Abstract This paper aims to provide stable landing methods and systems for hovering-type AUVs (autonomous underwater vehicles) on a seafloor, which will aid in seafloor investigations, such as gravity acceleration measurements near the seafloor. The proposed methods consist of two techniques. Firstly, a heading control method is proposed, in which the AUV is positioned to face currents before landing on the seafloor, thus reducing flow resistance. Secondly, a stability evaluation method is proposed, in which the landing quality is evaluated based on fast Fourier transform (FFT) analysis of its attitude. The methods were evaluated and verified based on data obtained from tank and sea experiments using an AUV Tri-TON. Thanks to the stability evaluation method, the landing stability was judged automatically with a success rate of 96% (27 of 28 cases). The heading control method also realized stable landing with a success rate of 80% (4 of 5 cases). To enhance the landing stability further, a buoyancy adjustment system was developed and verified using an AUV Tri-Dog 1. Thanks to the developed system, the stable landing was conducted successfully with a success rate of 100% (4 of 4 cases). The proposed methods and system will contribute to the stable landing of AUVs on the seafloor and enhance future seafloor surveys.

中文翻译：

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用于海底测量的自主水下航行器着陆方法

摘要 本文旨在为悬停式AUV（自主水下航行器）在海底提供稳定的着陆方法和系统，这将有助于海底调查，例如海底附近的重力加速度测量。所提出的方法由两种技术组成。首先，提出了一种航向控制方法，其中AUV在降落在海底之前定位为面向水流，从而减少流阻。其次，提出了一种稳定性评价方法，基于对着陆质量的快速傅里叶变换（FFT）分析来评价着陆质量。根据使用 AUV Tri-TON 的坦克和海上实验获得的数据对这些方法进行了评估和验证。借助稳定性评估方法，自动判断着陆稳定性，成功率为 96%（28 例中的 27 例）。航向控制方法也实现了稳定着陆，成功率为80%（5例中有4例）。为了进一步提高着陆稳定性，使用AUV Tri-Dog 1开发并验证了浮力调节系统。由于开发的系统，稳定着陆成功率为100％（4个案例中的4个）。所提出的方法和系统将有助于 AUV 稳定着陆在海底并加强未来的海底调查。