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

32 Dossier | iXblue DriX roll, pitch and yaw. The sensor’s inherent stabilisation characteristics combine with those of the platform to enable the system to operate effectively in rough seas. The sonar head is rated to a depth of 90 m, and Kongsberg claims a maximum mapping depth of 490 m, with its reach extended by an FM chirp capability. Typical applications for the EM 2040C include surveys of harbours after they have been dredged, searching for shipwrecks, mapping wildlife habitats, inspecting pipelines, continental shelf mapping, and conducting hydrographic surveys that comply with the specifications set by bodies such as the International Hydrographic Organisation (IHO) and Land Information New Zealand (LINZ). These requirements define minimum detection resolutions, which are often interpreted in terms of sounding density. IHO S44 Special Order surveys, for example, require about nine soundings per square metre. This order is reserved for limited areas such as docksides, where high vessel speeds are normally prohibited. The EM 2040C is designed to exceed these performance requirements. The company has also installed Teledyne Reson’s high-resolution SeaBat T50 MBES in integrated dual-head form. Operating at acoustic frequencies of between 200 and 400 kHz, the sonar generates an across-track receiver beam width of 0.5 º at 400 kHz, increasing to 1 º at 200 kHz, and achieves a depth resolution of 6 mm, according to the manufacturer. That was the sensor used by Bibby Hydromap for the Welsh offshore wind farm survey. During that operation, QPS Qimera Live software running on the DriX was controlled by technical staff on the support vessel so that the fully processed data could be downloaded from the DriX at the end of each mission. All the data was processed in real time from the support vessel, with little need for post- processing ashore, says Bibby. From R2 Sonic, iXblue has integrated the Sonic 2024 and 2026 MBES sonars. The 2024 is intended for USV operations such as support for dredging, offshore construction, and wind farm cable and tower surveys. It operates over the 170-450 kHz acoustic frequency range, with beam widths from 1 x 2 º at 200 kHz to 0.45 x 0.9 º at 40 kHz. An extension to 700 kHz is available as an ultra-high resolution option, and this generates a beam measuring just 0.3 x 0.6 º to create detailed 3D images of pipeline components, for example. The 2026 meanwhile is focused on advanced hydrography, research and seafloor characterisation applications. Its core operating frequency range is the same as that of the 2024, but it can add 90 kHz and 100 kHz options. Both exceed the requirements of the IHO S44 Special Order, says R2 Sonic. Underwater positioning technology built in-house has also been integrated by iXblue, namely the GAPS ultra-short base line (USBL) and the Ramses long base line (LBL) systems. Both use arrays of acoustic transponders and interrogators to exchange signals and calculate distances from transmission and reception times, and positions by triangulation. All USBL systems have vehicle- mounted transceiver heads to interrogate beacons. GAPS transceiver heads have three transducers 10 cm apart that create the short baseline and use phase differences in the incoming signal from a beacon to calculate the direction from which it came. LBL systems use networks of transponders as navigation reference points. GAPS is designed for locating and communicating with subsea assets, and combines a USBL antenna and a FOG-based INS in the same housing. According to iXblue, GAPS uses wideband transmissions and other acoustic techniques to overcome difficult sound propagation conditions, as well as a 3D acoustic array to enable tracking and communication from under the sea to shallow water. The Ramses system’s transponders also contain FOG-based INS units, and offer millimetric range measurement precision, says the company. GAPS also has a towfish tracking function. Future directions Eudeline describes the DriX as a mature product, one for which it is developing new capabilities and applications. Towfish tracking could prove valuable for it, as iXblue is developing a towing capability that should be available by the middle of this year. The DriX is also being offered for military applications such as high-speed bathymetry for rapid environmental assessment, mine warfare, disaster relief and anti-submarine warfare. In this last role it is likely to find itself towing new- generation passive sonar arrays, possibly as part of future cooperative multi-static sonar operations. April/May 2019 | Unmanned Systems Technology The iXblue GAPS ultra-short baseline positioning and comms head has been integrated into the DriX (Courtesy of iXblue)