Underway path-planning for an unmanned surface vehicle performing cooperative navigation for UUVs at varying depths

This paper reports on the optimized path-planning for an unmanned surface vehicle (USV) serving as a communication and navigation aid (CNA) for multiple unmanned underwater vehicles (UUV) performing surveys. This path-planning can occur prior to the survey (pre-deployment mode) based on the original planned paths for the survey UUVs or during the survey (underway mode) using in situ UUV positions reported acoustically by the survey UUVs. The underway mode has the advantage of integrating the actual UUV paths which may differ from the planned ones due to currents, re-planned missions, etc. This planner considers the relative depth of the CNA and survey UUVs, allowing the CNA to effectively aid survey UUVs in maintaining altitude over the sea floor, as is done in some UUV surveys. Results are presented from simulations and in-water validation trials for both path-planning modes. The underway planning mode is preferred since it adapts to changes in the survey UUV path during the mission. The advantage of bounding the distance between the CNA and any survey UUV to limit the survey UUVs´ position error is also highlighted.