MMaterialsgateNEWS 2016/11/07

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'Morphing' wing offers new twist on plane flight and manufacturing




The new concept is described in the journal Soft Robotics, in a paper by Neil Gershenfeld, director of MIT's Center for Bits and Atoms (CBA); Benjamin Jenett, a CBA graduate student; Kenneth Cheung PhD '12, a CBA alumnus and NASA research scientist; and four others.

Researchers have been trying for many years to achieve a reliable way of deforming wings as a substitute for the conventional, separate, moving surfaces, but all those efforts "have had little practical impact," Gershenfeld says. The biggest problem was that most of these attempts relied on deforming the wing through the use of mechanical control structures within the wing, but these structures tended to be so heavy that they canceled out any efficiency advantages produced by the smoother aerodynamic surfaces. They also added complexity and reliability issues.

By contrast, Gershenfeld says, "We make the whole wing the mechanism. It's not something we put into the wing." In the team's new approach, the whole shape of the wing can be changed, and twisted uniformly along its length, by activating two small motors that apply a twisting pressure to each wingtip.

Like building with blocks

The basic principle behind the new concept is the use of an array of tiny, lightweight structural pieces, which Gershenfeld calls "digital materials," that can be assembled into a virtually infinite variety of shapes, much like assembling a structure from Lego blocks. The assembly, performed by hand for this initial experiment, could be done by simple miniature robots that would crawl along or inside the structure as it took shape. The team has already developed prototypes of such robots.




This research, says Cheung, "presents a general strategy for increasing the performance of highly compliant -- that is, 'soft' -- robots and mechanisms," by replacing conventional flexible materials with new cellular materials "that are much lower weight, more tunable, and can be made to dissipate energy at much lower rates" while having equivalent stiffness.

Saving fuel, cutting emissions

While exploring possible applications of this nascent technology, Gershenfeld and his team consulted with NASA engineers and others seeking ways to improve the efficiency of aircraft manufacturing and flight. They learned that "the idea that you could continuously deform a wing shape to do pure lift and roll has been a holy grail in the field, for both efficiency and agility," he says. Given the importance of fuel costs in both the economics of the airline industry and that sector's contribution to greenhouse gas emissions, even small improvements in fuel efficiency could have a significant impact.


The "skin" of the wing also enhances the structure's performance. It's made from overlapping strips of flexible material, layered somewhat like feathers or fish scales, allowing for the pieces to move across each other as the wing flexes, while still providing a smooth outer surface.

The modular structure also provides greater ease of both assembly and disassembly: One of this system's big advantages, in principle, Gershenfeld says, is that when it's no longer needed, the whole structure can be taken apart into its component parts, which can then be reassembled into something completely different. Similarly, repairs could be made by simply replacing an area of damaged subunits.

"An inspection robot could just find where the broken part is and replace it, and keep the aircraft 100 percent healthy at all times," says Jenett.

Following up on the successful wind tunnel tests, the team is now extending the work to tests of a flyable unpiloted aircraft, and initial tests have shown great promise, Jenett says. "The first tests were done by a certified test pilot, and he found it so responsive that he decided to do some aerobatics."

Some of the first uses of the technology may be to make small, robotic aircraft -- "super-efficient long-range drones," Gershenfeld says, that could be used in developing countries as a way of delivering medicines to remote areas.

Source: Massachusetts Institute of Technology - 03.11.2016.

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