Cooperating teams of underwater drones could be used to inspect wind farms and other marine facilities, but they need to be able to communicate to work together. TNO has developed a technology that uses sound waves for efficient communication, which could be a breakthrough for the maritime sector.
According to Quincy Martina, Project Manager at TNO Acoustics and Sonar, working with underwater drones (or Autonomous Underwater Vehicles (AUVs), as they are known in the industry) requires meticulous preparation. “Your base of operations is usually a ship and you need to plan the mission carefully in advance,” he says. “What are the prevailing conditions? What are the expected risks? And, most importantly, what is the desired result and what is needed to achieve it?”
Underwater drones are safer
“In the end, it’s only the results that count,” says Maurits Huisman, Business Development Manager at TNO. “Underwater drones like AUVs could increase the efficiency and safety of offshore inspection and monitoring activities. This is dangerous work for divers, which is why you want to prevent using them as much as possible. Other inspection systems are limited by cables, for example, which decreases their usefulness.”
Sound as a means of communication
There were some misgivings about using AUVs, says Martina. “Wireless communication in sea water is always problematic, because radio signals do not travel far in it. So instead of using radio signals, we used sound waves, in much the same way as sonar. TNO has gained a lot of experience with this form of undersea communication.”
Data speed and range
Sound waves can enable drones to communicate under water. “Sound waves can be used both to control the AUVs and to transmit the data they collect,” says Martina. “Although slower than land-based 4G signals, the data speeds are sufficient for practical use. The range varies from a few hundred metres to dozens of kilometres, depending on the prevailing conditions and the frequency bandwidth.”
TNO is also working on improvements to the AUVs. “We are making the drones more autonomous,” explains Huisman. “This will enable them to carry out certain tasks without human intervention. We are also improving the cooperation between the systems, for example to enable them to assume tasks from another AUV if it malfunctions. You could also fit the underwater drones in a team with different types of sensors so that the team can collect a wider range of useful data. The AUV teams will be able to decide autonomously which data they need to collect to complete their assignment and where to collect it.” The technology has not reached this stage yet, but TNO is currently developing a system that will use acoustic modems and software to enable such autonomous decision-making.
“Wireless communication in sea water is always problematic, because radio signals do not travel far in it. So instead of using radio signals, we used sound waves”
A breakthrough for the maritime sector
TNO is currently looking for partners to further develop and demonstrate AUVs fitted with autonomous decision-making systems. “A successful demonstration of this technology could be a breakthrough for the maritime sector,” says Huisman. He sees offshore inspection and monitoring contractors as potential partners. “But we also welcome other stakeholders who want to bring this expertise and technology to the market together with us. We’re ready to go!”
Do you have any questions or are you interested in a collaboration? Please contact Maurits Huisman.