Stiffness investigation of synthetic flapping wings for hovering flight

Tests on a single active degree of freedom flapping platform are used to investigate the relationship between span-wise/chord-wise stiffness and hovering performance. The intended application is to establish constraints in a multi-objective optimization (thrust-power) that avoid selection of wings that perform poorly. It can also have utility as an alternative engine for identifying favorable performance. The procedure used to make the stiffness measurements is detailed along with the post-processing approach. Twelve wing designs, adapted from a previous study, were tested in both directions to extract a figure of merit that combines both stiffness values into a non-dimensional parameter (SC_ratio). The wings were also tested for thrust performance and current consumption across three different flapping frequencies (20, 25, and 30 Hz). A comparison is provided that identifies the added benefit of considering power consumption when selecting a wing for favorable performance. The data for 20 and 25 Hz flapping frequencies suggest a decrease in efficiency with increased SC_ratio, while the 30 Hz flapping frequency data was unimodal. This suggests the presence of a point or region on the spectrum of SC_ratio that provides optimum efficiency.