In this paper, we propose a navigation method of multiple AUVs and give a performance analysis on position estimation for a wide area survey. The key idea of the proposed method is alternating roles of the AUVs between Moving and Measuring Role (MMR) and Landmark Role (LR). AUVs in the MMR move based on the AUVs in the LR. On the other hand, AUVs in the LR keep their positions on the seabed to act as landmarks for the moving AUVs. By alternating their roles, the two groups of AUVs can observe in a wide area while maintaining a good position estimate. AUV position is estimated by mutual acoustic measurements of relative distance among AUVs and direction among them. These position measurements are fused with other on-board sensors such as Doppler velocity logger (DVL), fiber optic gyro (FOG) and depth sensor by particle filter for a robust position estimate against sensor noises and lack of measurements. We verified the performance of the method through navigation simulation based on the performance of sensors obtained during various experiments performed in a pool environment and at sea. In the simulation, the proposed method achieved a positioning error considerably smaller than dead reckoning and conventional navigation methods of a single AUV. In the proposedmethod, each AUV also achieved state estimation, suppressing deviation from its true position and heading due to alternating roles and evaluating outliers of positioning measurements by particle filter. Therefore, the proposed method is suitable for a wide area survey without sensor drifts and deviation from true state compared with conventional navigation methods.
- Acoustic positioning
- Multiple AUVs