Reduced order dynamic aeroelastic model development and integration with nonlinear simulation

Piloted and batch simulations of the aeroservoelastic response are essential tools in the development of advanced flight control systems. In these simulations the number of differential equations must be sufficiently large to yield the required accuracy, yet small enough to enable real-time evaluations of the aircraft flying qualities, The challenge of these conflicting demands is reinforced by nonlinearities in the quasi-steady equations of motion and by the complex characteristies of the oscillatory forces. Our solution to the problem is based on a unique formulation that eliminates the need for auxiliary state variables to represent the unsteady aerodynamics. We also address transformations from the mean flight path axes to a body axes coordinate system and describe how the structural dynamie equations of motion are integrated with the quasi-steady, nonlinear, six-degree-of-freedom plant model. The unified model, which accurately preserves the roots of the dynamic aeroelastic system, includes provisions for control surface inputs and atmospheric turbulence.