Optimised folding arms let a quadrotor squeeze through a 15 cm gap at 2 m/s

Researchers including Etor Arza, Luca Girardi, Stefano Mintchev and Kostas Alexis have described, in an arXiv paper, a method that designs drones with passively folding arms by testing candidate designs in a contact simulation of the gap-crossing task. The success rate in simulation guides the search towards better geometry and better arm stiffness.

The resulting prototype narrows from 31.3 to 14.1 cm when it touches the edges and passes through a 15 cm opening at a reference speed of 2 m/s. It tolerates approaching the gap up to 30 degrees off line and can fold its way along a confined passage 40 cm long. In free flight it adds only 2 mm of position error and under 1% electrical power compared with a rigid twin.