Excitable Spring-Wing Dynamics 2: Synchronous and asynchronous regimes of actuation in robophysical spring-wing systems

Flapping-wing insects are thought to have adopted one of two flight muscle actuation modes: periodic forcing of a resonant wing system, termed synchronous flight, and self-excited, asynchronous, forcing via delayed stretch activation (dSA) in flight muscles. Recently, observations have identified dSA in the flight muscle of hawkmoth (Manduca sexta), a synchronous flyer, suggesting that properties of synchronous and asynchronous modes may exist in the same muscle. We leveraged simulation and two robophysical spring-wing systems - one dynamically-scaled and one at insect scale - to study the interplay between synchronous forcing and asynchronous self-excitation in the same physical system. In this talk, we detail the construction and implementation of a self-excited spring-wing model based on measurements of insect muscle response. We show that wing kinematics suitable for flight only arise in either strongly synchronous or strongly asynchronous regimes. Interference between different oscillation timescales induces period-doubling and other effects that create a “valley of death” for flight performance in the intermediate regime. These results provide dynamical arguments for the sharp differentiation in insect phylogeny between synchronous and asynchronous insect flight actuation.