ORBi Open Repository and Bibliography
(213,405 recursos)
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.

1.
Numerical study of intrinsic features of isolas in a 2-dof nonlinear system - Detroux, Thibaut; Noël, Jean-Philippe; Masset, Luc; Kerschen, Gaëtan; Virgin, Lawrence N.
In the present paper, isolated response curves in a nonlinear system consisting of two masses
sliding on a horizontal guide are examined. Transverse springs are attached to one mass to provide the nonlinear restoring force, and a harmonic motion of the complete system is imposed by prescribing the displacement of their supports. Numerical simulations are carried out to study the conditions of existence of isolated solutions, their bifurcations, their merging with the main response branch and their basins of attraction. This is achieved using tools including nonlinear normal modes, energy balance, harmonic balance-based continuation and bifurcation tracking, and global analysis.

3.
Nonlinear ground vibration identification of an F-16 aircraft - Part 2: Parameter estimation using a frequency-domain subspace method - Dossogne, Tilàn; Noël, Jean-Philippe; Kerschen, Gaëtan; Peeters, Bart; Debille, Jan; Vaes, Mark; Schoukens, Johan
Although they are generally modelled as linear systems, aircraft structures are known to be prone to nonlinear phenomena. A specific challenge encountered with fighter aircraft, besides aeroelastic nonlinearity, is the modelling of the wing-to-payload mounting interfaces. For large amplitudes of vibration, friction and gaps may be triggered in these connections and markedly impact the dynamic behaviour of the complete structure. In this series of two papers, the nonlinear dynamics of an F-16 aircraft is investigated using rigorous methods applied to real data collected during a ground vibration test campaign. The present work focuses on the construction of an experimental mathematical...

4.
Nonlinear ground vibration identification of an F-16 aircraft - Part 1: Fast nonparametric analysis of distortions in FRF measurements - Vaes, Mark; Schoukens, Johan; Peeters, Bart; Debille, Jan; Dossogne, Tilàn; Noël, Jean-Philippe; Kerschen, Gaëtan
Although they are generally modelled as linear systems, aircraft structures are known to be prone to nonlinear phenomena. A specific challenge encountered with fighter aircraft, besides aeroelastic nonlinearity, is the modelling of the wing-to-payload mounting interfaces. For large amplitudes of vibration, friction and gaps may be triggered in these connections and markedly impact the dynamic behaviour of the complete structure. In this series of two papers, the nonlinear dynamics of an F-16 aircraft is investigated using rigorous methods applied to real data collected during a ground vibration test campaign. The present work focuses on the detection, qualification and quantification of...

5.
Nonlinear model updating by means of identified nonlinear normal modes - Song, Mingming; Renson, Ludovic; Noël, Jean-Philippe; Moaveni, Babak; Kerschen, Gaëtan
Modal parameters are the most common features used for linear model updating. Although the modal analysis theory does not hold for nonlinear dynamic systems, its popularity encouraged researchers to come up with an equivalent version of normal modes for nonlinear systems, i.e., nonlinear normal modes (NNMs). A nonlinear system vibrates in NNMs when all masses have periodic motions of the same period, and at any time, the position of all the masses is uniquely defined by the position of any one of them. This paper investigates the feasibility of nonlinear model updating by minimizing the difference between the model-predicted and...

6.
A frequency-domain method for identifying nonlinear vibrating structures - Noël, Jean-Philippe; Dossogne, Tilàn; Kerschen, Gaëtan
System identification, which refers to the construction of mathematical models from experimental data, plays a key role in the design process of engineering systems. In structural dynamics, the theoretical and experimental aspects of linear system identification have been successfully addressed since the early seventies, and mature analytical, computational and testing tools have emerged. Nonlinear system identification of vibrating structures has also enjoyed significant advances during the past few years. However, the common practice in industry is to ignore nonlinearities, arguably because their analysis is still regarded as impractical. The present work describes a rigorous nonlinear generalisation in the frequency domain...

14.
Satellite Orbits in the Atmosphere: Uncertainty Quantification, Propagation and Optimal Control - Dell'Elce, Lamberto
From the massive international space station to nanosatellites, all space missions share a common principle: orbiting an object requires energy. The greater the satellite's mass, the higher the launch cost. In astrodynamics, this translates into the motto ``use whatever you can''. This concept encompasses a broad spectrum of missions, e.g., the Earth's oblateness is exploited for sun-synchronous orbits and the kinetic energy of a planet is used to accomplish fly-by maneuvers. Nowadays, the same paradigm is coming on stream in the context of distributed space systems, where complex missions are envisaged by splitting the workload of a single satellite into...

18.
Measuring nonlinear distortions: from test case to an F-16 fighter - Vaes, Mark; Schoukens, Johan; Rolain, Yves; Peeters, Bart; Debille, Jan; Dossogne, Tilàn; Noël, Jean-Philippe; Grappasonni, Chiara; Kerschen, Gaëtan
What are the similarities and differences between the behavior of a small vibrating test system and an F-16 fighter? To find it out, we compare measurements of the test system to measurements from the bolted connection of the wing and the missile of a F-16 Fighter Falcon from the Belgian air force. These measurements were done during a ground vibration test (GVT) campaign. Essentially, the behavior of these systems match, even though the test system is only the heart of a self-study kit for nonlinear system identification and the F-16 is a complex real life mechanical structure. This clearly shows...

19.
A comparison of grey-box and black-box approaches in nonlinear state-space modelling and identification - Noël, Jean-Philippe; Schoukens, Johan; Kerschen, Gaëtan
In the present contribution, it is shown that, in the case of mechanical systems where nonlinearities are physically localised, the general structure of black-box nonlinear state-space models can be drastically simplified. A more parsimonious, grey-box state-space representation is derived, which is found to be compatible with Newton's second law of dynamics. For demonstration purposes, black-box and grey-box state-space models of the Silverbox benchmark, i.e. an electrical mimicry of a single-degree-of-freedom mechanical system with cubic nonlinearity, are identified using a maximum likelihood estimator. It is found that the grey-box approach allows to reduce markedly modelling errors with respect to a black-box...