Testing and Characterization of Hybrid Unmanned Aerial/Underwater Vehicle at the air-water interface

Hybrid Unmanned Aerial/Underwater Vehicles (HUA/UV's) have the challenge of robustly operating within and transitioning between two vastly different environments. To meet this challenge, an amphibious quadrotor was constructed and its transition performance quantified using motion capture under manual control. The approach is novel in that it performs transition without active buoyancy control or increasing the number of rotors. The loads across air-water transition were quantified using a controlled single motor-propeller pod and a six-axis load cell. Experimental results were compared against blade element momentum theory (BEMT). The BEMT model correlated well with experimental thrust data when the propeller was in 'fully in air' or 'fully in water' environments. A simplifying dimensional analysis of the model predicted first order relations between electronic speed controller measurable parameter of revolutions per minute against the variation in fluid density. Derived parameters of effective density, entry offset depth, and critical depth were introduced and discussed. The first order relations showed agreement with experimentally derived data, suggesting that "effective density" may have a role in enabling attitude regulation across the air-water interface.