Nonlinear Robust Approaches to Study Stability and Postcritical Behavior of an Aeroelastic Plant

Iannelli, Andrea; Marcos, Andrés; Lowenberg, Mark H

doi:10.1109/tcst.2017.2779110

Cited by 9 publications

(13 citation statements)

References 34 publications

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“…Moreover, it is interesting to observe that the structural parameters have opposite perturbations if grouped according to the affected degrees of freedom (i.e., plunge and pitch). Specifically, the plunge equilibrium sees a reduction in M s, 11 and an increase in K L h , while the pitch equilibrium sees an increase in M s, 22 and a reduction in K L α . This corresponds to getting the plunge and pitch natural frequencies closer, which is known to be detrimental in systems prone to binary flutter.…”

Section: Structural Uncertaintiesmentioning

confidence: 99%

“…Specifically, a standard procedure consists in discretizing the control surface stiffness in the interval [0, K β ] and performing for each value a linear flutter analysis, which then allows a diagram V f -LCO amplitude to be derived. An alternative formulation whereby gridding is avoided by making use of integral quadratic constraints lead in [22] to the proposal of the worst-case LCO curve for the cases where the system is also subject to parametric uncertainties. Previous studies thus confirm that freeplay has an uncertain softening effect on the associated stiffness, and thus, the addition of K β to the set of uncertainties is physically justified.…”

Section: Effect Of Control Surface Stiffness Uncertaintymentioning

confidence: 99%

“…The aims in UQ works devoted to aeroelastic problems are typically to investigate the effect of uncertainty on: the change of linear (or linearized) flutter speed [37]; features of the post-critical behavior (e.g., amplitude or frequencies of the LCO) [4,16]. Aimed at the latter goal, but building on different tools, namely robust control techniques, in [22] a method was developed to allow the degradation of the LCO properties in the worst-case scenario to be analyzed. Specifically, integral quadratic constraints were used to compute the worst-case LCO curve, which quantifies the increase in the amplitude of oscillations in the face of uncertainties.…”

Section: Introductionmentioning

confidence: 99%

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On the effect of model uncertainty on the Hopf bifurcation of aeroelastic systems

2021

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This paper investigates the effect of model uncertainty on the nonlinear dynamics of a generic aeroelastic system. Among the most dangerous phenomena to which these systems are prone, Limit Cycle Oscillations are periodic isolated responses triggered by the nonlinear interactions among elastic deformations, inertial forces, and aerodynamic actions. In a dynamical systems setting, these responses typically emanate from Hopf bifurcation points, and thus a recently proposed framework, which address the problem of robustness from a nonlinear dynamics viewpoint, is employed. Briefly, the notion of robust bifurcation margin extends the concept of $$\mu $$ μ analysis technique from the robust control theory. The main contribution of this article is a systematic investigation of the numerous scenarios arising in the study of nonlinear flutter when uncertainties in the model are accounted for in the analyses. The advantages of adopting this framework include the possibility to: quantify relevant information for the determination of the nonlinear stability envelope; gain a more in-depth understanding of the physical mechanisms triggering subcritical and supercritical Hopf bifurcations; and reveal properties of the nominal system by identifying isolated branches not straightforward to detect with conventional numerical approaches.

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Section: Structural Uncertaintiesmentioning

confidence: 99%

Section: Effect Of Control Surface Stiffness Uncertaintymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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On the effect of model uncertainty on the Hopf bifurcation of aeroelastic systems

2021

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“…1 Various aspects of the project leading up to the testing of the aircraft have already been presented. [2][3][4][5][6][7][8][9][10][11][12][13][14][15] In order to conduct the flight tests in a safe and efficient manner a number of ground tests were performed. The ground tests performed within FLEXOP can be divided in three categories: structural tests, flight systems tests and the integration tests.…”

Section: Introductionmentioning

confidence: 99%

Ground Testing of the FLEXOP Demonstrator Aircraft

Sodja

Breuker

Meddaikar

et al. 2020

AIAA Scitech 2020 Forum

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“…Recent work by the authors [20] proposed an approach combining integral quadratic constraints and describing functions methods to address the robustness of the postcritical behaviour of an uncertain system subject to hardnonlinearities (e.g. freeplay, saturation).…”

Section: Introductionmentioning

confidence: 99%

An extension of the structured singular value to nonlinear systems with application to robust flutter analysis

2020

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The paper discusses an extension of $$\mu$$ μ (or structured singular value), a well-established technique from robust control for the study of linear systems subject to structured uncertainty, to nonlinear polynomial problems. Robustness is a multifaceted concept in the nonlinear context, and in this work the point of view of bifurcation theory is assumed. The latter is concerned with the study of qualitative changes of the steady-state solutions of a nonlinear system, so-called bifurcations. The practical goal motivating the work is to assess the effect of modeling uncertainties on flutter, a dynamic instability prompted by an adverse coupling between aerodynamic, elastic, and inertial forces, when considering the system as nonlinear. Specifically, the onset of flutter in nonlinear systems is generally associated with limit cycle oscillations emanating from a Hopf bifurcation point. Leveraging $$\mu$$ μ and its complementary modeling paradigm, namely linear fractional transformation, this work proposes an approach to compute margins to the occurrence of Hopf bifurcations for uncertain nonlinear systems. An application to the typical section case study with linear unsteady aerodynamic and hardening nonlinearities in the structural parameters will be presented to demonstrate the applicability of the approach.

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Nonlinear Robust Approaches to Study Stability and Postcritical Behavior of an Aeroelastic Plant

Cited by 9 publications

References 34 publications

On the effect of model uncertainty on the Hopf bifurcation of aeroelastic systems

On the effect of model uncertainty on the Hopf bifurcation of aeroelastic systems

Ground Testing of the FLEXOP Demonstrator Aircraft

An extension of the structured singular value to nonlinear systems with application to robust flutter analysis

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