Structural Design and Real-World Flight Verification of a Downwash-Reducing UAV Equipped with Adaptive Rotors

This study addresses the challenge of excessive downwash generated by unmanned aerial vehicles (UAVs) during pinpoint weeding in agriculture. We propose a novel UAV design incorporating adaptive rotors that can tilt during flight to reduce the downward airflow that interferes with close-proximity operations. A single actuator drives the rotor-tilting mechanism via bevel and worm gears, enabling synchronized rotor movement and stable self-locking to protect the actuator from external vibrations. Experimental results demonstrated that, even under significant vibration, the tilt mechanism maintained precise angle control and effectively reduced downwash. Indoor flight tests confirmed stable performance across a range of rotor angles from 0° to 30°. Notably, wind speed measurements taken approximately one meter below the UAV showed a reduction of up to 80% in downwash at the maximum tilt angle. In outdoor tests, the UAV maintained reliable hovering even in moderate wind conditions, with no significant degradation in positional accuracy when rotor angles were adjusted during flight. These results indicate that a UAV equipped with adaptive rotors can achieve a balance between aerodynamic efficiency and downwash reduction, making it well-suited for pinpoint weeding.