UUV On-Board Path Replanning using PRM-A*

Path planning algorithms for unmanned underwater vehicles (UUVs) are broadly categorized into two sub-areas: global path planning and local path planning. A global path planner employs known information about the operational environment to return a path from the start point to the goal while avoiding any obstacles. Here obstacles are static, such as islands, docks, ship wrecks, etc. The path is determined prior to the UUV's departure. In contrast, a local path planner recalculates the path returned by the global path planner as needed to avoid unexpected moving obstacles such as ships, boats, swimmers, other UUVs, etc. In this paper, we present a novel local path planner for UUVs using an adaptation of the global path planning algorithm PRM-A* discussed in a companion article in this same conference [8]. It is assumed that the algorithm is implemented on-board the UUV and works in conjunction with sensors that can detect the position of the moving obstacles. The proposed local path planner allows the UUV to follow the original path returned by the global path planner, with deviations only as needed to avoid the newly detected obstacles. Thus, only the segment of the path being blocked by the obstacle is avoided, and the original path is otherwise retained. While the focus here has been on UUVs, the same approach can be applied for unmanned surface vehicles (USVs).