Acoustic emission system for a bat robot

Abstract

One of the more difficult challenges in producing a biomimetic bat robot is replicating the bats' biosonar emission capabilities. For mimicking horseshoe bats (Rhinolophidae), this means creating a high-power acoustic source that can also properly illuminate the noseleaf structure over a bandwidth of approximately 20 kHz. Computer tomography (CT) scans were used to inform an accurate noseleaf model which was then abstracted from life using three-dimensional mesh software. A waveguide was designed to direct sound from two electrostatic transducers into a small nozzle, creating a point source. Numerical acoustic simulations were used to optimize these waveguide shapes to obtain a good compromise between point source behavior, high output amplitudes, and minimal internal reverberation. Physical geometries were procedurally generated to create a three-dimensional design space with parameters eccentricity, length and convexity. Data from each waveguide were analyzed for volume, multidirectionality, and echoing. A second round of simulations was executed to determine the effect of nozzle width on the output. Findings indicated that waveguide convexity and eccentricity played primarily into echoing and increased length reduced output volume. As nozzle diameter increased, the output volume increased, but sound became unidirectional. Future research may include development of alternative emission systems without a need for waveguides.