Uncrewed Systems Technology 044 l Xer Technolgies X12 and X8 l Lidar sensors l Stan UGV l USVs insight l AUVSI Xponential 2022 l Cobra Aero A99H l Accession Class USV l Connectors I Oceanology International 2022

93 Accession Class USV | Digest run its thrusters to stay as close to the selected position as possible. “Eventually it finds where the current and wind are and points its nose into that and quite happily sits there,” Wittamore says. “Obviously, one takes a bit more energy than the other.” Reygar was able to build on earlier work on an autopilot for uncrewed survey vessels and draw on experience with dynamic positioning systems to create an autopilot for USS incorporating these behaviours, says Richard Crowder, Reygar’s IoT development manager. The software had to be tuned to take the Accession’s dynamics and manoeuvring capabilities into account. “We have our own dedicated control systems engineer who came out of the defence industry,” Crowder explains. “He knows all the values to tweak to tune all the PID controllers and so on.” The hardware is based on a custom PCB that connects to the navigation system and the PWM motor controllers and azimuth steering system for the thrusters, he adds. “We also have a PLC version in anticipation of changes to work boat regulations.” Underway SVP With any sonar work demanding high precision and accuracy, up-to-date information on the speed of sound through the water and its relationship to depth are vital. That often means stopping at regular intervals to lower an SVP through the water column to take measurements. Stopping is inconvenient and time- consuming, requiring towed sensors to be recovered and then redeployed, for example. Instead, Accession carries a newly developed Vigo underway profiling winch from C-MAX. It is important that the SVP falls through the water column as near vertically as possible to take accurate measurements, and the Vigo winch takes advantage of the natural behaviour of the Dyneema line in water to achieve this while the boat is moving, explains Hugh Frater, C-MAX’s lead software engineer on the project. “The interface between the water and the air acts as a pulley, if you can get the line off the drum without any real tension,” he says. “You either push the line out under power while monitoring the tension, or you allow the profiler itself to just pull the line off as it falls, which is how we work.” He adds that the profiler will still fall vertically whether the vessel is stationary or moving, because the pulley effect will put a 90 º bend in the line. The portion on the surface will lie flat and the profiler itself will maintain its position in the horizontal plane while it descends down the water column and the boat continues forward. “With this, we can do everything underway so we don’t have to stop the boat, and we can keep the efficiency of the survey going,” Williams notes. “We can take profiles constantly or whenever we want them.” Immediately after the Ocean Business show, USS trailered the Accession 425 to Germany for an offshore wind farm route survey job, after which there is the chance of some passive acoustic monitoring work listening for cetaceans. Further ahead, Williams is looking forward to upcoming consultation on a new Remotely Operated Uncrewed Vessel annex to UK maritime regulations that should remove the need to apply for mission-specific exemptions to rules designed for manned workboats. “It is an exciting and challenging time at the moment for anyone who wants to work with USVs in UK waters,” he says. Uncrewed Systems Technology | June/July 2022 Length: 3.5, 4.25 or 5.0 m Beam: 1.3 m Height: 1.65 m Draught: 0.6 m, depending on configuration and payload Weight: 750-1200 kg (fully laden and depending on vessel length) Hull type: monohull with reverse bow, glass-reinforced plastic construction Power and propulsion: Series-hybrid diesel electric, steerable thrusters Speed: 5-6 knots for surveys, 8 knots maximum Endurance: 12 hours to 20 days depending on configuration Range: 10-15 km with long-range wi-fi, unlimited with cellular or satcom coverage Launch & recovery: trailer or bespoke floating system Some key suppliers Autopilot: Reygar Underway profiling winch: C-MAX Bathymetric sonar: R2SONIC Bathymetric sonar: GeoAcoustics Bathymetric sonar: Reason Bathymetric sonar: EdgeTech Bathymetric sonar: Norbit Bathymetric sonar: Kongsberg Sub-bottom profiler: GeoAcoustics Sub-bottom profiler: Innomar Sub-bottom profiler: EdgeTech GNSS: SBG GNSS: Trimble GNSS: Hemisphere Satcom antenna: Intellian Satcom services: Iridium Collision avoidance: Marine AI Inertial navigation: SBG Systems Inertial navigation: Applanix Automatic Identification System: Weather Dock Sound velocity profiler: Valeport Sonar data compression: Hypack Sonar data compression: Qinsy Sonar data compression: BeamworX Sonar data compression: Eiva Thrusters: Torqeedo Batteries: Torqeedo Specifications