The Future of USV Multibeam Integration

EvoLogics, a high-tech provider of robotic solutions, sensor systems, and underwater data networks, is perhaps most immediately recognized among industry peers for designing and manufacturing the Sonobot 5 uncrewed surface vehicle (USV). The Sonobot is a well-established product with a remarkable track record in performing bathymetry, underwater object search, and subsea reconnaissance missions.

To further enhance the USV’s utility, reach, and accuracy, EvoLogics has made further steps to upgrade the system’s hardware, including, in April 2023, the unveiling of a new multibeam echosounder (MBES) option for the Sonobot 5—the EvoLogics Multibeam—at the Ocean Business conference in Southamption, UK.

During the summer of 2023, a team from EvoLogics’ Berlin-based HQ embarked on a demonstration tour to showcase the new multibeam platform to existing partners and clients. The MBES “roadtrip” garnered valuable feedback which in turn informed further upgrades to the integration of the sonar into the USV.

MIGHTY MULTIBEAM

Unlike single-beam echosounders, the multibeam echosounders offer superior coverage and 3D mapping. Releasing multiple sound waves concurrently, it efficiently maps extensive underwater areas, helping operators drastically reduce the required survey time.

The key strength of multibeam sonar technology lies in its capacity to generate higher-resolution imagery. Emitting a fan-shaped array of sound waves, it captures echoes from various angles, facilitating the creation of detailed 3D representations of underwater features.

Multibeam sonars deliver enhanced depth accuracy compared to their single-beam counterparts. Leveraging advanced algorithms, a MBES compensates for seabed complexities, mitigating the impact of factors like slope, refraction, and interference.

The Evologics Multibeam for the Sonobot 5 incorporates a Norbit OEM solution, an entry-class MBES designed for survey professionals. Featuring high-grade dual GNSS and INS positioning and motion control, standard across all Norbit echosounders, this system boasts 256 beams at 1.45° x 1°, a range exceeding 200 m, and a 50 Hz ping rate. These specifications enable professional surveying in accordance with the IHO’s S-44 standard.

The compact Norbit sonar interface unit (SIU) is fully embedded in the submergible pod of the Sonobot vehicle. Connected by a single cable for power and data link, the sonar head is easily detachable with a “slide-and-lock” mechanism for convenient transportation and storage.

In the pursuit of optimal performance, EvoLogics engineers created a custom-molded cover for the sonar head before the production of the first serial orders. This sleek cover not only enhances the hydrodynamic form of the USV but also adds to the unit’s robustness, providing crucial protection to the sonar-pod assembly.

The cover has also proven advantageous when performing multibeam sonar surveys in strong currents, as it minimizes drag and ensures efficient navigation through challenging conditions. It enables better utilization of the Sonobot’s powerful thrusters and aids in maintaining the steady survey speed during data collection.

The mechanical connection between the submergible pod and the sonar—the “slide-and-lock” mechanism—also underwent a rigorous test and evaluation process during the demonstration tour, resulting in some final design tweaks to optimize overall handling of the unit before and after field operations.

Weighing less than 32 kg, the Sonobot 5 with EvoLogics Multimeam measures 1.29 m (L) x 0.96 m (W) x 1.04 m (H, with antennas) making it the most compact and easy-to-handle USV equipped with a professional multibeam sonar on the market.

IN THE WATER

In November 2023, EvoLogics completed a survey of the Plessow Lake in Brandenburg, Germany (a regular testing site for the company’s latest innovations) with the upgraded Sonobot 5 USV. Notably, early trials at this site revealed an unexpected feature: a cairn-like mound formation on the lake floor, initially thought to be an ancient burial mound. EvoLogics shared the bathymetric data with the Association for Underwater Archaeology Berlin-Brandenburg for further evaluation. After a period of underwater archaeological scrutiny among experts, the feature was determined to be a geological phenomenon, likely a remnant of the last glacial period.

The mound subsequently became a focal point for testing bathymetric equipment. EvoLogics often returns to Plessow Lake with a Sonobot USV, taking advantage of the cairn’s unusual underwater features to help test and evaluate the MBES' capabilities in detecting and mapping underwater structures. The mound's elevation and shape create variations in the lake's bathymetry, providing a unique opportunity to evaluate the echosounder performance in measuring depths and generating detailed bathymetric data.

The survey plan chosen for the multibeam swath survey at the Plessow Lake was a crosshatch pattern, a series of intersecting parallel lines. This pattern ensured comprehensive data collection, eliminating any gaps in area coverage. During the survey, the complete sonar dataset was stored onboard the vehicle, with a live preview displayed to the operator at a shore-based command.

SYSTEM COMPATABILITY

EvoLogics Multibeam is compatible with the Norbit data collection tools DCT and NORdredge, web-based solutions for real-time monitoring of multibeam sonar operations. Norbit NORdredge was used for the live multibeam data preview at Plessow Lake, and even without post-processing of the full set of data points, the multibeam sonar data preview is more detailed than the single-beam bathymetry of the area.

EvoLogics Multibeam is also compatible with various third-party software packages supported by the Norbit WBMS sonar family. The data from the Plessow Lake survey was processed with QPS Qimera, revealing intricate details of the "cairn" feature on the lakebed.

This story was originally featured in ON&T Special Edition 2023. Click here to read more.