While drones typically use accelerometers to estimate the direction of gravity, how flying insects achieve this has been a mystery, as they have no specific sense of acceleration. In this study, a European team of scientists1 led by the Technical University of Delft in the Netherlands and involving a CNRS researcher showed that drones can assess gravity through visual motion detection and motion modeling together.
To develop this new principle, scientists studied optical flow, i.e. how an individual perceives movement relative to its environment. It’s the visual movement that sweeps across our retinas as we move. For example, when we’re on a train, trees next to the tracks pass faster than distant mountains. Optical flow alone is not enough for an insect to tell the direction of gravity.
However, the research team discovered that it was possible for them to find this direction by combining this optical flow with a modeling of their movement, i.e. a prediction of how they will move. The conclusions of the article show that using this principle it was possible to find the direction of gravity in almost all situations, except for some rare and specific cases, e.g. B. if the subject was completely immobile.
With such perfect stationary flights, the impossibility of finding the direction of gravity will momentarily destabilize the drone and thus set it in motion. This means that in the next moment the drone will regain the direction of gravity. These movements therefore generate slight vibrations reminiscent of insect flight.
Using this new principle in robotics could solve a major challenge that nature has also faced: how to get a fully autonomous system while limiting the payload. Future drone prototypes would be lighter by not requiring accelerometers, which holds great promise for the smallest insect-sized models.
Although this theory could explain how flying insects determine gravity, we have yet to confirm that they actually use this mechanism. Targeted new biological experiments are needed to prove the existence of these neural processes, which are difficult to observe in flight. This publication shows how the synergy between robotics and biology can lead to technological advances and new avenues in biological research.
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1 This research is the result of a European collaboration between two laboratories: the Micro Air Vehicle Laboratory at the Faculty of Aerospace Engineering at the Technical University of Delft in the Netherlands and the Institut des Sciences du Mouvement (CNRS/Aix Marseille Université) in France.
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