The Bot That Flies Like a Bat

Robot researchers have created a lightweight, agile drone that mimics one of nature’s greatest fliers.

Bat Bot’s real-life inspiration, the Egyptian Fruit Bat. (Ramezani, Chung, Hutchinson, Sci. Robot. 2, eaal2505 (2017))
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Imagine a drone that could bounce off a building instead of crashing into it, or move safely and seamlessly among workers at a skyscraper under construction. While most drones cause damage when they collide with objects or people, a new flying robot promises safer flights by mimicking bat behavior.

Called “Bat Bot”, the robot under development—discussed in today’s issue of Science Robotics—draws its inspiration from bats, one of nature’s most flexible flying creatures. “Bat flight is the holy grail of aerial robotics,” says Soon-Jo Chung, an associate professor of aerospace at Caltech and one of the paper’s authors. Quick banks and sudden dives allow bats to chase after insects, even in the dark, as they navigate by echolocation.

Bat Bot is able to perform these complex flight maneuvers without the sharp blades used in other aerial bots, and its soft, lightweight materials would be a big advantage for jobs involving close contact with humans, such as construction work.

Video: Caltech

Real bats have more than 40 joints in their wings, which helps to explain why they’re the envy of any aerobatics performer. But replicating bat flight has been a challenge for roboticists. (Birds are easier to mimic because their wings are more rigid.) Adding more joints to previous batlike drones made them heavier, and hard to get off the ground. Also, bat wings are more complex than bird wings. They include bones that deform during each wingbeat, a membrane-thin skin, and sensors in the wings that are believed to give the bat information about airflow.

Bat Bot’s creators reverse-engineered how bats move their wings, focusing on elements such as the side-to-side movement of the tail and the bending of shoulder, elbow and wrist. Then they created carbon-fiber bones that could simulate these motions, and covered them with ultra-thin, lightweight silicone skin. Actuators, sensors and magnetic encoders help control the bat’s movements. The whole thing weighs just 3.2 ounces.

To test their creation, the researchers set the bot free in a large indoor space: the Stock Pavilion at the University of Illinois at Urbana-Champaign. Working indoors allowed them to use a 30-meter by 30-meter net to protect the electronics inside Bat Bot after a fall. In separate flights, the drone successfully executed a straight flight, a banking turn, and a diving maneuver that is one of the signature moves of real bats pursuing prey. The robot even was able to steady itself after being launched off balance.

The researchers, led by Alireza Ramezani, a postdoctoral fellow at Urbana-Champaign, said that besides helping roboticists, Bat Bot contributes to biological studies of bat flight. Such studies use vision-based motion capture systems that don’t necessarily show all the detail of how wing movement contributes to a bat’s acrobatics.

“B2 can be used to reconstruct flight maneuvers of bats by applying wing movement patterns observed in bat flights, thereby helping us understand the role of the dominant DOFs [degrees of freedom in flight mechanisms] of bats,” the researchers wrote.

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