46 When not in use, the UAV is stored and recharged on the vehicle. The base includes a retention mechanism to keep it secure and a power supply to recharge its battery. The technology is proposed for prototypes later this year with a driver, and for fully autonomous offroad driving by 2030. Maritime In the oceans, swarms of autonomous underwater vehicles (AUVs) require accurate coordination and positioning to provide detailed surveys of the seabed. To overcome this challenge a sonar system on the surface can link to all of the AUVs in a swarm to provide coordination. The Autonomous Sparse-Aperture Multibeam Echo Sounder scans at surface-ship rates while providing sufficient resolution to find objects and features in the deep ocean, without the time and expense of deploying underwater vehicles. The echo sounder is a large sonar array, using a small set of ASVs that can be deployed via aircraft into the ocean, which can map the seabed at 50 times the coverage rate of an underwater vehicle and 100 times the resolution of a surface vessel. This approach provides the best of both worlds: the high resolution of underwater vehicles and the high coverage rate of surface ships. Large surface-based sonar systems at low frequency have the potential to determine the materials and profiles of the seabed, but typically do so at the expense of resolution, particularly with increasing ocean depth. Resolution is restricted because sonar arrays installed on large mapping ships are already using all of the available hull space, thereby capping the sonar beam’s aperture size. An array of underwater UUVs can operate at higher frequencies within a few hundred metres of the seafloor and generate maps, with each pixel representing 1 m2 or less, resulting in 10,000 times more pixels for that area. However, this comes with trade-offs: UUVs can be time-consuming and expensive to deploy in the deep ocean, limiting the amount of seafloor that can be mapped; they have a maximum range of about 1,000 m and move slowly to conserve power. The area coverage rate of UUVs performing high-resolution mapping is about 8 km2 per hour; surface vessels map the deep ocean at more than 50 times that rate. Instead, a collaborative array of 20 ASVs, each hosting a small sonar array, effectively forms a single sonar array that is 100 times the size of a large sonar array installed on a ship. The large aperture achieved by the array (measuring hundreds of metres) produces a narrow beam, which enables sound to be steered precisely to generate high-resolution maps at low frequency. However, this collaborative and sparse setup introduces some operational challenges. First, for coherent 3D imaging, the relative position of each ASV’s sonar subarray must be tracked accurately through dynamic, ocean-induced motions. Second, because sonar elements are not placed directly next to each other without any gaps, the array suffers from a lower signal-to-noise ratio and is less able to reject noise coming from unintended or undesired directions. To mitigate these challenges, a low-cost, precision-relative navigation system uses acoustic signal-processing tools and ocean-field estimation algorithms. These algos estimate depthintegrated water-column parameters to account for the temperature, dynamic February/March 2025 | Uncrewed Systems Technology A swarm of 20 autonomous marine craft creates a huge sparse sonar array (Image courtesy of MIT Lincoln Lab) An orbital swarm of autonomous small satellites (Image courtesy of Grainger College of Engineering at the University of Illinois Urbana-Champaign)
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