An unconventional adaptive flutter suppression actuation system: From modeling to experimentation

This paper contributes to the definition of an unconventional actuation system, intended specifically for slender/highly flexible wings' flutter suppression, and coupled with an adaptive control algorithm to handle post-flutter flight dynamics and uncertainties deriving from unpredictable degradation of the structural properties. The design and validation process of the novel actuation architecture is presented. It is based on a row of multiple small spoiler, located at fifteen percent of the mean aerodynamic chord and coordinated by a modified Model Reference Adaptive Control (MRAC) algorithm. The spoilers' concept design is optimized by Computational Fluid Dynamics (CFD) numerical simulation, afterwards realized and wind tunnel tested to derive the aerodynamic database by means of a six-axes force balance. The mathematical model has served to implement and validate the adaptive control algorithm for a wide range of condition. The modeled system is tested from on-design flutter speed and nominal structural stiffness to post-flutter speed and reduced structural stiffness through the analysis of the wing proper frequencies and phases, which has demonstrated to be very effective in testing the adaptivity of the control architecture. This approach proves the robustness of the proposed architecture before experimentation, which is performed through a custom-made wind tunnel apparatus. The two degree of freedom oscillations during flutter are successfully controlled in all conditions. This paper aims at defining a robust procedure for aeroelastic phenomena control system design, which employs a synergy of modeling, simulation and experimental approaches. Discussions and pertinent conclusions are outlined in the final section of the paper.