Advanced aeroelastic robust stability analysis with structural uncertainties

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doi:10.1007/s13272-020-00473-8

Abstract

Robust flutter analysis described in this paper is based on the robust control theory framework. Therefore, a time-domain linear fractional transformation representation of the perturbed aeroelastic system is modeled. Then, the robust stability is analyzed by means of the structured singular value mu, which is defined as an alternative measure of robustness. Robust flutter analysis deals with aeroelastic (or aeroservoelastic) stability analysis taking structural dynamics, aerodynamics and/or unmodeled system dynamics uncertainties into account. Flutter is a well-known dynamic aeroelastic instability phenomenon caused by an interaction between structural vibrations and unsteady aerodynamic forces, whereby the level of vibration may trigger large amplitudes, eventually leading to catastrophic failure of the structure. The primary motivation of the robust flutter analysis is that this method allows the computation of the worst-case flutter velocity which can support, for example, the flight test program by a valuable robust flutter boundary. This paper addresses the issue of an approach for aeroelastic robust stability analysis with structural uncertainties with respect to physical symmetric and asymmetric stiffness perturbations on the wing structure by means of tuning beams.

Highlights

The primary aim of this paper is to investigate the impact of the stiffness uncertainties of the wings in spanwise direction and handle each wing separately in case of symmetric and especially asymmetric stiffness distribution
For the realization of the stiffness parameter variations tuning beams have been generated with respect to the condensed FE model
This approach is suitable for varying of stiffness parameters by only adjusting material properties of the tuning beams like bending and torisonal stiffness while avoiding a modification of the full FE model

Summary

Introduction

The primary aim of this paper is to investigate the impact of the stiffness uncertainties of the wings in spanwise direction and handle each wing separately in case of symmetric and especially asymmetric stiffness distribution. The asymmetric stiffness perturbation is mentioned in [3] within the robust flutter analysis for aeroelastic systems as an important issue for future investigations. This paper starts with a brief mathematical introduction on the LFT representation of uncertain systems and provides an understanding of the definition and interpretation of within the robust stability analysis. The linear fractional transformation is a common framework for robust stability analysis of complex systems based on the small gain theorem [1].

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