GENERAL TECHNICAL FIELD
The invention relates to the field of the piloting aid in a shift phase
on the ground of an aircraft and more precisely an improved autonomous
guiding method during a taxiing phase.
PRIOR ART
During taxiing phases on the ground of an aircraft, the pilot of the
aircraft must steer the latter between the tracks and the airport
infrastructure totally safely despite reduced visibility.
To help the pilot in his task, there are guiding systems determining
the position of the aircraft with respect to indicators on the ground, such as
reflecting markings, studs or lamps, and using this information to guide the
aircraft along a reference trajectory to be followed.
But some taxiing areas such as cross-over areas may present
complex topology capable of causing errors in a guiding system, as shown
in figure 1. The latter in fact risks taking into consideration for calculating a
trajectory to be followed indicators inadequate and may then guide the
aircraft in a wrong direction. Such an error in trajectory may present
considerable security risks if the aircraft is guided out of a taxiway or else
on a track already occupied by another unit.
There is therefore a need for a method monitoring the guiding of an
aircraft so as to guide it correctly on a platform of an airport, even in
complex taxiing areas, and limiting the impact of a guiding error.
PRESENTATION OF THE INVENTION
The present invention thus relates according to a first aspect to a
method for guiding along a reference trajectory on a platform on the
ground an aircraft having on board at least one detector of a plurality of
indicators on the ground, said method comprising the following steps
performed by a data-processing module capable of being connected to
said at least one detector:
a) determining complex uncertainty areas of the platform geometrically
from a mapping of the platform,
b) near one of said determined uncertainty areas, selecting at least one
indicator from the plurality of indicators on the ground,
c) estimating the relative localization of the aircraft with respect to said
reference trajectory from data relating to said at least one selected
indicator transmitted by said at least one detector,
d) calculating a confidence index relating to the relative localization
estimated from the at least one selected indicator,
e) comparing the calculated confidence index to a predetermined
threshold,
f) when the calculated confidence index is greater than the predetermined
threshold, guiding the aircraft along the reference trajectory as a function
of the estimated relative localization.
Such a method guides the aircraft without risking have it follow a
trajectory different to the reference trajectory.
The calculation step of the confidence index of said at least one
selected indicator of the method according to the first aspect may be
performed as a function of the arrangement of said indicators on the
ground with respect to the reference trajectory.
The calculation step of the confidence index relating to the relative
localization estimated from said at least one selected indicator of the
method according to the first aspect may be performed as a function of the
position of the aircraft with respect to said at least one selected indicator
and of the reference trajectory.
This quantifies the confidence which may be accorded to an
estimation of localization of the aircraft as a function of the positions of the
indicators and of the aircraft with respect to each other and with respect to
the trajectory which the aircraft must follow.
When the confidence index relating to the estimated relative
localization is less than the predetermined threshold, the data-processing
module selects at least one new indicator on the ground, estimates the
relative localization of the aircraft with respect to the reference trajectory
from said at least one new selected indicator, calculates a confidence
index relating to the relative localization estimated from the at least one
new selected indicator and compares the calculated confidence index to
the predetermined threshold.
This means not guiding the aircraft from an estimated localization
insufficiently dependable and risking having the aircraft follow a wrong
direction, but rather finding a localization having a level of confidence
sufficient to be used to guide the aircraft.
When the confidence index relating to the estimated relative
localization is less than the predetermined threshold, the data-processing
module may transmit an alarm message requiring the aircraft to either be
piloted in manual mode or warning that the aircraft is switching to manual
mode.
This warns the pilot and asks him to assume control of the aircraft
or warns him of automatic switching to manual mode when the layout
indicators of the processing module do not perform sufficiently safe
guiding of the aircraft.
When the confidence index relating to the estimated localization is
less than the predetermined threshold, the data-processing module may
guide the aircraft from the reference trajectory.
This continues the guiding of the aircraft autonomously without
taking into account those data relating to the indicators on the ground
transmitted by the detectors. In this way this solution does not risk guiding
the aircraft in a wrong direction when the layout indicators are not
considered as dependable.
In a first variant embodiment, the processing module performs the
determination step of the uncertainty areas repeatedly over time.
In a second variant embodiment, the processing module performs
the determination step of the uncertainty areas when the aircraft enters the
taxiing phase.
This determines if the aircraft is risking encountering a complex
area needing a guiding method adapted to limit the risk of guiding the
aircraft in a wrong direction being deployed.
According to a second aspect, the invention relates to a computer
program product comprising code instructions for executing a guiding
method according to the first aspect, when this program is executed by a
processor.
According to a third aspect, the invention relates to a dataprocessing
module which may be connected to at least one detector of a
plurality of indicators localized on a platform on the ground, said at least
one detector being loaded on board an aircraft and said data-processing
module being configured for:
a) determining complex uncertainty areas of the platform
geometrically from a mapping of the platform,
b) near one of said determined uncertainty areas, selecting at
least one indicator from the plurality of indicators on the ground,
c) estimating the relative localization of the aircraft with respect
to a reference trajectory from data relating to said at least one
selected indicator transmitted by said at least one detector,
d) calculating a confidence index relating to the relative
localization estimated from the at least one selected indicator,
e) comparing the calculated confidence index to a
predetermined threshold,
f) when the calculated confidence index is greater than the
predetermined threshold, guiding the aircraft along the reference
trajectory as a function of the estimated relative localization.
According to a fourth aspect, the invention relates to a system for
guiding an aircraft along a reference trajectory on a platform on the ground
comprising: at least one detector, a plurality of indicators on the ground
and a data-processing module according to the third aspect.
Such computer program product, processing module and guiding
system have the same advantages as those mentioned for the method
according to the first aspect.
PRESENTATION OF THE FIGURES
Other features and advantages of the present invention will become
apparent upon reading the description which follows of an embodiment of
the invention. This description will be given with reference to the appended
drawings wherein:
- Figure 1 illustrates taxiing areas such as cross-over areas may
have complex topology;
- Figure 2 is a diagram showing an implementation of a guiding
method according to the invention;
- Figure 3 shows a guiding system according to an embodiment of
the invention;
DETAILED DESCRIPTION
With reference to Fig. 2, an embodiment of the invention relates to
a method for guiding an aircraft 1 along a reference trajectory on a
platform applied by a data-processing module 2 of a system for guiding an
aircraft illustrated in Fig. 3.
Such a system comprises indicators on the ground 4 used for
marking the taxiing areas of the platform and at least one detector 3
loaded on board the aircraft 1 and adapted for detecting the position of
such indicators on the ground. Such a detector senses the signals sent or
reflected by said indicators on the ground. Such a detector may for
example be an optical or optoelectronic sensor sensing light emitted by
light sources such as lamps or reflected by reflective markings. Such a
detector may also be a radiofrequency receiver receiving radio signals
emitted by antennas positioned on the ground.
Said detectors 3 may be connected to the processing module 2 so
as to provide it with measurement data allowing the processing module 2
to determine the relative localization of the aircraft 1 with respect to these
indicators 4.
The data-processing module 2 may include communication means
such as a communication interface COM, computing means such as a
computer CALC and storage means MEM. Such a computer may consist
in a processor or microprocessor, of the x-86 or RISC type for example, a
controller or micro-controller, a DSP, an integrated circuit such as an ASIC
or programmable circuit such as an FPGA, a combination of such
elements or any other combination of components giving the possibility of
applying the computing steps of the method described below. The MEM
storage means may consist in any type of computer bulk storage such as
a magnetic hard disc with a plate, an SSD disc, flash memory or further a
CD-ROM or DVD-ROM reader.
Said communication means COM may be used for communicating
with the detectors 3. The MEM storage means may notably be used for
storing one or several mapping representations of the airport platform on
which the aircraft 1 has to be guided.
The data-processing module 2 may be connected to at least one
computer of the aircraft or be integrated therein, so as to be able to
transmit to it commands for guiding the aircraft.
The method according to the invention proposes an improved
guiding of the aircraft along a reference trajectory for limiting the
probability of guiding errors during guiding in a complex area such as a
cross-over area.
While a guiding method is being performed, the relative localization
of the aircraft with respect to the reference trajectory is estimated from
data on indicators on the ground transmitted by the detectors, such as the
position of the indicators with respect to the plane. This estimation of the
aircraft localization is used to carry out guiding of the aircraft along this
reference trajectory. The method according to the invention proposes
verifying that the indicators on the ground considered for determining the
relative localization of the aircraft are pertinent with respect to the
reference trajectory to be followed. So if an aircraft is at a cross-over
between a rectilinear track and a curved track and the trajectory to be
followed by the aircraft must guide it along the rectilinear track, the method
according to the invention prevents the indicators localized along the
curved track being employed for guiding the aircraft. Such guiding could
assign to the aircraft the curved track instead of the rectilinear track and
would risk putting the aircraft in a dangerous situation.
For this, for a relative localization estimated from some indicators
on the ground, the method calculates a confidence index. Such a
confidence index represents the probability that these indicators on the
ground are appropriate for guiding the aircraft, given the trajectory
occupied by the latter.
More precisely, in reference to figure 2, during a determination step
E1, the data-processing module determines one or more complex
uncertainty areas of the platform geometrically from a mapping of the
platform. Such a determination step may be conducted at the start of a
taxiing phase. Alternatively, such a determination step may be performed
repeatedly over time during a taxiing phase.
During a selection step E2, the processing module selects from the
plurality of indicators on the ground detected by the detectors of the
aircraft at least one indicator. Such a selection step is performed when the
aircraft is in or near an uncertainty area determined during determination
step E1. These selected indicators are those the processing module will
then try to use to proceed with guiding the aircraft.
During an estimation step of relative localization E3, the processing
module 2 estimates the relative localization of the aircraft with respect to
the reference trajectory from data relating to selected indicators during the
selection step E2 transmitted by the detectors. This estimation may for
example govern the position of the aircraft with respect to an indicator or a
couple of indicators.
During a calculation step E4, the processing module 2 verifies the
pertinence of the selected indicators used during the estimation step of
relative localization E3 with respect to the reference trajectory to be
followed. For this the processing module calculates for the relative
localization estimated from these selected indicators a confidence index
indicating the probability that these selected indicators mark a path the
aircraft is best to take in following the reference trajectory.
According to a first embodiment, calculation of the confidence index
is performed as a function of the arrangement of the selected indicators
with respect to the reference trajectory. For example, indicators may be
considered as adapted if they are positioned along a trajectory similar to
the reference trajectory. The confidence index linked to these indicators
could be high. Inversely, if selected indicators form a curved line indicating
a bend whereas the reference trajectory is a straight line, the indicators
may be considered as inadequate and the associated confidence index
may be low.
According to a second embodiment, calculation of the confidence
index is done as a function of the position of the aircraft with respect to the
selected indicators and the reference trajectory. The processing module
may for example compare the position of the aircraft with respect to the
selected indicators and the localization of the aircraft with respect to the
reference trajectory. If the selected indicators are inadequate and do not
follow the reference trajectory, the aircraft following the reference trajectory
will move away from the selected indicators but not from the reference
trajectory. The gap between the relative position of the aircraft with respect
to the selected indicators and the relative localization of the aircraft with
respect to the reference trajectory may then have a sudden variation. The
confidence index associated with such inadequate indicators could be low.
Calculation of the confidence index may be a function of a level of
geometric complexity of the uncertainty area travelled by the aircraft or of
external conditions such as meteorological conditions. The confidence
index may be fixed to a very low value predetermined voluntarily when
conditions are fulfilled in which calculation of the confidence index is
known to give unreliable results.
During a comparison step E5, the processing module compares the
calculated confidence index to a predetermined threshold.
During a guiding step E6 the processing module guides the aircraft
along the reference trajectory as a function of the estimated relative
localization if the confidence index is greater than the predetermined
threshold. Once the relative localization has been recognized as
dependable, the processing module may use it to correct the trajectory of
the plane so that the latter properly follows the reference trajectory.
If the confidence index is less than the threshold, the estimated
relative position cannot be used for guiding the plane and the processing
module again executes the steps of selecting E2, estimating relative
localization E3, calculating E4 and comparing E5: the processing module
selects at least one new indicator, estimates the relative localization of the
aircraft from the new indicators, calculates the associated confidence
index and compares it to the predetermined threshold.
The processing module may repeat these steps provided the
confidence index remains under the threshold.
According to an embodiment, when a confidence index is less than
the threshold, the processing module may transmit an alarm message to
the pilot requiring the aircraft to be piloted in manual mode or warning that
the aircraft is switching to manual mode during a manual guiding step E7.
Such a message may for example be sent after a predetermined number
of negative comparisons, after a certain time has elapsed without a
confidence index being greater than the threshold or even when there is
no longer a new indicator for which no confidence index has been
calculated. The processing module then considers that the indicators
selected during the preceding steps do not allow reliable guiding of the
aircraft and the pilot should ensure manual guiding of the aircraft.
Switching to manual mode may be automatic on completion of emission of
the alarm message, for example after expiration of a countdown of
predetermined duration. In such an embodiment sending such a message
requiring manual guiding of the aircraft or automatic switching to manual
mode accompanied by an alert may be imposed by systematically fixing
during the calculation step E4 the confidence index at a very low value
predetermined voluntarily until the alarm message is sent.
5
Also, when a confidence index is less than the predetermined
threshold the processing module may decide to guide the aircraft from the
reference trajectory during an autonomous guiding step E8, without
considering the estimated relative localization or localizations since these
10 relative localizations have not been deemed reliable. The processing
module may also take into account information on absolute localization
provided for example by a GPS module. The aircraft continues to be
guided but blindly without using the information issued by the detectors.
According to an embodiment, if the aircraft is piloted in manual
mode and is in an uncertainty area, the processing module may still
execute the steps of selecting E2, estimating relative localization E3,
calculating E4 and comparing E5 and may propose that the pilot return to
automatic guiding mode when a confidence index is greater than the
predetermined threshold. The processing module has a relative
localization considered as reliable enabling it to perform automatic guiding
of the aircraft in the uncertainty area along the reference trajectory. The
automatic guiding mode may also be reinitiated automatically when a
confidence index is greater than the predetermined threshold.
According to an embodiment, when the aircraft exits an uncertainty
area, the processing module may propose that the pilot cease calculating
a confidence index for the estimated localization. Each estimated
localization is then considered as reliable and could be used for guiding
the aircraft without questioning the indicators selected to evaluate this
localization. The processing module may remain in this simplified guiding
mode provided the aircraft is not back near or in an uncertainty area.
The guiding method such as described correctly guides an
35 aircraft on a platform of an airport, even in complex taxiing areas.

I/We Claim:
1. A method for guiding along a reference trajectory on a platform on the
ground an aircraft (1) having on board at least one detector (3) of a
plurality of indicators on the ground (4),
said method comprising the following steps performed by a dataprocessing
module (2) capable of being connected to said at least one
detector:
a) determining (E1) complex uncertainty areas of the platform
geometrically from a mapping of the platform,
b) near one of said determined uncertainty areas, selecting (E2) at
least one indicator (4) from the plurality of indicators on the ground,
c) estimating (E3) the relative localization of the aircraft with respect to
said reference trajectory from data relating to said at least one
selected indicator transmitted by said at least one detector,
d) calculating (E4) a confidence index relating to the relative
localization estimated from the at least one selected indicator,
e) comparing (E5) the calculated confidence index to a predetermined
threshold,
f) when the calculated confidence index is greater than the
predetermined threshold, guiding (E6) the aircraft along the reference
trajectory as a function of the estimated relative localization.
2. The method according to the preceding claim, wherein the calculation
step of the confidence index of said at least one selected indicator
(E4) is performed as a function of the arrangement of said indicators
on the ground with respect to the reference trajectory.
3. The method according to claim 1, wherein the calculation step (E4) of
the confidence index relating to the relative localization estimated from
said at least one selected indicator is performed as a function of the
position of the aircraft with respect to said at least one selected
indicator and of the reference trajectory.
4. The method according to one of the preceding claims, wherein when
the confidence index relating to the estimated relative localization is
less than the predetermined threshold, the data-processing module
selects at least one new indicator on the ground, estimates the relative
localization of the aircraft with respect to the reference trajectory from
said at least one new selected indicator, calculates a confidence index
relating to the relative localization estimated from the at least one new
selected indicator and compares the calculated confidence index to
the predetermined threshold.
5. The method according to one of the preceding claims, wherein when
the confidence index relating to the estimated relative localization is
less than the predetermined threshold, the data-processing module
transmits an alarm message requiring the aircraft to either be piloted in
manual mode or warning that the aircraft is switching to manual mode
(E7).
6. The method according to one of the preceding claims, wherein when
the confidence index relating to the estimated localization is less than
the predetermined threshold, the data-processing module guides the
aircraft from the reference trajectory (E8).
7. The method according to one of the preceding claims, wherein the
processing module performs the determination step of the uncertainty
areas (E1) repeatedly over time.
8. The method according to one of the preceding claims, wherein the
processing module performs the determination step of the uncertainty
areas (E1) when the aircraft enters the taxiing phase.
9. A computer program product comprising code instructions for
executing a guiding method according to one of the preceding claims,
when this program is executed by a processor.
10. A data-processing module (2) which may be connected to at least one
detector (3) of a plurality of indicators (4) localized on a platform on the
ground, said at least one detector (3) being loaded on board an aircraft
(1) and said data-processing module (2) being configured for:
a) determining complex uncertainty areas of the platform geometrically
from a mapping of the platform,
b) near one of said determined uncertainty areas, selecting at least
one indicator from the plurality of indicators on the ground,
c) estimating the relative localization of the aircraft with respect to a
reference trajectory from data relating to said at least one selected
indicator transmitted by said at least one detector,
d) calculating a confidence index relating to the relative localization
estimated from the at least one selected indicator,
e) comparing the calculated confidence index to a predetermined
threshold,
f) when the calculated confidence index is greater than the
predetermined threshold, guiding the aircraft along the reference
trajectory as a function of the estimated relative localization.