| Abstract: | Micro air vehicles are inherently susceptible to wind because of reduced inertia and have lower aerodynamic efficiency due to the poor performance of airfoils at low Reynolds numbers. Cyclorotors can potentially overcome these challenges by using a horizontal rotation axis with blades paral-lel to it and cyclic pitch kinematics to produce lift. Dynamic pitching delays blade stall and altering pitch kinematics can quickly vector thrust increasing maneuverability. Design of cyclorotor-based aircraft is still in incipient stages, so this research experimentally investigated the aeromechanics, dynamics, and control of cyclocopter micro air vehicles. A cyclorotor design with cantilevered blades and elliptical, flat-plate airfoils was developed for low Reynolds number use. Parametric studies were conducted to understand the impact of pitch kinematics, blade shape, and blade size on performance. Flowfield velocity measurements were taken on the resulting optimized rotor using particle image velocimetry which revealed highly 3D flow across the entire blade span with large leading edge vortices, curved trailing wake, and highly vortical flow inside the rotor. A hover capable micro-scale aircraft (30-gram weight) was developed using two co-rotating cyclorotors and a single conventional nose rotor pointed vertically to counter pitch reaction torque. Stability and control was achieved by varying cyclorotor thrust and magnitude as well as nose rotor thrust. Flight testing showed that the aircraft was unstable and had two forms of dynamic gyroscopic coupling from the angular momentum of cyclorotors and nose rotor acting in different directions. Two additional cyclocopters were built to investigate methods of eliminating these couplings. On one, the single rotor was replaced with a coaxial rotor, balancing the vertical angular momentum. System identification was performed via flight testing to extract a linear flight dynamics model of this aircraft which showed passive stability in roll and yaw making it the first cyclocopter to exhibit these unusual characteristics. The second used four cyclorotors with front and rear rotors counter-rotating to balance torque, eliminating all gyroscopic couplings. With eight independent control parameters, this quad-cyclocopter was an over-actuated system, displayed superior performance, and was capable of performing a point hover within a range of different pitch attitudes. The electronic version of this dissertation is accessible from https://hdl.handle.net/1969.1/197397 |
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