Stability and Control of a High-Altitude-Long-Endurance UAV

This paper addresses stability analysis, control design, and simulation of high-altitude, long-endurance unmanned aerial vehicles. These aircraft are highly flexible and have very low structural frequencies. Hence, the separation between the elastic and rigid body motions no longer exists, and an approach that unifies these two motions must be used. The available data of the aircraft considered include the geometry of the aircraft, aerodynamic data, and mass, flexural rigidity, and torsional rigidity distributions. The wing of the aircraft is modeled as a flexible beam undergoing bending and torsion, whereas the remaining members are assumed to be rigid. The equations of motion are obtained by means of the Lagrangian equations in quasi coordinates. A perturbation approach separates the problem into nominal dynamics and perturbation dynamics. The equations for nominal dynamics are used to design desired maneuvers and to determine the corresponding structural deformations. The equations for perturbation dynamics are used to address stability of the aircraft on the desired flight paths, to design feedback controls to maintain stable flights, and to simulate the motion of the aircraft.