Assessment and Modeling of the Aerodynamic Ground Effect of a Fully-Actuated Hexarotor with Tilted Propellers

This letter investigates the ground proximity effects of a fully-actuated multirotor unmanned aerial vehicle (UAV). Different configurations of tilted rotors and a wide range of UAV heights relative to the ground are considered. In order to charac- terize the effect, an extensive experimental study was conducted on a static test-bench. The experimental results display a behav- ior differing from that previously observed for multirotors with co-planar propellers and single-tilted rotors. We demonstrate that the ground effect increases with angle when the UAV is near the ground, while the opposite occurs for areas further away. Two new ground effect models are proposed, one for co-planar and another for fully-actuated configuration. In both cases, the models are dependent on the propeller radius, the distance between the rotors, the height of the UAV and the fountain effect. In addition, in the fully-actuated configuration, the model also depends on the inclina- tion of the rotors. Finally, the proposed models are integrated into the UAV control architecture using the Aerodynamic Power Model Inversion (APMI) module, showing a significant improvement in flight accuracy when the ground effect is considered.