Uncrewed Systems Technology 046

52 exhaustive water tests before taking on trial projects in partnership with various companies, not just to showcase what its technology could do but also to gather r&d data on how the early YUCO performed in different waters and missions. “The Jerico European Research Program in Ireland with the Marine Institute there was our first real validation of what was by that time – autumn 2021 – the complete, off-the-shelf YUCO. The test consisted first of several short deployments and then a longer mission stretching multiple lengths of Galway Bay,” Simon recounts. “The latter was a 15 km mission, with occasional surfacing halfway along the bay. The institute’s operators literally went for a coffee while the AUV was working, then went to the pre-planned recovery point 300 m away. “The YUCO was right on time; they retrieved it, extracted three-and-a-half hours of data, and that was it. On its first try, our finished product had proven that it could be programmed and deployed entirely by oceanographers who had mostly never used an AUV before, and be trusted to gather detailed data fully autonomously, so that its operators could do something other than slaving away in the water.” Anatomy of the YUCO All the standard-issue parts of the YUCO are housed in the rear section, known informally as the ‘never-open section’, which occupies about two-thirds of the vessel’s total length. Simon explains, “We know that when something is going to be submerged, we want as far as possible to prevent any chance of interactions with the internal electronics, O-rings or anything like that, because it’s just going to create the risks of water ingress into the hull. We wanted the routine with this AUV to be: you pick it up with its embedded payload, deploy it, retrieve it, clean it and store it again.” The top of the never-open section has a translucent mast containing the YUCO’s antennas for wi-fi and GPS, as well as an array of LEDs for visibility, and a connector for charging the battery and inserting a ‘key’ tool for switching the AUV on and off. This section’s hull is water-tested and sealed to give the 300 m depth rating; materials and the design are optimised for hydrodynamics and mechanical rigidity. In addition to the battery, the inside holds all the main control electronics, receivers for wi-fi and GPS, and the AHRS for navigation (including Seaber’s navigation algorithms). About the hull are a single rear thruster and three fins displaced at 120 º to each other, which enable the YUCO to dive, ascend, spiral and turn. On the front of the rear sections are four protrusions. One is a pressure sensor that measures the YUCO’s distance from the surface, another is a data comms connector for the payload section. “It’s important to us that the payload isn’t just powered by the AUV but synchronised to its navigation measurements, and that everything it measures can be read and analysed by the SeaPlan software, as well as being recovered via the interface it provides,” Simon comments. “Working with a separate dedicated storage for the data that has to be re-synchronised after downloading is really painstaking.” Also inside the dry section is a system for maintaining the centre of balance when the payload is changed. Seaber is considering patenting that so cannot disclose it publicly for now. “And if necessary, for instance if a customer has made a custom payload of their own, there are mounting points on the front for them to add counterweights, so even then the end- user’s modification work can be kept external to the dry section to keep them from opening the never-open section,” Simon adds. In contrast to the rear, which is identical on every YUCO, the front sections take many different shapes, up to 50 cm in length, depending on the sensor being installed. The back part of this front section is commonly the ‘main’ cylinder that has numerous inlets and contains the DVL and payload, while the very front is a nose that can be open or closed (depending on the need for water-sampling flows). It can be empty or contain a secondary sensor such as a GoPro camera. “The front is very variable, but as long as the nose is neutrally buoyant it can be of different shapes. It is fairly long too, but the AUV remains quite manoeuvrable. October/November 2022 | Uncrewed Systems Technology The YUCO is powered by a thruster constructed using a Blue Robotics reference design, with three fins as control surfaces and a 600 Wh lithium-ion battery