ORBi Open Repository and Bibliography
In may 2007, the ULg's Administrative Board (joined in June 2007 by the FUSAGx) decided to create an institutional repository and defined a strong institutional self-archiving policy to increase the visibility, accessibility and impact of the University's publications (Board's decision).
This decision led to the official launch, in November 2008, of the ORBi platform including both the Academic Bibliography and the Institutional Repository of the Wallonia-Europe University Academy.
Uncertainty quantification of the aerodynamic force of a convex-shaped spacecraft in free-flow regime - Dell'Elce, Lamberto; Kerschen, Gaëtan
Non-spherical gravitational effects and aerodynamic force are the dominant perturbations for low-Earth-orbiting spacecraft. If the former can be modeled with arbitrary accuracy for most applications, it is not possible for the latter. Uncertainties in the aerodynamic force invalidate any attempt to perform deterministic propagations of the position of the spacecraft, regardless the duration of the simulation. However, the effect of drag, which is largely the main component of the force, is a monotonic decrease of the semi-major axis of the orbit, so that these uncertainties are a major concern for long-term predictions. The purpose of this study is the characterization,...
Analytic solution for the relative motion of satellites in near-circular low-Earth orbits - Martinusi, Vladimir; Dell'Elce, Lamberto; Kerschen, Gaëtan
The paper presents the solution to the problem of the relative motion between two satellites orbiting Earth under the influence of the oblateness and atmospheric drag perturbations. Starting from the analytic solution to the problem of the absolute motion, the closed-form equations of motion are obtained. No simplifying assumptions are made on the relative dynamics.
Analytic Propagation for Satellites in Near-Circular Low-Earth Orbits - Martinusi, Vladimir; Dell'Elce, Lamberto; Kerschen, Gaëtan
The present work is focused on providing an analytic model for the motion of an low-Earth-orbiting satellite. The model incorporates the two dominant perturbations, namely the atmospheric drag and the Earth oblateness. While the latter is modeled by the second zonal harmonic J 2 , both constant and exponential density distribution models of the atmosphere are considered. The satellite orbit is assumed to be almost circular. Closed-form equations of motion are obtained, even time-explicit in the case of a constant atmosphere. The analytic predictions are carefully validated against direct numerical simulations. The resulting model is suitable to be incorporated in...
Testing of a Spacecraft Structure with Non-Smooth Nonlinearities - Renson, Ludovic; Noël, Jean-Philippe; Kerschen, Gaëtan
The dynamics of the SmallSat, a real-life spacecraft possessing a complex isolation device with multiple nonsmooth nonlinearities is investigated. Experiments show that nonlinearities induce modal interactions between modes with non-commensurate linear frequencies. A model of the structure with a simplified description of the nonlinear connections is first built using techniques available in industry. Numerical continuation is then exploited to compute nonlinear normal modes and uncover interaction phenomena that can jeopardize the structural integrity.
Rapport Final, Projet BLISK, Convention RW 6247 : BLaded dISK - Lecomte-Beckers, Jacqueline; Paydas, Hakan
L’unité MMS de l’ULg s’est concentrée dans le cadre de ce projet sur les aspects
métallurgiques des composants produits de manière à garantir dès le départ leur qualité et
ainsi adapter les paramètres de fabrication. D’autre part, elle a également étudié les
relations microstructures – propriétés mécaniques et s’est occupée de la caractérisation
mécanique et thermophysique des composants soudés par friction et claddés dont la structure a été
Bridging the gap between Nonlinear Normal Modes and Modal Derivatives - Sombroek, Cees; Renson, Ludovic; Tiso, Paolo; Kerschen, Gaëtan
Nonlinear Normal Modes (NNMs) have a clear conceptual relation to the classical linear normal modes (LNMs), yet they offer a solid theoretical framework for interpreting a wide class of non-linear dynamical phenomena with no linear counterpart. The main difficulty associated with NNMs is that their calculation for large-scale models is expensive, particularly for distributed nonlinearities. Repeated direct time integrations need to be carried out together with extensive sensitivity analysis to reproduce the frequency-energy dependence of the modes of interest.
In the present paper, NNMs are computed from a reduced model obtained using a quadratic transformation comprising LNMs and Modal Derivatives (MDs)....