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Projecte llegit

Títol: A system to determine the inertia tensor of small satellites

Estudiants que han llegit aquest projecte:

Director/a: GIL PONS, PILAR

Departament: FIS

Títol: A system to determine the inertia tensor of small satellites

Data inici oferta: 01-02-2019     Data finalització oferta: 01-10-2019


Estudis d'assignació del projecte:
    GR ENG SIST AEROESP
Tipus: Individual
 
Lloc de realització: EETAC
 
Segon director/a (UPC): GUTIÉRREZ CABELLO, JORDI
 
Paraules clau:
CubeSat, SolidWorks, physical pendulum, ineria tensor, satellite
 
Descripció del contingut i pla d'activitats:
Attitude control of a satellite relies upon a precise determination of its inertia tensor, but determining the inertia tensor of a complex system, as is the case of satellites, completely escapes analytical methods. Even though the inertia tensor can be obtained by means of CAD models, this method is subject to a degree of uncertainty due to required approximations in the materials definition of some of the devices. Furthermore, cabling is often difficult to integrate into CAD designs, then introducing a further source of error.

In this Degree Thesis, we propose the design of a physical pendulum that can determine all the components of the inertia tensor, as well as the position of the centre of mass, with better accuracy than the one found in standard CAD software.
 
Overview (resum en anglès):
Context: Attitude control of a satellite relies upon a precise determination of its inertia tensor. However, the determination of the inertia tensor of a complex system, as is the case of satellites, completely escapes analytic methods. Even though the inertia tensor can be obtained by means of CAD models, this method is subject to a degree of uncertainties due to required approximations in the materials definition and the geometry of some components. Furthermore, cabling is often difficult to integrate into CAD designs, which may introduce an additional source of error.

Aims: In this Degree Thesis, we propose the design of a torsion pendulum which will allow us to determine all the components of the inertia tensor of a CubeSat-type object. We intend to achieve more efficiency and better accuracy than performing standard CAD simulations.

Methodology: Our starting point is a general idea of a pendulum, Our sketch involves a set of fixed parts, mostly with structural purposes, and a set of mobile parts. The latter must be able to rotate about the axis of a torsion fiber. Besides, it must connect to a platform on top of which the CubeSat whose tensor of inertia we intend to determine will be placed. By measuring the period of rotation of the mobile parts (which include the platform and CubeSat), it is easy to derive the inertia moment of rotating set about the axis given by the torsion fiber. The detailed design of the pendulum was executed with the software SolidWorks. Foundations of Classical Mechanics and rotation matrix Algebra, as well as the software MatLab were required to develop the operation analysis of the proposed pendulum.

Results: We designed, obtained detailed maps, and developed stress analysis calculations of the pendulum. Besides, we completed the mathematical analysis which allows to build the inertia tensor of a CubeSat, by using individual inertia moments, derived from a set of period measurements obtained with different orientations of the CubeSat. Finally, we used basic error analysis to show that the components of the inertia tensor can be obtained with the desire precision by using feasible period measurements.

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