Designing a Bathymetric Sensor Using Absolute Pressure Sensors Arranged on a Regular Polyhedron

In oceanic environments, compact underwater drones must determine their positional information, including water depth, to move autonomously because wireless communication underwater is challenging. However, current bathymetric sensors often lack high accuracy, energy efficiency, and cost-effectiveness. We propose a spherical bathymetric sensor that uses multiple absolute pressure sensor elements, allowing precise water depth measurement without being affected by dynamic pressure caused by waterflow as well as offering low energy consumption and cost-effectiveness. This sensor has a spherical design with 12 absolute pressure sensor elements arranged in a regular dodecahedron, connected by a flexible Kiri-origami circuit. The water depth is determined by compensating for waterflow-induced error using sensor data and linear regression. We evaluated our method using both simulations and experiments. The sensor reduced waterflow-induced errors to within 7.5 mm in simulations and 5 mm in a water tunnel at a speed of 2.0 m/s. By comparison, conventional methods without error compensation showed errors exceeding 100 mm under the same conditions. The sensor was also validated to predict depth at different depths, resulting in a 6.5 mm error. These results suggest that our proposed sensor can effectively measure water depth for compact underwater drones.