Members of the MAV team hold different versions of their mini-airplane.
One week remained before the ninth annual International Micro-Aerial Vehicle competition in South Korea, and the Lehigh team was running out of time.
The six mechanical engineering students on the Lehigh MAV squad had spent most of the school year preparing for the contest.
They had built a tiny plane weighing 37 grams and measuring six inches wide, and they had tested it on every campus venue imaginable, flying it in Packard Lab Auditorium, moving to the lawns of the Asa Packer Campus, and finally challenging the larger fields and stiffer headwinds of Goodman Campus.
But as the contest loomed, the students were far short of meeting the contest’s main requirement – that they fly their MAV for 15 uninterrupted minutes.
Despite hours in the lab and on the field and hours of tinkering, adjusting and refining, the Lehigh MAV team, in their best effort, had managed to keep their tiny plane in the air for just two minutes and 45 seconds – less than one-fifth of the required time – before they departed for Korea.
Permeating the last uninvestigated realm of flight
Micro-aerial vehicles, says Richard Kurz ’05, captain of Lehigh’s 2005 MAV team, represent the “last uninvestigated realm of flight.” The American military is keenly interested in the lightweight mini-planes, he says, because of the potential they hold for “expendable surveillance.”
One day, military leaders hope, MAVs equipped with cameras will fly into unfriendly territory, snap photos of enemy troops and terrorists, and send information back to soldiers who otherwise would have to risk life and limb to learn the same data.
The MAV competition holds contests for surveillance, endurance and ornithoptery. The object of the surveillance contest is to direct a MAV equipped with a mini-camera to fly half a mile, take a clear photo of a symbol on the ground, and transmit the photo back to the navigator. Ornithopters, which have flapping wings like insects and birds, must fly in an elliptical or figure-eight pattern, around a series of poles.
The endurance contest, which the Lehigh MAV team entered, rewards the smallest MAVs that stay aloft the longest times – up to 15 minutes in the air.
Lehigh teams first entered international MAV competitions in 2002. The 2005 Lehigh squad was not as large, as experienced or as well-funded as many teams competing in South Korea, but it made up for its shortcomings.
After designing a computer-aided model of its plane, the Lehigh team machined a thermo-forming mold and used a waterjet cutter to trim the wings. They fitted their MAV with a tiny lithium battery, a miniature propeller, and a radio-controlled motor not much bigger than a thimble.
To optimize the MAV’s lift, the students designed the largest possible wingspan. To maximize roll and pitch control, they combined two control features – elevators and ailerons – into one set of elevons. To reduce weight, they made the elevons from carbon fibers and the wings from Depron, a meat-tray material used by supermarkets.
The students spent hours in the lab and on the flying field re-designing their plane, redoing calculations, and tinkering with servos and receivers. They did their work as part of an independent study course taught by Joachim Grenestedt, an associate professor of mechanical engineering and mechanics at Lehigh.
Trying to navigate a dinghy battered by ocean waves
Flying a MAV is like piloting a life-size airplane – the more flight hours you log, the better you perform. Thus the team designated Pat Boyle ’05 as pilot and gave him several store-bought remote control “trainer planes” to practice with. Angela Capece ’05 was named MAV launcher so she could perfect the art of throwing the craft directly into the wind without unintentional flicks or curves.
The team quickly learned that a larger plane is vastly easier to control than a tiny plane, which, like a dinghy battered by ocean waves, reacts to every slight change in wind pressure.
They also noticed differences in wind conditions between the Goodman and Asa Packer campuses.
“The Goodman Campus actually sits in a basin,” Boyle said between test flights on a breezy day in late April, “which causes the wind gusts to be stronger here than they are on the main campus.”
“We’re also fighting Mother Nature doing this at the hottest time of day,” said Kurz, “when the wind is strongest.”
The MAV team’s goal, the students explained, was the same as a real pilot’s – to achieve enough altitude to be able to practice maneuvers.
“We have to get the plane to the right altitude for an extended period of time before we can do any maneuvers,” said Boyle. “We have to learn how to recover from gusts of wind when the plane is flying in a circle.”
On several successive test flights, the MAV nosedived seconds after leaving Capece’s hand. Finally, an adjustment to the center of gravity allowed the MAV to rise into the air and the tiny craft zigged and zagged lazily from left to right and back, staying aloft for more than 40 seconds and crossing the road before it fell to the lawn.
“It’s really gratifying when it flies,” said Kurz. “I suppose it’s like watching your kid walk for the first time.”
Persistence and quality equals the most promising MAV
The plane that ended up being "most promising" in Korea.
As the spring semester progressed, the MAV team members fine-tuned their aircraft and raised funds for the trip to Korea. They drove twice to Philadelphia to give a presentation and to consult with engineers at Boeing, which gave the team half of its $11,000 budget.
In March, with their best flight times barely topping a minute, several team members flew to Tucson to seek tips from seasoned MAV pilots at the University of Arizona.
In April, Kurz gave a presentation on the MAV team’s work at the engineering college’s undergraduate Engineering Research Symposium. He won third place and donated his prize money to the team.
On May 16, Capece, Boyle, Russ Newbold ’06 and Tom Gilronan ’06 boarded a plane for South Korea. Kurz and Jonathan Winter ’06 could not attend. Kurz is manager of the Lehigh University Choir, which toured Germany and the Czech Republic in May. Winter, a member of Lehigh’s crew team, stayed behind to compete in a meet.
On May 20, at Seoul’s Konkuk University, which hosted the MAV competition, the Lehigh team was given five tries to achieve the elusive 15-minute benchmark. The first three tries looked anything but promising, as the team recorded times of two and a half minutes, one minute, and less than a minute.
At that point, the team paused to talk things over with members of other teams and to make adjustments to the rudder and the elevons. On the advice of one competitor, Boyle eased off on the throttle, using it mostly to control altitude.
The advice and the adjustments paid off when the Lehigh MAV flew six minutes on its fourth try.
Then, says Boyle, “we got lucky.” The weather, which had started off overcast, chilly and windy in the morning changed, and the winds calmed.
On their fifth try, Lehigh’s MAV team members kept their craft aloft for 15 minutes. The team did not win first place in the endurance contest, but it was one of only three teams out of the nine competing to break the 15-minute mark.
“Last year, we flew our plane for 30 seconds and won an award for prettiest MAV,” says Kurz. “This year, we achieved a 15-minute flight and we won an award for most promising MAV.”
The Lehigh team will enter next year’s MAV competition with a veteran squad. Boyle and Kurz are staying a fifth year at Lehigh, Boyle to start on a graduate degree and Kurz to finish a second B.S. in electrical engineering. Winter, Newbold and Gilronan will be seniors. Capece, the only non-returning member, has taken a job with Bettis Atomic Power Lab in Pittsburgh.
“We’re looking for new members,” says Boyle. “We’re going to hold an in-house competition this fall.”
What lessons did the students learn?
“It really helps to get another point of view,” says Boyle. “We were looking at the problem so long that we could no longer see what was wrong. Going to Arizona was a big jumping point. It gave us new eyes to see the problem when we were banging our heads against the wall.”
“Persistence,” says Kurz in a word. “We were missing something really small. The airplane wasn’t flying and everyone said it should.
“When I got back from Europe, there was an e-mail waiting for me. When I saw that we stayed in the air 15 minutes, I was pretty excited. It was amazing to see how much progress we’d made. Our goal was 15 minutes and we made it.”
“The students were ingenious,” said Phil Dunford, director of Rotorcraft Systems Engineering for Boeing in Philadelphia.
“They demonstrated valid, real-word engineering techniques in their approach to the MVA project. We’re impressed with the quality and detail of their work.”
Posted on Thursday, July 28, 2005