Nature-inspired in-flight foldable rotorcraft.

The paper presents a novel rotary wing platform, that is capable of folding and expanding its wings during flight. Our source of inspiration came from birds' ability to fold their wings to navigate through small spaces and dive. The design of the rotorcraft is based on the monocopter platform, which is inspired by the flight of Samara seeds. The wings are constructed by applying origami techniques to fold them in flight. Two configurations are presented, featuring active or passive mechanisms for wing-folding depending on specific application requirements. The two configurations can reduce their overall footprint by approximately 39% and 69% while in flight. A cyclic controller is implemented for controlling the translational motion, where the direction is controlled by pulsing the motors at a specific instance during each cycle of rotation. We have presented experimental results to prove the control of our platform in different modes while in flight. The presented platforms enhance the practical uses of the monocopter platform by providing it with the ability to reduce its footprint while in flight actively, or by allowing them to dive through the air without any additional actuator.