Time-variant biomimetic beamforming baffle prototypes augmented with local shape features

Abstract

Horseshoe bats are known to exhibit non-rigid pinna deformations as part of their biosonar behaviors. During these deformation cycles, the pinnae of the animals alternate between upright and bent shape configurations that differ in their overall geometry as well as in the shapes and relative positions of local shape features. Artificial baffle prototypes have been designed to emulate these deforming bat pinnae. The prototype shapes were designed by augmenting an obliquely truncated cone with biomimetic local shape features. The prototype was implemented using elastic (synthetic rubber) materials. The deformation of the structure was accomplished through a simple actuation mechanism that was inserted on the back side of the artificial pinna. Features of the horseshoe bat pinna that have been evaluated for this study include a prominent vertical ridge that runs along the entire inner pinna surface, the antitragus along with the lateral incisions that separate it from the back portion of the pinna, and a pinna-edge incision near the tip of the pinna. An experimental analysis of deforming prototypes has demonstrated that such biomimetic local shape features affect the beampattern of the static artificial pinna shape as well as the time-varying properties of the deforming prototype.