Rotor Array Synergies for Aerial Modular Reconfigurable Robots

Abstract

Aerial Modular Reconfigurable Robots (AMRRs) are scalable systems consisting of rotor modules capable of rearrangement during flight. The potential to dynamically change any shape for a given task poses the question: what arrangements offer the most aerodynamic benefit for the task of flying? Answering this requires understanding how adjacent rotors in various configurations influence each another. Intuitively, aerodynamic models such as momentum theory suggest that close rotor proximity decreases performance due to the upstream rotor flow fields interacting. However, effects such as vortex interaction or viscous flow entrainment (used by the Dyson bladeless fan) may offer benefits not captured by the modelling assumptions of computational analysis or simulation. Thus, this work takes an experimental approach, testing thrust performance of rotors in independent configurations of lines, square lattices, and hexagons with various inter-rotor spacings. It was found that inter-rotor spacing did not significantly change thrust performance, but that hexagonal arrangements outperformed line and grid lattices. Smoke tests indicated that hexagon configurations entrained air in the central cavity resulting in a thrust improvement. An inter-rotor spacing of 1.51 rotor diameters gave the best performance increase, roughly equal to that of an additional rotor. This suggests that by placing rotors in an array of six hollow hexagonal honeycombs, thrust performance could theoretically be increased by up to 27.3 per cent, for no additional mass.