The evolution of bat robots

Abstract

The extraordinary skills of bats in supporting dexterous mobility in complex environments based on just two pulsed trains of one-dimensional biosonar echoes has attracted attention from engineers for several decades already. To explore whether it is possible to reproduce at least certain of these capabilities, a diverse set of “bat robot” prototypes have been built. The earliest, most basic of these systems were limited to estimating the distance of sonar targets based on the acoustic time-of-flight. From there, systems improved to take advantage of more echo waveform features, e.g., for target recognition. Two (or more) receivers were introduced to exploit binaural differences, e.g., for target tracking. Rigid ear rotations served to enhance the signal-to-noise ratio be focusing on a target or to determine target direction from the echo amplitudes received across a scan. Biomimetic emission and reception baffle shapes, i.e., “noseleaves” and “pinna,” were added to narrow the sonar beams and create direction-depended spectral signatures. Deformations of flexible baffle structures that mimic the muscular actuation of the noseleaf and pinna shapes seen in bats have been added to these systems. Mobility of the entire systems has been provided by mounting them on pan-tilt units, robot arms, mobile robots, and drones.