U.S. patent application number 11/381192 was filed with the patent office on 2010-07-08 for method for reducing the turbulence and gust influences on the flying characteristics of aircraft, and a control device for this purpose.
Invention is credited to Klaus-Uwe Hahn.
Application Number | 20100171002 11/381192 |
Document ID | / |
Family ID | 37111416 |
Filed Date | 2010-07-08 |
United States Patent
Application |
20100171002 |
Kind Code |
A1 |
Hahn; Klaus-Uwe |
July 8, 2010 |
METHOD FOR REDUCING THE TURBULENCE AND GUST INFLUENCES ON THE
FLYING CHARACTERISTICS OF AIRCRAFT, AND A CONTROL DEVICE FOR THIS
PURPOSE
Abstract
A control device for aircraft for reducing the turbulence and
gust influences on the flying characteristics is designed to
generate an additional incidence angle drive signal for control
surfaces on surfaces which generate an air force, in particular
wing and/or tailplane as a function of an instantaneous bank angle
(.PHI.) and sideslip angle (.beta.).
Inventors: |
Hahn; Klaus-Uwe; (Wendeburg,
DE) |
Correspondence
Address: |
WHITHAM, CURTIS & CHRISTOFFERSON & COOK, P.C.
11491 SUNSET HILLS ROAD, SUITE 340
RESTON
VA
20190
US
|
Family ID: |
37111416 |
Appl. No.: |
11/381192 |
Filed: |
May 2, 2006 |
Current U.S.
Class: |
244/76C |
Current CPC
Class: |
G05D 1/0816 20130101;
B64C 13/16 20130101 |
Class at
Publication: |
244/76.C |
International
Class: |
B64C 13/16 20060101
B64C013/16 |
Foreign Application Data
Date |
Code |
Application Number |
May 3, 2005 |
DE |
102005020660.3-22 |
Claims
1. A control device for aircraft for reducing the turbulence and
gust influences on the flying characteristics, comprising: a
sideslip angle sensor for determining the instantaneous sideslip
angle (.beta.); a bank angle sensor for determining the
instantaneous bank angle (.PHI.); and controller for generating an
additional incidence angle drive signal for control surfaces on
said aircraft which generate an air force as a function of the
instantaneous bank angle (.PHI.) and sideslip angle (.beta.), said
additional incidence angle drive signal being provided to be added
to a main drive signal for the control surfaces, wherein the
control device determines the drive signal as a function of a
component (.alpha..sub.Wf) of the wind incidence, caused by a
vertical air mass movement, on the plane of symmetry of the
aircraft, using the formula: .alpha. Wf = cos ( .phi. ) [ f ( H . V
) - .theta. + cos ( .phi. ) ( .alpha. + q r AoA V ) + sin ( .phi. )
( .beta. - r r AoS V ) ] ##EQU00008## where .PHI. is the bank
angle, {dot over (H)} is the vertical velocity of the aircraft, V
is the airspeed of the aircraft with respect to the surrounding
air, .theta. is the longitudinal attitude angle of the aircraft,
.alpha. is the angle of attack, q is the pitch rate of the
aircraft, r.sub.AoA, is the distance between the incidence angle
sensor and the center of gravity of the aircraft, r is the yaw rate
and r.sub.AoS is the distance between the sideslip angle sensor and
the center of gravity, and f ( H . V ) ##EQU00009## is a function
of the ratio of the vertical velocity {dot over (H)} to the
airspeed V.
2-4. (canceled)
5. The control device as claimed in claim 4, wherein the control
device is designed to determine the drive signal using the function
f ( H . V ) equal to H . V or arcsin ( H . V ) . ##EQU00010##
6-8. (canceled)
9. A method for reducing the turbulence and gust influences on the
flying characteristics of aircraft, comprising the steps of:
determining the instantaneous sideslip angle (.beta.); determining
the instantaneous bank angle (.PHI.); and generating an additional
incidence angle (.alpha..sub.Wf) control signal for control
surfaces of said aircraft which generate an air force as a function
of the control signal, said additional incidence angle drive signal
being provided to be added to a main drive signal for the control
surfaces, said control signal being a function of the instantaneous
bank angle (.PHI.) and sideslip angle (.beta.), said main drive
signal together with the superimposed control signal controlling
the control surfaces wherein said generating step uses the formula:
.alpha. Wf = cos ( .phi. ) [ f ( H . V ) - .theta. + cos ( .phi. )
( .alpha. + q r AoA V ) + sin ( .phi. ) ( .beta. - r r AoS V ) ]
##EQU00011## where .PHI. is the bank angle, {dot over (H)} is the
vertical velocity of the aircraft, V is the airspeed of the
aircraft with respect to the surrounding air, .theta. is the
longitudinal attitude angle of the aircraft, .alpha. is the angle
of attack, q is the pitch rate of the aircraft, r.sub.AoA is the
distance between the incidence angle sensor and the center of
gravity of the aircraft, r is the yaw rate and r.sub.AoS is the
distance between the sideslip angle sensor and the center of
gravity, and f ( H . V ) ##EQU00012## is a function of the ratio of
the vertical velocity {dot over (H)} to the airspeed V.
10. (canceled)
11. The method as claimed in claim 9, wherein the function is f ( H
. V ) equal to H . V or arcsin ( H . V ) ##EQU00013##
12. The control device as recited in claim 1 wherein said
additional incidence angle drive signal generated is for a
wing.
13. The control device as recited in claim 1 wherein said
additional incidence angle drive signal generated is for a
tailplane.
Description
FIELD OF THE INVENTION
[0001] The invention relates to a method for reducing the
turbulence and gust influences on the flying characteristics of
aircraft, and to a control device for this purpose.
BACKGROUND OF THE INVENTION
[0002] The flying characteristics of aircraft, in particular of
airplanes, are disadvantageously influenced by turbulence and gusts
in the air masses surrounding the aircraft. In particular, a large
increase in lift, low wing loadings and high airspeeds as well as
low altitudes have negative influences on the turbulence and gust
behavior of aircraft. These result in a deterioration to passenger
comfort and in an increase in structural loads. However, strong
turbulence ("clear air turbulence" CAT) can occur even at high
altitudes and can produce considerable structural loads, and can
even lead to danger to the aircraft occupants.
[0003] A system for reducing gust loads and for damping structural
oscillations is described in O'Connel, R. F.: "Design, Development
and Implementation of an Active Control System for Load Alleviation
for a Commercial Airplane", in: AGARD Report No. 683, 1979 and in
rolling vehicles, G.; Ellgoth, H.; Beuck, G.: "Identification of
Dynamic Response, Simulation and Design of a Highly Nonlinear
Digital Load Alleviation System for a Modern Transport Aircraft",
in; 17th ICAS Congress, Stockholm, Sweden, based on the principle
of signal (feedback closed loop system). However, this control
system reacts only after the flying characteristics resulting from
turbulence and/or gusts have already notably changed.
[0004] A control method based on the principle of application of
disturbance variables in order to reduce gust loads and to improve
passenger comfort is known from Bohret, H.; Krag, B.; Skudridakis,
J.: "OLGA--An Open Loop Gust Alleviation System", in: AGARD CP No.
384, Toronto, Canada, 1985. In this case, the flying
characteristics are not changed, with a reaction taking place to
the original disturbance itself, and compensating for it before the
disturbance caused by turbulence or gusts acts on the aircraft
itself.
[0005] Comparable control methods are also described in Hahn,
K.-U.; Konig, R.: "LARS--Auslegung eines fortschrittlichen
Boenabminderungssystems mit ATTAS", (LARS--design of an advanced
gust reduction system using ATTAS), in: Deutscher Luft and
Raumfahrtkongress, (German Aviation Space Flight Congress), 1991
and in Hahn, K.-U.; Konig, R.: "ATTAS Flight Test and Simulation
Results of the Advanced Gust Management System LARS", in: AIAA
Atmospheric Flight Mechanics Conference, Hilton Head Island, S.C.,
USA, 1992.
[0006] When using the principle of signal feedback (closed loop),
the reaction of the aircraft to the gusts is measured and is fed
back to the wing control surfaces in order to reduce this reaction.
This does not require any complex calculation of the gust angle.
However, accelerations results from flight maneuvers are also fed
back via the control system and can counteract the pilot
commands.
[0007] In the case of open-loop control methods, the angle of
attack of a gust must be known precisely. This must be determined
from sensor signals. The control surfaces of the wings and of the
tailplane are adjusted as a function of the gust angles of attack
in such a way that additional lift forces and pitch moments caused
by the gusts are compensated for. In this case, the handling
characteristics of the aircraft remain unchanged. However, the
efficiency of the control system is highly dependent on the
accuracy of the calculation of the gust angle of attack, and on the
degree of deflection of the control surfaces.
[0008] The control method based on the principle of application of
disturbance variables, in which the so-called wind incidence angle
is calculated from air data and inertial data is described in
Konig, R., Hahn, K-U.: "Load Alleviation and Rights Musing
Investigations using ATTAS", in: 17th ICAS Congress, Stockholm,
Sweden, 1990. The wind incidence angle is the additional incidence
angle which changes the lift and results from atmospheric
turbulence and gusts. Only the aircraft longitudinal movement is
taken into account, in order to avoid complex gust vector
determination. The wind incidence angle .alpha..sub.W is calculated
using the following formula:
.alpha. w = .alpha. L - .theta. + H . V + q r s V ##EQU00001##
In this case, .alpha..sub.L is the incidence angle measured by an
incidence angle sensor (for example aircraft), .theta. is the
longitudinal attitude angle, also referred to as the pitch angle,
{dot over (H)} is the instantaneous vertical velocity of the
aircraft, V is the airspeed of the aircraft with respect to the
air, q is the pitch rate of the aircraft and r.sub.s is the
distance between the wind attack sensor and the center of gravity
of the aircraft.
[0009] The stated variables are defined unambiguously in DIN 9300
"Luft-und Raumfahrt; Begriffe, Gro.beta.en und Formelzeichen der
Flugmechanik" (aviation and space flight; terminology, variables
and formula symbols for flight mechanics).
[0010] The pitch angle is in this case the angle between the
aircraft longitudinal axis in the aircraft-fixed coordinates system
and the node axis k.sub.1 as the projection of the aircraft-fixed
aircraft longitudinal axis x.sub.f onto the geodetic horizontal
plane, that is to say the x.sub.g-y.sub.g-plane. The pitch rate q
is the angular velocity of the aircraft about the aircraft lateral
axis y.sub.f.
[0011] The described control method is not suitable for adequate
turbulence and gust compensation when in turning flight as a result
of the simplified consideration of only the aircraft longitudinal
movement, particularly when sideslip angles also occur in this case
between the lateral axis and the lateral force axis of the
aircraft.
SUMMARY OF THE INVENTION
[0012] One object of the invention is to provide an improved method
for reducing the turbulence and gust influences on the flying
characteristics of aircraft, as well as a corresponding control
device, in order nevertheless to determine a sufficiently accurate
additional incidence angle drive signal without any complex gust
vector determination, independently of the flight motion of the
aircraft, that is to say even when in turning flight.
[0013] The object is achieved by the method and the control device
of the type mentioned initially, according to the invention, in
that the additional incidence angle drive signal is determined for
control surfaces on surfaces which generate an air force, in
particular wing and/or tailplane of the aircraft as a function of
an instantaneous bank angle and sideslip angle.
[0014] The bank angle and the sideslip angle can easily be
determined in a known manner by means of sensors, and can be
determined from measurement data available in an aircraft for the
attitude, position and velocity of the aircraft.
[0015] It is particularly advantageous when the formula mentioned
initially for calculation of the wind incidence angle is modified
in such a way that the component .alpha..sub.Wf of the wind
incidence angle caused by a vertical air mass movement is
determined on the plane of symmetry of the aircraft using the
following formula:
.alpha. Wf = cos ( .phi. ) [ f ( H . V ) - .theta. + cos ( .phi. )
( .alpha. + q r AoA V ) + sin ( .phi. ) ( .beta. - r r AoS V ) ]
##EQU00002##
In this case, .PHI. is the bank angle, {dot over (H)} is the
vertical velocity of the aircraft, V is the airspeed of the
aircraft with respect to the surrounding air, .theta.0 is the
longitudinal attitude angle of the aircraft, .alpha. is the
incidence angle of the wings of the aircraft, q is the pitch rate
of the aircraft, r.sub.AoA is the distance between the incidence
angle sensor and the center of gravity of the aircraft, r is the
yaw rate and f.sub.AoS is the distance between the sideslip angle
sensor and the center of gravity.
f ( H . V ) ##EQU00003##
is a function of the ratio of the vertical velocity to the
airspeed. The bank angle .PHI. is used for correct transformation
to the aircraft-fixed coordinate system, and the sideslip angle
.beta., as additional influences.
[0016] The stated variables are defined unambiguously in DIN 9300,
to which reference is made.
[0017] It is particularly advantageous for the determination of the
drive signal to be formed using the function
f ( H . V ) equal to H . V or arcsin ( H . V ) ##EQU00004##
DESCRIPTION OF THE DRAWING FIGURES
[0018] The invention will be explained in more detail in the
following text using the attached drawings by way of example, in
which:
[0019] FIG. 1 shows a block diagram of a device for determination
of the wind incidence angle;
[0020] FIG. 2 shows a block diagram of open-loop control of control
surfaces on wings and on the tailplane as a function of the wind
incidence angle;
[0021] FIG. 3 shows a definition of axes and angles in the geodetic
(g) and aircraft-fixed (f) coordinate system in accordance with DIN
9300;
[0022] FIG. 4 shows a definition of axes and angles in the
aircraft-fixed (f), aerodynamic (a) and experimental (e) coordinate
system in accordance with DIN 9300.
[0023] FIG. 5 shows a cross-sectional view of a wing in order to
illustrate the change in the air force vector as a consequence of
an upward wind gust.
DETAILED DESCRIPTION OF THE INVENTION
[0024] FIG. 1 shows a block diagram of a control device for
determination of the wind incidence angle .alpha..sub.Wf in the
vehicle-fixed coordinate system which, after high-pass filtering,
is used as a drive signal .alpha..sub.Wf.sup.II for open-loop
control based on the disturbance-variable application
principle.
[0025] The velocity V of the aircraft with respect to the air is
determined by means of an air data system. The geodetic vertical
velocity {dot over (H)} of the aircraft is determined either from
the air data system as the barometric altitude change {dot over
(H)}.sub.baro, from the inertial reference system (IRS) as {dot
over (H)}.sub.inertial or with the aid of complementary filtering
from the barometric altitude signal {dot over (H)}.sub.baro and the
inertial vertical acceleration {dot over (H)}.sub.inertial.
Furthermore, the inertial reference system (IRS) is used to detect
the bank angle .PHI., the longitudinal attitude angle .theta., the
pitch rate q and the yaw rate r. The incidence angle .alpha. is
detected by an incidence angle sensor. The sideslip angle .beta. is
detected by a sideslip angle sensor. All of the sensor signals are
conditioned (signal conditioning) at least in such a way that they
are calibrated and synchronized.
[0026] The component .alpha..sub.Wf caused by a vertical air mass
movement of the wind incidence angle on the aircraft plane of
symmetry is defined in the aircraft-fixed coordinate system using
the formula:
.alpha. Wf = cos ( .phi. ) [ f ( H . V ) - .theta. + cos ( .phi. )
( .alpha. + q r AoA V ) + sin ( .phi. ) ( .beta. - r r AoS V ) ]
##EQU00005##
The factors cos(.phi.) and sin(.phi.) and the sideslip angle .beta.
are used to correctly determine the wind incidence angle
.alpha..sub.Wf on the aircraft plane of symmetry resulting from a
vertical air mass movement even when the boundary conditions
change, for example when turning. The vertical wind component
acting on the aircraft plane of symmetry produces the wind
incidence angle .alpha..sub.Wf, which acts as an additional
incidence angle on the wing and thus causes a change in lift. It is
advantageous to filter the calculated wind incidence angle
.alpha..sub.Wf by means of a high-pass filter. If necessary, any
constant sensor errors, slow sensor drifts and very low-frequency
air mass movements (which are not relevant for gust loads) are
filtered out in the case of the filtered wind incidence angle
.alpha. II Wf ##EQU00006##
produced in this way. The effective component .alpha..sub.Wf can be
compensated for, for example, with the aid of control surfaces for
direct lift control.
[0027] FIG. 2 shows a block diagram of an open-loop control system,
in which the component .alpha..sub.Wf of the wind incidence angle
on the aircraft plane of symmetry is applied to the control signals
as a disturbance variable in order to control the control surfaces
on the wings and on the tailplane (in general the elevator). The
control surfaces on the wings are used for direct lift control.
[0028] The delay time T.sub.T1 takes account of the delay time of
the gust disturbance from the location of the incidence-angle or
sideslip-angle measurement to the lift-generating wing. The wind
incidence angle
.alpha. II Wf ##EQU00007##
delayed by the delay time T.sub.T1 is multiplied by the gain factor
K1 and, after low-pass filtering, is used as a difference
manipulated variable for controlling the control surfaces on the
wings.
[0029] Different difference control signals, which in some cases
are delayed by T.sub.T1 or (T.sub.T1+T.sub.T2), are supplied to the
tailplane control surfaces in order to control the pitch moment
budget.
[0030] The measurement variables which are used to determine the
wind incidence angle .alpha..sub.Wf will be explained in more
detail in the following text with reference to FIGS. 3 and 4, with
reference also being made to DIN 9300.
[0031] FIG. 3 shows the aircraft-fixed coordinate system with the
index "f". The aircraft-fixed coordinate system is defined by the
aircraft longitudinal axis x.sub.f, the aircraft lateral axis
y.sub.f and the aircraft vertical axis z.sub.f. Furthermore, a
first node axis k.sub.1 is defined as the projection of the
aircraft longitudinal axis x.sub.f onto the geodetic horizontal
plane x.sub.g, y.sub.g. The longitudinal inclination or the pitch
angle is the angle between the aircraft longitudinal axis x.sub.f
in the aircraft-fixed coordinate system and the first node axis
k.sub.1. The pitch angle is at right angles to the horizontal plane
x.sub.g, y.sub.g between the node axis k.sub.1 and the longitudinal
axis x.sub.f in the aircraft-fixed coordinate system.
[0032] The bank angle or roll angle .phi. is defined between a
second node axis k.sub.2 and the aircraft lateral axis y.sub.f in
the aircraft-fixed coordinate system. The second node axis k.sub.2
lies in the geodetic horizontal plane x.sub.g, y.sub.g and is at
right angles to the first node axis k.sub.1. The yaw angle, the
pitch angle and the roll angle .phi. are referred to together as
Euler angles. These Euler angles are not at right angles to one
another, so that the sequence of the individual rotations in the
transformation from the aircraft-fixed coordinate system to an
aerodynamic coordinate system and vice versa is important.
[0033] FIG. 4 shows the aerodynamic coordinate system x.sub.a,
y.sub.a, z.sub.a with the index "a". An aircraft-fixed coordinate
system x.sub.f, y.sub.f and z.sub.f is also shown. FIG. 4 also
shows the experimental coordinate system (index "e"). The lateral
axis of the aircraft y.sub.f and the y.sub.e axis in the
experimental coordinate system coincide: y.sub.f=y.sub.e. The
z.sub.a axis in the aerodynamic coordinate system and the z.sub.e
axis in the experimental coordinate system coincide:
z.sub.a=z.sub.e.
[0034] The z axis in the aerodynamic coordinate system forms the
lift axis z.sub.a=z.sub.e. The y axis in the aerodynamic coordinate
system forms the lateral force axis y.sub.a.
[0035] The sideslip angle .beta. is the required rotation angle
about the z.sub.a=z.sub.e axis in order to change the x.sub.e axis
to the x.sub.e axis to the x.sub.a axis.
[0036] The incidence angle .alpha. is the required rotation angle
about the y.sub.f=y.sub.e axis in order to change the x.sub.e axis
to the x.sub.f axis.
[0037] V denotes the airspeed vector with respect to the air, which
is sketched as an arrow.
[0038] FIG. 5 shows a cross-sectional view of a wing T with an
incident flow. The left-hand image shows the relationships during
steady-state flight in a steady-state atmosphere. The airspeed
V=V.sub.0 of the aircraft (V=velocity of the incident flow onto the
wing T) generates an air force F.sup.A=F.sub.0.sup.A. If an upward
wind gust now acts on the wing, the magnitude and direction of the
airspeed V change. The magnitude of the airspeed becomes slightly
larger (V>V.sub.0), and the wing T of the airspeed becomes
slightly larger (V>V.sub.0) and the flow strikes the wing T from
a steeper direction. In comparison to the original incident flow
direction of the wing T, the upward wind gust would generate the
wind incidence angle (=additional incidence angle) .alpha..sub.W.
The two effects lead to an increase in the resultant air force
F.sup.A=F.sub.0.sup.A. The direction of the resultant air force
F.sup.A is also slightly changed by .alpha..sub.W. However, the
change in the magnitude of the resultant air force F.sup.A is the
dominant factor.
* * * * *