Springs and wings: robophysical and biological investigations inform the design, energetics, and control space for effective flapping wing flight

Flying insects and robots possess a wide range of elastic structures that may enable energy saving in flapping wing flight. However, there is little direct experimental evidence of flight energy reduction through spring-like elements. Furthermore, the implications of a resonant flight system, such as the material and mechanical demands of the thorax, and the control and perturbation responses, are poorly understood. Here we present an overview of how elastic structures in flapping wing flight can improve flight energetics while at the same time altering control capabilities. We present these arguments through a non-dimensional representation of flapping-wing systems, supported by biological and robophysical experiments. This approach enables us to compare the energetic and control implications for flapping wing systems with elastic structures across the relevant spatial scales of flying insects and robots.