Analysis of Flexible Aircraft Dynamics Using Bifurcation Methods

Modern commercial aircraft designs are continuously driven towards more slender wing configurations in order to meet performance and general mission requirements. Consequently, these aircraft are characterized by flexible structures that undergo large deformations, and in turn the frequency separation between the flexible and rigid-body modes is greatly reduced. The associated coupling can, in the presence of nonlinearities, introduce effects on the flight dynamics of such vehicles that conventional methods may not adequately predict, leading to the potential of degraded handling qualities. This paper evaluates the effects of flexibility on the dynamics, stability, and control of elastic aircraft using an analysis framework based on bifurcation and continuation tools, linked to classical analysis methods. Results based on variations of a Rockwell B1 model demonstrate the suitability of the approach in revealing dynamic coupling between rigid-body and flexible modes in regions of the flight envelope in which nonlinearities are significant. Furthermore, the efficiency of this approach relative to traditional nonlinear simulation is discussed. The robustness of idealized control law designs to unmodeled elastic modes is also investigated.

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