Title: Facility for Satellite Formation Flying Control System Verification
1Facility for Satellite Formation Flying Control
System Verification
- Veres, S.M., Gabriel, S.B., Lincoln, N.K.
- University of Southampton
- (United Kingdom)
- s.m.veres_at_soton.ac.uk, Tel 44-2380 597754
- Supported by EPSRC, EADS Astrium, Aero-Astro
2Outline of talk
Purpose of the facility Modes of operation The
GSF Testing The HIL Testing Software
support Future developments Availability Conclusio
ns
University of Southampton, UK
3Purpose of the facility
- To complement software based system testing
with - Control system hardware testing on the ground as
much as possible using real sensors and actuators - To provide hardware-in-the-loop simulations for
operation in space - To allow experiments with control algorithms and
test their long term reliability
University of Southampton, UK
4Two modes of operation
- A two phase approach is taken to test a
satellite formation flying system -
- Testing of the processors and communication
electronics with a limited number of sensors and
actuators (gyros, reaction wheels and air-jets)
This is called ground-based satellite frames
testing (GSFT). - Testing of the actual control algorithms, as they
would be used in space, using hardware in the
loop simulations control electronics are real
but the sensor, actuator and physical dynamics
are simulated. This is called hardware in the
loop testing (HILT).
University of Southampton, UK
5The GSF Testing
- GSFT (ground-based satellite frames testing )
allows testing of systems software and hardware
in operation with real components - solid state gyros (actual)
- accelerometers (actual)
- reaction wheels (actual)
- on board computers (actual)
- communication electronics (actual)
- propulsion substitutes (similar in dynamics)
University of Southampton, UK
6GSF Testing frames
Satellite frame that can rotate around a central
point (3DOF)
Base disk that glides on a table surface with
very low friction (2DOF)
7Space ground dynamical differences
- From a dynamical point of view, the essential
differences are
On the ground
In space
gravitational torques on the ground low
rotation friction on pin point air resistance
more significant Low translational friction on
BTU 5 DOF with constraints
gravity gradient torques in space No rotational
friction No translational friction 6 DOF no
constraints
University of Southampton, UK
8Testing of satellite autonomous cooperation
Frames in preparation for testing
University of Southampton, UK
9GSFT facility is capable to test
- 1.1 Suitability of the operating systems on
onboard hardware - 1.2 Functioning of the agent based software
architecture. - 1.3 Communication devices as they would be used
in space, so that the system integrity and
reliability can be assessed. - 1.4 Some control devices, nearly as they would be
used in space. Control moment gyros, reaction
wheels and propulsion substitutes are to be
tested with real dynamics and not only based on
manufacturer's descriptions. - 1.5 The on board sensor and camera system can be
similar or identical to that used in space. Its
connection, data throughput and functionality, as
part of the overall on board digital hardware,
can be tested.
University of Southampton, UK
10Metrology infrastructure
University of Southampton, UK
11Features of the table setup
- The precision-level table rests on a reinforced
concrete slab supported by a passive vibration
isolation system to remove ground vibrations. - Surrounding curtain rails which have been
tailored for the facility exclude light
interference from the outside. Internal
lightening provides homogenous light conditions
when used. - The ceiling drape has the potential to imitate a
portion of the sky with imitation stars. - Ready made frames are provided that can be used
to mount custom electronics brought by satellite
companies or academics. Custom frames can be
manufactured on site in the EDMC facility of the
School of Engineering Sciences.
University of Southampton, UK
12Metrology features
A calibrated 9 camera based observation system
which can monitor the positions and attitudes of
each frame in realtime. The highly sensitive
solid state gyros and the camera based position
and attitude estimates are processed through a
data fusion system which provides realtime
estimates of the 12 dimensional state of each
frame moving on the table.
1 cm accuracy for coarse formation flying
University of Southampton, UK
13Available GSFT frames
- 3 with model aircraft propeller actuation (8
bidirectional actuators in each frame) - 3 frames with air-jet actuators (16
unidirectional actuators on each frame) - and 3 frames for future customer use
University of Southampton, UK
14Hardware in the Loop Testing (HILT)
Onboard computer network with communications (as
in space)
Actuator signals (hardware simulated)
Dynamics of the satellite group (software
simulated)
Sensor signals (hardware simulated)
3D visualisation
University of Southampton, UK
15HILT Features
- It can use exactly the same control algorithm as
in space. - It can use the same control electronics and agent
based software architecture as GSFT no new
setup needed - It can use the same power electronics and
filtering devices as in space, the actuator
outputs are replaced by mock-up simulated loads
with similar dynamics as space certified
actuators, the sensors are replaced by analogue
I/O board outputs that are generated through
simulation software. - Actual sensor voltages are generated using D/A
converters and the actuator signal voltages
sampled by A/D converters
University of Southampton, UK
16Software support metrology and control
algorithms for the GSFT frames
Feedback linearization based controller
University of Southampton, UK
17Anticipated use testing of multi-agent systems
on hardware
University of Southampton, UK
18Future developments
- Precision positioning using laser range finders
- System verification software added
- Compliance with software standards
- Ready made modules with hardware standards
- Etc
University of Southampton, UK
19Conclusions
- Facility almost ready for industrial use
- Efficient design low cost maintenance great
value for money in contracted use - GSFT and HILT are complementary the two
together address all important issues before
space use - Systems are customizable frame size and
additional electronics can be produced on order
from us - We provide dynamical metrology and software
system for HILT
THANK YOU !
University of Southampton, UK