On the control of aeroelastic/flight dynamic integrated stability of maneuvering aircraft

Fully-coupled equations of nonlinear rigid-body motion and linearized structural dynamics of flexible aircraft are presented using a coordinate system verifying the practical mean-axis constraints. Linearized equations around aeroelastic trim conditions are obtained and implemented for complex configurations described by a Finite Element Method structural model and by a Doublet Lattice Method aerodynamic model. A state-space representation of the linearized system is ultimately obtained using a rational function approximation of small-disturbance fully-unsteady aerodynamics. The state-space flexible aircraft model simultaneously includes rigid-body, elastic, and aerodynamic state variables, and can be used to study integrated flight dynamic/aeroelastic stability as well as response to both control inputs and gust disturbances. The model is applied to a representative flying-wing configuration to design an optimum controller for body freedom flutter suppression and gust alleviation. Open-loop and closed-loop numerical results are presented to point out influence of coupling effects between rigid-body and elastic degrees-of-freedom on control of flexible vehicles