(Credit:
MIT)
Micro Air Vehicles (MAVs) may be small, but they're costly, so researchers have devised ways for them to fly in GPS-denied urban and indoor environments where they could otherwise get lost or crash.
Existing highly-precise, non-GPS navigation units are too large, heavy, and expensive to install on an MAV. But the Robust Robotics Group at MIT's Computer Science and Artificial Intelligence Laboratory addressed this problem by developing algorithms that allow a miniature robo-quadrocopter to estimate their relative position, identify a clear path and then fly through dense air space.
"The size, weight, and budget limitations of micro air vehicles (MAVs) typically preclude high-precision inertial navigation units that can mitigate the loss of GPS," according to the MIT release. "We are developing estimation and planning algorithms that allow MAVs to use environmental sensors such as range finders to estimate their position, build maps of the environment, and fly safely and robustly."
The laser range-finder estimates the MAV's position, yaw angle, and altitude information from surrounding landscape out to about a 12 foot range.
In recent tests, the MAV navigated cluttered offices and unknown hallways and found its way through other unmapped environments by using its onboard laser scanners and cameras to build its own map, according to MIT.
MIT's secret sauce is based on the Belief Roadmap (BRM) algorithm, which performs searches in the MAV's "information space" to determine the "minimum expected cost path for the vehicle," according to a learned paper on the subject. Anything that mentions the Unscented Kalman Filter is worth a click.(PDF)
Nekton Research's Transphibian uses Nektor flexible fins for both propulsion and control.
(Credit: Nekton Research)One contender for that task is the Transphibian, a 3-foot-long autonomous underwater vehicle (AUV) created by Durham, N.C.-based Nekton Research. The Transphibian is designed to identify mines and map the seabed by swimming and crawling through places where troops or ships are likely to follow. Soon, the company hopes to field a type of "kamikaze" suicide model armed with 14 pounds of plastic explosive that can self-destruct and take nearby mines with it. Meanwhile, the human operator stays safely behind the joystick.
This class of AUV is expected to "replace mine-sweeping ships and perform dangerous jobs now done by specialized divers," according to the Naval Surface Warfare Center in Panama City Beach, Fla. The military will spend $50 million acquiring AUVs in the next five years, according to one estimate.
AUV mine clearing is not only safer, according to proponents; it's about 20 times faster.
Case in point: an AUV mine-clearing operation in Iraq allowed the U.S. Navy to clear nearly a square mile of harbor in 16 hours--something that would have taken divers 21 days working without the technology, the Navy told the Associated Press.
No easy task: "The closer in you get to any port or harbor, the greater amount of clutter you will encounter--tires, rocks, coral reefs," a Navy spokesman told the AP. "To screen out all that clutter is a huge job and it takes some very, very technologically advanced sensors."
Still, advances in autonomous vehicles are moving so fast, there's no way the Transphibian class will remain state-of-the-art for long. For instance, it uses flexible fins for both propulsion and control, and hybrid gliders for thrust, completely bypassing exposed props. These innovations allow it to clamber over debris and operate in rough water, according to the manufacturer.
However the Navy is spreading its bets by funding another project at MIT's Bio-Instrumentation Systems Laboratory. Scientists there hope to leapfrog other AUVs and produce one "that can hover, turn, store energy and do all the things a fish does." It does this by mimicking the fin action of the bluegill sunfish, according to the university. The scientists have reportedly already successfully tested a fin made from a thin, flexible, cutting-edge, conductive polymer that replicates the fin motions that propel the sunfish.
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