Gravity-Aided Navigation of Underwater Vehicles via Alternating Line Small-Domain Matching Method

Gravity matching algorithm is a core research issue of underwater inertial navigation system (INS)/gravity integrated navigation. Terrain contour matching (TERCOM), as a sequence matching representative, suffers from the low-efficiency problem of traversing all in-domain grids and the out-of-domain mismatching (OM) problem of the domain boundary limitation. To address these two issues, this article proposes a novel alternating line small-domain matching method (ALSM) for gravity-aided navigation of underwater vehicles. In detail, the optimal matching position on the line is determined by the alternating grid line-based prematching mechanism, which enables the autonomous underwater vehicle (AUV) to quickly approach its real position. Then, the online optimal matching position is used as the center to apply a local small-domain rematching mechanism to determine the optimal matching position within the domain, thereby improving matching reliability. The experimental results verify the outstanding matching performance of the proposed method for improving the underwater navigation positioning efficiency and matching reliability. Moreover, three track tests in different gravity zones show that its positioning efficiency, compared with TERCOM, is improved by 93% on average, the number of OM is reduced by up to 93%, and the average matching accuracy is no more than one grid resolution, in which the proposed algorithm is further proved to be suitable by positioning in different gravity zones.