Hybrid Tightly-Coupled SINS/LBL for Underwater Navigation System

The application of long baseline aided strap-down inertial navigation system (SINS/LBL) has been demonstrated to be an effective solution for accumulative position errors of underwater vehicles (UVs). To address the inefficient positioning when available hydrophones are few in acoustic array, a hybrid tightly-coupled SINS/LBL is presented for underwater navigation system. The system is composed of SINS, LBL and pressure sensor (PS). The hybrid positioning model based on slant range, slant-range rate, slant-range difference and slant-range rate difference is established according to the location principle of time of arrival (TOA) and time difference of arrival (TDOA) when the number of available hydrophones is two. TDOA positioning model based on slant-range difference and slant-range rate difference is adopted when the number of available hydrophones is more than two. The two tightly-coupled SINS/LBL models could be switched with each other as the number of available hydrophones changes in acoustic array. This paper used experimental data obtained from an unmanned surface vehicle (USV) to validate the navigation performance. Compared with single tightly-coupled SINS/LBL model, the proposed method can provide faster error convergence and more accurate submerged position fixes.