Improvising and Adapting

John Alerding '12 makes final adjustments to his flapping wing model before capturing data to describe the movement of its wings. -- VMI Photo by John Robertson IV.

Research Project Uses Photogrammetry and 3-D Printer to Explore Flapping Wing Technology   

LEXINGTON, Va., March 7, 2012 -- Faculty and cadets at VMI have been working to improve technologies vital to the operation of a new generation of flying vehicles. The group is working in cooperation with Wright-Patterson Air Force Base in Ohio to advance the evolution UAVs -- unmanned aerial vehicles -- and their smaller cousins, MAVs -- micro air vehicles.

“Where we’re making a contribution is working with these fairly small flapping-wing type vehicles and developing the software and methodology for controlling them,” said Col. Joe Blandino, professor of mechanical engineering. “We’re a small part, but it’s a very interesting part.”

Cadet John Alerding ’12, a mechanical engineering major, worked as an intern last summer at the Air Force Institute of Technology at Wright Patterson, where he analyzed how the shape of flapping wings change as they billow.

“The importance of determining the dynamics of these wings throughout the flapping cycle is to ultimately understand the aerodynamics of the wing,” said Alerding. “The billowing membrane wing constantly changes shape throughout a flapping cycle as a result of inertial loading generated by the high acceleration of the flapping motion and the complex interaction between the membrane and the air.”

Alerding has been working on a senior design project since the beginning of the academic year to develop a computer model that will describe the motion of these flapping wings.

In January, Alerding also built a physical model that will validate the computer model. It uses an electric motor to flap a pair of wings. He employed photogrammetry, a technique that measures the relative position of reflective targets on an object with an array of digital cameras and computers. The images can then be processed to create a 3D model of the object’s real-life movement.

“The easiest, least intrusive method to accurately determine the deformation of the wing at different stages of the flapping cycle is through photogrammetry,” said Alerding. “Once the 3-D positions of certain points on the wing are determined, these positions can be compared to the same point locations on the computer model.”

Advances in photographic technology have made applications like these possible.

“It’s amazing how high-speed digital photography has opened up this field,” said Blandino. “Now we can look at not just static shapes, but moving objects as well.”

This same photogrammetry system, which includes six high speed digital cameras and seven computers, was bought in 2009 for around $140,000 with a National Science Foundation grant. It has been used to analyze the vibrations of a reflective film, the movements of a deployable boom for use in space, and the shape of bat wings in flight.

Alerding used a 3-D printer to fabricate some elements of his flapping wing model. These printers build objects by laying thin layers of polymer over one another. Getting the model to perform as he designed it was a matter of improvising and adapting.

“You have to realize that everything is not going to work perfectly the first time,” said Alerding. “You need to be just as creative [as], if not more than, when you originally designed your mechanism in order to make your design function as you want it to.”

--John Robertson IV