U.Va. Engineering UnBound

UNBOUND Fall 2012

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Professor of Mechanical Engineering Hillary Bart-Smith and her team at the Bio-Inspired Engineering Research (BIER) lab have been designing, building and refining a prototype submersible robot that not only mimics one of nature's smartest and most elegant swimmers but could also revolutionize underwater propulsion as we know it. "There's no better place to look for solutions T to this than nature, which has optimized its designs over millions of years," says graduate research assistant Trevor Kemp (MAE '06) of the project's inspiration: the manta ray. "Everything we know about manta rays hey say imitation is the highest form of flattery, and if that's true, then a certain marine creature has a lot to smile about these days. For the past few years, Associate indicates that they swim efficiently, are highly maneuverable and stealthy, and show good burst acceleration," he adds. "Additionally, batoid rays, in general, seem to be a scalable platform, because we see some species as small as about one foot in wingspan, and manta rays can be more than 20 feet in wingspan." The design was originally inspired by a in active tensegrity structures have taken this project to the point where we are close to truly mimicking how rays swim," says Bart-Smith of the cable-and-rod network that's embedded in CREATE SOLVE EMPOWER from a National Science Foundation CAREER grant and the David and Lucile Packard Foundation, and a multidisciplinary team of marine biology, neural control, hydrodynamics, hydroacoustics, electro-active materials and mechanical engineering researchers from four universities (SEAS, West Chester University, UCLA and Princeton), Bart-Smith and her team have now been able to take the idea to new heights — or depths, rather. "Our theoretical and experimental advances diving trip in Australia taken by Princeton University Professor of Mechanical and Aerospace Engineering (and project collaborator) Alexander Smits, where he was struck by the creature's maneuverability and speed. Smits began experimenting with mechanical applications of manta ray-inspired shapes in his lab (where Bart-Smith worked before coming to Virginia) several years ago, but the research only really got going when the Office of Naval Research awarded her and her team at the Engineering School a $6.5 million grant in 2008. Thanks to that grant, additional funding the prototype's pectoral fins to reproduce the undulations that give rays their renowned thrust. "Couple this with advances in computational fluid dynamic modeling, and we can now start exploring questions of both how and why they swim the way they do." Besides swim-testing the Mantabot (as the prototype has been nicknamed), the team has been using video and CT scans to study and compare the internal morphology and fluid dynamics of real manta rays with the prototype at West Chester University Marine Biology Professor Frank Fish's (yes, that's his real name) lab to refine the design. Once they figure out how to program it to swim with the speed, agility and endurance of a real ray, Bart-Smith believes the design will be "the ideal platform for the next generation of underwater vehicles." According to BIER lab nanoporous materials researcher Jianzhong "Joe" Zhu, who's in charge of fabrication and testing of the Mantabot, applications for such an autonomous vehicle might include searching for and rescuing lost swimmers, detecting underwater mines, pollution monitoring, surveillance and locating submarines. But it's easy to see how the impact of this novel propulsion design could easily go far beyond these relatively basic tasks. "As we work toward improving the MPG for cars, we should also think about improving fuel efficiency for aquatic vehicles," says Kemp, who works on implementing the project's tensegrity structures and hydrodynamic testing. "If we can improve the efficiency of ships and submarines with biologically inspired designs, not only would we save energy but it could allow for longer range missions … and reduce the environmental impacts." However, all that is still further down the road. Even though in testing the prototype is beginning to move like a real ray, the Mantabot has a ways to go in the speed department — something that will likely be crucial in military, scientific or commercial applications. So, while it will be a little while before the prototype can give Michael Phelps a run for his money, a little patience seems reasonable, considering nature had several million years to perfect what the BIER lab and its partners have already accomplished in four. U.Va. ENGINEERING UNBOUND 9 TEXT: MATT BIERCE / PHOTO: TOM DALY

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