Bedrock Ocean AUV | Digest energy by 2030. That’s a target of at least 2000 active offshore turbines. The US has approximately eight and only recently started providing power. That’s a gaping chasm between demand and supply.” The Phins 9 Compact occupies an 88.9 mm (diameter) by 130 mm cylindrical space inside the payload half’s dry section, and through its FOG IMU it maintains a position accuracy within 0.02% of the distance travelled when aided by DVL. This is sufficient for Bedrock’s needs as most initial offshore construction products will run no deeper than 100 m, so the AUV can surface quickly and often enough to regain its GNSS position. With a runtime exceeding 10 hours, concerns over the energy efficiency of constant surfacing and diving can be deemed unnecessary. Additionally, the AUV’s Nortek DVL500 maintains bottom velocity readings from a 0.1 m to 200 m distance from the seafloor, up to an 8 Hz ping rate, and with an accuracy of 0.01 mm/s. A custom housing for the navigation system has been made by Bedrock, and after integration the DVL is bolted to the Phins 9 Compact and calibrated in-house based on close advisement from Exail. A Blueprint USBL/ACOMM transceiver is installed onboard as well, should an end-user want such real-time position querying at their GCS and lack qualms about the extra surface-side equipment needed. This also preserves the option for vehicle-to-vehicle comms for teaming and advanced autonomous docking behaviour. Collision avoidance The first design of Bedrock’s forward perception system used a single-beam echosounder. “That would simply tell us whether there was something forward of the AUV or not – a very binary ‘go or don’t go’ approach, because the minimum viable product goal of the first-gen perception system was to just not hit anything,” Chiau muses. “But, as you operate nearer to the seafloor, terrain changes much more chaotically, so your reaction time to your surroundings needs to speed up while staying within the control bandwidth of the vehicle.” Knowing better systems were needed, Bedrock went directly to Norbit, much as it had with Exail. As the former was already using the latter’s multibeam sonar, the American company asked the Norwegian supplier if it could build a low-power, wide-swath, forward-looking sonar, now dubbed the FLS-42 (it was also at this time that Bedrock asked after the aforementioned SBP-42 sub-bottom profiler, now used in its low-fly AUV configuration). “It is more reliable to scan farther ahead, because then you can process the terrain, having mapped the contours, and feed it into the path planning to achieve the best constant altitude path for the sensors without phase lag; for instance, by waiting for a notable ‘bump’ before finally adjusting its height,” Chiau says. That means Bedrock’s OEM version of the FLS-42 has a 90° vertical swath, resulting in a large, 400 kHz fan that extends above and below the front of the AUV, and detects terrain changes up to 50 m away. “Now, not only do we not hit anything, but that FLS enables us to run all kinds of algorithms for terrain-centric navigation and obstacle avoidance,” Chiau says. “For instance, if we’re surveying under a structure, we can put in a special command to avoid surfacing if an object has been detected upwards of the AUV, or in a ‘keep out’ zone, and there’s all sorts of other behaviours we can tailor, based on perception-based risk factors like that.” Importantly, neither the FLS-42 or other sonars on Bedrock’s AUV emit frequencies below 200 kHz, which has been a crucial design choice for gaining clearance for near-shore operations from governmental environment agencies as such frequencies are harmless to marine mammals. This prevents the need for requiring thirdparty protected species observers or Incident Take Authorisations. 55 Uncrewed Systems Technology | August/September 2024 Survey data is processed at the edge in real-time using an nVidia Jetson TX2, installed in the front of the AUV
RkJQdWJsaXNoZXIy MjI2Mzk4