Bio-inspired inertial sensing by flapping wings

Abstract

How hawk moths and many other flying insects acquire information on body rotations outside of the visual system is still unknown. Vision is important for flight stability, but generally believed to be too slow to explain fast reflexes during maneuvers and hovering for species such as the Manduca sexta. Insects in the Diptera order (the true flies) acquire angular velocity information with their halteres, club-like organs that once evolved from their hind wings, with strain sensors at their base to detect deformation during turns. The hawk moth wing is richly equipped with strain sensors, but the function of these sensors is still unknown. Could these wing-based strain sensors be used to detect deformation caused by body rotation? To investigate this hypothesis, an Euler-Lagrange model, a Finite-element model, and a robotic model of a flapping at plate were subjected to inertial rotations. The difference in strain between the left and the right side of the wing base indicated wing twist in all computational models. Bending strain is two orders larger than the strain due to twist, making experimentally detecting twist challenging. Wing twist was confirmed for three out of four rotation conditions, be it at different frequencies than expected from simulation. Two strain gauges measuring twist at the wing base proved to be capable of detecting wing twist, but not sufficiently robust to act as an angular velocity sensor. Future work could shed light on whether it is in fact the large array of sensors found on insect wings that allows a more robust sensing of wing deformation as a result of inertial rotations.