. As a combination of the
embodiments (5.) and (7.) the stern engine 20 and the fins 21 can
be omitted. In this embodiment the ducted fans 17 and 19 have to
cause and stabilize the movement of the airship. This is the most
energy demanding mode of all embodiments proposed. [0138] 9. For a
simplified flight control, like described in the subchapter
"Simplified Motion Control" of chapter "Hover Mode" the position of
the eight ducted fans can be varied as long as the symmetry
conditions described in chapter "Symmetry Conditions" are
maintained. Especially the distance of the ducted fans relative to
the center of buoyancy of the airship can be decreased along the
x-axis. [0139] 10. The at least one engine that is producing thrust
in the longitudinal (forward) direction of the airship and that is
embodied by the the stern engine 20 in the first embodiment, can be
mounted to different positions on the airship in further
embodiments: [0140] 10.1. A bow engine could replace stern engine
20. [0141] 10.2. In addition to the stern engine 20 an engine at
the airship's bow tip can be used in order to increase forward
thrust and flight stability. [0142] 10.3. At least one engine could
be mounted to the gondola 22 of the airship. [0143] 10.4. At least
one engine could be mounted to a position along the hull 24 of the
airship.
[0144] Thus the scope of the embodiments should be determined by
the appended claims and their legal equivalents, rather than by the
examples given.
* * * * *
References