Drones are no longer limited to just military uses but have become quite useful in capturing aerial views, delivering goods and for recreational purposes.

But, while they have also been relied on in disaster management to assess damage, their search-and-rescue skills are still being refined.

Researchers at Purdue University in the United States have engineered a hummingbird-inspired robot, which is designed to easily manoeuvre through collapsed buildings and cluttered spaces and could be useful in finding trapped victims.

This device is trained to fly using machine learning algorithms, which allow it to mimic the hummingbird’s natural movement.

After learning from a simulation, the robotic bird “knows” how to move around on its own like a hummingbird would and, with artifical intelligence, can also teach itself new tricks.

Even though the robot can’t see yet, for example, it senses by touching surfaces, which alters an electrical current that the researchers realised they could track.

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

The team will present their work at the 2019 IEEE International Conference on Robotics and Automation in Montreal, next Monday.

Drones can’t be made infinitely smaller because they wouldn’t be able to generate enough lift to support their weight.However, hummingbirds don’t use conventional aerodynamics — and their wings are resilient.

“The physics is simply different; the aerodynamics is inherently unsteady, with high angles of attack and high lift. This makes it possible for smaller, flying animals to exist, and also possible for us to scale down flapping wing robots,” Deng explained.

Researchers have been trying for years to decode hummingbird flight so that robots can fly where larger aircraft cannot. In 2011, the company AeroVironment, commissioned by DARPA, an agency within the US Department of Defense, built a robotic hummingbird that was heavier than a real one but not as fast, with helicopter-like flight controls and limited manoeuvrability. It required a human to be behind a remote control at all times.

Deng’s group and her collaborators studied hummingbirds themselves for multiple summers in Montana. They documented key hummingbird manoeuvres, such as making a rapid 180-degree turn, and translated them to computer algorithms that the robot could learn from when hooked up to a simulation.

The robots could fly silently just as a real hummingbird does, making them more ideal for covert operations. And they stay steady through turbulence, which the researchers demonstrated by testing the dynamically scaled wings in an oil tank.

The robot requires only two motors and can control each wing independently of the other, which is how flying animals perform highly agile manoeuvres 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 said.

Moving forward, researchers plan on adding a battery and sensing technology like a camera or GPS.