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24 Dossier | Cellula Robotics Solus-LR and lowered down a slipway and into the water. The trailer can also recover the craft, by attaching a cable to its nose and winching it onto the rollers. “Boat ramps are common in harbours, as are cranes, and we don’t really want to have to use more than four people to recover, refuel and relaunch the vehicle – certainly not a typical 2000 t support vessel with 50 crew members,” Woodroffe notes. “With the Solus-LR, you can eliminate the large support vessel entirely, and instead just have a far smaller boat or even a USV nearby acting as a convenient point of data upload and GNSS corrections.” System architecture Project leadership was provided by control systems manager Tristan Crees and program manager Todd Mawhinney, with Crees bearing chief responsibility for all electrical and software systems (including actuators). “Like our CEO, I worked at International Submarine Engineering (ISE) for 12 years as its lead AUV pilot, starting in 2002. I worked with its Explorer family of UUVs and put its GUI and other software into place,” Crees says. “So I had the most direct UUV experience of anyone in Cellula, so things like how to take the panels off, how to connect the cables routinely for pre and post-dives, what can go wrong; I’ve been there. I brought a lot of that to our team meetings.” The vehicle’s structural concept is based around an open, flooded aluminium frame with a series of spar- like stiffener rings (with syntactic foam throughout) enabling it to be structurally sound, and fibreglass skin panels covering it. This flooded-frame design speeds maintenance and sensor swaps, since closed and pressurised UUV hulls are more time-consuming to open and modify internally. Calculating the structural strengths and drag coefficients was carried out in- house, and several shapes for the UUV were run through CFD software to find the best balance between drag and packing density for sensors and electronics. The vehicle’s nose houses a forward- looking obstacle avoidance sonar, which enables objects to be detected up to 150 m ahead of the vehicle. The sonar is a multi-beam unit with a range of 150 m (0.5 m minimum), a 120 x 10 º FOV and an update rate of 20 Hz. That gives enough information and time for the vehicle to manoeuvre around an obstacle. In the section directly behind the nose is the navigation canister, a pressurised housing that contains the Solus-LR’s main CPU and several key systems February/March 2020 | Unmanned Systems Technology The hydrogen power system and suction anchor were critical parts of Cellula’s proposal for this large, long-endurance UUV (Courtesy of Cellula Robotics) The turning radius has to be less than 30 m at 1 m/s forward speed. The turning rate is slower than on other, smaller UUVs but that’s intentional