The Effects of Propellers Tilted Inward On Hover Rigidity In Rotary Wing UAVs

Rotary Wing UAVs (RWUAV) with control inputs (thrust, pitch torque, roll torque, yaw torque; 4 at total) less than the degree of freedom (3 angular motion, 3 linear motion; 6 at total) can move in the X-Y plane by rotating the thrust vectors, i.e their bodies. Deflections caused by external disturbances like winds are also eliminated by angular positioning which creates tractions against disruptive drag forces. However, the fact that the thrust vectors (propeller axis) placed perpendicular to the flight plane do not intersect in space carries the outer center of rotation of the platform to infinity, causing linear acting forces to deflect the system in the same direction in both translation and rotation. This coupling leads to an increase in the net deflection of the geometric center. It is observed that the deflection of the geometric center decreased and converged to the pure translation curve as the propeller placement angles decreased. With the study reported here, it has been analytically modeled and demonstrated how inward tilted propellers increase the hover stiffness of the platform against external disturbances. For future studies, the phenomenon suggesting inward tilted propellers may enhance the platform maneuverability by forming the outer rotation center (thrust vectors’ intersection point) is developed.