Springs and Wings: Robophysical investigation of unsteady flapping wing dynamics

Flying insects are thought to achieve energy-efficient flapping flight by storing and releasing elastic energy in their muscles, tendons, and thorax. However, the dynamics of even simple elastic elements coupled to nonlinear, unsteady aerodynamic forces may make controlling flapping motions via muscle force inputs challenging. In previous work, we examined the resonance properties of a dynamically-scaled robophysical system consisting of a rigid wing actuated by a motor in series with a spring. In this talk, we describe experiments to study the control implications of operating spring-wing transmissions on and off resonance. We consider the response of systems to changing control inputs and external perturbations. We conduct robophysical experiments and model simulations measuring the response of elastic flapping wing systems to realistic control inputs and external perturbations that simulate environmental interactions like wind gusts or collisions. We vary mechanical parameters of the system and track results across a non-dimensional parameter space, enabling comparisons across length scales. The results suggest that series-elastic flapping wings designed for maximum efficiency experience commensurate losses to control authority but may be more robust to external perturbations.