Concurrent control and plant identification to support overall noise reduction of autonomous underwater vehicles

Commercial, off-the-shelf (COTS) autonomous underwater vehicles (AUVs) are not usually designed to be low-noise in the 100 Hz–10 kHz band. Options to mitigate the noise include mechanical re-design, adaptive filtering of the noise on any acoustic sensor using the vehicle as a platform, or active noise control (ANC). The first of these options eliminates the benefits of using a COTS platform. The second option can be attractive but is most effective for propulsor noise (and not other sources like the depth sounder) and does not mitigate the issue if multiple vehicles are used in coordination. An on-board projector can enable ANC of the vehicle noise. For small, nearly acoustically compact vehicles, the directionality of propulsor noise is not very complex, suggesting global control using a limited set of the acoustic sensors as a control metric. This paper explores methods for performing concurrent control of narrow-band vehicle noise while performing the low-noise, broad-band plant identification necessary to support the control. In addition to the reductions in self noise (on a single vehicle and multiple vehicles), the ability to use the information in the plant estimate to perform “quiet” depth sounding is explored.