Novel Cyclorotor Pitching Mechanism for Operation at Curtate and Prolate Advance Ratios

Abstract

A cyclorotor is a horizontal axis propeller capable of producing thrust in or extracting energy from a fluid. The ability to vary the direction and magnitude of thrust, operate more quietly and at higher advance ratios than traditional rotors makes them attractive for a wide range of aircraft applications. Moreover, recent research has enabled cyclorotors to exceed the efficiency of traditional rotors in hovering conditions. However, until the present work, no mechanism existed to achieve the blade pitching kinematics necessary for efficient flight at high curtate and prolate advance ratios. A novel cyclorotor pitching control mechanism was designed and constructed to actuate cyclic pitching schedules for operation at curtate and prolate advance ratios, i.e. hovering and cruise flight conditions. This mechanism employs a four degree of freedom three dimensional cam larger than the rotor radius. The position of the cam is altered to enable pitch variations to account for changes in advance ratio, as well as alter the pitching schedule, to vary the magnitude and direction of thrust. Preliminary testing demonstrated the ability to produce pitching schedules for advance ratios from 0 to 0.85. Operating challenges resulting from improper blade mass distribution and cam bearing geometry were identified and corrected.