‘Dual robot’ drone simplifies underwater monitoring

The 'dual robot' drone, which has undergone tests at Empa and the aquatic research institute Eawag in Switzerland, has measured water in lakes for signs of microorganisms and algal blooms, and could in future be used to monitor climate clues like temperature changes in Arctic seas.

The researchers developed the drone to improve researchers’ ability to quickly deploy monitoring drones to aquatic environments. Dubbed MEDUSA (Multi-Environment Dual robot for Underwater Sample Acquisition) the drone could also help monitor and maintain offshore infrastructure like underwater energy pipelines and floating wind turbines.

In a statement, Professor Mirko Kovac, principal investigator on the project and director of the Aerial Robotics Lab at Imperial and head of the Robotics Centre at Empa, said: "MEDUSA is unique in its dual robot design, with a flight component that reaches difficult-to-access areas and a diving component that monitors water quality. Our drone considerably simplifies robotic underwater monitoring by performing challenging tasks which would otherwise require boats."

The researchers have tested MEDUSA in laboratory environments at Imperial, Empa, and in field environments including lakes in Switzerland. MEDUSA is described in IEEE Xplore.

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The drone flies using remotely controlled multirotors, which allows MEDUSA to travel long distances with high payloads, fly over obstacles, and manoeuvre through difficult terrain.

The multirotor flies to a hard-to-reach aquatic environment before landing on the water and deploying its tethered mobile underwater pod with attached camera and sensors to depths of up to 10m. The drone operator remotely adjusts the pod's depth and three-dimensional position in the water using buoyancy control and jets. At all times, the user is guided by real-time video and sensor feedback from the pod.

Once samples are taken, the drone coils the tether to reunite with the pod before taking off and flying back to the user.

While the underwater pod design is new, the aerial drone design is an industry standard, meaning MEDUSA systems can be easily constructed and deployed using industrial operational frameworks.

Boats are used by ecologists to reach and monitor aquatic areas, but MEDUSA could help reduce the risk to humans of travelling to difficult-to-reach aquatic environments. This could be particularly useful in the Arctic Ocean, where changes in ocean temperatures, acidity, salinity, and currents can offer critical clues about the global climate crisis.

Professor Kovac said: "We have much to learn from the Earth's water: by monitoring ecological parameters we can identify trends and understand the factors affecting water quality and the health of the ecosystem in a changing climate.

"MEDUSA's unique ability to reach difficult places and collect aquatic images, samples and metrics will be invaluable for ecology and aquatic research and could support our understanding of local climate in difficult-to-access environments like the Arctic."

According to Imperial, the next round of testing involves developing shape-shifting metamorphic drones within the newly approved ERC Consolidator grant, called ProteusDrone, with international partners at Empa.
The research was supported by UKRI’s EPSRC.