A Bio-Inspired Flying Robot Sheds Light on Insect Piloting Abilities.pdf

Current Biology 17, 329–335, February 20, 2007 a2007 Elsevier Ltd All rights reserved DOI 10.1016/j.cub.2006.12.032Report A Bio-Inspired Flying Robot Sheds Light on Insect Piloting AbilitiesNicolas Franceschini,1,* Franck Ruffier,1 and Julien Serres1 1Biorobotics Lab Movement and Perception Institute Centre National de la Recherche Scientifique and University of the Mediterranean 163 Avenue de Luminy, CP938 Marseille F-13288, cedex 9 France Summary When insects are flying forward, the image of the ground sweeps backward across their ventral view- field and forms an ‘‘optic flow,’’ which depends on both the groundspeed and the groundheight. To ex- plain how these animals manage to avoid the ground by using this visual motion cue, we suggest that insect navigation hinges on a visual-feedback loop we have called the optic-flow regulator, which controls the ver- tical lift. To test this idea, we built a micro-helicopter equipped with an optic-flow regulator and a bio- inspired optic-flow sensor. This fly-by-sight micro- robot can perform exacting tasks such as take-off, level flight, and landing. Our control scheme accounts for many hitherto unexplained findings published during the last 70 years on insects’ visually guided perfor- mances; for example, it accounts for the fact that hon- eybees descend in a headwind [1], land with a constant slope [2], and drown when travelling over mirror- smooth water [3]. Our control scheme explains how insects manage to fly safely without any of the instru- ments used onboard aircraft to measure the ground- height, groundspeed, and descent speed. An optic- flow regulator is quite simple in terms of its neural implementation and just as appropriate for insects as it would be for aircraft [4]. Results and Discussion According to Kennedy’s ‘‘optomotor theory,’’ flying in- sects have a ‘‘preferred’’ retinal velocity with respect to the ground below [5, 6]. In response to wind, for ex- ample, they may adjust their groundspeed or ground- h