The butterflies of micro aerial ‘bots

Johns Hopkins engineers are aiming their high-speed video cameras at some of the prettiest bugs on the planet in an effort to improve next-gen insect-size flying machines.

A number of US defense agencies are funding the research in the hopes that future micro aerial vehicles (MAVs) will eventually be capable of conducting reconnaissance, search-and-rescue and environmental monitoring missions without risking human lives.

“For military missions in particular, these MAVs must be able to fly successfully through complex urban environments, where there can be tight spaces and turbulent gusts of wind,” explained researcher Tiras Lin. “These flying robots will need to be able to turn quickly. But one area in which MAVs are lacking is maneuverability.”

To address that shortcoming, Lin has been studying butterflies. 

“Flying insects are capable of performing a dazzling variety of flight maneuvers… In designing MAVs, we can learn a lot from flying insects.”

Lin used high-speed video cameras to analyze the flight dynamics of painted lady butterflies, while examining how changes in mass distribution associated with the wing flapping and body deformation of a flying insect help it engage in rapid aerial twists and turns. 

“Ice skaters who want to spin faster bring their arms in close to their bodies and extend their arms out when they want to slow down,” he said. 

”These positions change the spatial distribution of a skater’s mass and modify their moment of inertia; this in turn affects the rotation of the skater’s body. An insect may be able to do the same thing with its body and wings.”

Lin’s research seems to have already paid off, as the Johns Hopkins student recently announced a key discovery. 

To be sure, earlier studies indicated that an insect’s delicate wings possess very little mass compared to the bug’s body. As a result, scientists concluded that changes in spatial distribution of mass associated with wing-flapping did not need to be considered when analyzing an insect’s flight maneuverability and stability. 

“[However], we found out this commonly accepted assumption was not valid, at least for insects such as butterflies,” Lin confirmed. “We learned that changes in moment of inertia, which is a property associated with mass distribution, plays an important role in insect flight, just as arm and leg motion does for ice skaters and divers.”