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A Semi-empirical approach for the modelling and analysis of microvibration sources on-board spacecraft.

Addari, Daniele (2017) A Semi-empirical approach for the modelling and analysis of microvibration sources on-board spacecraft. Doctoral thesis, University of Surrey.

Text (PhD Thesis)
Daniele Addari - PhD Thesis - A Semi-empirical Approach for the Modelling and Analysis of Microvibration Sources on-board Spacecraft.pdf - Version of Record
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The term microvibrations generally refers to accelerations in the order of micro-gs and which manifest in a bandwidth from a few Hz up to say 500-1000 Hz. The need to accurately characterise this small disturbances acting on-board modern satellites, thus allowing the design of dedicated minimisation and control systems, is nowadays a major concern for the success of some space missions. The main issues related to microvibrations are the feasibility to analytically describe the microvibration sources using a series of analysis tools and test experiments and the prediction of how the dynamics of the microvibration sources couple with those of the satellite structure. In this thesis, a methodology to facilitate the modelling of these phenomena is described. Two aspects are investigated: the characterisation of the microvibration sources with a semi-empirical procedure which allows derivation of the dynamic mass properties of the source, also including the gyroscopic effect, with a significantly simpler test configuration and lower computational effort compared to traditional approaches; and the modelling of the coupled dynamics when the source is mounted on a representative supporting structure of a spacecraft, including the passive and active effects of the source, which allows prediction of the structure response at any location. The methodology has been defined conducting an extensive study, both experimental and numerical, on a reaction wheel assembly, as this is usually identified as the main contributory factor among all microvibration sources. The contributions to the state-of-the-art made during this work include: i) the development of a cantilever configured reaction wheel analytical model able to reproduce all the configurations in which the mechanism may operate and inclusive of the gyroscopic effect; ii) the reformulation of the coupling theory which allows retrieving the dynamic mass of a microvibration source over a wide range of frequencies and speeds, by means of the experimental data obtained from measurements of the forces generated when the source is rigidly secured on a dynamometric platform and measurements of the accelerations at the source mounting interface in a freefree suspended boundary condition; iii) a practical example of coupling between a reaction wheel and a honeycomb structural panel, where the coupled loads and the panel response have been estimated using the mathematical model and compared with test results, obtained during the physical microvibration testing of the structural panel, showing a good level of agreement when the gyroscopic effect is also taken into account.

Item Type: Thesis (Doctoral)
Subjects : Structural Dynamics, Microvibration, Reaction Wheel, Vibration, Noise, Dynamic Mass, Coupling,
Divisions : Theses
Authors :
Addari, Danieledaniele.addari@gmail.com0000-0002-3438-2081
Date : 31 January 2017
Funders : Innovate UK (former Technology Strategy Board), SSBV Space & Ground Systems Ltd
Copyright Disclaimer : I hereby declare that the contents of this thesis except where specific reference is made to the work of others, are original and have not been submitted in whole or in part for consideration for any other degree or qualification in this, or any other university. This thesis is my own work and contains nothing which is the outcome of work done in collaboration with others, except where specifically acknowledged. Daniele Addari 27th September 2016
Contributors :
ContributionNameEmailORCID, Guglielmo
Depositing User : Daniele Addari
Date Deposited : 06 Feb 2017 12:23
Last Modified : 31 Oct 2017 19:02

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