Meeting Abstract
In order to draw inspiration from birds for improving the design of flying robots, we need accurate time-resolved force measurements of flying birds in vivo. A new system developed by our lab, an aerodynamic force platform (AFP), has been used to measure the vertical lift forces of hovering Anna’s hummingbirds and Pacific parrotlets. The AFP is a control volume that encloses the bird and integrates the Navier-Stokes equations mechanically to measure the aerodynamic force generated by the bird with force sensors attached to the ceiling and floor. Like all measurement systems, there is inherent noise due to the natural frequencies in each component. The structural and acoustic resonance of the volume determine precision, as in terrestrial force plates. Currently it is not fully understood how the coupling between the structural and acoustic resonance can be optimized to improve precision. We study a linearized small-amplitude acoustic model (Helmholtz Equation) of the air volume coupled with models of the top and bottom force plate of the volume (harmonic oscillators). This simplified model, which ignores essential momentum terms in the Navier-Stokes equations for calculating force transfer, enables us to derive design principles. It shows how the resonances need to be decoupled to reduce small amplitude noise and improve precision of in vivo measurements. To determine the validity of the design principles derived based on this simple model we compare our simulations with experiments.
