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Títol: Contribution to Attitude Orbit Control System (AOCS) for CubeCat-8


Estudiants que han llegit aquest projecte:


Director/a: PARK, HYUK

Departament: FIS

Títol: Contribution to Attitude Orbit Control System (AOCS) for CubeCat-8

Data inici oferta: 17-07-2022     Data finalització oferta: 17-03-2023



Estudis d'assignació del projecte:
    GR ENG SIST AEROESP
Tipus: Individual
 
Lloc de realització:
UPC
    Departament: CommSensLab
 
Nom del segon director/a (UPC): Adriano Camps
Departament 2n director/a:
 
Paraules clau:
CubeSat, UPC NanoSat Lab, Space Engineering, Attitude Determination and Control System
 
Descripció del contingut i pla d'activitats:
' Brief description of the CubeCat-8
CubeCat-8 is a mission which will be achieved with the union of
NanoSat Lab from Universitat Politècnica
de Catalunya (UPC), as the team leader, Institut d'Estudis
Espacials de Catalunya (IEEC), as contributor
with 3Cat-Gea provider and i2Cat, as contributor with software
for Federated Satellite Systems
experiment. The platform selected would be a Standard 6U ISIS
platform.
The payload is meant to be formed by the following technology
demonstrators:
- Deployable Fresnel Zone Plate (FZP) antenna
- 2 X 1P PocketQube deployer
- Federated Satellite Systems experiment
- X-band transmitter
- IENAI electric thruster system with electrospray technology.
And the following scientific payloads:
- Polarimetric hyperspectral camera + data compression
- GNSS-Radio Occultations (using deployable FZP deployable
reflector)
' Brief description of the AOCS System, the AOCS parts to be
implemented at CubeCat8 and the tasks expected for implementation
of CubeCat-8 AOCS system
The objective of the AOCS system is to provide the mission with
controllers that allow the successful
accomplishment of the mission goals. In the case of the 3Cat-8
mission, the most important objective is
to maintain Nadir pointing during the development of the mission
objectives.
The Nadir pointing in the X axis is required by the camera
(scientific payload) in the perpendicular axis,
that has to point to the horizon during the mission. Also, the
antenna communicating with the ground
station is in X axis to allow communications while doing the
Nadir pointing. Despite this mode being
required during all the mission the controllers will have to
change, as the conditions of the system will
change from the original stowed CubeSat, to the configuration
with the thruster activated or the antenna
deployed.
Additionally, to the Nadir pointing, other control modes could be
required in different events. The usage
of a reaction wheel, requires a de-saturation mode. In the event
of low battery levels, the satellite will
start Sun pointing. And finally, in the case that the thruster is
not aligned with the Z axis, a mode to set
the thrust vector and the speed vector in the same direction will
be designed.
The de-saturation mode has two aims. To prevent reaching too high
or too low angular rates, and also to
ensure an efficient consume of power. The reaction wheel was
added to control the rotation of the Z axis.
When the magnetic field is parallel to one of the axes of the
magnetorquers, the rotation in that axis is
impossible to achieve, and so 1 DoF is lost. Due to the polar
orbit of the mission, when crossing the
equator, the magnetic field will be nearly parallel to the Z
axis. The reaction wheel won't be necessary out
of this zone, and so the de-saturation mode will be enabled when
not in use.
In the case of a perfect polar Sun-synchronous orbit, Nadir
pointing mode will be equivalent to Sun
pointing. Expecting the Orbit to not be ideal, the Sun pointing
mode will trade off a perfect Nadir pointing
to achieve perpendicularity between the sunlight and the panels.
This will only be needed to recharge
batteries in case the power consumption is too high.
The thrust vector pointing, TVP, is a mode with the aim to
maximize the height raised of the orbit when
the thruster is working. In the case of a thrust vector in the
same direction of the velocity, this mode will
act the same as the Nadir pointing. Being the thruster off
center, this generates a momentum in the
satellite. To minimize the momentum generated the thruster could
be rotated towards the center of mass.
In this case this mode will rotate the satellite, so the thrust
vector is parallel again with the velocity vector.
 
Overview (resum en anglès):
This final degree thesis describes the development and implementation of an ADCS simulator for the 3Cat-8 mission of the UPC NanoSat Lab, which enables the calculation of the
actuators and controller variables. Additionally, based on the ADCS simulator, specially focuses on the ATHENA ionic thruster control analysis ensuring the proper ADCS actuators
sizing of the spacecraft.
The control is solely achieved by magnetic actuators. It is shown that the satellite can maintain the desired orientation with low angular rates, required during the orbital raising maneuver. A new configuration of the control stability with linear attitude dynamics for satellite thruster, based on a control algorithm using attitude quaternion and angular velocity feedback is also described.
To conclude, the presented numerical results prove the efficiency of the applied method based on initial theoretical considerations and the design measurements of the satellite and the thruster.


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