Sea Trial of Acoustic Positioning of 10 Targets per Second

The authors are developing combined aerial and underwater drones to address the manpower shortage in Japan for inspecting and monitoring aging water area infrastructure and fishing facilities (fixed nets, fish preserves, etc.), An aerial drone transports an underwater drone from land, and after landing on the water, the underwater drone is deployed to perform monitoring tasks, controlled remotely from the land. The underwater drone's location is obtained using acoustic positioning. In the future, to efficiently monitor a large number of targets, it is anticipated that multiple underwater drones will be used simultaneously, and there will be scenarios where divers collaborate with the drones. To verify the performance of the acoustic positioning system for the combined aerial and underwater drones in locating multiple targets, the authors conducted sea area experiments. Positioning of 10 targets per second was confirmed using time-division multiplexing. The positioning error (standard deviation of detected coordinates) was less than 6 cm, demonstrating sufficiently high accuracy. Pingers were also attached to an underwater drone and divers, realizing their simultaneous positioning. In the future, the authors plan to attempt the simultaneous positioning of more targets by using code-division multiplexing as well.