Although humans can fly with the help of copious engineering, Mother Nature has already come up with much simpler ways to soar, like the way a maple tree’s spinning seeds scatter by floating on the wind like unpowered helicopters. It’s a beautifully efficient design, and one that inspired this similarly lightweight drone that can even record video—despite constantly spinning.
We’ve seen other researchers look towards the mighty maple tree for inspiration before, including engineers from Northwestern University in Evanston, Illinois, who created sensor-laden microchips with tiny wings that allow them to passively float on a breeze and spin as they descend, making them easier to distribute across large areas without requiring each microflier to have its own power source.
Researchers from City University of Hong Kong also took inspiration from the unique way a maple tree sows its seeds, but to help design a battery-powered drone that would instead sip power to help boost flight times. As impressively capable as most quadcopter drones are these days, the four propeller setup that helps keep them stable while providing impressive in-flight agility also requires a significant amount of power and chunky batteries onboard to stay aloft.
In a recently published paper in the journal Science Robotics, the researchers detail their design for a bicopter primarily built around two wings with a symmetrical layout—like the rotors atop most helicopters—that places the electronics and batteries in the middle of the device. The bicopter’s wing span is almost 24-inches across, but it was built with a lightweight frame and other materials that weigh in at just 35 grams with a small battery attached. The drone also relies on two small, electric-motor driven propellers near the tip of each wing to keep it spinning at around 200 rpm, while the wings provide the necessary lift to stay aloft.
The drone’s design keeps it inherently stable in flight, which means that microprocessors that continually adjust the speed of each motor to achieve stability—something quadcopters are dependent on—aren’t needed. So, with a 250 mAh battery attached and a minimal amount of electronics to power, the drone stayed in a constant stable hover for just over 24 minutes in testing, which is impressive performance given its minimal weight.
But the market for drones really exploded once they became powerful enough to carry cameras with them. There’s not much practical use for a lightweight flying device that does nothing but fly. Drones like DJI’s new Mini 3 Pro use cameras attached to stabilizers to capture amazingly smooth footage during a flight, but attaching a camera to a drone that constantly spins at 200 rpm would normally produce nothing but dizzying footage.
The researchers came up with a clever workaround, though. They attached a tiny 22-gram camera to the drone and synced its framerate to the drone’s spinning, so to record forward-facing footage, the camera only captures a frame once every 360-degree rotation. Using this trick, the drone was actually able to record four (mostly) stable videos in different directions at 3.5 fps each.
Is this design going to supplant what companies like DJI are doing with camera drones? Not immediately, but it demonstrates new approaches to controlled flight with significantly reduced power demands, which could help increase flight times and the distance a drone can cover in a single outing.