Investigating Underactuated Swashplateless Uncrewed Aerial Vehicle Designs

Abstract

Vertical take-off and landing (VTOL) micro-uncrewed aerial vehicles (micro-UAVs) are increasingly deployed where compactness, payload constraints, and low-maintenance operation are important. Conventional rotorcraft achieve thrust vectoring through swashplate-driven cyclic and collective pitch control, but the swashplate and linkages increase part count, integration effort, and potential failure modes. This thesis investigates underactuated, swashplateless rotor and propeller mechanisms that exploit passive dynamics and cyclic shaft excitation to generate thrust-vectoring authority with reduced complexity.

The thesis reviews prior swashplateless actuation concepts and develops a modelling workflow that links mechanism kinematics and hub dynamics with rotor aerodynamics, enabling simulation of thrust-vector response and vibration signatures under representative control inputs. Based on these foundations, a constrained three-degree-of-freedom (C3D) swashplateless hub is proposed and prototyped. The mechanism provides vectoring through controlled hub motion while retaining passive compliance, and it is paired with a vibration-mitigation structure intended to reduce control-induced loads.

For real-time implementation on low-level microcontrollers, lightweight estimation and disturbance-inference methods are developed. Using shaft-speed/encoder waveforms, a mean-path sinusoidal solver extracts amplitude, phase, and bias features related to rotor vector and external disturbances. Simulation studies, bench measurements, and platform tests (where available) assess mechanism behaviour, control response, and vibration characteristics. Overall, the results indicate that underactuated swashplateless mechanisms can reduce integration burden while maintaining practical thrust-vectoring authority for micro-UAV applications, and the thesis provides design principles, simulation tools, and embedded estimation methods to support further development of compact VTOL platforms.