A Complete Aeroservoelastic Model: Incorporation of Oscillation-Reduction-Control into a High-Order CFD/FEM Fighter Aircraft Model

Flight testing for aeroservoelastic clearance is an expensive and time consuming process. Large degree-of-freedom nonlinear aircraft models using Computational Fluid Dynamics coupled with Finite Element Models (CFD/FEM) can be used for accurately predicting inviscid aeroelastic phenomena in all flight regimes including subsonic, supersonic and transonic. With the incorporation of an active feedback control system (FCS), these models can be utilized to reduce the flight test time needed for aeroservoelastic clearance. A complete CFD/FEM/FCS model can be used for full simulations including the dynamics of the fluid, the airframe, the actuators, and the FCS. Accurate CFD/FEM models are computationally complex, rendering their runtime ill suited for adequate FCS design. In this work, a complex, large-degree-of-freedom, transonic, inviscid CFD/FEM model of a fighter aircraft is fitted with a FCS for oscillation reduction. A linear reduced order model (ROM) of the complete aeroelastic aircraft dynamic system is produced directly from the high-order non-linear CFD/FEM model. This rapid runtime ROM is utilized for the design of the FCS, which includes models of the actuators and common nonlinearities in the form of rate limiting and saturation. An oscillation reduction controller is successfully demonstrated via a simulated flight test utilizing the high-order non-linear CFD/FEM/FCS model.