Study of Flexible Aircraft Body Freedom Flutter with Robustness Tools

Abstract

General rightsThis document is made available in accordance with publisher policies. Please cite only the published version using the reference above. Full terms of use are available: http://www.bristol.ac.uk/pure/about/ebr-terms Features that complicate its study are the presence of multiple modal instabilities, and the dierent inuence that system parameters have on each of them. The robust analysis framework based on Linear Fractional Transformation modeling and structured singular value µ analysis is used in this work to study the BFF problem in a systematic way. The analyses performed showcase the potential of these methods, not only in supplying a characterization of the system in terms of its robustness, but also in gaining further understanding of the BFF problem and reconciling the results with physical features. It is also shown that the robust modeling analysis framework complements the conventional, state of practice, methods while allowing the study of highly coupled systems (of which the exible aircraft is an example) to be addressed in an incremental and methodological manner.

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

“…Note that this vector features the same sign-grouping as those in (21), thus the same physical mechanism of instability commented before is predicted by the solver. It is also worth remarking that Program 1 has the frequency as decision variable, whereas was applied at discrete frequencies (Fig.…”

“…nonlinear flutter is better understood, its effect on robustness is relatively unexplored and should be considered when making the simplifying assumption of zero trim states [36]. Note also that the margin k m for these two scenarios is within less than 1% from the maximum singular value of the absolute magnitude of the perturbation matrix in (21). This is very important, since LB and UB were shown to be close around the peak of Fig.…”

H∞ Control Design for Active Flutter Suppression of Flexible-Wing Unmanned Aerial Vehicle Demonstrator

“…More recently, the H ∞ techniques have been applied to the design of AFS controllers for the X-56A model [11] as well as to the related Mini MUTT UAV [10]. The X-56A and the Mini MUTT are flying-wing UAVs and, as such, are subjected to a strong coupling between flexible and rigid modes, a phenomenon known as body freedom flutter (BFF) [5,22]. The FLEXOP demonstrator, on the other hand, has a more conventional configuration with a well-distinguishable fuselage and V-tail, which leads to flutter modes with a less pronounced coupling with the rigid dynamics.…”

Full-Span Flying Wing Wind Tunnel Test: A Body Freedom Flutter Study

“…Theoretical analysis methods for the BFF problem include classical frequency domain method [1], state space method [2], robust modeling and analysis framework research method [3], fully coupled linearization method under aeroelastic trimming conditions [4]. The theoretical analysis of BFF shows that for the HARFFW, the BFF speed is significantly lower than that results calculated based on the cantilever wing model; the elastic degrees of freedom of the aircraft, the structural characteristics of the fuselage and the wing structure characteristics will have significant impact on the BFF characteristics.…”