Purdue University researchers have engineered flying robots that behave like hummingbirds, and could ultimately go to places where UAS can't. 

The robots are trained by machine learning algorithms based on various techniques the bird uses naturally every day, meaning that after the robot learns from a situation, it “knows” how to move around on its own like a hummingbird would, such as knowing when to perform an escape maneuver.

The robot can also teach itself new tricks, thanks to the combination of artificial intelligence with flexible flapping wings. For example, the robot can’t see as of right now, but it senses by touching surfaces. Each touch alters an electrical current, which the researchers realized they could track.

“The robot can essentially create a map without seeing its surroundings,” explains Xinyan Deng, an associate professor of mechanical engineering at Purdue.

“This could be helpful in a situation when the robot might be searching for victims in a dark place – and it means one less sensor to add when we do give the robot the ability to see.”

Researchers note that as a result of the way that conventional aerodynamics work, UAS can’t be made infinitely smaller, because they wouldn’t be able to generate enough lift to support their weight.

Hummingbirds, however, don’t use conventional aerodynamics, and their wings are resilient, researchers say. 

“The physics is simply different; the aerodynamics is inherently unsteady, with high angles of attack and high lift,” Deng says.

“This makes it possible for smaller, flying animals to exist, and also possible for us to scale down flapping wing robots.”

During multiple summers in Montana, Deng’s group and her collaborators studied hummingbirds themselves, documenting their key maneuvers, such as making a rapid 180-degree turn. These maneuvers were translated to computer algorithms that the robot could learn from when hooked up to a simulation.

After conducting more study on the physics of insects and hummingbirds, Purdue researchers were able to build robots smaller than hummingbirds—and even some as small as insects, researchers note—without compromising the way that they fly. Deng says that the smaller the size, the greater the wing flapping frequency, and the more efficiently they fly.

The robots have 3D-printed bodies, wings made of carbon fiber and laser-cut membranes. One hummingbird robot that researchers have built weighs 12 grams, which is the weight of the average adult magnificent hummingbird. The hummingbird robot can lift up to 27 grams, more than twice its weight. 

By designing their robots with higher lift, the researchers have more room to work with to eventually add a battery and sensing technology, such as a camera or GPS. Right now, the robot needs to be tethered to an energy source while it flies, but researchers say that this won’t be the case for much longer.

The robots could fly silently like a real hummingbird, which would make them especially useful for covert operations. They also stay steady through turbulence, which was demonstrated by researchers when they tested the dynamically scaled wings in an oil tank.

The robot only needs two motors and can control each wing independently of the other; the same way that flying animals perform highly agile maneuvers in nature.

“An actual hummingbird has multiple groups of muscles to do power and steering strokes, but a robot should be as light as possible, so that you have maximum performance on minimal weight,” Deng says.

Along with being useful for search and rescue operations, the robots would also allow biologists to study hummingbirds more reliably in their natural environment through the senses of a realistic robot.

“We learned from biology to build the robot, and now biological discoveries can happen with extra help from robots,” Deng says.