Aeroelastic systems have the peculiarity of changing their behavior with flight conditions. Within such a view, it is difficult to design a single control law capable of efficiently working at different flight conditions. Moreover, control laws are often designed on simple linearized, low-fidelity models. A fact introducing the need of a scheduled tuning over a wide operational range. Obviously such a design process can be time consuming, because of the high number of simulations and flight tests required to assure high performance and robustness. The present work aims at proving the high flexibility of neural network-based controllers, testing their adaptive properties when applied to typical fixed and rotary wing aircraft problems. At first the proposed control strategy will be used to suppress the limit cycle oscillations experienced by a rigid wing in transonic regime. Then as a second example, a controller with the same structure will be employed to reduce the hub vibrations of an helicopter rotor with active twist blades.

This paper compares two periodic control methods, the optimal H2 and the periodic static output feedback (POF), to reduce the helicopter rotor vibrations. Actively twisted blades with Macro-Fibre Composite (MFC) piezoelectric actuators are used. The design model is based on a simplified aerodynamic model and on a multi-body model of the Bo 105 isolated rotor with the original blades replaced by actively twisted ones. The performance of the two controllers in alleviating hub loads is verified with improved simulations based on a free-wake model

a b s t r a c tThe formulation described in this paper leads to the electro-elastic characterization of the sectional properties of elastic anisotropic prismatic beams with embedded piezoelectric devices. The related matrix is derived by analyzing a set of two-dimensional electro-elastic problems defined on the beam section. These problems allow to compute both the so-called beam de Saint-Venant's solutions and the beam deformation field induced by an electric potential difference imposed between the piezoelectric conductive laminae. The results are compared to those obtained with three dimensional finite element models.

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