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.
Dynamics of a Strongly Nonlinear Spacecraft Structure Part I: Experimental Identification - Noël, Jean-Philippe; Renson, Ludovic; Kerschen, Gaëtan
The present paper addresses the identification of a real-life spacecraft structure possessing a strongly nonlinear component with multiple mechanical stops. The complete identification procedure, from nonlinearity detection and characterization to parameter estimation, is carried
out based upon experimental sine-sweep data collected during a classical spacecraft qualification campaign.
Dynamics of a Strongly Nonlinear Spacecraft Structure Part II: Modal Analysis - Renson, Ludovic; Noël, Jean-Philippe; Kerschen, Gaëtan
The present paper investigates the dynamics of a real-life spacecraft structure possessing a strongly nonlinear component with multiple mechanical stops. A full-scale finite element model is built for gaining additional insight into the nonlinear dynamics that was observed experimentally in a companion paper (Part I). To this end, advanced techniques and theoretical concepts such as numerical continuation and nonlinear normal modes are exploited.
Experimental evidence and numerical prediction of nonlinear modal interactions in a real-life aerospace structure - Renson, Ludovic; Noël, Jean-Philippe; Kerschen, Gaëtan
During the last decade, the existence of nonlinear behaviour in spacecraft dynamic testing was frequently attested. However, current practice in industry is still to ignore nonlinearities, arguably because their analysis is regarded as impractical. The objective of the present contribution is to show that there now exists experimental and numerical methodologies which can deal with nonlinear phenomena in real-life structures. Specifically, this study investigates nonlinear modal interactions evidenced during the qualification campaign of the SmallSat spacecraft developed by EADS-Astrium. The ability to understand and reliably predict such interactions is of utmost importance as they may involve energy transfer between modes...
Nonlinear Modal Analysis of Conservative and Nonconservative Aerospace Structures - Renson, Ludovic
The concept of nonlinear normal modes (NNMs) provides a solid and rigorous theoretical framework for the analysis of the nonlinear oscillations of mechanical systems. If NNMs have been studied since more than fifty years, it is only very recently that contributions dealing with their numerical calculation have been reported in the literature. Although these methods pave the way for the application of NNMs to more complex systems, they have not yet reached the necessary maturity. In this context, the purpose of this research is (i) to further investigate the performance of an existing method for computing the NNMs of conservative...
A Frequency-domain Approach to Subspace Identification of Nonlinear Systems, Application to Aerospace Structures - Noël, Jean-Philippe
The construction of mathematical models from experimental data is an essential step in the design process of engineering systems. The different tasks involved in this activity, from the measurement and processing of data to the validation of the model, fall into the general field of system identification. 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...
Robust rendez-vous planning using the scenario approach and differential flatness - Dell'Elce, Lamberto; Kerschen, Gaëtan
There is a growing interest in uncertainty handling in the spacecraft dynamics community. In particular, robust optimization of spacecraft maneuvers is regarded as an important challenge. This paper proposes an optimal control approach for orbital rendez-vous planning under stochastic dynamics and constraints. The method combines differential flatness theory with the scenario approach for optimization under uncertainties. By mapping state and control variables into a set of flat outputs, the enforcement of dynamics equations and boundary conditions is automatically satisfied. The rigorous foundations of the scenario approach lead to a finite-dimensional formulation of the problem which guarantees the feasibility of the...
Nonlinear generalization of Den Hartog's equal peak method for nonlinear primary systems - Habib, Giuseppe; Detroux, Thibaut; Kerschen, Gaëtan
This study addresses the mitigation of one problem nonlinear resonance of a mechanical system. In view of the narrow bandwidth of the classical linear tuned vibration absorber, a new nonlinear absorber, termed the nonlinear tuned vibration absorber (NLTVA), is introduced in this paper. One unconventional aspect of the NLTVA is that the mathematical form of its restoring force is tailored according to the nonlinear restoring force of the primary system. The NLTVA parameters are then determined using a nonlinear generalization of Den Hartog's equal-peak method. The mitigation of the resonant vibrations of a Duffing oscillator is considered to illustrate the...
Identification of a Time-varying Beam Using Hilbert Vibration Decomposition - Bertha, Mathieu; Golinval, Jean-Claude
The present work is concerned by modal identification of time-varying systems. For this purpose, a method based on instantaneous frequency identification and synchronous demodulation is used to extract modal components from recorded signals. The proposed method of iterated sifting process is based on the Hilbert Vibration Decomposition (HVD) technique which is used to extract the instantaneous dominant vibrating component at each iteration. A source separation preprocessing step is introduced to treat multiple degree-of-freedom systems in an optimal way. Sources are used as reference signals to get a single instantaneous frequency of each mode for the demodulation on all the channels....
Comparison of parameterization schemes for solving the discrete material optimization problem of composite structures - Duysinx, Pierre; Guillermo Alonso, Maria; Tong, Gao; Bruyneel, Michaël
Optimal design of composite structures can be formulated as an optimal selection of material in a list of different laminates. Based on the seminal work by Stegmann and Lund, the optimal problem can be stated as a topology optimization problem with multiple materials. The research work carries out a large investigation of different interpolation and penalization schemes for the optimal material selection problem. Besides the classical Design Material Optimization (DMO) scheme and the recent Shape Function with Penalization (SFP) scheme by Bruyneel, the research introduces a generalization of the SFP approach using a bi-value coding parameterization (BCP) by Gao, Zhang...
Comparison of parameterization schemes for solving the discrete material optimization problem of composite structures - Duysinx, Pierre; Guillermo Alonso, Maria; Gao, Tong; Remouchamps, Alain; Bruyneel, Michaël
In the context of weight reduction challenges in aerospace, automotive, and energy engineering problems, composite materials are gaining a revived interested. Because of the problem complexity and the large number of design variables, their design of composite structures is greatly facilitated by using optimization techniques.
While several formulations have been proposed for composite structure design, Stegmann and Lund  have showed that composite optimization can take advantage of the topology optimization approach. The fundamental idea of the Discrete Material Optimization (DMO) approach is 1/ to formulate the composite optimization problem as an optimal material selection problem in which the different...