In a significant step towards creating a new sensor for robotics, UK researchers from the universities of Strathclyde and Leeds have recreated the basic hardware for artificial echolocation.
Bats are capable of imaging their surroundings in great detail using echolocation. To apply similar methods to human engineering systems requires the capability to measure and recreate the signals used, and to understand the processing applied to returning echoes. In this work, the emitted and reflected echolocation signals of Rousettus aegyptiacus are recorded while the bat is in flight, using a wireless sensor mounted on the bat. The sensor is designed to replicate the acoustic gain control which bats are known to use, applying a gain to returning echoes that is dependent on the incurred time delay. Employing this technique allows emitted and reflected echolocation calls, which have a wide dynamic range, to be recorded. The recorded echoes demonstrate the complexity of environment reconstruction using echolocation. The sensor is also used to make accurate recordings of the emitted calls, and these calls are recreated in the laboratory using custom-built wideband electrostatic transducers, allied with a spectral equalization technique. This technique is further demonstrated by recreating multi-harmonic bioinspired FM chirps. The ability to record and accurately synthesize echolocation calls enables the exploitation of biological signals in human engineering systems for sonar, materials characterization and imaging.
In a first step, the team mounted miniature wireless microphone sensor on six Egyptian fruit bats. This allowed them to record the bats' double-click echolocation calls, and its returning echoes, during the bats' flight.
The team then went on to create an ultrasonic loudspeaker and electronics that accurately reproduces the bats' clicks. Their system recreates the bats' natural acoustic gain control which allows bats to emit high-intensity calls, while still hearing the weak echoes returning from surrounding objects.
The researchers are now planning to apply their methods to positioning of robotic vehicles.
Original article in Bioinspiration & Biomimetics: Wireless recording of the calls of Rousettus aegyptiacus and their reproduction using electrostatic transducers