References of "Kerschen, Gaëtan"
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See detailNonlinear Dynamic Analysis of Aerospace Structures
Kerschen, Gaëtan ULg; Noël, Jean-Philippe ULg; Renson, Ludovic ULg et al

Conference (2012, October)

Current practice in industry is to rely on linear finite element simulations. However, nonlinearity is a frequent occurrence in engineering structures. It is at the origin of rich and complex dynamical ... [more ▼]

Current practice in industry is to rely on linear finite element simulations. However, nonlinearity is a frequent occurrence in engineering structures. It is at the origin of rich and complex dynamical phenomena that cannot be observed in linear structures. Solving both the direct and inverse problems in nonlinear structural dynamics therefore warrants the development of appropriate methodologies. The focus of the presentation will first be on the inverse problem. We will describe the different steps of the nonlinear system identification process and discuss the current capabilities of existing methods. The presentation will then address the direct problem during which the identified model is used for accurately predicting the structure’s dynamic characteristics. A rigorous nonlinear extension of modal analysis will be presented, and we will show that it represents a very useful framework for understanding nonlinear dynamical phenomena and supporting design decisions. Two real-life aerospace structures will be considered for illustrating the proposed developments. [less ▲]

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See detailThe OUFTI-1 nanosatellite system in mid-2012: architectures of ground and space segments
Denis, Amandine ULg; Pisane, Jonathan ULg; Crosset, Nicolas ULg et al

Conference (2012, September)

We describe the current status of the OUFTI-1 nanosatellite project, the main payload of which is an innovative D- STAR radiocommunication system. We describe the architectures of the ground and space ... [more ▼]

We describe the current status of the OUFTI-1 nanosatellite project, the main payload of which is an innovative D- STAR radiocommunication system. We describe the architectures of the ground and space segments. [less ▲]

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See detailTime- and frequency-domain subspace identification of a nonlinear spacecraft
Noël, Jean-Philippe ULg; Marchesiello, Stefano; Kerschen, Gaëtan ULg

in Proceedings of the ISMA International Conference on Noise and Vibration Engineering 2012 (2012, September)

The present paper discusses the identification of the SmallSat spacecraft, a real-life nonlinear space structure developed by EADS-Astrium. To this end, two nonlinear subspace identification techniques ... [more ▼]

The present paper discusses the identification of the SmallSat spacecraft, a real-life nonlinear space structure developed by EADS-Astrium. To this end, two nonlinear subspace identification techniques formulated in the time and frequency domains are exploited, referred to as the TNSI and FNSI methods, respectively. The frequency response functions (FRFs) of the underlying linear spacecraft and the nonlinear coefficients are estimated by these approaches. The nonlinear component comprises an inertia wheel mounted on a support, the motion of which is constrained by eight elastomer plots and mechanical stops. This application is challenging for several reasons, which include high modal density, the discontinuous nature of the nonlinearities and order selection of the identified reduced model. [less ▲]

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See detailFinite element computation of nonlinear normal modes of nonconservative systems
Renson, Ludovic ULg; Deliège, Geoffrey ULg; Kerschen, Gaëtan ULg

in Proceedings of the ISMA 2012 conference (2012, September)

Modal analysis, i.e., the computation of vibration modes of linear systems, is really quite sophisticated and advanced. Even though modal analysis served, and is still serving, the structural dynamics ... [more ▼]

Modal analysis, i.e., the computation of vibration modes of linear systems, is really quite sophisticated and advanced. Even though modal analysis served, and is still serving, the structural dynamics community for applications ranging from bridges to satellites, it is commonly accepted that nonlinearity is a frequent occurrence in engineering structures. Because modal analysis fails in the presence of nonlinear dynamical phenomena, the development of a practical nonlinear analog of modal analysis is the objective of this research. Progress in this direction has been made recently with the development of numerical techniques (harmonic balance, continuation of periodic solutions) for the computation of nonlinear normal modes (NNMs). Because these methods consider the conservative system, this study targets the computation of NNMs for nonconservative systems, i.e. defined as invariant manifolds in phase space. Specifically, a new finite element technique is proposed to solve the set of partial differential equations governing the manifold geometry. The algorithm is demonstrated using different two-degree-of-freedom systems. [less ▲]

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See detailTransport Methods for the Numerical Computation of Nonlinear Normal Modes
Renson, Ludovic ULg; Blanc, François; Touzé, Cyril et al

Conference (2012, July)

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See detailLow-order local modelling of structural nonlinearities
Noël, Jean-Philippe ULg; Kerschen, Gaëtan ULg

in Proceedings of the XVIIIth Symposium on Vibrations, shocks and noise (VCB 2012) (2012, July)

The present paper addresses the problem of characterising structural nonlinearities in view of system identification. A low-order local modelling strategy is proposed and encapsulated in a recently ... [more ▼]

The present paper addresses the problem of characterising structural nonlinearities in view of system identification. A low-order local modelling strategy is proposed and encapsulated in a recently-introduced frequency-domain nonlinear subspace method for the estimation of model parameters. The complete methodology is first demonstrated using two academic examples, namely a Duffing oscillator and a five-degree-of-freedom system comprising two nonlinearities. The identification of an experimental beam involving nonlinear geometrical behaviour is finally addressed. [less ▲]

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See detailA new subspace-based approach to identify nonlinear mechanical structures in the frequency domain
Noël, Jean-Philippe ULg; Kerschen, Gaëtan ULg

in Proceedings of the 16th IFAC Symposium on System Identification (2012, July)

This paper introduces a new frequency-domain subspace-based method for the identification of nonlinear mechanical systems. The technique exploits frequency data and interprets nonlinearities as feedback ... [more ▼]

This paper introduces a new frequency-domain subspace-based method for the identification of nonlinear mechanical systems. The technique exploits frequency data and interprets nonlinearities as feedback forces exciting the underlying linear system. It is demonstrated using two academic examples, a Duffing oscillator and a five degree-of-freedom system comprising two nonlinearities. [less ▲]

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See detailExperimental identification of a nonlinear space structure
Noël, Jean-Philippe ULg; Renson, Ludovic ULg; Kerschen, Gaëtan ULg et al

in Proceedings of the 12th European Conference on Spacecraft Structures, Materials and Environmental Testing (2012, March)

The present paper addresses the experimental identification of a nonlinear space structure, the SmallSat spacecraft developed by EADS-Astrium. The nonlinear component comprises an inertia wheel mounted on ... [more ▼]

The present paper addresses the experimental identification of a nonlinear space structure, the SmallSat spacecraft developed by EADS-Astrium. The nonlinear component comprises an inertia wheel mounted on a support, the motion of which is constrained by eight elastomer plots and mechanical stops. Robust techniques are applied to measured data to detect, characterise and quantify nonlinear behaviour. [less ▲]

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See detailNonlinear Modal Analysis of the SmallSat Spacecraft
Renson, Ludovic ULg; Noël, Jean-Philippe ULg; Kerschen, Gaëtan ULg et al

in Proceedings of the European Conference on Spacecraft Structures, Materials & Environmental Testing (2012, March)

Non-linear elements are present in practically all spacecraft structures. When such non-linear effects are important linear modal analysis can no longer be applied. The development of a non-linear ... [more ▼]

Non-linear elements are present in practically all spacecraft structures. When such non-linear effects are important linear modal analysis can no longer be applied. The development of a non-linear analogue of linear modal analysis is therefore an important endeavor. The objective of this paper is to show that nonlinear normal modes (NNMs) represent a useful and practical tool in this context. A full-scale spacecraft structure is considered and is modeled using the finite element method. Its NNMs are computed using advanced numerical algorithms, and the resulting dynamics is then carefully analyzed. Nonlinear phenomena with no linear counterpart including nonlinear modal interactions are also highlighted. [less ▲]

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See detailContract 21539/08/NL/SFe - Advancement of mechanical verification methods for non-linear spacecraft: Nonlinear identification using a subspace-based method in the frequency domain
Noël, Jean-Philippe ULg; Renson, Ludovic ULg; Kerschen, Gaëtan ULg

Report (2012)

The objective of this technical note is to explore the applicability of a newly introduced nonlinear system identification technique to spacecraft structures. To this end, numerical experiments are ... [more ▼]

The objective of this technical note is to explore the applicability of a newly introduced nonlinear system identification technique to spacecraft structures. To this end, numerical experiments are conducted using a finite element model of the SmallSat spacecraft. A detailed introduction to the method, referred to as the frequency-domain nonlinear subspace identification (FNSI) method, is provided and its major assets are commented. Random-type and sine-sweep excitations are considered and identification results are extensively discussed. [less ▲]

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See detailContract 21539/08/NL/SFe - Advancement of mechanical verification methods for non-linear spacecraft: Modal analysis using nonlinear normal modes.
Renson, Ludovic ULg; Noël, Jean-Philippe ULg; Kerschen, Gaëtan ULg

Report (2012)

The objective of this technical note is to explore the applicability of nonlinear modal analysis to spacecraft structures. To this end, algorithms for the continuation of periodic solutions are applied to ... [more ▼]

The objective of this technical note is to explore the applicability of nonlinear modal analysis to spacecraft structures. To this end, algorithms for the continuation of periodic solutions are applied to the finite element model of the SmallSat spacecraft. Nonlinear normal modes and their corresponding frequencies of oscillation are computed, and the results are discussed. [less ▲]

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See detailIdentifying and computing nonlinear normal modes
Cammarano, A.; Carrella, A.; Renson, Ludovic ULg et al

in Proceedings of the SEM IMAC XXX Conference (2012, February)

Non linear normal modes offer a rigorous framework, both mathematical and physical, for theoretical and experimental dynamical analysis. Albeit still in its infancy, the concept of non linear normal modes ... [more ▼]

Non linear normal modes offer a rigorous framework, both mathematical and physical, for theoretical and experimental dynamical analysis. Albeit still in its infancy, the concept of non linear normal modes has the potential of providing to both the academic and the industrial establishment a powerful tool for the analysis of non linear dynamical systems. However, in order to exploit the full potential of this theory (and its associated simulation capability), there is need to integrate it with other branches of non linear structural dynamics: namely, in order for the non linear normal modes of a real - physical - structure to be computed, there is need to identify and quantify its non linearity. In this paper, an identification method based on the measured Frequency Response Function (FRF) is employed to identify and quantify the system's non linearity before computing the system's non linear normal modes. [less ▲]

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See detailApplication of the restoring force surface method to a real-life spacecraft structure
Noël, Jean-Philippe ULg; Kerschen, Gaëtan ULg; Newerla, Alfred

in Proceedings of the International Modal Analysis Conference (IMAC) XXX (2012, January)

Many nonlinear system identification methods have been introduced in the technical literature during the last thirty years. However, few of these methods were applied to real-life structures. In this ... [more ▼]

Many nonlinear system identification methods have been introduced in the technical literature during the last thirty years. However, few of these methods were applied to real-life structures. In this context, the objective of the present paper is to demonstrate that the Restoring Force Surface (RFS) method can provide a reliable identification of a nonlinear spacecraft structure. The nonlinear component comprises an inertia wheel mounted on a support, the motion of which is constrained by eight elastomer plots and mechanical stops. Several adaptations to the RFS method are proposed, which include the elimination of kinematic constraints and the regularization of ill-conditioned inverse problems. The proposed methodology is demonstrated using numerical data. [less ▲]

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See detailEffective particles and classification of periodic orbits of homogeneous granular chains with no precompression
Starosvetsky, Y.; Jayaprakash, K.R.; Vakakis, A.F. et al

in Physical Review. E : Statistical, Nonlinear, and Soft Matter Physics (2012), 85

We develop a systematic methodology for classifying the periodic orbits of homogeneous ordered granular chains with no dissipation, under the assumption that all granules oscillate with the same frequency ... [more ▼]

We develop a systematic methodology for classifying the periodic orbits of homogeneous ordered granular chains with no dissipation, under the assumption that all granules oscillate with the same frequency. The analysis is based on the idea of balancing linear momentum for sets of auxiliary models consisting of “effective particles.” The auxiliary models may be defined for any given finite, ordered granular chain composed of n identical granules (beads) that interact with each other through strongly nonlinear Hertzian interaction law. In turn, the auxiliary models may be effectively used for theoretically predicting the total number of periodic orbits and the corresponding amplitude ratios of the granules. Good correspondence between the theoretical models and results of direct numerical simulations is reported. The results presented herein can be used to understand the complex intrinsic dynamics of ordered granular media, and to systematically study the generation of mode localization in these strongly nonlinear systems. The derived analytical models can be utilized to predict the response of the effective particles, and based on that, to predict primary pulse transmission in periodic layered media with granular interfaces. Moreover, our analysis can be extended to the general class of nonlinear chains of particles with smooth interacting potentials and possible separation between particles during the motion. [less ▲]

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See detailPropellantless rendez-vous of QB50 nanosatellites
Dell'Elce, Lamberto ULg; Kerschen, Gaëtan ULg

in Proceedings of the 63rd IAC (2012)

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See detailTowards a “concurrent design facility (CDF)” for nanosatellites: a back-of-the-envelope calculation of the overall energy budget of OUFTI-1
Denis, Amandine ULg; Crosset, Nicolas ULg; Pisane, Jonathan ULg et al

Conference (2012)

We give a very compact account of the overall energy budget of the OUFTI-1 nanosatellite, thereby providing a useful guide for future designs, as well as an explanation of why a nanosatellite can ... [more ▼]

We give a very compact account of the overall energy budget of the OUFTI-1 nanosatellite, thereby providing a useful guide for future designs, as well as an explanation of why a nanosatellite can, energetically, survive and do useful tasks in space. [less ▲]

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See detailOrbital rendez-vous using differential drag in the QB50 constellation
Dell'Elce, Lamberto ULg; Kerschen, Gaëtan ULg

in Proceedings of the AIAA/AAS Astrodynamics Specialist Conference (2012)

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See detailDesign of an uncertain prestressed space structure: an info-gap approach
Hot, A.; Cogan, S.; Foltete, E. et al

in Proceedings of the 30th International Modal Analysis Conference (2012)

Uncertainty quantification is an integral part of the model validation process and is important to take into account during the design of mechanical systems. Sources of uncertainty are diverse but ... [more ▼]

Uncertainty quantification is an integral part of the model validation process and is important to take into account during the design of mechanical systems. Sources of uncertainty are diverse but generally fall into two categories: aleatory uncertainties due to random processes and epistemic uncertainty resulting from a lack of knowledge or erroneous assumptions. This work focuses on the impact of uncertain levels of prestress on the behavior of solar arrays in their stowed configuration. In this context, snubbers are inserted between two adjacent panels to maintain contact and absorb vibrations during launch. However, under high excitation loads, a loss of contact between the two panels may occur. This results in impacts that can cause extensive damages to fragile elements. In practice, the specific load configuration for which the separation of the two panels occurs is difficult to determine precisely since the exact level of prestress applied to the structure is unknown. An info-gap robustness analysis is applied to study the impact of this lack of knowledge on the prestress safety factor required to avoid loss of contact. The proposed methodology is illustrated using a simplified model of a solar array. [less ▲]

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