In context
In May 2024, deep-sea exploration was accelerating globally, with manned submersibles like China's Jiaolong and Fendouzhe playing increasingly vital roles in marine resource development. Accurate underwater positioning remained a critical challenge, as acoustic positioning—particularly ultra-short baseline (USBL) systems—was the primary means for tracking these vehicles. However, USBL accuracy was often degraded by hydrophone installation deviations, a problem that researchers at the Chinese Academy of Sciences sought to address.
What was reported
Researchers from the Institute of Acoustics, Chinese Academy of Sciences, proposed a positioning correction method for full-ocean-depth manned submersibles equipped with multi-element USBL systems. The method combines phase correction with Toeplitz correction to mitigate the impact of hydrophone installation errors in the x and y directions, which otherwise lead to significant angular and positional errors.
The approach first analyzes how installation deviations affect DOA estimation, then applies a phase correction that exploits the relationship between phase differences of non-adjacent hydrophones, followed by a Toeplitz correction to refine the covariance matrix. The corrected matrix is then used with the TLS-ESPRIT algorithm for direction-of-arrival estimation.
Simulations using a 32-element array with 0.055 m spacing and up to 10% installation error showed that the proposed method reduced average positioning errors to as low as 19.30% of uncorrected values in the x direction, 27.87% in y, and 29.12% in z, outperforming traditional Toeplitz correction alone. The method also avoided over-correction issues seen with Toeplitz when deviations were small, and maintained accuracy across various target positions.
Why it mattered
This work offered a practical, easy-to-implement solution to a persistent problem in underwater acoustic positioning, potentially improving the reliability of USBL systems not only for manned submersibles but also for other underwater vehicles. Enhanced positioning accuracy is crucial for safe deep-sea operations, including scientific exploration and resource extraction, and could influence future designs of acoustic positioning arrays.
“The proposed algorithm is simple, easy to implement, and effective, and can effectively improve the positioning accuracy.”
Source: 《机器人》期刊 (robot.sia.cn) · Published 2024-05-08 · “针对全海深载人潜水器的超短基线定位校正”