Mini helicopter masters insect navigation trick:
As insects fly forwards the ground beneath them sweeps backwards through their field of view. This “optical flow” is thought to provide crucial cues about speed and height. For example, the higher an insect’s altitude, the slower the optical flow; the faster it flies, the faster the optical flow.Previous experiments involving bees suggest that optical flow is crucial to landing. Maintaining a constant optical flow while descending should provide a constant height-to-groundspeed ratio, which makes a bee slowdown as it approaches the ground. Distorting this optical flow can cause them to crash land instead.
Now Nicolas Franceschini at the University of the Mediterranean in Marseilles, France, and colleagues have shown the same technique may explain more general flying behaviours.
They fitted a miniature helicopter with a simple software feedback loop to ensure that optical flow remains constant as it flies along. This allowed the tethered micro-copter to take off gracefully, maintain altitude over varying terrain and land, all without any means of directly measuring its speed or height. A video produced by the researchers shows the micro-copter in action (43.7 MB .avi format, requires DivX).