Wind Tunnel Testing of a Variable-Pitch Quadrotor UAV Isolated Rotor

This paper deals with the aerodynamics characterization of a variable-pitch quadrotor UAV isolated two-bladed teetering rotor in working conditions far beyond hover, in terms of free stream velocity incident on rotor disk and its angle of attack. The survey conducted is addressed to evaluate rotor forces, power and flapping angles behavior in forward flight (not only for trimmed conditions) and to investigate the rotor mean inflow in descent, especially in Vortex Ring State (VRS). A dedicated analytical model for the rotor aerodynamics was developed, in both above operating regimes of interest, with a level of detail and complexity suitable for flight mechanics purposes. Modeling results were validated carrying out a proper wind tunnel experimental campaign on the full scale complete rotor system of the considered UAV, minimizing test duration and equipment costs. The experimentally validated model for rotor aerodynamics was coupled with quadrotor rigid body equations of motion and adopted for control synthesis applications.