This thesis work was carried out between October 2021 and March 2022 at Stellar Project srl. The main objective is the development of a dynamic model of the pointing system of an optical telecommunications terminal in free space (Free Space Optical Communication). The terminal trasmitter is an integrated and fundamental part of Quango, a small satellite for QKD optical telecommunication, subsidized by the European Commission. The main requirement of an opto-mechanical terminal is to reduce the pointing error and therefore to align in the best possible way the receiving terminal with the transmitting one for the entire duration of the transmission. It's called Pointing Acquisition and Tracking (PAT) system. In the particular case of Quango, the PAT is composed of four main elements: a Coarse Pointing Mirror, an Off Axis System of two mirrors that act as a concentrating telescope, a Fast Steering Mirror and a Quadrant Detector for the measurement of the pointing error. These four elements are related to each other by a power and electronics subsystem. In this work, we focused in particular on the study of the propagation of the optical beam and on the kinematics of mirrors. The control of the system was validated on the two models of approximation of reality regarding the phenomenon of the propagation of the laser beam. Furthermore, a first approximation analysis of the variation of the pointing error as a function of the distance between the transmitting and receiving terminal was prepared. Finally, the issue of internal control of the Fast Steering Mirror was explored in order to correct its intrinsic disturbances. As a basis for the above-described work, the industrial heritage of Stellar Project was used; they have infact developed an innovative payload for optical telecommunications called Lasercube. The modeling software was MATLAB / Simulink.
Questo lavoro di tesi è stato svolto tra ottobre 2021 e marzo 2022 presso Stellar Project srl. L’obiettivo principale è lo sviluppo di modello dinamico del sistema di puntamento di un terminale per telecomunicazioni ottiche in spazio libero (Free Space Optical Communication). Il terminale, che svolgerà la funzione di trasmettitore, è parte integrante e fondamentale di Quango, un piccolo satellite per la telecomunicazione ottica a crittazione quantistica, sovvenzionato dalla Commissione Europea. Il principale requisito di un terminale opto-meccanico è quello di abbattere l’errore di puntamento e quindi di allineare nel miglior modo possibile il terminale ricevente con quello trasmittente per tutta la durata della trasmissione. Si parla quindi di sistema Pointing Acquisition e Tracking (PAT). Nel caso particolare di Quango, il PAT è composto da quattro elementi principali: un Coarse Pointing Mirror per il puntamento grossolano, un Off Axis System di due specchi che fungono da telescopio concentratore, un Fast Steering Mirror per il puntamento fine e un Quadrant Detector per la misurazione dell’errore di puntamento. Questi quattro elementi sono messi in relazione tra di loro da un sottosistema di potenza ed elettronica di controllo. In questo lavoro, ci si è concentrati in particolar modo sullo studio della propagazione del fascio ottico e sulla cinematica degli specchi. Si è validato il controllo del sistema su due modelli di approssimazione della realtà riguardo al fenomeno della propagazione del fascio laser. Inoltre, è stata preparata un’analisi in prima approssimazione della variazione dell’errore di puntamento in funzione della distanza tra terminale trasmittente e ricevente. Infine, si è approfondita la tematica del controllo interno del Fast Steering Mirror per correggerne i disturbi intrinseci. Come base per il sopradescritto lavoro ci si è avvalsi dell’heritage industriale di Stellar Project che ha sviluppato un payload innovativo per le telecomunicazioni ottiche chiamato Lasercube. Il software di modellazione che è stato utilizzato è MATLAB/Simulink.
Sviluppo del modello dinamico del sistema di puntamento di un terminale per telecomunicazioni ottiche
GHEDIN, MATTIA GREGORIO
2021/2022
Abstract
This thesis work was carried out between October 2021 and March 2022 at Stellar Project srl. The main objective is the development of a dynamic model of the pointing system of an optical telecommunications terminal in free space (Free Space Optical Communication). The terminal trasmitter is an integrated and fundamental part of Quango, a small satellite for QKD optical telecommunication, subsidized by the European Commission. The main requirement of an opto-mechanical terminal is to reduce the pointing error and therefore to align in the best possible way the receiving terminal with the transmitting one for the entire duration of the transmission. It's called Pointing Acquisition and Tracking (PAT) system. In the particular case of Quango, the PAT is composed of four main elements: a Coarse Pointing Mirror, an Off Axis System of two mirrors that act as a concentrating telescope, a Fast Steering Mirror and a Quadrant Detector for the measurement of the pointing error. These four elements are related to each other by a power and electronics subsystem. In this work, we focused in particular on the study of the propagation of the optical beam and on the kinematics of mirrors. The control of the system was validated on the two models of approximation of reality regarding the phenomenon of the propagation of the laser beam. Furthermore, a first approximation analysis of the variation of the pointing error as a function of the distance between the transmitting and receiving terminal was prepared. Finally, the issue of internal control of the Fast Steering Mirror was explored in order to correct its intrinsic disturbances. As a basis for the above-described work, the industrial heritage of Stellar Project was used; they have infact developed an innovative payload for optical telecommunications called Lasercube. The modeling software was MATLAB / Simulink.File | Dimensione | Formato | |
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https://hdl.handle.net/20.500.12608/28992