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Parametric analysis of optomechanical mountings based on hexapodal kinematics
No full textLAUREA MAGISTRALEQuesto lavoro è incentrato sull' analisi di una cinematica esapodale per ottenere una montatura funzionale e parametrizzata che permette di studiare differenti condizioni operative e di sopravvivenza. Lo studio viene fatto definendo prima tutti i parametri geometrici della struttura. Successivamente si da spazio alle proprietà meccaniche e termiche dei materiali considerati per poter incominciare a definire la vera e propria analisi strutturale fatta attraverso gli elementi finiti. I carichi e le condizioni al contorno possono essere modificate in qualsiasi momento. Il prodotto finale è un software versatile dotato di interfaccia che, una volta inseriti tutti i parametri, permette lo studio delle situazioni più varie. Successivamente il codice viene validato attraverso la realizzazione di esperimenti efficaci.This work is focused on the analysis of optomechanical mountings based on hexapodal kinemat-
ics architecture to obtain efficient supports and proper alignment of an optical device. It has
been implemented a parametrized approach considering different conditions of load in terms of
operative and survival conditions for the analysis. The project is organized in the following steps:
- Definition of the structure with all the geometrical parameters as input for the code. Any type of initial condition (dimension and shape) can be considered starting from the kinematic chain between each part.
- Definition of all the parameters required for the analysis. All the physical proprieties of
the materials are defined in terms of mechanical and thermal behaviour.
- Definition of the proper mesh, with the selection of proper elements type, boundary conditions and applied loads.
Thanks to these three steps is possible to obtain practically any layout. Realistic survival and
operational requirements of both ground and space based application has driven the analyses
done. A comparison between the numerical simulations and a real example has been done to
validate the modelling technique. The final result is a validated code with an users interface,
and a parametric analysis of the behaviour of the optomechanical mountings based on hexapodal kinematics architecture
Alignment and integration of large optical systems based on advanced metrology
No full textDOTTORATOL'allineamento dei sistemi ottici è un aspetto cruciale da considerare durante la fase di progettazione degli strumenti astronomici. Con l'aumentare delle dimensioni dei telescopi e dei relativi strumenti, si sviluppa parallelamente anche l'esigenza di disporre di strumenti di misura flessibili per soddisfare i requisiti scientifici.
Lo sviluppo delle tecniche di allineamento per piccoli strumenti è ben validato nella storia della strumentazione optomeccanica ed astronomica in particolare; tuttavia, esse non possono sempre essere applicate a strumenti di grande dimensione. In questa tesi si propone una procedura che consente di valutare la posizione di elementi ottici all’interno di grandi volumi con grande precisione, permettendo di raggiungere gli obiettivi scientifici riducendo al contempo la durata dell’intero processo di allineamento e il costo dello stesso.
In questo lavoro è valutata la possibilità di utilizzare un laser tracker come strumento essenziale per l'allineamento e per il monitoraggio dello stesso.
Il caso di studio presentato è MORFEO che è uno strumento di prima generazione dell’Extremely Large Telescope (ELT) europeo. Lo studio consiste nella realizzazione di un software che permetta di valutare la collocazione ottimale all'interno dello strumento del Laser tracker considerando principalmente la posizione nominale dei target misurati (SMR in base alla predizione dell’accuratezza e della ripetibilità delle misure. Questa analisi è fatta da due fasi: la prima considera il modello di errore fornito dal produttore del tracker. Il secondo si basa su una serie di test e caratterizzazioni eseguite in laboratorio per determinarne le prestazioni. I risultati ottenuti sono stati infine convalidati utilizzando un dimostratore semplificato di un elemento optomeccanico misurato utilizzando una Coordinate Measurement Machine (CMM).The alignment of optical systems is a crucial aspect to be considered in the design phase of astronomical instruments. As the size of telescopes and the related instruments is increasing, also the needs to have flexible measuring tools is developing in parallel to satisfy the scientific requirements.
The development of the alignment techniques for small instruments is well validated throughout the history of the Optomechanical and astronomical instrumentation, nevertheless those techniques cannot be applied on large ones. This thesis proposes a procedure that allows to evaluate the position of optical elements in large volume very precisely. This enables the achievement of the scientific goals by minimizing the alignment procedure duration the costs.
In this work it is evaluated the possibility to use a laser tracker as essential embedded tool for the alignment and for the monitoring of the instrument, or better, evaluate if the uncertainty of the tracker measuring the optical elements stay within the alignment requirements.
The case study presented here is MORFEO which is a first-light instrument for the European Extremely Large Telescope. The study consists in the realization of a software that optimizes the position of the tracker inside the instrument considering the nominal position of the targets measured (SMRs) and the possible vignetting based on the prediction of the accuracy and repeatability of the measurements. This analysis is made by steps: the first one considers the error model gave from the manufacture of the tracker. The second one is based on a series of tests and characterizations performed in laboratory to determine more accurately the performances. The results obtained have been validated using a dummy version of an optomechanical element measured by using a Coordinate Measurement Machine (CMM).DIPARTIMENTO DI MECCANICAEngineering Design and Manufacturing for the Industry of the Future34MATTA, ANDREABERNASCONI, ANDRE
Optimizing topology in astronomical optomechanics for additive manufacturing
No full textLAUREA MAGISTRALEQuesta tesi, sviluppata in collaborazione con il Politecnico di Milano e l’Osservatorio As
tronomico di Brera di INAF, si concentra sull’applicazione dell’ottimizzazione topologica
(TO) volta alla produzione additiva (AM) di optomeccaniche di strumenti astronomici. Il
caso studio riguarda le strutture di supporto assiali del Calibration Unit Folding Mirror
(CUFM), uno specchio dello strumento MORFEO per l’Extremely Large Telescope del
European Southern Observatory. L’uso della AM in astronomia promette benefici come
riduzioni di massa, consolidazione dei componenti e il miglioramento delle prestazioni ot
tiche, rendendo questo lavoro, che non ha precedenti in letteratura, di grande interesse
per l’INAF e la comunità scientifica. L’analisi agli elementi finiti (FEA) è stata impiegata
utilizzando Abaqus per verificare la conformità della struttura originale con le specifiche
tecniche del CUFM e per stabilire un riferimento per il confronto con i design ottimizzati.
Questi sono stati ottenuti utilizzando il modulo Tosca di Abaqus per la TO, interpretati
con Altair Inspire e analizzati per la stampabilità usando Autodesk Netfabb. Python è
stato utilizzato per estrarre la geometria della superficie deformata del CUFM da Abaqus
e MATLABèstato impiegato per analizzare i dati utilizzando l’espansione polinomiale di
Zernike per stimare le aberrazioni del fronte d’onda causate dalle deformazioni del CUFM
sotto carico. Il miglior risultato della TO, ottenuto utilizzando il metodo proprietario
di Mass Interpolation Material Penalization (MIMP) di Dassault Systèmes, è stato inte
grato con parti dell’assieme originale. Questa struttura ibrida minimizza le deformazioni,
ottenendo allo stesso tempo la consolidazione dei componenti, la riduzione della massa e
una buona stampabilità. Il lavoro discute le difficoltà affrontate, inclusi i lunghi tempi
di calcolo e l’uso di diverse applicazioni software. Conclude con un riepilogo dei risultati
e futuri sviluppi, sottolineando l’importanza crescente della tecnologia AM nel promuo
vere la ricerca astronomica e nello sviluppo di strutture di supporto più efficienti per la
strumentazione astronomica.This thesis, developed in collaboration with Politecnico di Milano and INAF’s Astronom
ical Observatory of Brera, focuses on the application of topology optimization (TO) to
astronomical instrument optomechanics for additive manufacturing (AM). The case study
involves the whiffletree axial support structures of the 1-meter elliptical Calibration Unit
Folding Mirror of the MORFEO instrument, designed for the Extremely Large Telescope
of the European Southern Observatory. The use of AM in the astronomical field promises
significant benefits, including mass reduction, part consolidation, and enhanced optical
performance. Consequently, the present work, which has no prior exploration in the liter
ature, is of strong interest to INAF and the scientific community. Finite Element Analysis
(FEA) was employed using Abaqus to verify the compliance of the original structure de
sign with the mirror’s technical specifications and to establish a benchmark for comparing
optimized designs. These optimized designs were obtained using Abaqus’ Tosca module
for TO, interpreted with Altair Inspire, and analyzed for printability using Autodesk Net
fabb. Python was used to extract the deformed mirror surface geometry from the FEA
outputs, while MATLAB was utilized to analyze the data using the Zernike polynomial
expansion to estimate wavefront aberrations caused by mirror deformations under loading.
The best TO output, obtained using Dassault Systèmes’ proprietary Mass Interpolation
Material Penalization (MIMP) method, was integrated with parts of the original assem
bly. This hybrid structure effectively minimizes mirror deformations while achieving part
consolidation, mass reduction, and ease of manufacturability. This thesis presents the
encountered challenges, including long computational times and the complexities arising
from the use of different software applications. It provides a summary of findings and
recommendations for future work, while stressing that the positive outcome of this study
highlights the growing importance of AM technology in advancing astronomical research
and developing more efficient support structures for astronomical instrumentation
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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