Stabilizing MEMS system lifts hovering vehicle’s chances

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Oct. 19, 2004 – It can hover. It can spy. Now, if it can only keep quiet. Honeywell International Inc. successfully completed demonstration flight tests in August for an aerial surveillance vehicle designed to scope out places too dangerous for soldiers. Called an organic air vehicle (OAV), the doughnut-shaped aircraft proved it could take off vertically, dart about, hover over a point of interest, redirect itself and land.

It’s part of a series of unmanned vehicles being developed through the Defense Advanced Research Projects Agency (DARPA) to gather intelligence on enemies without putting lives at risk. Video cameras mounted for forward and downward viewing relay information to military personnel miles away. The OAV also can carry sensors to monitor hazardous materials or mines.

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But keeping the OAV from nose-diving during its aerial acrobatics has been a multiyear challenge for designers. Honeywell drew on its experience with MEMS technology to create a resilient system that can withstand buffeting winds, rain and other jarring conditions.

“It is extremely hard to stabilize,” said Ben Simmons, vice president of Defense and Space Electronic Systems Surface Programs at Honeywell. “MEMS have been a key enabler of the whole technology, with their light weight and small size.”

Honeywell’s MEMS gyros and accelerometers have provided stability and control in products as diverse as aircraft and missiles. The OAV uses a MEMS inertial measurement system along with a global positioning system receiver and a processor for flight management.

The OAV team also needed to develop sophisticated software that would be compatible with the sensor platform, according to Vaughn Fulton, Honeywell’s program manager for unmanned aerial vehicles.

The OAV gets its hovering capability from a fan placed in its center, Fulton said. Tucking the fan blades inside the vehicle improves safety, too, he said. “The key attribute of the ducted fan is thrust, and it’s safer than the three rotors typically employed in a hovering craft,” Fulton said.

Honeywell tested the vehicle at the U.S. Army McKenna Military Operations in Urban Terrain grounds at the Soldier Battlefield Lab in Fort Benning, Ga., and at Honeywell’s facilities in Minneapolis. It functioned in the cold northern climate as well as hot and humid southern weather, Fulton said.

DARPA awarded two $3-million contracts in 2001 to teams led by Morris Township, N.J.-based Honeywell and Micro Craft Inc. in California. The initial program called for a demonstration that the OAV is a viable technology, Fulton said. Honeywell is seeking a second DARPA award to develop a larger and more robust vehicle. Fulton describes the current model as being similar “to a cut-off trash can.”

Engineers still must overcome one hurdle before the OAV can be a contender for the military. The OAV fails as a stealthy device because fan and motor noise announce its approach, giving would-be enemies time to react.

“It’s an acoustics challenge,” Fulton said, but one that his team is prepared to tackle. “It’s an extremely noisy platform.”

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