If Drones Had 'Claws,' They Might Be Able To Fly For Longer

May 6, 2019
Originally published on May 6, 2019 5:55 pm

Small drones can do big jobs: Firefighters can use them to find hot spots in blazes, environmental monitors can find the source of hazardous chemical leaks. One just delivered a human kidney for transplant surgery.

But it takes lots of power to spin four helicopter blades fast enough to keep a quadcopter-type drone in the air. Most can only stay aloft for about 30 minutes.

So an international team of roboticists is trying to extend the time a drone can stay on the job. For inspiration, they turned to birds.

"Birds usually fly somewhere and they stay at the top of the roof or some tree branches," says Kaiyu Hang a roboticist at Yale University. "Then they look for their prey or they just stay there without flapping their wings all the time and they can still observe what is happening around them."

And observing takes a lot less energy than flying.

Hang and his colleagues developed a claw-like landing system that lets a drone grab on to a branch or pole, turn off its engines and continue to make observations while it's perched. Hang describes his work in the journal Science Robotics.

The team's new system also provides a way of landing even when there isn't a good place to land.

"We have developed a modularized landing gear framework that allows the drone to not only perch on some structures, but also rest on some structures when perching is not possible," Hang says.

By resting, Hang means the quadcopter can essentially lean against a ledge and stay there using just two of its four rotors — saving energy.

The ability to perch can be handy for a number of other reasons, too.

"If you perch, for example, underneath a bridge or underneath the eaves of a building you can ride out storms or bad weather that would make it hard to fly," says Stanford University's Mark Cutkosky.

The new landing system Hang and his colleagues have invented does have some drawbacks. For one thing, it adds weight to the drone. That means it takes more energy to keep the drone aloft.

"So there had better be a good trade-off in terms of really improving mission time in order to pay for that added weight," Cutkosky says.

And for now, a human has to fly the drone onto the perch site.

To make the landing system really useful, the drone would be able to land on its own. So the question is "what sorts of strategies can we use that would allow this system to discover perch-able sites?" Cutkosky says.

The Yale team has already begun integrating the drone's computer with its on-board camera, so it might not be too long before drones are able to decide on their own where to settle down for a rest.

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ARI SHAPIRO, HOST:

Small drones have lots of practical applications. They can help firefighters find hot spots. They can let environmental monitors pinpoint the source of hazardous chemical leaks. But small drones have a problem. They can't fly for very long. NPR's Joe Palca reports on a new solution.

JOE PALCA, BYLINE: Small quad copters have become extremely popular. You see them at sporting events or outdoor concerts, maybe around your neighborhood. But it takes a lot of power to spin four helicopter blades fast enough to keep a quadcopter in the air.

KAIYU HANG: If you fly it with full battery, you can use it for at most, like, 25 minutes to half an hour.

PALCA: Kaiyu Hang and his colleagues at Yale University are trying to extend the time a drone can stay on the job. And for inspiration, they turn to birds.

HANG: Birds usually fly somewhere. They stay at the top of the roof or some tree branches, and then they look for their prey or they just stay there without, you know, flapping their wings all the time. And then they can still observe what is happening around them.

PALCA: And observing takes a lot less energy than flying. Hang and his colleagues developed a claw-like landing system that lets a drone grab on to a branch or pole and turn off its engines. And Hang says their new system allows a drone to save energy even when no suitable branch is available.

HANG: We have developed, like, modularized landing gear framework that allows the drone to not only perch on some structures, but also the drone can rest on some structures when perching is not possible.

PALCA: By resting, Hang means the quadcopter can essentially lean against the ledge and stay there using just two of its four rotors, saving energy. Hang describes his work in the journal Science Robotics. Mark Cutkosky also works on drone landing systems. He's at Stanford University. He says the ability to perch can be handy for a number of reasons.

MARK CUTKOSKY: If you perch, for example, underneath a bridge or underneath the eaves of a building, you can ride out storms or bad weather that would make it hard to fly.

PALCA: Cutkosky says the Yale team's new landing system does have some drawbacks. For one thing, it adds weight to the drone. That means it takes more energy to keep it aloft.

CUTKOSKY: So there had better be a good tradeoff in terms of really improving mission time in order to pay for that added weight.

PALCA: Another drawback is, for now, a human has to fly the drone to the perch site. To make the landing system really useful, the drone should be able to land on its own. So the question is...

CUTKOSKY: What sorts of strategies can we use that would allow this system to discover perchable sites?

PALCA: Cutkosky says the Yale team has already begun integrating the drone's computer with its onboard camera. So he thinks before too long, drones will be able to decide on their own where to settle down for a rest. Joe Palca, NPR News.

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