Research




 

The research performed at S3L centers around 4 main themes: 

  1. NONLINEAR VIBRATIONS
  2. AEROSPACE STRUCTURES
  3. ORBITAL MECHANICS
  4. NANOSATELLITES 


TOPIC 1: NONLINEAR VIBRATIONS.

Nonlinearity is a frequent visitor to engineering structures which can modify --- sometimes catastrophically --- their behavior. For instance, in an aircraft, besides nonlinear fluid-structure interaction, typical nonlinearities include backlash and friction in control surfaces and joints, hardening nonlinearities in the engine-to-pylon connection, and saturation effects in hydraulic actuators. Nonlinearity may give rise to complex dynamic phenomena including jumps, bifurcations, limit cycles, chaos, etc. Any attempt to apply traditional linear techniques to capture the dynamics of a structural system possessing such phenomena is bound to failure. 

The objective of our research is to account for nonlinear phenomena in engineering structures instead of ignoring them as  is the common practice. Specifically, our research activities focus on the development of effective methodologies for (i) nonlinear modal analysis [1,2], (ii) system identification [3,4] and (iii) numerical continuation and bifurcation analysis [5].

Our research also intends to go one step further: it proposes not only to model nonlinearities but to take advantage of the richness and complexity of nonlinear dynamics for the design of engineering structures, for instance for vibration mitigation using nonlinear vibration absorbers [6]. An ERC Starting Grant was also obtained in 2012 for the development of a new vibration absorber [7].

Selected publications

[1] Nonlinear normal modes, Part I: A useful framework for the structural dynamicist, G. Kerschen, M. Peeters, J.C. Golinval, A.F. Vakakis, Mechanical Systems and Signal Processing 23 (2009), 170-194.

[2] Nonlinear modal analysis of a full-scale aircraft, G. Kerschen, M. Peeters, J.C. Golinval, C. Stephan, AIAA Journal of Aircraft, in press.

[3] Past, present and future of nonlinear system identification in structural dynamics, G. Kerschen, K. Worden, A.F. Vakakis, J.C. Golinval, Mechanical Systems and Signal Processing 20 (2006), 505-592.

[4] Frequency-domain subspace identification for nonlinear mechanical systems, J.P. Noel, G. Kerschen, Mechanical Systems and Signal Processing 40 (2013), 701-717.

[5] Nonlinear normal modes, Part II: Toward a practical computation using numerical continuation, M. Peeters, R. Viguié, G. Sérandour, G. Kerschen, J.C. Golinval, Mechanical Systems and Signal Processing 23 (2009), 195-216.

[6] Nonlinear Targeted Energy Transfer in Mechanical and Structural Systems, A.F. Vakakis, O. Gendelman, L.A. Bergman, D.M. McFarland, G. Kerschen, Y.S. Lee, Springer, 2009.

[7] ERC Starting Grant, The Nonlinear Tuned Vibration Absorber (NOVIB), 2012, PI: G. Kerschen.


TOPIC 2: AEROSPACE STRUCTURES.

The objective of this research is to address the mechanical and thermal behaviors of aerospace structures. This research is closely linked with topic 1, as most aerospace structures exhibit nonlinear dynamical behaviors [1]. Among the different topics that are studied, one can cite the finite element model reduction of thermal systems [2], ground vibration testing of aircraft and spacecraft [3,4] and the robustness of design decisions [5].

Selected publications

[1] Nonlinear dynamic analysis of aerospace structures, G. Kerschen, J.P. Noel, L. Renson, J.C. Golinval, 2012 LMS European Aerospace Conference, Toulouse, France (2012).

[2] Thermal model reduction using the super-face concept, L. Masset, O. Bruls, G. Kerschen, 25th European Workshop on Thermal and ECLS Software, Noordwijk, The Netherlands (2011).

[3] Assessment of nonlinear system identification methods using the SmallSat spacecraft structure, G. Kerschen, L. Soula, J.B. Vergniaud, A. Newerla, 29th International Modal Analysis Conference, Jacksonville, USA (2011).

[4] Nonlinear dynamic analysis of an F-16 aircraft using GVT data, J.P. Noel, L. Renson, G. Kerschen, B. Peeters, S. Manzato, J. Debille, International Forum of Aeroelasticity and Structural Dynamics IFASD}, Bristol, UK (2013).

[5] Design of an uncertain prestressed space structure: an info-gap approach, A. Hot, S. Cogan, E. Foltete, G. Kerschen, F. Buffe, J. Buffe, S. Behar, 30th International Modal Analysis Conference, Jacksonville, USA (2012).

 

TOPIC 3: ORBITAL MECHANICS.

Orbital lifetime estimation is a problem of great timeliness and importance in astrodynamics. In view of the stochastic nature of the thermosphere and the complexity of drag modeling, any deterministic assessment of orbital lifetime is likely to be bound to failure. Our research performs uncertainty quantification of satellite orbital lifetime estimation [1]. Another facet of our research deals with optimal control techniques applied to the rendez-vous of nanosatellites under the action of differential drag [2].

Selected publications

[1] Uncertainty quantification of the orbital lifetime of a LEO spacecraft, L. Dell'Elce, G. Kerschen, AAS/AIAA Astrodynamics Specialist Conference, Hilton Head, USA (2013). 

[2] Comparison between analytical and optimal control techniques in the differential drag based rendez-vous, L. Dell'Elce, G. Kerschen, 5th International Conference on Spacecraft Formation Flying Missions and Technologies, Munich, Germany (2013).

 

TOPIC 4: NANOSATELLITES

S3L currently participates in the design of the OUFTI-1 nanosatellite [1]. The innovative feature of OUFTI-1 is its payload: the D-STAR digital radiocommunication system. D-STAR is a recently-developed amateur radio protocol that provides several built-in including simultaneous voice and data transmission. S3L also participates in the design of the QARMAN CubeSat proposed by the von Karman Institute for Fluid Dynamics.

 Selected publications

[1] OUFTI-1: The CubeSat developed at the University of Liège, S. Galli, J. Pisane, P. Ledent, A. Denis, J.F. Vandenrijt, P. Rochus, J. Verly, G. Kerschen, L. Halbach, 5th CubeSat Developers' Workshop}, San Luis Obispo, USA (2008).


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