How tiny drones inspired by bats could save lives in dark and stormy conditions

WORCESTER, Mass. — Don’t let the fog machine, spooky lights and fake bats fool you: Worcester Polytechnic Institute’s robotics lab isn’t throwing a Halloween party.

Rather, it is a testing ground for tiny drones that can be deployed in search and rescue missions, even in dark, smoky or stormy conditions.

“We all know that when there’s an earthquake or tsunami, the first thing that goes down is the power lines. A lot of times it’s at night and you won’t wait until the next morning to go rescue the survivors,” said Nitin Sanket, assistant professor of robotics engineering. “So we started looking at nature. Is there a creature in the world that can do this?”

Sanket and his students found their answer in bats and the winged mammal’s highly sophisticated ability to echolocate or navigate via reflected sound. With a grant from the National Science Foundation, they are developing small, inexpensive, energy-efficient aerial robots that can fly where and when current drones cannot operate.

Last month, rescuers in Pakistan used drones to find people stranded on rooftops by massive flooding. In August, a rescue team used a drone to find a California man trapped for two days behind a waterfall. And in July, drones helped find a stable route for three miners who spent more than 60 hours locked underground in Canada.

But as drones become more common in search and rescue operations, Sanket and other researchers want to move beyond the manually operated individual robots used today. A key next step is developing aerial robots that can be deployed in swarms and make their own decisions about where to search, said Ryan Williams, an associate professor at Virginia Tech.

“This type of deployment – ​​autonomous drones – effectively sucks,” he said.

Williams solved this problem with a recent project that involved programming drones to choose search trajectories in coordination with human researchers. Among other things, his team used historical data from thousands of missing persons cases to create a model predicting how a person would behave if they got lost in the woods.

“And then we used that model to better localize our drones, to search in places where the chances of finding someone were higher,” he said.

At WPI, Sanket’s project addresses other limitations of current drones, including their size and perception capabilities.

“Current robots are big, bulky, expensive and cannot operate in all kinds of scenarios,” he said.

In contrast, his drone fits in the palm of his hand, is made mostly from cheap materials, and can operate in the dark. A small ultrasonic sensor, similar to those used in automatic faucets in public toilets, mimics the behavior of bats, sending out a high-frequency sound pulse and using the echo to detect obstacles in its path.

In a recent demonstration, a student used a remote control to launch the drone in a well-lit room, then again after turning off all but a faint glow of red lights. As it approached a transparent Plexiglas wall, the drone stopped and moved backwards several times, even with the lights off and with fog and fake snow swirling in the air.

“Currently, search and rescue robots mainly operate in broad daylight,” Sanket said. “The problem is that search and rescue operations are boring, dangerous and dirty tasks that often take place in the dark. »

But the development has not gone smoothly. Researchers realized that the noise from the bat robot’s propellers interfered with the ultrasound, requiring 3D printed shells to minimize interference. They also used artificial intelligence to teach the drone to filter and interpret sound signals.

However, there is still a long way to go to match bats, which can contract and compress their muscles to listen for only certain echoes and detect something as small as a human hair several meters away.

“Bats are amazing,” Sanket said. “We are far from what nature has achieved. But the goal is that one day in the future we will be there and these elements will be useful for deployment in nature.”