Date: Jan 16, 2014 Author: David Hambling Source: NewScientist
They might not seem at all stable as they batter into light bulbs but moths have inspired an autopilot for drones.
Small drones find it difficult to fly in strong winds and cluttered environments. So Physical Sciences Inc (PSI) based in Andover, Massachusetts, in association with the US military, filmed hawk moths to see how they manage to stay aloft.
The firm used a motion-tracking system familiar to film-makers, attaching reflective beads to moth wings and recording the moth's flight via high-speed cameras. The moth's ability to react very quickly to disturbances in the air seems to be key to its success. While moths do collide with things, they can recover quickly. "Typically they recover stability in about one wing beat," says PSI's Thomas Vaneck.
The resulting algorithms have been built into a new quadrotor drone, unveiled this month, called InstantEye. This weighs less than 500 grams but can fly in winds of more than 88 kilometres per hour. Simple toys like the Parrot ARMovie Camera struggle to fly in gusts much stronger than 15 km/h, while professional drones can cope with 50 km/h but are far bigger and more expensive. To fly InstantEye the operator simply moves the joystick in the desired direction and the autopilot works out the best flight path, taking weather conditions into account.
Unlike other quadrotors, InstantEye doesn't need expensive camera stabilisation to spy on targets. Its camera locks on to the surface below so the drone can hover in place, within centimetres of a target if needed. "Our autopilot is so fast and precise that it allows the whole camera to remain steady even when the weather is frightful," says Vaneck.
Like the moth, the drone recovers rapidly from a collision rather than crashing. The drone has been used to inspect electrical towers, providing close-up images so that human inspection is unnecessary.
"Nature is obviously better at robust flying than man-made machines," says Arthur Richards at the University of Bristol, UK. But he suspects rotor blades may prove more fragile than moth wings. PSI is supplying InstantEyes to the US military and plans to include sonar to aid autonomous navigation and help determine whether windows are open for stealth missions.