WORCESTER, MA. — Don't be fooled by the smoke machine, spooky lights, and faux bats: Worcester Polytechnic Institute's robotics lab isn't throwing a Halloween party.
Instead, it is a testing ground for tiny drones that can be used in search and rescue missions even in darkness, smoke or storms.
“We all know that when there's an earthquake or tsunami, the first thing that goes down is the power lines. It often happens at night, and you're not going to wait until the next morning to go and rescue the survivors,” said Nitin Sanket, assistant professor of robotics. “So we started studying nature. Is there a creature in the world that can actually do this?”
Sanket and his students found the answer in bats and in winged mammals' highly sophisticated ability to echolocate, or navigate by reflected sound. With the help of a National Science Foundation grant, they are developing small, low-cost, and energy-efficient aerial robots that can fly where and when current drones cannot operate.
Last month, emergency workers in Pakistan used drones to find people stranded on rooftops. massive floods. In August, a rescue team used a drone to find an injured California man. trapped for two days behind the waterfall. And in July, drones helped find a stable route three miners who spent more than 60 hours trapped underground in Canada.
But while drones are becoming more common in search-and-rescue operations, Sanket and researchers in other countries want to move beyond the standalone, manually operated robots used today. A key next step is to develop aerial robots that can be deployed in swarms and make autonomous decisions about where to look, said Ryan Williams, an assistant professor at Virginia Tech.
“This type of deployment—autonomous drones—is effectively zero,” he said.
Williams addressed this problem with a recent project that involved programming drones to select search trajectories in coordination with human searchers. Among other things, his team used historical data from thousands of missing person cases to create a model that predicted how a person would react if lost in the woods.
“And then we used that model to better localize our drones and look for places with a higher probability of finding someone,” he said.
Sanket's project at WPI aims to address other limitations of existing drones, including their size and sensing capabilities.
“Current robots are large, bulky, expensive and cannot handle all scenarios,” he said.
By contrast, its drone fits in the palm of your hand, is made mostly from inexpensive hobby materials, and can operate in the dark. The small ultrasonic sensor, not unlike those used in automatic faucets in public toilets, mimics the behavior of a bat by sending out a pulse of high-frequency sound and using the echo to detect obstacles in its path.
During a recent demonstration, a student used a remote control to fly a drone in a brightly lit room, and then again, turning off everything except a faintly glowing red light. As it approached the transparent plexiglass wall, the drone repeatedly stopped and backed up, even with the lights off and fog and artificial snow swirling in the air.
“Currently, search and rescue robots mostly work in broad daylight,” Sanket said. “The problem is that search and rescue is boring, dangerous and dirty work that often has to be done in the dark.”
But development did not go entirely smoothly. The researchers realized that the noise from the flying robot's propellers interfered with the ultrasound, so 3D printing of the housings was required to minimize the interference. They also used artificial intelligence to teach the drone to filter and interpret audio signals.
However, there is a long way to go to match bats, which can contract and clench their muscles to listen only to certain echoes and can detect something the size of a human hair from several meters away.
“Bats are amazing,” Sanket said. “We're a long way from what nature has achieved. But the goal is that one day in the future we'll be there and they'll be useful for use in the wild.”
