TY - CONF
T1 - An EGNOS Based Navigation System for Highly Reliable Aircraft Automatic Landing
T2 - ENC GNSS 2009 PROCEEDINGS
Y1 - 2009
A1 - DE LELLIS, E
A1 - CORRARO, F
A1 - CINIGLIO, U
A1 - GAGLIONE, S
A1 - CANZOLINO, P
A1 - GARBARINO, L
A1 - NASTRO, V
AB -
Highly precise navigation is the core technology
required for many applications, such as automated
aerial refuelling (AAR), sea-based joint precision
approach and landing systems (JPALS), stationkeeping, unmanned aerial vehicles (UAV) swarming
and formation flight and unmanned ground vehicles
(UGV) convoys. Advances in the above mentioned
technology are possible considering the future
GNSS framework, given that adequate
characterization of new GNSS devices are
performed and that new algorithms are developed
that fully exploits the functionalities made available
by the future GNSS systems. In this paper both
aspects are considered, with specific reference to the
use of GPS/EGNOS for reliable fixed wing aircraft
automatic landing applications.
For what concern experimental characterization of
the satellite based navigation system GPS/EGNOS,
the main aim of the activity was to describe the
broadcasted messages to enhance the navigation
accuracy and integrity of the core GNSS-1 elements
GPS and GLONASS, and to exploit how the data
can be used to compute and analyze the
performance in terms of Required Navigation
Performance (RNP) parameters. The paper describes
the algorithm implemented to process the
broadcasted EGNOS SIS in order to obtain a
position solution and integrity information
compliant with RTCA DO229C. Moreover, the
paper presents test procedures and experimental
results that may be used as a design guideline for
monitoring manufacturing compliance and, in
certain cases, for obtaining formal DO229C
certification of equipment design and manufacture.
On the other hand, concerning the development of
new algorithms for Guidance, Navigation & Control
of fixed wing vehicles, that are already compatible
with the future GNSS framework, it was initially
considered a suite of navigation sensors with
accuracy similar to the one obtainable by EGNOS.
In order to overcome the effects due to an
insufficient accuracy, the satellite measures can be
in fact integrated with different sensor sources
allowing a high precision navigation and an
improvement of the integrity and reliability of
navigation solutions. By means of an appropriate
sensor suite, described in the next, and of a sensor
fusion algorithm we obtained a high precision level
in navigation measurements that, for instance,
allows a high autonomous precision approach and
landing. A very simple but effective sensor fusion
algorithm based on the use of complementary
filtering technique has been implemented.
Moreover, some critical autonomous functionality,
such as Autolanding, will utilize the GPS integrity ignal in its decision-making logic for evaluating the
key-decisions regarding the possible execution of an
altitude recovery manoeuvre and, in case, also
considering a degraded mode by changing the
desired performances at touch down, with the aim to
be still compatible with the current navigation
system precision. In this way the integrity
information provided by EGNOS is efficiently used
for achieving a higher safety level during
autonomous flight operations.
The selected on-board software architecture is
actually fully compliant to the use of EGNOS based
GPS units, without requiring any upgrade and the
proposed sensor fusion algorithms have been
already developed being basically compatible with
integrity information coming from the future GNSS
sensors. Anyway, in the presented first phase of
flight experiments, we used a coarse DGPS unit,
because EGNOS is still in the testing phase. The
next steps are to perform autonomous GN&C flight
experiment with EGNOS constellation with a
runway completely not instrumented.
In the first part of the paper, concerning EGNOS
system characterization, is presented an overview of
EGNOS (chapter 2), are described the processing of
the SBAS Signal-In-Space correction and integrity
data and the related algorithm to estimate the
integrity supplied by the system (chapter 3), the
classes of equipment at which the test requirement
are referred and the equipment performance and test
procedure focusing on processing requirements and
the validation performance assessment logic to
assess the performance achievable with EGNOS
(chapter 4). In its second part, describing the
development of GNC algorithms already compatible
with the future GNSS framework, the paper deals
with the autolanding algorithms (chapter 6), the
sensor fusion algorithms to achieve the desired
navigation precision and the methodologies
developed in order to safely manage the possible
presence of sensor failures (chapter 5), the
preliminary results of the real time validation with
hardware in the loop simulation (chapter 7) and,
finally, the algorithm performances achieved during
the first experimental flights by using the CIRA
experimental flying platform (chapter 8).
JF - ENC GNSS 2009 PROCEEDINGS
ER -