Estimating AUV Motion Using a Dual-Sided Synthetic Aperture Sonar

The navigation and localization of autonomous underwater vehicles (AUVs) in complex underwater environments are challenging. Synthetic aperture sonar (SAS) can provide a precise measurement of its platform motion. Single-sided micronavigation has been used to aid AUV navigation. However, the conventional time delay estimation method in the displaced phase center antenna algorithm is not adequately robust due to phase wrap errors. In addition, it is difficult to estimate sway and heave using a single time delay estimate based on single-sided noninterference SAS. This article proposes a dual-sided SAS micronavigation algorithm that makes use of a robust method for estimating time delays between redundant phase centers of adjacent pings. The proposed dual-sided method allows the estimation of both vehicle sway and heave using a single time delay estimate from each side of the vehicle. The theoretical standard deviations for the surge, sway, and heave estimates are derived. Simulation demonstrates the advantage of the proposed time delay estimation method compared to the conventional one. Additionally, a quantitative comparison between the proposed and conventional time delay estimation methods is shown to prove that the proposed method outperforms the conventional method. Experimental validation is performed via comparisons between single- and dual-sided micronavigation, Doppler velocity log, and GPS-aided inertial navigation system, which is taken as the gold standard to calculate errors.