Chapter µ-Nautilus, an autonomous lightweight profiler with depth control and configurable sampling time

Abstract

Coastal lagoons, such as Mar Menor, hold significant ecological importance but are vulnerable to environmental disruptions from resource exploitation. Continuous monitoring is crucial for understanding critical situations and assessing recovery efforts. Manual sampling, as used in Mar Menor, is costly and yields limited results. Therefore, demand exists for automatic methods to enhance data collection and reduce operational tasks. This paper presents the design of a compact autonomous submersible profiler, µ-Nautilus, building upon the previous s-Nautilus model. It weighs 11 kg, which is half the weight of its predecessor. µ-Nautilus aims to stop at a configurable depth with less than 20 cm depth error using a single 750 cm3 ballast tank for control. Cascade control is employed, and satisfactory depth control (±15 cm error) is obtained during tests at sea. µ-Nautilus is powered by batteries with a capacity of 12.8Ah and 11.1V to run the ballast tank and 16.75Ah and 3.6V for the rest of the electronics. It can operate autonomously for 48 days performing cycles every 6 hours, suitable for the cleaning frequency needed due to fouling in Mar Menor.