Flapping micro air vehicles inspired by swifts

Flapping micro air vehicles inspired by swifts

  3:50:00 PM    Science Lover

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Scientists have designed a micro aircraft that will be able to flap, glide and hover like a bird.

This shows the wake of a swift in slow forward flight, the new design mimics these birds to improve MAV performance. Credit: William Thielicke

Researchers from the Biomimetics-Innovation-Centre in Germany have been inspired by birds to produce a new versatile design of Micro air vehicle (MAV) that combines flapping wings, which allow it to fly at slow speeds and hover, with the ability to glide, ensuring good quality images from any on-board camera.

"In birds, the combination of demanding tasks like take-off, travelling long distances, manoeuvring in confined areas and landing is daily practice," explains PhD researcher Mr. William Thielicke, who is presenting this work at the Society for Experimental Biology Annual Conference in Glasgow on the 2nd of July.

Micro air vehicles (MAVs) are small unmanned
aircraft, often used for rescue or reconnaissance
missions in areas where it would be dangerous
or impractical for humans to go. Credit: William
Thielicke

This innovative design was inspired by one bird in particular, the swift. "We know that swifts are very manoeuvrable and they can glide very efficiently. So we thought these birds would be a very good starting point for an energy efficient flapping-wing MAV," says Mr. Thielicke.

While fixed wing MAVs are energy efficient, their manoeuvrability is low. The new design would allow the flapping wing MAV to glide, improving energy efficiency and ensuring good images but when needed it can also slow its flight and manoeuvre in confined spaces.

"Although the models are not yet ready to be used, initial tests are positive and we hope that this design will combine the best of both worlds," says Mr. Thielicke.

Provided by Society for Experimental Biology

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A Plane That Lands Like a Bird

A Plane That Lands Like a Bird

  6:22:00 AM    Science Lover

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Everyone knows what it's like for an airplane to land: the slow maneuvering into an approach pattern, the long descent, and the brakes slamming on as soon as the plane touches down, which seems to just barely bring it to a rest a mile later. Birds, however, can switch from barreling forward at full speed to lightly touching down on a target as narrow as a telephone wire. Why can't an airplane be more like a bird?

A smoke visualization still of the actual vortex wake behind our glider during a free-flight high angle of attack landing. (Credit: Jason Dorfman/CSAIL)

MIT researchers have demonstrated a new control system that allows a foam glider with only a single motor on its tail to land on a perch, just like a pet parakeet. The work could have important implications for the design of robotic planes, greatly improving their maneuverability and potentially allowing them to recharge their batteries simply by alighting on power lines.

Birds can land so precisely because they take advantage of a complicated physical phenomenon called "stall." Even when a commercial airplane is changing altitude or banking, its wings are never more than a few degrees away from level. Within that narrow range of angles, the airflow over the plane's wings is smooth and regular, like the flow of water around a small, smooth stone in a creek bed.

A bird approaching its perch, however, will tilt its wings back at a much sharper angle. The airflow over the wings becomes turbulent, and large vortices -- whirlwinds -- form behind the wings. The effects of the vortices are hard to predict: If a plane tilts its wings back too far, it can fall out of the sky. Hence the name "stall."

The smooth airflow over the wings of a normally operating plane is well-understood mathematically; as a consequence, engineers are highly confident that a commercial airliner will respond to the pilot's commands as intended. But stall is a much more complicated phenomenon: Even the best descriptions of it are time-consuming to compute.

Reap the whirlwind

To design their control system, 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 who defended his dissertation this spring, first developed their own mathematical model of a glider in stall. For a range of launch conditions, they used the model to calculate sequences of instructions intended to guide the glider to its perch. "It gets this nominal trajectory," Cory explains. "It says, 'If this is a perfect model, this is how it should fly.'" But, he adds, "because the model is not perfect, if you play out that same solution, it completely misses."

So Cory and Tedrake also developed a set of error-correction controls that could nudge the glider back onto its trajectory when location sensors determined that it had deviated from it. By using innovative techniques developed at MIT's Laboratory for Information and Decision Systems, they were able to precisely calculate the degree of deviation that the controls could compensate for. The addition of the error-correction controls makes a trajectory look like a tube snaking through space: The center of the tube is the trajectory calculated using Cory and Tedrake's model; the radius of the tube describes the tolerance of the error-correction controls.

The control system ends up being, effectively, a bunch of tubes pressed together like a fistful of straws. If the glider goes so far off course that it leaves one tube, it will still find itself in another. Once the glider is launched, it just keeps checking its position and executing the command that corresponds to the tube in which it finds itself. The design of the system earned Cory Boeing's 2010 Engineering Student of the Year Award.

The measure of air resistance against a body in flight is known as the "drag coefficient." A cruising plane tries to minimize its drag coefficient, but when it's trying to slow down, it tilts its wings back in order to increase drag. Ordinarily, it can't tilt back too far, for fear of stall. But because Cory and Tedrake's control system takes advantage of stall, the glider, when it's landing, has a drag coefficient that's four to five times that of other aerial vehicles.

From spy planes to fairies

For some time, the U.S. Air Force has been interested in the possibility of unmanned aerial vehicles that could land in confined spaces and has been funding and monitoring research in the area. "What Russ and Rick and their team is doing is unique," says Gregory Reich of the Air Force Research Laboratory. "I don't think anyone else is addressing the flight control problem in nearly as much detail." Reich points out, however, that in their experiments, Cory and Tedrake used data from wall-mounted cameras to gauge the glider's position, and the control algorithms ran on a computer on the ground, which transmitted instructions to the glider. "The computational power that you may have on board a vehicle of this size is really, really limited," Reich says. Even though the MIT researchers' course correction algorithms are simple, they may not be simple enough.

Tedrake believes, however, that computer processors powerful enough to handle his and Cory's control algorithms are only a few years off. In the meantime, his lab has already begun to address the problem of moving the glider's location sensors onboard, and although Cory will be moving to California to take a job researching advanced robotics techniques for Disney, he hopes to continue collaborating with Tedrake. "I visited the air force, and I visited Disney, and they actually have a lot in common," Cory says. "The air force wants an airplane that can land on a power line, and Disney wants a flying Tinker Bell that can land on a lantern. But the technology's similar."

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Flying car takes off !

Flying car takes off !

  9:27:00 PM    Science Lover

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The first flying automobile – equally at home in the sky and on the road – took to the skies on Wednesday. Dubbed the Transition, the two-seat aircraft – designed by US-based company Terrafugia (terra-FOO-gee-ah), Inc – is capable of taking off and landing at local airports, and even being driven on any road.

In fact, transforming from plane to car takes the pilot less than 30 seconds.

“This breakthrough changes the world of personal mobility,” said Carl Dietrich, CEO of Terrafugia – a name that means “escape from land” in Latin.

“Travel will now become a hassle-free, integrated land-air experience. A pilot who encounters bad weather could simply land at a small airport and continue the trip by road. It’s what aviation enthusiasts have been striving for since 1918,” he said.

Dietrich claimed that Transition is capable of flying 720 km on a single tank of petrol, at a speed of 180kmph.

While on land, the vehicle boasts of top speeds of up to 150kmph, he added.

For its first flight, the Transition was flown by Phil Meteer, Colonel, USAFR at Plattsburgh International Airport in New York.

Categorised as a Light Sport Aircraft, the Transition will now undergo additional advanced flight and drive testing, and a pre-production prototype will be built and certified before first delivery.

Dietrich said he had already received 40 orders despite an expected price of $2,00,000 (Rs 1 crore approx). Still, he accepted concerns over its price.

Left: Terrafugia CEO Carl Dietrich refuels the petrol-based Transition flying car at a
regular petrol pump Right: The Transition at take-off

“For an airplane that’s very reasonable, but for a car that’s very much at the high end,” he admitted.

Fabricated out of modern composite materials, the plane has front wheel drive on the road and a propeller for flight. Both the modes are powered by unleaded petrol from a regular pump.

Also, with its wings folded, it can fit in an ordinary garage or parking space.

“This is the first really integrated design where the wings fold up automatically and all the parts are in one vehicle,” Dietrich said.

As for learning to fly, the company CEO believed that almost anyone could become a pilot in as little as 20 hours of flight time in a Transition-specific course.

“Existing pilots,” he said, “could get comfortable quickly with the familiarisation training included with every Transition delivery.”

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