Accurate and efficient survey of the seafloor by multiple AUVs using alternating landmark navigation — Sea experiments using three AUVs

Abstract

This paper presents the latest results of sea experiments conducted pertaining to a navigation method for wide-area surveys of the seafloor using multiple autonomous underwater vehicles (AUVs). Self-localization is essential for AUV navigation, and AUVs are typically supported by a long base line or super-short base line (SSBL). Here alternating landmark navigation (ALN) was proposed as an alternative to these methods. In this approach, each AUV alternately becomes a landmark, which remains stationary on the seafloor, while the other AUVs navigate using acoustic positioning relative to the landmark AUV. Our goal is to complete surveys near the seafloor using only AUVs; the ALN approach realizes stable navigation without any surface support. The ALN method was implemented using three AUVs: “Tri-Dog 1,” “Tri-TON,” and “Tri-TON 2.” These were the first experiments in a sea environment using these three AUVs. Through the analysis of past sea experiments, the state estimation method was revised, resulting in improved accuracy in real time compared with the results in previous experiments. Through the sea experiments, it was verified that the ALN method can execute an efficient and accurate survey of the seafloor.