How can flying insects distinguish above and below?
Flying insects can determine the direction of gravity even though they have no acceleration sensors. A team has developed a theory that could explain this.
Researchers regularly look to nature for solutions to certain problems. Bionics - an invented word made up of biology and technology - have already copied dolphin tracking systems or the barb of the burdock and used it to develop the Velcro fastener. Even Leonardo da Vinci was inspired by birds for his flying machines. But why shouldn't this also work the other way round? Can technical solutions provide deeper insights into unsolved biological phenomena?
A team from Delft University of Technology, France's Centre national de la recherche scientifique (CNRS) and the University of Aix-Marseille has now shown that drones can estimate the direction of gravity by having their sensors optically detect the movements around them and combine this with modelling their own movement, i.e. predicting how they will move. These results, which the researchers published in the journal Nature", are an important step towards the development of tiny autonomous drones. It may also explain how flying insects distinguish between up and down. This demonstrates how the synergy between robotics and biology can lead to technological advances and new biological research approaches.
While drones normally use accelerometers to estimate the direction of gravity, the way flying insects do this has been a mystery because they have no specific sense of acceleration. The scientists therefore investigated optical flow, which is the way an individual perceives movement in relation to its surroundings. This is the visual impression that passes over our retina when we move. For example, when we sit on a train, the trees next to the tracks pass by faster than the mountains further away. However, the visual flow alone is not enough for an insect to detect the direction of gravity. The research team then discovered that combining optical flow with a prediction of movement makes it very possible for an insect to develop a sense of gravity.
The researchers' experiments with flying robots show that this principle leads to stable but slightly oscillating attitude control. According to the scientists, the oscillations are indeed strongly reminiscent of insect flight. Testing the conjecture could prove difficult, however, as it involves brain processes that are difficult to monitor during an animal's flight. "While this hypothesis can theoretically explain how flying insects determine gravity, we still need confirmation from biological experiment that they actually use this mechanism," the researchers said, according to a statement from the institutes involved.
Spectrum of Science
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