Friday, January 17, 2014

Flight of the robot jellyfish

Here’s my other little piece for Nature news. The videos of this thing in flight, provided on the Nature site, are rather beautiful.


Its transparent wings fixed to a delicate wire framework recall the diaphanous, veined wings of an insect. But when the flying machine devised by applied mathematicians Leif Ristroph and Stephen Childress of New York University rises gracefully into the air, the undulations of its conical form resemble nothing so much as a jellyfish swimming through water, the device’s electrical power lead trailing like a tentacle. It is, in short, like no other flying machine you have seen before.

This is not the first small artificial ornithopter – a flying machine capable of hovering like a dragonfly or hummingbird by the beating of its wings. But what distinguishes Ristroph and Childress’s craft from those like the flapping insectoid robots reported by researchers at Harvard last year [1], with a wingspan of barely 3 cm, is that it can remain stable in flight with the movement of its wings alone, without the need for additional stabilizers or complex feedback control loops to avoid flipping over. The new ornithopter has four droplet-shaped wings of Mylar plastic film about 5 cm wide, arranged around a spherical body, attached to an articulated carbon-fibre framework driven by a tiny motor and weighing no more than 2.1g in total. It can execute forward flight and stable hovering, and can right itself automatically from tilting. The motion of the wings generates a downward jet, as do the undulations of a jellyfish bell. The absence of this strategy among flying animals, the researchers say, remains a mystery. The work is reported in the Journal of the Royal Society Interface [2].

1. Ma, K. Y., Chirarattananon, P., Fuller, S. B & Wood, R. J. Science 340, 603-607 (2013).
2. Ristroph, L. & Childress, S. J. R. Soc. Interface 20130992 (2014).

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