Soft landing: Drone collects DNA samples from thin, wiggling branches
The newly developed quadcopter is equipped with a force sensor and software to adapt its landing in the treetops to the stiffness of the branches.
Researchers at ETH Zurich have developed a drone that can land semi-autonomously on tree branches.
(Bild: Gottardo Pestalozzi)
(Hier finden Sie die deutsche Version des Beitrags)
Climate change and human expansion into historically species-rich habitats have led to a sometimes dramatic decline in global biodiversity. However, it is difficult to quantify the extent of this decline. For some years now, the analysis of so-called environmental DNA (eDNA) has become established for this purpose. This is DNA that is released into the environment in small quantities. The sequencing of such samples can be used to catalog species living there. But while eDNA from the sea can be obtained relatively easily from water samples, obtaining eDNA on land is more difficult.
Now, Emanuele Aucone of ETH Zurich and colleagues have developed a drone that can land semi-autonomously on tree branches to collect DNA samples. To do this, it is first steered over the branch by remote control and then autonomously sets down to land. A sticky film captures the surrounding eDNA. In an outdoor test sampling seven trees in the Swiss lowlands, the drone actually enabled the identification of various species.
Drone hovers more than it lands
"Landing" only approximately describes the drone's action, however - it's more of a careful nudge that the drone is performing. The researchers wanted the quadcopter to be able to land on very thin branches. But it's impossible to tell exactly how stable such a branch is during the approach. The autonomous landing mechanism therefore had to function independently of the stiffness of the branch. The researchers solved this with a kind of cage that surrounds the drone.
A horizontal and a vertical tire are connected at points with a force sensor in the center. Software measures the forces that occur when landing from different directions and, by regulating the rotors, tries to set a predetermined force at the point of contact with the branch without the machine starting to slide, or tilt. Since the contact force is very small, the machine hovers over the branch more than landing directly on it.
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However, the Swiss researchers are not the first to have built a drone that can land more or less elegantly on branches or poles. That's because this capability allows, for example, drones to fly to a target and park them in a way that saves energy. In 2019, researchers at Stanford University presented mechanical grippers that function similarly to the feet of birds of prey and close around a branch extremely quickly on contact. A balance algorithm then ensures that the drone remains stably seated.
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