Unmanned Systems Technology 036

32 Built to order High-end AUVs are not made in large quantities, and the number of Sabertooths built so far is a little more than 10. With the smaller ROVs, Siesjo says, it makes sense to talk of monthly production rates, but the larger vehicles are built to order and sometimes in anticipation of a particular order. Delivery times are usually around six months or more. While the Sabertooth was designed in Sweden, and is assembled and tested there, much of the component-level manufacturing takes place in workshop facilities in Fareham, in the UK – parts including the e-pods, thrusters, battery packs and circuit boards are made there. The motors used in the thrusters are brushless direct current types, and Saab buys in core motor components such as the rotors and stators from suppliers who make marine oilfield- qualified parts, including Kollmorgen and Coercive Systems. “We don’t build things unless we have to,” Siesjo says. “If you take a thruster for example, the design, waterproof housing and drive electronics are made in-house, but low-level components such as the core brushless motor parts are items that we buy but are made to our own specification.” While Saab makes extensive use of 3D printing in its smaller vehicles (such as the Sea Wasp) for components in the hull to keep size and weight down, in the Sabertooth its use has been limited so far to a few components in the cooling system. Siesjo notes that there are very few suppliers who can print parts that will stand up to the underwater environment. “The sort of things that you would normally print for use in UAVs are not suited to underwater uses, as they contain too much air and will not stand up to pressure, even if they are not used for hull parts,” he says, adding that there is a fair market for anyone who can develop methods for printing parts that work reliably in deep water. Future combinations The current Sabertooth is optimised for a particular combination of range, endurance, capacity, ruggedness and other attributes, which could be adjusted with other emphases, Siesjo says. “The whole point of the iCON component thinking is to make variations of the same technology but in different shapes to cope with different requirements. I’m pretty sure we are going to see intervention-oriented vehicles, not so streamlined but better at handling manipulators, and more streamlined ones with longer ranges,” he says. February/March 2021 | Unmanned Systems Technology Dossier | Saab Sabertooth AUV Depth rating: 1200 m or 3000 m in sea water Length: 3.7-4.1 m Height: 45-67 cm Width: 1.4 or 1.35 m Launch weight: 1200-1500 kg Pressure hulls: two Pressure hull materials: aluminium alloy or carbon fibre reinforced plastic Structural framework: A4 stainless steel Thrusters: six, based on the core of the Saab SM9 Lights: two LED lamps, equivalent to 400 W halogen Interfaces: RS-232/RS-485, Gigabit Ethernet, additional in-house intelligent devices Auxiliary voltages: 24 VDC and 250 VDC (unregulated) Forward speed: 4 knots Forward thrust: 100 kgf Lateral thrust: 90 kgf Vertical thrust: 160 kgf Battery capacity: 30 kW/h Endurance: more than 14 hours Some key suppliers Wireless optical underwater comms: BlueCom (Sonardyne) Core electric motor components: Coercive Systems Core electric motor components: Kollmorgen Bathymetric sonar: EdgeTech Subsea docking station: Equinor Manipulator: Hydro-Lek Digital multi-frequency profiling sonar: Imagenex Colour/monochrome cameras: Kongsberg Depth sensor: Paroscientific Data collection software: QPS Acoustic navigation: Sonardyne Low-light camera: Teledyne Bowtech Emergency location strobe: Teledyne Bowtech Battery cells: Kokam Specifications We don’t build things unless we have to. For a thruster, say, the electronics are made in-house, but not the low- level components