Issue 37 Unmanned Systems Technology April/May 2021 Einride next-gen Pod l Battery technology l Dive Technologies AUV-Kit l UGVs insight l Vanguard EFI/ETC vee twins l Icarus Swarms l Transponders l Sonobot 5 l IDEX 2021 report

46 Digest | Dive Technologies AUV-Kit foam blocks with essentially no post- processing,” Lebo says. As mentioned, the Dive-LD has been designed as a flooded-hull system, and the company anticipates its future projects to follow this approach, given the complexity and cost associated with using AUVs built with fully pressurised hulls. To keep the sensitive electronics protected against saltwater, they are housed in small titanium pressure vessels from Prevco. While Prevco makes pressure housings from a wide range of materials, Dive chose titanium for its superior corrosion resistance and strength-to-weight ratio compared with other options such as aluminium or ceramic, particularly with customers operating down to 6000 m in mind. Power and propulsion For energy storage, Dive has sourced Kraken Robotics’ pressure-tolerant SeaPower AUV batteries. As per the Dive- LD’s requirement, the packs are rated to 6000 m; they house lithium-polymer cells for a total of 93 kWh and deliver up to 6 kW of power for the thruster (for when a ‘sprint’ speed, say, is needed). “We keep a high bus voltage in our batteries in order to provide high power directly to our thruster to achieve 8 knots speeds when needed,” Lebo says. “Our power distribution system is designed to control each subsystem independently using switchable relays.” The thruster itself is a 6 kW direct-drive electric motor system from Tecnadyne. Lebo notes, “This is a COTS system that we were drawn to as it does not have any shaft seals. It has a strong reliability track record, and it’s very efficient at the low speeds that are needed for long- endurance, persistent missions, but it also delivers the sprint speeds when needed.” Dive’s kit is developed to output AUV designs that are configured to steer, roll and pitch using a system of four independent rotary BLDC servo motors that control four flaps arranged in an X-configuration (at 45 º intervals) at the rear. Lebo adds, “Those servos are COTS too, and their motors and gears are encased in an oil-filled housing for pressure tolerance.” Autonomous navigation The autonomy for the Dive-LD and the AUV-Kit consists of two core components. The first is a vehicle controller, co- developed with Virginia Tech’s Center for Marine Autonomy and Robotics through a Sponsored Research Agreement to use its ROS code base and configure it for Dive’s AUVs. The controller covers the scripted autonomy – the conventional approach of waypoints for navigation and survey, based on dead reckoning and acoustic positioning and localisation. To ensure a consistent and reliable stream of navigation measurements April/May 2021 | Unmanned Systems Technology A 6 kW direct-drive electric thruster from Tecnadyne powers the Dive-LD’s cruising, diving and surfacing Kraken Robotics’ pressure-tolerant SeaPower AUV batteries provide 93 kWh of energy for the Dive-LD’s 10-day endurance