Analyzing butterfly flight for better MAV maneuverability

Although micro aerial vehicles (MAVs) could be very useful in search and rescue, exploration and environmental monitoring missions, due to their small size they still lack maneuverability. Johns Hopkins University (JHU) engineers are using high-speed video cameras to figure out how butterflies manage to fly with amazing grace and agility in order to improve maneuvering capabilities of these small airborne robots.

“This research is important because it attempts to not only address issues related to bio-inspired design of MAVs, but it also explores fundamental questions in biology related to the limits and capabilities of flying insects”, said Rajat Mittal, a professor of mechanical engineering who supervises the research.

The high-speed video research was conducted by Tiras Lin, a Whiting School of Engineering undergraduate, who observed 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”, said Lin. “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.”

In collaboration with graduate student Lingxiao Zheng, Lin used three video cameras capable of recording 3,000 one-megapixel images per second to mathematically document the trajectory and body conformation of painted lady butterflies which flap their wings about 25 times per second. JHU researchers anchored the cameras in fixed positions and focused them on a small region within a dry transparent aquarium tank in order to get three-dimensional data and analyze the movement of the insects’ wings and bodies in minute detail.

“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”, said Lin.

These findings oppose earlier findings from other researchers who concluded that changes in spatial distribution of mass associated with wing-flapping did not need to be considered in analyzing an insect’s flight maneuverability and stability, at least for insects such as butterflies.

After providing new data for MAV designers and may be useful to biologists who study insect flight dynamics, Lin plans to use the same technique to reveal how fruit flies manage to land upside down on perches.