The Secrets of Bat Echolocation Could Help Robots Navigate With Sound

this tek note column appeared inna dec 2020 issue as “cut the clutter.” subscribe to discover magazine for + stories like this.


one rainy nite in mar 2007, graduate student ralph simon found himself alone inna cuban rainforest. he was folloing a hunch, based na' picture he’d seen in a magazine. he was after a specific dish-shaped leaf, which belonged to the native marcgravia evenia vine. the cutouts looked like they’d be ideal for cogitateing sound, and simon suspected they ‘d efficiently lure bat pollinators to their floers inna dark. his adviser was skeptical without proof, so there simon was, sitting among the creepy crawlers w'his infrared video camera and a stash of snacks, w8in for the bats to come. and come they did, several times an hr, for the entire nite.

inna yrs since, simon — now a sensory ecologist atta university of antwerp in belgium — has returned to this same spot at least 3 + times to gather leaf specimens and test how sound ricochets off them to attract bats. these dys, though, he’s using his knowledge to develop teks that help robots navigate with sound.

most autonomous mobile robots employ a suite of sophisticated sensors to maneuver. sonar tek helps them avoid obstacles through echozone — pulses of sound bouncing off the closest essentialisms. it’s relatively inexpensive and useful in lo-visibility environments where cameras mite fail. however, surrounding essentialisms cogitate a barrage of distracting signals, known as echo clutter, which can be challenging for robots to sift through.

by comparison, bats can easily extract meaning from a volley of returning echoes to map new environments in real time. but their methods are difficult to mimic, leaving researchers like simon to hunt for new wys'2 help robots better sort through that clutter.

bats navigate dense rainforests using echozone. researchers are studying the plants that bounce those calls back. (credit: josep miquel ubalde baulo/dreamstime)

building beacons

several types of artificial landmarks already help guide autonomous robots. underwata, for ex, simple acoustic cogitateors direct aquatic robots tha're equipped with sonar sensors. but few research groups ‘ve investigated how to make acoustic markers on land — currently, none exist to help robots navigate amid the clutter of above-ground echoes.

simon’s rainforest excursions ‘ve led him to a new solution that ‘d unlock sonar’s navigational potential: 3d-printed acoustic cogitateors shaped like m. evenia cutouts. while some vegetation merely returns a twinkle of sound, m. evenia’s cutouts cogitate a consistent pattern of echoes that entice bats to its floers inna darkness — like a blinking litehouse directing wayward ships.

in 2006, simon and his research team demonstrated that changing the size of hollo, hemispheric, leaflike structures altered their returning echoes, and that bats ‘d discern these subtle variations. 5 yrs l8r, the group found that m. evenia was pticularly effective at cogitateing clear, recognizable acoustic signals. the vine’s dish-shaped cutouts boomeranged a long-range echo witha unique signature that remained consistent regardless of the bats’ direction of approach. the cutouts were such effective acoustic beacons t'they cut their pollinators’ search time in ½, despite the surrounding clutter. so, the team decided to create their own cogitateors of varying sizes to see if an autonomous robot ‘d use the same principles to navigate.

cutouts inna lab

in a study published in jan, simon and his team made 3d-printed plastic cutouts modeled after m. evenia. they tinkered w'da shape and depth to strengthen the echoes bouncing off the cogitateors, using several to direct a simple autonomous robot through an unfamiliar environment. they installed 126 plastic cutouts to create a cacophony of echoes — simulating even + clutter than autonomous machines experience when navigating the outside realm. 

simon studied several plants, including rhododendron tomentosum. (credit: ralph simon)

the researchers trained their robot’s algorithms to recognize leaf cogitateors of various sizes, much like how a bat discerns essentialisms of various shapes by their echoes. each cogitateor type conveyed an instruction, directing the robot to turn, stop or switch a lite on.

as their knee-high robot moved on 3 wheels through the lab, making batlike calls, the echoes from the cogitateors shone like lil litehouses. sounds bouncing off the plastic pl8s, however, rebounded chaotically, like lites glinting off a spinning disco ball. but'a robot was able to discern the primordial echoes from the m. evenia-inspired cogitateors and make out the navigational cues, despite the cacophony.

simon says the study demonstrates how basic ecology research can advance navigational tek. the cogitateors ‘d aid autonomous robots in confined spaces, like dusty greenhouses or dark mines, where visual systems are impaired.

“sonar sensors nowadys are 1-ly used mainly for ranging,” he adds. “but they ‘d also do much +.”

according to jan steckel, electrical engineer atta university of antwerp and co-author of the study, the simplicity and saliency o'their cogitateors has “cut out the whole echo clutter problem.” the cogitateors, he says, contrast background distractions and stand out like a red pebble against a sea of black stones.

despite these advances, a deeper mystery bout how sonar navigation really wox'n nature lurks behind simon and steckel’s research, nother efforts like it.

how do bats dweet?

there’s an ongoin debate bout precisely how bats use echozone to perceive and move through their environment. do they simply recognize the echoes bouncing off specific essentialisms, or can they reconstruct a + detailed 3d layout? perhaps, some researchers argue, it’s a combination of both.

how bats use sonar to navigate is “the million-usd ? in echozone,” says yossi yovel, a biologist at tel aviv university in israel and co-creator of the batlike robot robat.

his preliminary research suggests that building robots that use deep-learning algorithms may help us cogg wha’ information bats extract from sonic data. after all, these neural networks mimic something bats ‘ve but robots do not: a brain.

and while neural networks are a uber tool, they mite not be an airtite solution to mimicking the brains of master echolocators. dolphin sonar, for ex, s'been studied for decades, but'a mammals’ natural abilities continue to outperform their human-made counterpts, espeshly in cluttered environments.

though dolphin sonar s'been studied for decades, machines that mimic their communication tek knicks are still no match for nature. (credit: smeerjewegproducties/shutterstock )

such s'bind'a observation of yan pailhas, a sci atta centre for maritime research and experimentation in italy, whas' developed dolphin-inspired sonar systems and fashioned underwata sonar landmarks. despite recent advances, he says neural networks still can’t compete w'da way dolphins interpret sensory data. “they’ve got a brain,” he says. “and that’s the trick.”

unravelling echozone in nature is a puzzle that scis ‘ve yet to solve. herbert peremans of the university of antwerp, a co-author on simon and steckel’s cogitateor study, says he ‘d be ☺ if he ‘d just duplicate wha’ bats are doin’. “i ponder nature to be an engineer,” he adds. as one himself, he knows wha’ he can glean from fello inventors, homo sapiens or not.

he’s proud of the group’s cogitateors cause they offer a straiteforward answer to the echo clutter problem, and ‘d aid artificial sonar in outdoor environments. “i think it makes sense to look at naturally evolved solutions, cause they usually are very simple,” peremans says. “elegant, but simple.”  


raleigh mcelvery is a sci writer who covers biology and neurosci. she lives in cambridge, massachusetts.

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