The perch-landing is tested.
Researchers at the University of Illinois have successfully duplicated the control mechanisms that allow birds to perform a soft landing, such as perching on a human hand.
These robot-like birds, or 'ornithopters', would be able to interact much more easily with humans than other micro-aerial vehicles that fly in the style of planes and helicopters.
"The ability to perform perched landings on a human hand endows our robot with the ability to operate around humans," says Aditya Paranjape, a post-doctoral scholar working on this project.
The project is based on Paranjape's PhD thesis and journal articles written with Soon-Jo Chung, an assistant professor in the Department of Aerospace Engineering at Illinois who is also working on the project.
"In contrast with insects, bird-sized robotic aircraft carry some meaningful payloads and can pick up some small objects and carry them to a human - like a robotic pigeon messenger," says Paranjape.
The complex perch manoeuvre can be broken down into two steps: a gliding phase that allows the robot to get into position, followed by a pitch upwards with an instant climb and rapid deceleration.
"High position accuracy is required to autonomously land on small objects such as a hand or a tree branch," says Paranjape.
While the principals of ornithopters can be traced back hundreds of years to the first flying machines, and unmanned micro-aerial vehicles to the mid 1980s, the researchers claim this is the first demonstration of one landing on a human hand.
"Of all manoeuvres executed by flapping wing aircraft in a gliding phase, a perched landing is arguably the most challenging," says Paranjape.
This new technology could have implementations for both the military and the general public.
"Unmanned aerial vehicles [are] capable of operating closely with human soldiers in tight urban environments for intelligence, surveillance, and reconnaissance applications," says Paranjape.
In addition to this, the delicate nature of the perch-landings means that the robots could be used as companions for elderly and disabled people, helping to fetch objects and relay video messages.
Bird-like robots are more agile and manoeuvrable than most other types of micro-aerial vehicles due to their flapping wings and horizontal rather than vertical tail.
The ability of the robots to glide conserves an enormous amount of energy, especially during the intensive processes of descending and landing.
While the horizontal tail allows for increased speed, it does sacrifice a certain amount of control.
"A vertical-tailless aircraft is inherently unstable in the lateral-directional motion," Paranjape says.
But this can largely be compensated with an automatic controller, a relatively cheap addition to contemporary electronic systems.