Unmanned Systems Technology 022 | XOcean XO-450 l Radar systems l Space vehicles insight l Small Robot l BMPower FCPS l Prismatic HALE UAV l InterDrone 2018 show report l UpVision l Navigation systems

28 Dossier | XOcean XO-450 running power-hungry sensors. It features a series hybrid propulsion system based on well-established technology, so a lot of XOcean’s development effort has gone into calculations to match its components to the power requirements. The heart of the power system is a marinised Yanmar diesel generator that is used to charge a 5 kWh lithium- polymer battery pack, supplemented by the solar panels. The pack and the rest of the electrical power conditioning and distribution system, including cabling and connectors, is well-proven maritime-standard equipment supplied by Mastervolt. The task for XOcean was to determine how much power they had to sustain, and therefore what the capacity of the generator, fuel tank, batteries, and the solar panels and charging system had to be, Carlisle says. Propulsion loads The system has a power budget of about 1 kW, at least half of which is taken by the propulsion, although it can be traded off if more power is needed for the sensors by reducing speed or mission duration. “If you slow the vessel down, you can go for months,” says Ives. “If you reduce your speed, the percentage contribution from the solar panels just goes up.” Carlisle notes, “The equation for how much power you are going to consume through your propulsion system is related to the velocity cubed, so a small reduction in speed gives you a large reduction in power required. “Of course the inverse is also true, but by the time you get down to 3.5 knots you’re in a nice, energy-efficient place.” Both propulsion and steering are provided by two DC pod thrusters, one on each hull. They are fixed devices so directional control comes from differential thrust. October/November 2018 | Unmanned Systems Technology The marinised Yanmar diesel generator is housed along with its fuel supply in the USV’s centre pod, and recharges the vessel’s batteries (Courtesy of XOcean) The hub of the power management system is the compartment housing the Mastervolt Mass Combi 24/2600- 60 inverter/charger combination (Courtesy of XOcean) Reversible electric thrusters provide all the forces required for propulsion and steering through differential thrust (Author’s image)