In West Lafayette, Indiana, the renowned ornithologist Xinyan Deng stretches out her hand to serve as a platform for a magnificent turquoise and dark green hummingbird. It hovers just above her palm, wings beating rapidly to keep it airborne, but otherwise remaining perfectly stationary. Although several types of bird can hover in this way, it’s something hummingbirds are extraordinarily talented at. They are even capable of hovering at a flower in a gusty wind, continually adjusting their position so as to remain next to their target. Which is one of the reasons Deng is so interested in them.
Except that we’re lying. Well, kind of. Professor Xinyan Deng is not a renowned ornithologist. She’s an Associate Professor of Mechanical Engineering in Purdue University’s Bio-Robotics Lab, a laboratory that’s dedicated to building the next generation of robots inspired by nature. And Deng’s hummingbird is not a real flesh-and-blood hummingbird. It’s an impressive robotic reproduction of the real thing: not only the same size, shape, and (thanks to a specially designed body cover) appearance as its inspiration, but also capable of many of the same feats — hovering very much included. While it currently has to be tethered to the ground to provide power and stability, the team responsible for creating it is excited that they may have finally cracked one of the natural world’s most unusual modes of flying.
“[The] hummingbird is a unique species whose size is in between insects and other birds,” Deng told Digital Trends. “Summer is coming and you can see them in your backyard hovering, dashing, and chasing one another. They can hover like insects [using] high-frequency beating wings, and they can also fly acrobatically like birds by actively morphing their wings. Most birds cannot hover, while most insects cannot deform their wings actively. Hummingbirds can do both, and their stable and agile flight makes them nature’s little flying wonders. If you want to build a small [micro air vehicle] (MAV) which can achieve both hover and highly maneuverable flight, [the] hummingbird is the ideal animal to study.”
This, in a nutshell, is what makes Purdue’s Bio-Robotics Lab so interesting. It’s midway between a biology lab and a cutting edge robotics house. It does what engineers often refer to as “reverse-engineering,” meaning to take an existing product apart to see how it works and how it can be recreated. Only in this case it’s not about disassembling a smartphone or other gadget developed by a rival manufacturer and figuring out how to replicate its functionality. It’s mining the natural world for problem-solving solutions that evolution has long since answered, but scientists and engineers are still struggling with.
By modeling the locomotion principles of everything from flying insects to fish, Purdue’s Bio-Robotics Lab wants to work out the secrets behind the world’s most impressive, efficient animals — and then turn these insights into new, bio-inspired robots able to navigate in the air, on land, or in the sea in a way previous roboticists have never dreamed of.
An aerial marvel
The team’s hummingbird robot is the latest impressive example of this. Equipped with just two actuators, it can achieve hovering, trajectory tracking, and an assortment of impressively acrobatic maneuvers in the air. All of this is carried out in a diminutive body with the same size, weight, and wingbeat frequency as a typical magnificent hummingbird (Eugenes fulgens).
“It has independently controlled wings like [the real animals] do, which makes it highly agile.”
“It has independently controlled wings like [the real animals] do, which makes it highly agile,” Deng continued. Each of these wings can move individually, changing their direction upward of 30 times each second. By varying the movements of each wing, even by a minute amount, the hummingbird robot (hummingbot?) is able to display impressive flying dynamics far beyond all but the most agile of drones.
In addition, the robot’s wing motors can sense changes in wing kinematics, such as when they meet resistance. This allows them to make dynamic adjustments on the fly to avoid possible wing damage. And that’s not the end of its winning credentials, either.
“It is safe to the touch, resilient to gusts and impacts, and can cope with considerable wing area loss and vehicle wear-and-tear,” said Deng. “It generates lift more than twice the amount of its weight, and can be made autonomous once we add the battery onboard. It is also natural-looking and could fly quietly, making it a nice alternative or complementary to conventional drones.”
Real hummingbirds spend most of their time eating. They use up an astonishing amount of energy, which must be constantly replenished by feeding on flower nectar, tree sap, insects, and pollen. Provided that Purdue can crack the battery problem, its robot hummingbird will utilize its time for far more practical applications.
Machines such as this, “can coexist with humans in future smart cities.”
“This type of robot can be used in confined or cluttered spaces — for example, indoor navigation or search and rescue [missions] in collapsed buildings,” she said. Due to its lack of spinning quadcopter blades, the robot is also capable of interacting with people without risk of hurting them. As a result, Deng said that machines such as this, “can coexist with humans in future smart cities, and be used in a variety of commercial, industrial, defense applications.”
To robotics fans, it’s yet another example of just how fast robots are developing here in 2019. And, hey, even the most ardent of technophobes must feel somewhat reassured at the prospect of a future in which the sky is filled with hundreds of robot hummingbirds. As sci-fi dystopias go, that one’s not too bad!
Three separate papers describing the robot hummingbird project are due to be presented at the 2019 International Conference on Robotics and Automation in Montreal, Canada, later this month.
