Origami-Inspired Collapsible Structures for Small Rotorcraft Collision Resilience and Landing

This article reports on the design, fabrication, and testing of flexible, collapsible structures inspired by origami and kirigami that can be used to protect small rotorcraft from collision impacts and to serve as landing gear. Twenty structures created from variations of Pako Pako, Magic Ball, and Herringbone fold patterns were laser cut from cardstock and evaluated experimentally. Some of the Pako Pako structures were designed to have graduated mechanical stiffness. An empirical procedure based on acceleration measurements has been developed that enables quantitative evaluation of each structure based on the characterization parameters of peak acceleration, peak velocity, translational kinetic energy, impact duration, mass, and mechanical stiffness. Structures were mounted onto the front of a radio-controlled (RC) car and driven on a linear test track into a rigid wall. Accelerations measured during the collisions were numerically integrated to determine velocities over the impact and collapse/compression of the structures. Flight tests conducted with small RC quadcopters demonstrated that the collapsible structures could successfully be used to mitigate collisions, enough to enable the quadcopters to continue flying after a direct impact and to land indoors or on outdoor terrain with varying slopes and surfaces. Based on trade-off comparisons between the evaluative metrics of the cases studied, conical Pako Pako structures with uniform stiffness are shown to be the most effective for collision resilience and landing.