Drone swarms open up new opportunities

From aerial photography to crowd control, from recreational uses to warfare in Ukraine... There are countless applications for drones. A team at IMT Atlantique had decided to go further: they are working on the implementation not of a single drone, but of an entire fleet, made up of dozens, or even hundreds, of these devices. Yann Busnel, head of the school's Network Systems, Cybersecurity and Digital Law Department (SRCD), gave a remarkable presentation on this subject in Rio de Janeiro, Brazil, last December, at the GlobeCom 2022 conference, organised each year by the IEEE, a world-class scholarly society that aims to stimulate innovation in communications.

Originally, Yann Busnel is a specialist in distributed algorithms - in other words, the way in which several computers work together to perform complex tasks, each of them taking charge of a part of it. We took this idea and applied it to drones," he explains. "These devices are becoming cheaper and cheaper, and more and more autonomous and efficient. This opens up new opportunities."

Helping the rescue services in the event of a disaster

With his colleagues Christelle Caillouet, David Coudert and Igor Dias Da Silva, from the Université Côte d'Azur and Inria, he has been working on the use of a swarm of drones during a disaster - tsunami, earthquake, avalanche, etc. "After a disaster, the communication network is usually down," explains the researcher. We could therefore launch a fleet of drones, which would exchange messages with each other to coordinate, and could thus fly in a "structured" manner. This would make it possible to recreate a sort of network, capable of communicating with objects connected to the ground - smartphones, for example - to geolocate victims and send their coordinates to rescue teams. Articles on the subject have been published in 2019 and 2020 *.
Subsequently, Yann Busnel and his small team continued their work with a chair at Rennes Métropole, in partnership with Rennes School of Business, dedicated to disaster management, on issues such as evacuating the population in the event of war or imminent danger. Fleets of drones could be used to analyse crowd movements and/or coordinate rescue operations.

The team also looked at battery-operated connected objects, which are increasingly common in many fields, and with which swarms of drones could communicate. For example, in precision agriculture: connected sensors installed on vine plants could be used to detect and prevent frost or disease episodes, as well as to supply controlled doses of fertiliser or phytosanitary products... Fleets of drones could also be used in oceanography, to monitor maritime surfaces.

Remote recharging of batteries of connected objects

Another area in which swarms of drones could be useful is the factory of the future. Industrial sites have more and more sensors, responsible for carrying out a host of measurements," notes Yann Busnel. But most of this equipment is battery-powered. Even if their electricity consumption remains very low - especially as they are most often in a 'dormant' state - the problem arises of recharging these batteries. How do you do that?
This is where a fairly recent technology comes into play: wireless recharging by radio frequency, with the wave emitted by a drone's antenna carrying energy. It is therefore possible to power devices remotely, within a few seconds: all you have to do is have a drone equipped with a powerful battery fly over them. "We can further improve the set-up by using an algorithm planning the route of the drones in order to recharge the entire fleet," explains Yann Busnel. All of this is based on complex calculations: the flight altitude and optimal position of the drones must be determined in order to simultaneously supply a series of devices, and the time required for each recharge must be specified... A system that could also prove useful in the case of large warehouses.
Swarms of drones could therefore find a great many applications. In addition to Industry 4.0, they could be used to refit large ships, monitor natural areas and even manage biodiversity. "High-flying drones could collect various data on wild animals - their behaviour, size, numbers, etc." These swarms could thus contribute to achieving the UN's Sustainable Development Goals (SDGs).
So far, the team has focused on theoretical research and computer simulation. But they are now planning to go up a gear. The next step is proving their concept, in particular checking whether interference or other phenomena can disrupt the operation of drone fleets. As part of the chair at Rennes School of Business, a dozen drones have just been ordered for real-life testing. The team also plans to take on other doctoral students. And it is filling applications to find funding. "We are working on a subject that is still in its infancy. But we have many projects," says Yann Busnel. "We are only at the beginning of the story."