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22 In conversation | Adrian Thomas flaps in phase with the one on the right), except during high acceleration, during which all the wings flap in phase. “We used flow visualisations to investigate their aerodynamic efficiency, because the existing literature insisted that was why they flap out of phase, but we found that there are actually only marginal aerodynamic benefits,” the professor says. “What dragonflies actually get from that is an incredibly stable hover. It’s an active form of vibration damping, so their eyesight – or FPV camera, in the Skeeter’s case – gets an incredibly clear image for hunting prey and other targets.” The company therefore sees enormous benefits for survey and photography UAVs, in both small and heavy-lift classes, for users needing sharp imagery without having to add weight for vibration damping. Animal Dynamics is also in talks with Centeye, in Washington DC, which specialises in insect-inspired obstacle avoidance and attitude-heading stabilisation, and with Graham Taylor, head of Oxford University’s animal flight group and a former student of Thomas’. He has been producing match filters for motion detection in flies, as such filters are highly attuned to changes in pitch and rotation. “Insect-inspired camera technology can isolate-out the motion the UAV expects to see owing to self-movement, and then pick out navigational errors, using the difference between an expected image and what it’s actually seeing. All the calculations happen on the camera chip, outputting data on the turn rate and on what’s changed in the environment without having to be sent to an autopilot or central processor,” Prof Thomas says. “So many animals have that advantage: they can filter out all the information they don’t need, to quickly calculate what they do need. That could save so much power and weight for UAVs, it would be mad not to leverage that.” The Stork While Malolo is still a series of lab demonstrators, and the Skeeter is in the late stages of its r&d (and currently undergoing test flights by clients), the company’s Stork UAV system is now going through certification. As discussed in UST 33 (August/ September 2020), the Stork features a three-wheeled, skeletal airframe and flies using parafoils. This approach is inspired by biomimetics and Prof Thomas’ background as a champion paraglider. “The wing design I first won the British National Championships with, back in 2006, was taken almost entirely from albatross wings, which of course meant fantastic gliding at speed. It was a bit pitch-unstable but it gave substantial gains in performance,” he says. Parafoils are designed with longitudinal ribs, and distort into rigid 3D structures as they fill with air through openings at their front. The distortions resemble what biologists call ‘hydrostatic skeletons’ – boneless, muscle-based structures such as worms, molluscs or human tongues, which have evolved everywhere on Earth but are largely untapped in the world of mechanics. “We have built subtle inspirations from such skeletons into the design of the weaves and planforms of the Stork’s parafoil cloth – as well as from birds, since they work at the same Reynolds numbers and flow regime as paragliders – to optimise them for drag, load distribution and other things,” Prof Thomas adds. “There’s also a laminar-to-turbulent transition at about the point where we fly, so a subtle change in aerofoil shape results in a factor-of-two effect on drag. Eagles and similar birds’ wings can October/November 2020 | Unmanned Systems Technology So many animals can filter out the information they don’t need, to calculate what they do need. That could save power for UAVs The Stork will be able to select safe landing and take-off zones using computer vision being developed by Animal Dynamics