AUV navigation with a single seafloor station based on mutual orientation measurements

We propose an AUV navigation method based on a single seafloor station. The key idea is acoustic mutual orientation and communication. The AUV firstly sends a signal to the station and then receives the reply with a hydrophone array to estimate direction and distance to the station. On the other hand, the station estimates the direction to the AUV by receiving the signal with a hydrophone array, and sends the information back to the AUV. Then, the AUV can estimate its position and orientation at the station-fixed coordinates without drifts. Furthermore, these measurements are fused with other on-board sensors such as DVL, angular rate gyro and depth sensor by particle filter, a probabilistic approach, in order to realize stable positioning robust against sensor noises and lack of measurements. A pair of acoustic device named ALOC (Acoustic LOcalization and Communication) has been built. A series of sea trials were carried out in September 2010 using a testbed AUV Tri-Dog 1 and a seafloor station mounted with ALOC at Kagoshima Bay in Japan. Although orientation measurements made by the station was not sent in real-time, the performance of the method was verified through simulations based on the actual measurements.