OVERCOMING STOPOVERS IN CYCLOIDAL ROTOR PROPULSION INTEGRATION ON AIR VEHICLES

A cyclorotor (also known as a cyclocopter or cyclogiro) is a rotating-wing system where the span of the blades runs parallel to the axis of its rotation. The pitch angle of each of the blades is varied cyclically by mechanical means such that the blades experiences positive angles of attack at both the top and bottom positions of the azimuth cycle. The resulting time-varying lift and drag forces produced by each blade can be resolved into the ver-tical and horizontal directions. Varying the amplitude and phase of the cyclic blade pitch can be used to change the magnitude and direction of the net thrust vector produced by the cyclorotor. Compared to a conventional rotor, each spanwise blade element of a cyclorotor operates at similar aerodynamic conditions (i.e., at similar flow velocities, Reynolds numbers, and angles of inci-dence), and so the blades can be optimized to achieve the best aerodynamic efficiency. Moreover, because the blades are cycli-cally pitched once per revolution (1/rev), unsteady flow mecha-nisms may delay blade stall onset and in turn may augment the lift produced by the blades. Albeit proposed to MAV-scale, its use on large scale vehicles turns problematic, and we proposed in this paper to address their stopovers. Furthermore, since the thrust vector of a cyclorotor can be instantaneously set to any direction perpendicular to the rotational axis, a cyclorotor-based air vehicle may ultimately show better maneuverability and agility as compared to a classical powered conventional ro-∗Address all correspondence to this author. tor system. One major drawback of a cyclorotor is its relatively large rotating structure which might offer a weight penalty when compared to a conventional rotor