The influence of external disturbances on the control of the aircraft in the horizontal plane
To side winds. When the ACS, roll forming specified by law (3), for all forms of feedback servo inevitable appearance of static error by the action of crosswinds. This is because the signal yaw angle due to the longitudinal axis rotation of the aircraft in the wind direction to eliminate the slip can be balanced only lateral displacement signal. Indeed, the
.
whence
,
ie more or less cross wind speed, the greater the error. Dynamics of the process is as follows. Crosswind plane communicates with the line of the path. As more errors ACS tilts LA. Since at LA roll unfolds at a rate proportional to the rate of the signal reduces the roll. When the lateral velocity component balances wind speed, increasing the error stops.
If ACS generates a specified list according to the laws (4) - (6), then the effects of crosswinds is provided through the flight of a given path without static error. In fact:
,
as
well
as
in
the steady state
,
then
.
It
is provided
at
the rate of
rotation
of
the
plane
nosed
into
the wind
at
an angle
.
The
impact of
continuous
disturbing
moment.
Under
the action
of
constant
disturbing
moment
heel
(for
example, the
case of asymmetric
discharge
cargo)
in
a steady
process
.
Therefore,
when
Jos
servo
roll
forming
specified
by
law (3)
-
(5)
appears static
error.
The
behavior of
an
aircraft with
ACS
is
described
by
the following equations
;
;
.
Solving these equations, we obtain an expression for the static error
,
ie
the
plane will fly
with
aileron,
maintaining a
given rate,
with zero bank
angle,
but with a
lateral
deviation
from
the
specified path
.
And to the action of disturbing moment roll plane on hold given path should: Jos used for servo control law (6); when the law of formation of heel (3) - (5) apply SOS or IOS servo.
Speed control of flight
Speed
control of
the
flight
is
carried out in
two
main
controls:
•
changes in
engine
thrust;
•
elevator.
Control
airspeed
change
thrust.
Control
airspeed
change
thrust
is
mainly used
in
rectilinear motion,
and in particular, the motion of the
aircraft on
final
approach.
Automatic
performing
stabilization
speed
by
changing the
thrust
of the engines,
commonly called autothrottle
(AT).
Changing
the
traction
machine
carries
through
the
lever
engine
control
(throttle)
.
Automatic traction needed for a cruise flight with simultaneous stabilization trajectory CM LA. An example of such a regime can serve as the approach mode. If traction control is a direct effect on the longitudinal forces acting on the aircraft. Control law with AT Jos can be written as
.
In the study of the dynamics of the aircraft in speed with AT need to add the equations of motion of the aircraft equations describing the control laws of the AT and ACS. We assume that the channel pitch deviation ACS stabilizer keeps a straight trajectory. Then the system of equations describing the movement of aircraft on the speed with AT is thus reduced to the following:
;
;
.
The
first
equation
is
the
projection
of
forces on the
longitudinal
axis,
the second characterizes
the change in
traction
at
a deviation
ORE.
The
engine
is
described by
inertial
element.
The
third equation
determines
the deviation
ORE
AT.
The
inertia
of
the process
can
be neglected.
For
the analysis of
the
dynamic properties of
the
system "plane
- AT"
in
the management of
the
flight speed
necessary
to o
btain
the
transfer function
.
Block diagram corresponding to equation is shown in Fig.
Transfer control circuit diagram of the form
The
analysis
of
the transfer function
leads
to the following
conclusions:
-
dynamic
properties of the
control
loop
"aircraft
-
AT"
describes the element
of
the second order;
-
dynamic
properties of
the
considered
control
loop
determined
by the properties
aircraft
engine
performance
(gain
and time
constant)
and
the parameters of
the
AT;
-
increase
in factor
contributes
to the
natural
frequency of the
control
loop,
and
-
damping
factor.
Changing
parameters
AT
(coefficients
and
)
can
affect
the quality of
the
transition process;
there
is a
static
error
in
completing the
speed
setpoint:
.
The
presence of
antibodies
in
the
control
law
of
the integral of
the
velocity
signal
will
provide
astatic
stabilization
speed.
Speed control with the help of the elevator. Airspeed control deflection of the elevator is used if not imposed stringent requirements for the movement of aircraft on the desired path. The elevator in the management rate deviates by law
.
If you change the speed of flight elevator deflected to increase the angle of attack. Changing the angle of attack will change the lift and drag forces. As a result, the trajectory will be bent, and flight speed will vary. If we assume that the aircraft at a deviation of the elevator goes instantly to a given angle of attack, the closed-loop transfer function is equal to
,
where
the coefficients
of
the denominator
are
functions of
aerodynamic
design
aircraft,
and
transmission
coefficients
of
the control law.
Change
gear
ratios
and
you
can
adjust
the
values
of the coefficients
,
,
and
and
ensure
stability
of
the closed
loop.
However,
under
the law
(6.)
Is
not always possible
to
obtain the desired
transition.
From
the analysis of
the
transfer function we
can also
conclude
that
the
management of
the
speed using
the
elevator
there
is
a
static error
that
is fixed
in
the
control
law to
introduce
an additional
integral
term.
Stabilization
of
flight
speed
in
principle
possible
to provide
exposure
to
the
drag
with
brake
flaps.
However,
this method
of
stabilization
rate
is
not favorable,
as in
the original
flight
mode
for
speed
control
in
one
and the other
side
of
the
brake pads
should
be rejected
by
some amount,
resulting in increased
drag
aircraft.