Modeling and experimental identification of quadrotor aerodynamics

Kaya, D. Derya
The aim of this study is to obtain mathematical models for aerodynamic forces and moments of rotors of a quadrotor helicopter, and estimate their parameters through wind tunnel tests for hover, vertical climb, and forward flight conditions. The main factors which determine the movement of a quadrotor UAV are the aerodynamic forces and moments in three axes created by four rotors of the vehicle. Hence, accurate calculation of rotor forces and moments in varying flight conditions are essential to establish a precise simulation of the vehicle. For this purpose, analytical models for aerodynamic forces and moments of a rotor are derived using blade element and momentum theories. These models predict the aerodynamic rotor forces and moments generated by air flows around the blades due to blade rotation and vehicle motion on all three axes. Parameters of the mathematical models are then identified through experimental force and moment measurements obtained in a wind tunnel at various rotor speed, free stream velocity, and vehicle angle of attack values. Since the analytical model cannot capture certain experimentally observed dependencies, an empirical rotor model has been developed by surface fitting a second order polynomial model to test data. The developed model allows us to accurately predict aerodynamic loads on a quadrotor in various rotor speeds and flight conditions.