A newly developed wing architecture could greatly simplify the manufacturing process and reduce fuel consumption by improving the wing’s aerodynamics. It is based on a system of tiny, lightweight subunits that could be assembled by a team of small specialized robots, and could ultimately be used to build the entire airframe. Credit: Kenneth Cheung/NASA
High-tech wizardry by MIT and NASA engineers will allow some aircraft to return to their roots, with a new kind of bendable, “morphing” wing. Wright brothers accomplished their first powered flight more than a century ago, and controlled the motion of their Flyer 1 aircraft using wires and pulleys that bent and twisted the wood-and-canvas wings. This system was quite different than the separate, hinged flaps and ailerons that have performed those functions on most aircraft ever since.
The new wing architecture, which could greatly simplify the manufacturing process and reduce fuel consumption by improving the wing’s aerodynamics and agility, is based on a system of tiny, lightweight subunits that could be assembled by a team of small specialized robots, and could be used to build the entire airframe. The wing would be covered by a “skin” made of overlapping pieces that might resemble scales or feathers.
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 2 small motors that apply a twisting pressure to each wingtip. The basic principle behind the new concept is the use of an array of tiny, lightweight structural pieces, “digital materials,” that can be assembled into a virtually infinite variety of shapes. 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.
The individual pieces are strong and stiff, but the exact choice of the dimensions and materials used for the pieces, and the geometry of how they are assembled, allow for a precise tuning of the flexibility of the final shape. For the initial test structure, the goal was to allow the wing to twist in a precise way that would substitute for the motion of separate structural pieces (such as the small ailerons at the trailing edges of conventional wings), while providing a single, smooth aerodynamic surface.
Other Applications: this method could lead to robotic arms and legs whose shapes could bend continuously along their entire length, rather than just having a fixed number of joints. 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.
Wind-tunnel tests of this structure showed that it at least matches the aerodynamic properties of a conventional wing, at about 1/10 the weight. 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, 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 different. Similarly, repairs could be made by simply replacing an area of damaged subunits.
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. http://news.mit.edu/2016/morphing-airplane-wing-design-1103
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