Abstract:
As rotor diameter and inertia increases, the quickness of the thrust response to pilot inputs slows, yielding negative implications to handling qualities and limitations on scaling electric propulsion. This study presents a novel approach to alleviating these scaling effects by introducing a pitch-lag coupled hinge to the root of 40" and 50" diameter props. The impacts of chordwise hinge placement and hinge angle are examined and compared to a baseline rigid rotor to provide physical understanding of the rotor dynamics. It is shown that a coupled hinge can be designed to maintain propeller efficiency for a design thrust, while increasing the sensitivity of thrust to rotor speed and the maximum thrust of an RPM-limited rotor. Finally, the dynamic implications of this are tested using a first-order motor model. When a 40" diameter trimmed rotor is set to max throttle, rotors with a coupled hinge angle achieve a 6% higher thrust in 9% less time. The dynamic response improvement scales favorably when the rotor diameter is increased. For the 50" diameter rotor, the introduction of pitch-lag coupling reduces the time constant of the rotor’s thrust response by 32%.