Using hobby airplane parts worth about $15, a postdoctoral researcher at New York University built a tiny, super-light flying robot that fundamentally rethinks how small aircraft can fly.
Many drones mimic insects for design inspiration, but that line of thinking also poses challenges: Bugs are unstable flyers and have to use a sensor in their brains to keep themselves upright. As they tip to one side, they use their wings to flap back into place. Insect-inspired drones also have to use sensors, making them more expensive.
The jellyfish-like design, on the other hand, stays stable just because of how it moves. NYU researcher Leif Ristroph, along with others at the university's Applied Math Lab, first came up with the design after some experimentation.
Using a wind tunnel that moves air up and down to simulate flapping wings, the researchers found that a hollow pyramid-like shape was especially good at staying stable. "That was the direct inspiration, and then we were kind of basically looking to build a free-flying device that mimicked those same basic movements," Ristroph says.
They turned the sides of the pyramid into flapping wings, and only then did they notice it moves like a jellyfish; just like a jellyfish contracts itself to push water downward, this tiny robot uses a similar motion to propel itself through air.
The flapping motion keeps it stable. "It's a nice property to have, especially as we make the robots smaller and smaller," Ristroph says. "It’s a minimal design. It has the fewest parts and equipment you would need to have that stability...it will also be simpler to make at small scales."
Next, the researchers plan to hook the tiny robot up with a battery. Right now, the prototype is plugged in, so it can only fly as far as the wire allows. "If you want to have a practical device you’d have to get a battery on board, which means improving the lift a little bit so it can bear that extra weight," Ristroph explains. The researchers also plan to add controls so it can be directed from a distance.
The team also plans to test other shapes. Now that they've stumbled upon the resemblance to the jellyfish, they may take that farther, experimenting with a bell-like membrane instead of wings.
While Ristroph is most interested in testing the aerodynamics of the design, he hopes that someone else will decide to actually manufacture something similar, whether as a toy or as a functioning drone.
"We're not engineers, so maybe we're not the right people to do that. But hopefully other people get excited about the basic design, improve upon it, and make it into something that’s more feasible commercially."