CBL - Campus del Baix Llobregat

Projecte llegit



Departament: FIS


Data inici oferta: 13-07-2017     Data finalització oferta: 13-03-2018

Estudis d'assignació del projecte:
Tipus: Individual
Lloc de realització:
    Departament: FIS, TSC
Paraules clau:
satellite, cubesat, ADCS, actitud, control, B-dot
Descripció del contingut i pla d'activitats:
The purpose of this Master Thesis will be the development of the control part of the Attitude and Determination Control System (ADCS). There will be three different phases during mission, and the ADCS should provide the attitude performance required in all of them.

At the beginning of the mission, in the commissioning phase, the ADCS will start in the detumbling mode, and the system should be able to reduce the angular velocity below a certain range using only the magnetorquers as actuators. The satellite includes a deployable helicoid antenna with a shape at the top where the GNSS signals are received. This antenna will be deployed at the end of this phase, changing the satellite structure and displacing the gravity centre; hence, the dynamic behaviour will variate.

During the nominal phase, the ADCS will use the gravity gradient, caused by a deployable mechanism that will change the mass distribution, to point towards nadir and the magnetic field to damping the state. Therefore, performing a semi-active control system.

At decommissioning phase, the ADCS will contribute to discharge the batteries and gives some control in the re-entry.
To perform the system will be necessary to characterize the inertia tensor and it dynamics response in the different mission phases, define the control strategies and the requirements to follow it.

As well as the control algorithm development, all the software simulators should be created especially for the 3 CAT-4.
Overview (resum en anglès):
The goal of this Master Thesis (MT) is the development and simulation of detumbling algorithms for the Attitude Determination and Control System (ADCS) of the 3Cat-4 nanosatellite. The difficulty of the ADCS will be given by the correct nadir pointing of its antenna before and after the gravity boom (GB) deployment, and its efficiency depends dramatically on its angular rate. The control law should be versatile due to the change of the mass distribution after the GB deployment, but also robust, simple and compatible with the limited resources of the 1U CubeSat platform.

This MT started after the 3Cat-4 proposal was accepted in the ESA’s “Fly Your Satellite!”, and hence, the ADCS was in its most initial phase. The lacked of the mission requirements and the required physical models settled down the kick-off of subsystem development. Therefore, firstly, it was established the ADCS requirements and, in parallel, was studied the mass properties for the different configurations of the satellite and developed ideal models.

Once the initial characterization of the spacecraft was done, came the necessity of analyse the environmental in orbit conditions, from the point of view of the attitude control. The 3Cat-4 launch is expected from the ISS, consequently, it will follow its orbit. At this attitude, the atmospheric and radiation pressure, the Earth magnetic field and the gravity gradient, once the GB deployment, are the most notably perturbation sources.

The B-dot controller algorithm is the most relevant detumbling controller for nanosatellites. It provides the simplicity and robustness required only with two consecutives magnetic field measurements or a combination of a measurement of the magnetic field and the angular rate and using magnetorquers as actuators. The suitability is clear due to its low consumption of resources and its high efficiency.

Finally, is presented the simulations developed for the different configurations where it can be seen the high efficiency of the B-dot controller in the ideal dynamic models. Also, once of the project has rich higher level of maturity and real models has been provided, new tests have been performed for the new models, showing that the B-dot controller still provides an efficient solution for the detumbling mode.

© CBLTIC Campus del Baix Llobregat - UPC