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Posts Tagged ‘aerodynamics’

Using hundreds of images of the sky and land, Australian researchers developed an algorithm that compares the blue sky to the red-green colors of the ground to determine the horizon. Then they outfitted a UAV with some low-resolution wide-angle cameras, so the aircraft could see 360 degrees of landscape while flying.

They took the UAV to a field and made it fly a barrel roll, a full loop and an Immelmann turn, and it didn’t crash. The aircraft’s perception of the horizon matched the researchers’ observations, according to Saul Thurrowgood, a researcher at the The Vision Centre in Queensland, Australia.

Bees make complex aerobatic maneuvers to reach pollen, communicate the location of food and scout for intruders near their hives. Although researchers are not sure how they do it, they know the bees stabilize themselves by watching the horizon. In a study last year, researchers at the University of Queensland examined honeybees landing on various surfaces, and watched the bees align their antennae nearly perpendicular with the surface before alighting.

Current aircraft use gyroscopes to determine orientation, but this can be unreliable, especially over long distances, according to Thurrowgood. A stabilization method that relies on visual cues could be more reliable. The key is finding out how low-res it can go — lower-res images can be obtained faster, but they might not be as accurate.

The method could conceivably be adopted for a wide range of aircraft, Thurrowgood said. The research group is presenting a paper on their findings this week at the 11th Australasian Conference on Robotics and Automation.

[University of Queensland]

Using computer algorithms, MIT researchers have designed a foam glider with a single motor on its tail that can perch like a bird. The work has implications for robotic planes, potentially allowing them to recharge their batteries by perching on power lines, according to MIT News.

Watch a bird careening through the trees, and you might wonder how it can suddenly stop and alight on a single branch. There are certainly no flying machines capable of such aerobatics.

It’s because birds take advantage of a phenomenon called stall -- not a word you usually want to hear in aviation.

Birds come to a stop by tilting their wings back at sharp angles. This creates turbulence and large, unpredictable whirlwinds behind the wings. If an airplane pointed its wings up in this way, it would lose lift and fall out of the sky. But MIT researchers wanted to take advantage of stall -- specifically, post-stall drag -- to help a plane come to a controlled landing.

It’s difficult to predict how the wing whirlwinds will manifest, so MIT Associate Professor Russ Tedrake, a member of the Computer Science and Artificial Intelligence Laboratory, and Rick Cory, a PhD student in Tedrake’s lab, had to model what a stall looks like.

They also found they had to create error-correction controls to tweak the glider’s path in case it deviated from its flight plan. Using algorithms developed at MIT, they were able to calculate the degree of deviation that the controls could compensate for, MIT News says. The result is a model that looks like a series of tubes, which includes all the possible trajectories and the tolerance of the error-correction controls.

Once the glider is launched, it keeps checking its position and executing the command that corresponds to the flight path “tube” it is in.

To stop, it tilts itself up in a dangerous-looking stall and wafts forward, ultimately reaching a tiny perch, where it alights.

The team used wall-mounted cameras and an external computer to monitor the glider’s position and run the control algorithms. To expand the technology to robotic airplanes that interest the Air Force, more powerful on-board processors would be needed. Meanwhile, Tedrake's lab has already begun to address moving the glider's location sensors onboard, according to CSAIL.

[MIT]

The German Aerospace Centre (DLR) is developing a heat-resistant, 8-sided rocket that can re-enter the atmosphere without breaking up or suffering much damage, according to The Local. It would be the only rocket capable of guiding itself home.

The flat-sided nose cone has eight faces, which provides better aerodynamics and cheaper construction than a round nose. Last week, DLR scientists unveiled the 8-foot nose cone for the SHEFEX II program, short for “sharp-edged test flight,” at the DLR headquarters near Munich. It will make its first test flight next March in Australia.

Hendrik Weihs, the DLR’s project leader, says the goal is to create, step-by-step, a reusable space glider. Germany funded the $16 million project.

It would be an improvement over current ballistic systems like those used by Russia and China, which are incapable of a controlled re-entry.

The SHEFEX II rocket could be controlled as it descends from about 60 miles above Earth. Once it reaches roughly 12 miles, a parachute would guide it home.

One major problem is keeping the nose cool, and that’s where the multiple facets come in. They will deflect the heat of re-entry so that only the apex will get extremely hot. What’s more, gas will be pushed through the apex to act as a buffer.

After initial unmanned tests in the Australian Outback next spring, it’s possible DLR could stage a manned flight, with cooperation from the European Union and the U.S., Weihs says.

[The Local]

A new blimp built in Switzerland uses artificial muscles to glide through air as a fish moves through water, and it doesn't require engines or noisy propellers to do it.

The Airfish is about 26 feet long and looks like a giant flying trout. Airfish is filled with helium and made of special polymers that make it move.

The designers, led by Christa Jordi and colleagues from EMPA, the Swiss federal laboratories for materials testing and research in Dübendorf, replaced traditional motors with swaths of acrylic polymers on each side of the Airfish. The polymers connect to carbon electrodes, and when a voltage moves across them, the electrodes are attracted to each other, compressing the polymers. The Airfish is forced to flex like a contracting muscle. By alternating the voltages applied to each side of the vehicle, the team can make the ship shimmy like a fish. Membranes on the tail move it back and forth, too.

The team modeled the Airfish after rainbow trout because they're versatile swimmers, but aren't especially quick or agile. They programmed software to mimic the rhythm of the trout's motion, and ran it on a computer attached to lithium-polymer batteries in the airship's gondola, New Scientist reports.

The combined motion of the tail and the body make the Airfish move forward at roughly 1.5 feet per second, akin to a slow walking speed. Airfish studies are reported in the journal Bioinspiration & Biomimetics.

More work needs to be done to determine how the Airfish will act in certain windy conditions. But it's so graceful and quiet that the researchers hope TV broadcasters might favor it for capturing footage of sporting events. Here's to the Goodyear Airfish.

[New Scientist]