Vibration and Mobility Analysis of Hovering Rotary Wing UAV for Adaptive FSO Beam Alignment

Unmanned aerial vehicles (UAVs) are regarded as a potential platform for deploying airborne free space optical (FSO) fronthaul/backhaul links. The challenge emerges from the UAV hovering mobility which deteriorates beam alignment. To solve this challenge, we conducted two hover flights using a quadrotor UAV to measure vibration levels and hover fluctuations offering practical insights into the position and orientation changes of mobile FSO terminal. We obtained vibration- and hover movement-induced deviations along three axes in quadrotor states–position, attitude, linear velocity, and rotational velocity. We present a measurement-based system model to formulate the impact of UAV state variations on vertical FSO links for deviated hover trajectories. The experimental results demonstrate significant horizontal and vertical displacements, azimuth and elevation angular errors, which cause pointing errors that need continuous high-speed adjustments to ensure robust beam alignment.