Fly-by-Feel Aeroservoelasticity

Abstract

Recent experiments have suggested a strong correlation between local flow features on the airfoil surface such as the leading edge stagnation point (LESP), transition or the flow separation point with global integrated quantities such as aerodynamic lift. “Fly-By- Feel” refers to a physics-based sensing and control framework where local flow features are tracked in real-time to determine aerodynamic loads. This formulation offers possibilities for the development of robust, low-order flight control architectures.

An essential contribution towards this objective is the theoretical development showing the direct relationship of the LESP with circulation for small-amplitude, unsteady, airfoil maneuvers. The theory is validated through numerical simulations and wind tunnel tests.

With the availability of an aerodynamic observable, a low-order, energy-based control formulation is derived for aeroelastic stabilization and gust load alleviation. The sensing and control framework is implemented on the Nonlinear Aeroelastic Test Apparatus at Texas A&M University. The LESP is located using hot-film sensors distributed around the wing leading edge. Stabilization of limit cycle oscillations exhibited by a nonlinear wing section is demonstrated in the presence of gusts. Aeroelastic stabilization is also demonstrated on a flying wing configuration exhibiting body freedom flutter through numerical simulations.