Unified Aeroelastic and Flight Dynamic Formulation via Rational Function Approximations

A unified aeroelastic and flight dynamic formulation is sought to take into account the influence of aeroelastic effects on the flight dynamic behavior of the whole aircraft in a format fully compatible with the aeroelastic, flight dynamics, and automatic control disciplines. By allowing the inclusion of gravity-related terms, vertical acceleration-related aerodynamic stability derivatives, and lift and drag forces due to forward-velocity perturbations into the rational function approximation matrices, the traditional quasi-steady flight dynamic equations of motion are fully recovered. Closed-form solutions are presented for translational and rotational degrees of freedom in the aeroelastic model. The General Atomics-Aeronautical Systems (GA-ASI) Predator® unmanned aerial vehicle is used to numerically demonstrate the unified aeroelastic modeling framework. The results indicate that this approach reproduces, with a high degree of fidelity, the underlying quasi-steady flight dynamic model when no elastic modes are included in the aeroelastic model. Comments are provided to determine the approximate number of elastic modes that need to be included in the aeroelastic model to accurately model its flight dynamic behavior.