U.S. patent application number 15/516271 was filed with the patent office on 2017-10-19 for rotor speed management.
The applicant listed for this patent is Sikorsky Aircraft Corporation. Invention is credited to Bryan S. Cotton, Matthew T. Luszcz, Steven D. Weiner.
Application Number | 20170297694 15/516271 |
Document ID | / |
Family ID | 55631217 |
Filed Date | 2017-10-19 |
United States Patent
Application |
20170297694 |
Kind Code |
A1 |
Luszcz; Matthew T. ; et
al. |
October 19, 2017 |
ROTOR SPEED MANAGEMENT
Abstract
A flight control system for a rotorcraft includes a controller
configured to receive input indicative of ambient conditions,
determine a threshold rotor blade tip speed based on the input, and
to output rotor control commands to prevent rotor blade tips from
exceeding the threshold speed. An aircraft includes an airframe, a
main rotor assembly operatively connected to the airframe, and a
flight control system as described above. The flight control system
is operatively connected to control the main rotor assembly. It is
contemplated that the main rotor assembly can be a counter rotating
coaxial main rotor assembly including an upper rotor assembly with
a plurality of blades and a lower rotor assembly having a plurality
of blades, wherein the flight control system is operatively
connected to control both upper and lower rotor assemblies to
prevent any blade tips of the upper and lower rotor assemblies from
exceeding the threshold speed.
Inventors: |
Luszcz; Matthew T.; (US)
; Weiner; Steven D.; (Stratford, CT) ; Cotton;
Bryan S.; (Rockford, IL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Sikorsky Aircraft Corporation |
Stratford |
CT |
US |
|
|
Family ID: |
55631217 |
Appl. No.: |
15/516271 |
Filed: |
September 30, 2015 |
PCT Filed: |
September 30, 2015 |
PCT NO: |
PCT/US2015/053163 |
371 Date: |
March 31, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62058424 |
Oct 1, 2014 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B64C 27/57 20130101;
F16D 13/52 20130101; B64D 35/06 20130101; B64C 13/50 20130101; B64C
27/008 20130101; B64C 27/32 20130101; B64C 13/04 20130101; B64C
27/14 20130101; B64C 27/51 20130101; B64C 27/467 20130101; F16D
13/74 20130101; B64D 39/00 20130101; B64C 2027/8209 20130101; B64C
2027/8227 20130101; G05D 1/0202 20130101; G05D 1/08 20130101; B64C
27/80 20130101; G05D 1/0858 20130101; B64C 27/78 20130101; F16H
37/02 20130101; B64C 13/503 20130101; B64C 27/52 20130101; B64C
2027/8272 20130101; F16F 15/02 20130101; B64C 27/82 20130101; G05D
1/0077 20130101; B64C 27/001 20130101; F05D 2270/021 20130101; G05D
1/0204 20130101; B64C 2027/004 20130101; F02C 9/28 20130101; G05D
1/0816 20130101; B64C 27/322 20130101; B64C 27/48 20130101; B64C
2027/8263 20130101; B64C 7/00 20130101; B64C 2027/8236 20130101;
B64C 1/0009 20130101; F16D 13/72 20130101; B64C 19/00 20130101;
B64C 27/10 20130101; B64C 2027/8281 20130101; B64C 27/08 20130101;
B64D 45/02 20130101; B64C 13/18 20130101; B64C 27/12 20130101; B64C
2201/024 20130101; B64D 39/06 20130101; B64C 27/006 20130101; B64C
27/473 20130101; F05D 2220/329 20130101; B64C 27/16 20130101; B64C
27/54 20130101; B64C 27/33 20130101 |
International
Class: |
B64C 27/57 20060101
B64C027/57; B64C 27/10 20060101 B64C027/10 |
Claims
1. A flight control system for a rotorcraft comprising: a
controller configured to receive input indicative of ambient
conditions, determine a threshold rotor blade tip speed based on
the input, and to output rotor control commands to prevent rotor
blade tips from exceeding the threshold speed.
2. The system recited in claim 1, wherein the threshold speed is
Mach 0.9 at the ambient conditions.
3. The system recited in claim 1, wherein controller is configured
to output rotor control commands for control of coaxial main rotor
assembly including an upper rotor assembly with a plurality of
blades and a lower rotor assembly with a plurality of blades,
wherein the rotor control commands prevent any blade tips of the
upper and lower rotor assemblies from exceeding the threshold
speed.
4. The system as recited in claim 1, wherein the controller is
configured to receive input indicative of ambient conditions
including ambient air temperature.
5. The system as recited in claim 1, wherein the controller is
configured to receive input indicative of ambient conditions
including prevailing wind speed.
6. The system as recited in claim 1, wherein the controller is
configured to receive input indicative of ambient conditions
including prevailing wind direction.
7. An aircraft comprising: an airframe; a main rotor assembly
operatively connected to the airframe; and a flight control system
as recited in any of the preceding claims, wherein the flight
control system is operatively connected to control the main rotor
assembly.
8. An aircraft as recited in claim 7, wherein the main rotor
assembly is a counter rotating coaxial main rotor assembly
including an upper rotor assembly with a plurality of blades and a
lower rotor assembly having a plurality of blades, wherein the
flight control system is operatively connected to control both
upper and lower rotor assemblies to prevent any blade tips of the
upper and lower rotor assemblies from exceeding the threshold
speed.
9. An aircraft as recited in claim 7, further comprising at least
one of an ambient air temperature sensor, a rotor speed sensor, a
prevailing wind speed sensor, and/or a prevailing wind direction
sensor, operatively connected to provide input to the flight
control system.
10. A method of controlling rotor speed on a rotorcraft comprising:
receiving input from sensors indicative conditions ambient to a
rotor; determining a threshold rotor blade tip speed based on the
input; and controlling rotational speed of the rotor to prevent any
blade tips of the rotor from exceeding the threshold speed.
11. The method as recited in claim 10, wherein the threshold speed
is Mach 0.9 at ambient conditions.
12. The method as recited in claim 10, controlling rotation speed
includes controlling both rotors of a coaxial dual rotor main rotor
assembly to prevent any blade tips of the two rotors from exceeding
the threshold speed.
13. The method as recited in claim 10, wherein receiving input
includes receiving air temperature input from an air temperature
sensor.
14. The method as recited in claim 10, wherein receiving input
includes receiving prevailing wind speed input from a prevailing
wind speed sensor.
15. The method as recited in claim 10, wherein receiving input
includes receiving wind direction input from a wind direction
sensor.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to U.S. Provisional Patent
Application No. 62/058,424 filed Oct. 1, 2014, the contents of
which are incorporated by reference herein in their entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
[0002] The present disclosure relates to aircraft control systems,
and more particularly to flight control systems such as used in
controlling rotors of rotorcraft.
2. Description of Related Art
[0003] A limiting factor on the rotor of rotorcraft is the sound
barrier. The effective air speed at any given point on a rotor
blade in motion is a function of the rotational speed, the radius
to the point of interest from the center of rotation, and the
forward flight speed of the rotorcraft. The further away from the
center, the greater the effective air speed at that point on the
rotor blade. The tip of the advancing rotor blade therefore has the
highest effective air speed when the rotor is operating at high
rotational speed and high forward flight speed. If the rotational
speed is high enough, the tips of the rotor blades will exceed the
sound barrier and the air flow at the tips will transition from an
incompressible regime to a compressible regime. Typical blades are
designed to operate efficiently only in the incompressible regime
of fluid dynamics, and do not perform as efficiently in the
compressible regime. At high rotational and forward flight speeds,
as the blade tips exceed Mach 1.0, the advancing blade tips can
precipitously lose lift and/or experience increased drag and
vibration due to shock formation. This problem is traditionally
self-correcting, since the reduced efficiency when blade tips
exceed Mach 1.0 tends to offset excess power applied to the rotor,
thus keeping the rotor speed in equilibrium. However, that
equilibrium speed is not optimal for efficient flight.
[0004] Such conventional methods and systems have generally been
considered satisfactory for their intended purpose. However, there
is still a need in the art for improved rotor speed management. The
present disclosure provides a solution for this need.
SUMMARY OF THE INVENTION
[0005] A flight control system for a rotorcraft includes a
controller configured to receive input indicative of ambient
conditions, determine a threshold rotor blade tip speed based on
the input, and to output rotor control commands to prevent rotor
blade tips from exceeding the threshold speed. The threshold speed
can be Mach 0.9 at the ambient conditions. The controller can be
configured to output rotor control commands for control of coaxial
main rotor assembly including an upper rotor assembly with a
plurality of blades and a lower rotor assembly with a plurality of
blades, wherein the rotor control commands prevent any blade tips
of the upper and lower rotor assemblies from exceeding the
threshold speed. The controller can be configured to receive input
indicative of ambient conditions including ambient air temperature,
prevailing wind speed, and/or prevailing wind direction.
[0006] An aircraft includes an airframe, a main rotor assembly
operatively connected to the airframe, and a flight control system
as described above. The flight control system is operatively
connected to control the main rotor assembly. It is contemplated
that the main rotor assembly can be a counter rotating coaxial main
rotor assembly including an upper rotor assembly with a plurality
of blades and a lower rotor assembly having a plurality of blades,
wherein the flight control system is operatively connected to
control both upper and lower rotor assemblies to prevent any blade
tips of the upper and lower rotor assemblies from exceeding the
threshold speed. The aircraft can include at least one of an
ambient air temperature sensor, a rotor speed sensor, a prevailing
wind speed sensor, and/or a prevailing wind direction sensor,
operatively connected to provide input to the flight control
system.
[0007] A method of controlling rotor speed on a rotorcraft includes
receiving input from sensors indicative conditions ambient to a
rotor, determining a threshold rotor blade tip speed based on the
input, and controlling rotational speed of the rotor to prevent any
blade tips of the rotor from exceeding the threshold speed.
[0008] These and other features of the systems and methods of the
subject disclosure will become more readily apparent to those
skilled in the art from the following detailed description of the
preferred embodiments taken in conjunction with the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] So that those skilled in the art to which the subject
disclosure appertains will readily understand how to make and use
the devices and methods of the subject disclosure without undue
experimentation, preferred embodiments thereof will be described in
detail herein below with reference to certain figures, wherein:
[0010] FIG. 1 is a side elevation view of an exemplary embodiment
of a rotorcraft constructed in accordance with the present
disclosure, showing the main rotor assembly with upper and lower
coaxial counter rotating rotors, and schematically indicating the
flight control system; and
[0011] FIG. 2 is a schematic view of the flight control system of
FIG. 1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0012] Reference will now be made to the drawings wherein like
reference numerals identify similar structural features or aspects
of the subject disclosure. For purposes of explanation and
illustration, and not limitation, a partial view of an exemplary
embodiment of an aircraft in accordance with the disclosure is
shown in FIG. 1 and is designated generally by reference character
100. Other embodiments of aircraft in accordance with the
disclosure, or aspects thereof, are provided in FIG. 2, as will be
described. The systems and methods described herein can be used to
improve blade tip speed management in rotors such as in
rotorcraft.
[0013] Aircraft 100 includes an airframe 102, a main rotor assembly
104 operatively connected to airframe 102, and a flight control
system 106. Flight control system 106 is operatively connected to
control main rotor assembly 104, translational thrust rotor
assembly 116, tail fairing assembly 118, and one or more engines
120, as well as to receive inputs for flight control, as indicated
by the large arrows in FIG. 1.
[0014] Main rotor assembly 104 is a counter rotating coaxial main
rotor assembly including an upper rotor assembly 108 with a
plurality of blades 110 and a lower rotor assembly 112 having a
plurality of blades 110. Flight control system 106 is operatively
connected to control both upper and lower rotor assemblies 108 and
112 to prevent any blade tips 114 of the upper and lower rotor
assemblies 108 and 112 from exceeding a threshold speed.
[0015] Referring now to FIG. 2, aircraft 100 includes at least one
of an ambient air temperature sensor, a rotor speed sensor, a
prevailing wind speed sensor, and/or a prevailing wind direction
sensor, operatively connected to provide input to the flight
control system 106, as indicated by the senor inputs 122 in FIG. 2.
Flight control system 106 includes a controller 124, e.g., a flight
control computer, configured to receive input indicative of ambient
conditions, e.g., from sensor inputs 122. Controller 124 also
receives flight inputs 126, which can include any suitable inputs
such as control input from a pilot, autopilot, guidance system, or
the like. Controller 124 determines a threshold rotor blade tip
speed based on the input. Controller 124 outputs rotor control
commands to prevent rotor blade tips 114 from exceeding the
threshold speed. The threshold speed can be Mach 0.9 at the ambient
conditions, or any other suitable Mach number at ambient conditions
for a given airfoil, airframe or application. For state of the art
airfoils, maintaining tip speeds at or below Mach 0.9 mitigates or
avoids the compressible flow regime effects, e.g., from exceeding
the speed of sound, that might otherwise reduce blade efficiency
and increase drag on the blades 110. For example, this can improve
maximum cruise speed, range, and/or endurance compared to
conventional systems. Those skilled in the art will readily
appreciate that improvements in airfoil design can increase this
threshold Mach number to a value closer to Mach 1.0, and that the
threshold speed can be set at any suitable Mach number for a given
application.
[0016] The threshold speed is based on the speed of sound at a
given air temperature, so Mach 0.9 for example, corresponds to a
different tip speed depending on ambient air temperature. The tip
speed itself varies with rotational speed of the respective blade
110 as well as the aircraft speed and direction as well as any wind
speed and direction. Using prevailing wind speed and direction from
aircraft sensors accounts for both wind and aircraft movement,
e.g., wind speed and direction, and aircraft speed and direction
can all be accounted for as input from a true air speed sensor.
Controller 124 uses this information to control the rotational
speed of rotors 108 and 112 from ever exceeding a rotational speed
that would cause tips 114 from exceeding the speed of sound, given
air temperature, aircraft movement, and wind. A tip speed
corresponding to Mach 0.9 at ambient conditions suffices as a
threshold for preventing tips 114 from exceeding the speed of
sound.
[0017] Controller 124 is configured, e.g., with machine readable
instructions stored in memory 128 and/or processed in CPU 130, to
receive input, determine the threshold speed, and output rotor
control commands for control of coaxial main rotor assembly 104
e.g., through engine interface 134 and/or rotor interface 132, to
control the rotational speed of rotors 108 and 112, wherein the
rotor control commands prevent any blade tips 114 of the upper and
lower rotor assemblies 108 and 112 from exceeding the threshold
speed as described above.
[0018] In this embodiment controller 124 is also connected to
control translational thrust rotor assembly 116 and tail fairing
assembly 118, as indicated by translational thrust interface 136
and tail fairing interface 138. Other embodiments can have other
means of separately controlling the translational thrust rotor,
such as when said rotor is powered by a separate source/engine. The
two-way arrows in FIG. 2 indicate that in addition to issuing
commands to the interfaces 132, 134, 136, and 138, controller 124
can also receive feedback from the respective interfaces and base
control commands on said feedback. The controller interface 140
interfaces the input/output of flight control system 106 with the
CPU 130 and memory 128 of controller 124.
[0019] A method of controlling rotor speed on a rotorcraft, e.g.,
aircraft 100, includes receiving input from sensors, e.g., from
sensor inputs 122, indicative conditions ambient to a rotor, e.g.,
rotors 108 and 112. The method also includes determining a
threshold rotor blade tip speed based on the input, and controlling
rotational speed of the rotor, e.g., rotors 108 and 112, to prevent
any blade tips, e.g., tips 114, of the rotor from exceeding the
threshold speed.
[0020] In addition to limiting maximum tip speed, it is also
contemplated that the systems and methods used herein can be used
to maintain tip speed above a predetermined minimum speed. It is
also contemplated that the systems and methods described herein can
be used to maintain blade tip speed between a predetermined maximum
and a predetermined minimum speed.
[0021] The methods and systems of the present disclosure, as
described above and shown in the drawings, provide for tip speed
management with superior properties including improved efficiency
and effectiveness. While the apparatus and methods of the subject
disclosure have been shown and described with reference to
preferred embodiments, those skilled in the art will readily
appreciate that changes and/or modifications may be made thereto
without departing from the scope of the subject disclosure.
* * * * *