Development of a UAV-scale cyclocopter
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Copyright 2019 by the Vertical Flight Society. This paper discusses the detailed vehicle design, control strategy, gimbal testing and tethered flight testing of a 17-pound novel unmanned aerial vehicle (UAV) utilizing cycloidal rotors, known as a cyclocopter. Cycloidal rotors (or cyclorotors) are a horizontal-axis rotary-wing concept. The current vehicle configuration features two identical cyclorotors rotating in the opposite directions positioned at the front and rear of the vehicle. The cyclorotors utilized in the vehicle design were optimized through an extensive experimental parametric study. At an operating Reynolds number of 200,000, the optimal cycloidal rotor configuration had a chord-by-radius ratio of 0.66, 3 blades featuring a blade aspect ratio (span/chord) of 4 and a NACA 0020 airfoil, rotor aspect ratio (span/diameter) of 1.33 and pitch amplitude of 35 deg and obtained a figure of merit of 0.6. The final cyclorotor geometric parameters chosen for the UAV were a 6 in. chord, 18 in. span, and 18 in. diameter. The novel cyclorotor design features a revolutionary split-blade with independent collective and cyclic pitch control for the left and right blade halves. The independent pitch kinematics allows the vehicle to achieve both roll and yaw control while maintaining a compact and light-weight design. Pitch control was achieved using differential rotational speed between front and rear rotors. A stateof- the-art 1.7-g autopilot was integrated onto the vehicle for attitude stability through feedback control. Attitude stability of the vehicle was verified through a series of experiments on a three degree-of-freedom gimbal stand. The vehicle's ability to liftoff and remain stable in pitch and yaw was verified through tethered flight tests.
