KONGSBERG EM2040 MBES:
At the end of 2011, Ifremer became the first client to integrate the Kongsberg EM2040 multibeam echosounder (MBES) on an AUV. This high-resolution, multi-frequency echosounder opens up new possibilities in the fields of bathymetry, water column data analysis, and reflectivity imaging.
Used during the 2012 FUTUNA scientific campaign, this MBES demonstrated its potential, but also highlighted areas for improvement. Notably, the sensitivity to acoustic interference with other AUV sensors was identified as an issue. This problem was addressed between 2013 and 2014 by implementing synchronization of the acoustic equipment, which required extensive testing and development to establish various usage scenarios.
Above is an illustration of the use of the EM2040 echosounder on the wreck of La Lune during the ESSAUV12-2 mission
The ESSAUV13 technical campaign on Le Suroît introduced an innovative approach by deploying two AUVs from the same vessel. The dives were organized in a "24/7" schedule with 12-hour shifts. A specific onboard installation was designed by the 2IDM service to support this operation.
As part of the consolidation efforts, the design of the control fins was overhauled. The original ISE actuators had issues with both precision, which affected navigation stability, and reliability, leading to frequent dive interruptions and cumbersome maintenance.
The fin design was therefore reworked internally, focusing on both mechanical and electrical aspects to enhance precision and robustness. A first prototype was tested during the ESSAUV12-3 campaign, followed by further development and the production of an initial series in 2013 and 2014.
The development and validation of a new generation of Li-ion batteries in partnership with the company Accuwatt has made it possible to extend diving autonomy to around twenty hours, compared to 15 hours previously.
It is also worth noting the development and operational transfer of the RAMSES positioning system on AUVs from 2019 to 2022. This so-called "synthetic long baseline" or "sparse LBL" system allows for highly precise real-time geo-referencing of the autonomous vehicle's navigation for certain applications. This system uses one or more fixed acoustic beacons deployed on the seabed.
