Imagine an aircraft small enough to fit in the palm of your hand, yet able to fly into damaged buildings to search for survivors or onto battlefields to detect toxic chemicals.
"Micro Air Vehicles" capable of these and other tasks are the goals for a new program proposed by the Defense Advanced Research Projects Agency (DARPA). The technical challenges of building such air vehicles will be the focus for a two-day conference at the Georgia Institute of Technology February 19-20.
The agenda for the "First International Conference on Emerging Technologies for Micro Air Vehicles" includes 17 technical presentations from more than a dozen organizations studying the rapidly-expanding area, as well as presentations from officials of DARPA and the Defense Airborne Reconnaissance Office (DARO).
"When you approach technical people with this idea, their first response is that you cannot build an aircraft this small and make it useful," said Dr. Sam Blankenship, conference co- chair and coordinator of the "MicroFlyer" program, the Georgia Institute of Technology's micro air vehicle effort. "But many people, including us, think you can do this."
Designers of micro air vehicles face formidable challenges and a host of unknowns.
No flying vehicles of this size currently exist, meaning designers must look to birds and insects for information about flight principles on a scale this small. Researchers believe aerodynamic principles governing aircraft with six-inch wings may be significantly different from those that have guided aircraft design since the Wright Brothers' 1903 airplane.
"There may be something about very small sizes that changes the aerodynamics," Blankenship explained. "The Wright Flyer made smaller and smaller and smaller ultimately won't work, and we'll probably have to use some other method to get efficient motion in an aircraft this small. We may have to learn from insects and birds."
Beyond basic aerodynamic techniques, severe weight restrictions demand new types of flight controls, power sources, propulsion systems and avionics to fit within the 50 grams (two ounces) allowed for the vehicle and its payload.
Full-sized aircraft use motors and hydraulic actuators to move wing and tail structures that provide directional control, for instance. Because of the weight associated with those devices, however, MicroFlyers must use radically different control techniques.
Georgia Tech engineers are developing innovative control concepts. Research Engineer Robert Roglin in the Georgia Tech Research Institute (GTRI) is investigating electrically-actuated piezoelectric structures that differentially alter lift. Robert J. Englar, a principal research engineer in GTRI, is applying techniques for directing engine thrust across the wings.
Researchers at several institutions are studying tiny jet turbine engines, pulsejets, ducted fans and other concepts for propulsion. But since the MicroFlyers could contact humans during their search missions, whirring rotor blades or exposed propellers may be too dangerous to use.
Batteries or other electrical sources offer another challenge, as do guidance and navigation systems -- and the tiny payloads that will transmit television images or sniff the air for contaminants. Recent advances in micro electro-mechanical systems (MEMS) and microelectronics technology give engineers confidence that systems that tiny could one day be practical.
At Georgia Tech, for instance, researchers have been working to integrate multiple functions into single chips. Progress to date has demonstrated integrated image acquisition, processing and data compression, including demonstration of optical-through- wafer interconnects. Drs. Joy Laskar, Nan Marie Jokerst, Martin Brooke, April Brown and Scott Wills in the School of Electrical and Computer Engineering make up this project team developing the chips.
Researchers including Nile Hartman and Bob Schwerzel in GTRI are working on the area of miniaturized integrated-optic chemical and biological sensor systems.
Though flown under human control, the MicroFlyers must be independent enough to avoid obstacles and maintain stable flight by themselves.
"Flying a remote-controlled helicopter is extremely difficult, and even experienced people crash them all the time," Blankenship said. "These aircraft will need autonomy so we don't have to spend a lot of time training people to operate them."
Since they may search environments containing toxic chemicals or biological hazards, the MicroFlyers must also be inexpensive enough to be thrown away. Designers are aiming at a $1,000 per-unit cost for the expendable vehicles.
The effort to design MicroFlyers involves many different technical challenges, so Blankenship believes only organizations with broad interdisciplinary expertise will be successful in building them.
"We're not really sure what will turn out to be the most difficult challenge," he added. "Nobody has ventured into this realm before."
Speakers at the conference include Dr. James McMichael, proposed director of the micro Air Vehicle (microAV) program in the Defense Advanced Research Projects Agency, and Col. Michael Francis, former director of the microAV program.
Information about the conference can be found on the World Wide Web
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