Unmanned Systems Technology 025 | iXblue DriX I Maintenance I UGVs I IDEX 2019 I Planck Aero Shearwater I Sky Power hybrid system I Delph Dynamics RH4 I GCSs I StreetDrone Twizy I Oceanology Americas 2019

Dossier | iXblue DriX 28 position,” he says. “That took some time of course, because there is a huge difference between making actuators for a measurement table and making them for autonomous ships at sea.” Actuator duty cycle Getting that right took effort in optimising the rudder system’s duty cycle. “We realised from the beginning that if you take an engineer working in a lab who has no operational experience, he or she is going to try to correct every tiny deviation from the programmed course,” says Eudeline. “From a sailor’s point of view though you don’t want your rudder to move, say, 1000 times a minute, that’s not the way it’s going to work. “It has to be heavy duty, and you have to find the right balance between accuracy and reliability, as well as the maximum time before failure.” How well all that works in practice was demonstrated in a test survey around the Gwynt y Mor wind farm off the coast of North Wales, which is operated by Innogy Renewables UK. The survey was carried out by seabed data acquisition company Bibby HydroMap over five days in August 2018. Eudeline notes that the weather conditions during the test were a sea state of between three and four and a 3 knot cross-current, conditions under which it can be difficult for a small vessel to maintain its programmed course over ground (COG). “The largest error for the DriX as far as COG was concerned was 2 m,” he says. “So it is pretty accurate.” Launch and recovery From the programme’s inception, Eudeline emphasises, the team knew there would be no point in developing a USV intended for operation from ships without an efficient and reliable means of putting it into the water and bringing it back aboard. Traditional ways of doing that involve hooking the vehicle up to davits, cranes or A-frames, which are tricky to operate, he says, because the motions of the USV on the water are very different from those of the much larger mother ship. iXblue therefore also developed a dedicated launch and recovery system. The DriX Deployment System (DDS) consists of a floating cradle that resembles an RHIB, into which the DriX manoeuvres itself. The cradle is towed by the support vessel and has all the attachments that enable the ship’s lifting devices to bring it aboard. The cradle’s displacement and dimensions are close enough to those of the USV for them to ride the waves in a similar manner, making it much easier to bring them together. Also, the DDS has its own positioning sensors, and it radios its position to the DriX during recovery so that its autopilot can compare the two positions and calculate a course that will bring it safely into the cradle. The DDS is part of what Eudeline calls the DriX ecosystem, which also April/May 2019 | Unmanned Systems Technology Survey operations around the Gwynt y Mor wind farm off the coast of North Wales proved the accuracy of DriX’s helming system, straying no more than 2 m from its planned course despite difficult currents (Courtesy of iXblue)