81 of 5 knots, with 4 knots the standard cruising speed. Engineered to be neutrally-buoyant in water, it navigates using a combination of sensors, including an INS, sonars, five cameras (one nose-mounted, the others oriented around the vehicle’s circumference for 360° visibility) and a 3D inclinometer. It is also connected to the surface during operations via a fibreoptic tether for real-time telemetry and survey data streaming. “When the vehicle operates in the customer’s plant it will have two operating modes,” Turetta says. “One is an autonomous mode without the tether; it will perform the first inspection. To do that we’re upgrading it with additional AI software layers, so it can understand the topography of the tunnels, robustly avoid obstacles and perform other intelligent tasks by itself with high reliability.” In this mode, the X-300 Explorer will be equipped with a multibeam echosounder for measuring the structural health of the tunnel and checking for the presence of any obstacles within them that might hinder fluid dynamics. “Once the customer has checked the data from the autonomous inspections, they’ll look into whether there are any points that need closer inspection and evaluation,” Turetta says. “In the second mode, the tether will be reinstalled and the AUV will autonomously navigate between points of interest to reduce operator workload, although it can be steered by the operator using real-time visual data from the nose camera to view their points of interest up close and in various controlled angles.” To create the Explorer (as a derivative of the Genoa-headquartered company’s X-300 AUV model), a variable-buoyancy system was removed from the standard X-300 design. So the vessel is tuned to be neutrally buoyant for each mission, based on the salinity of the water, as reported by the user. “This allowed us to reduce the length of the Explorer AUV by roughly 40 cm from either end, compared with the standard X-300. We also installed a transceiver for the fibre-optic tether, but that’s a very small component, about the size of a credit card, so comparatively easy to integrate,” Turetta adds. In addition to the fibre-optic tether reassuring owners and inspectors that the value of the uncrewed data collection is just as good as them being there themselves in real time, Turetta says the tether used is a thin, nimble component that allows the AUV to move as freely as if it were untethered – up to a maximum length of 5 km. This is in contrast to the heavy, movement-constraining, powerand-comms umbilicals typical of ROVs, which would have been unsuitable for navigating the bends and turbine blades in the tunnel. “Our first customer, at a hydroelectric company in Italy, requested something suitable for exploring a submerged tunnel with turbines inside that joined two lakes at differing altitudes,” Turetta recounts. “Normally, to explore such tunnels, the owner first empties them using valves at either end and then people can enter for inspection. But these specific tunnels had never been explored since their construction around 50 years ago, so using an AUV was critical to protect human inspectors in case the tunnels’ structural integrity was unsafe.” Lake surveys Like Italy, Switzerland is home to a number of lakes and water bodies that form part of the country’s wealth of natural beauty spots. However, there is a growing awareness of problems with their condition, as Gallus Kaufmann, co-founder and business developer at Tethys Robotics, tells us. “The lakes and rivers outwardly look beautiful, blue and perfect, but if you look inside them with underwater robots there will sometimes be visibility of 20 cm distance; maybe even 10 cm only, which is very, very low,” he remarks. UUVs | Insight Uncrewed Systems Technology | February/March 2025 The Tethys ONE has been engineered to autonomously hold position while surveying in currentprone shallows like those in the lakes and rivers of Switzerland (Image courtesy of Tethys Robotics)
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