Spiral path planning for docking of underactuated vehicles with limited FOV

This paper proposes a novel approach for constructing a docking path for underwater vehicles, using a new spiral resulting of combining the Fermat and logarithmic spirals. The proposed spiral path has two properties that will help solve some of the challenges of docking autonomous underactuated vehicles (AUVs). The first property is that the spiral path reaches the entrance of the docking station without curvature, allowing a smooth transition when entering the docking station. The second is that the AUV never exceeds a certain bearing angle with respect to docking station. This last feature allows AUVs equipped with navigation sensors which have a reduced field of view (FOV), such as cameras or acoustic positioning systems, to always preserve the docking station inside the FOV. Furthermore, the paper presents an interpolation of the spiral using waypoints that are connected with segments of logarithmic spirals. This makes it possible to apply existing guidance laws to follow the docking spiral. The proposed spiral docking path has been experimentally tested using an autonomous underwater vehicle.