The Estimation of Ocean-current Velocity for AUV Using Optimization-Based Alignment

Doppler velocity log (DVL) can provide velocity information for the strap-down inertial navigation system (SINS), and it is widely used in the field of navigation for autonomous underwater vehicles (AUVs). However, in deep-sea scenarios, the DVL's output is the velocity relative to the ocean currents since it works in the water-tracking mode. The ocean-current velocity brings systematic errors to the SINS/DVL integrated navigation system, which leads to the degradation of navigation positioning accuracy. Therefore, estimating and compensating for the current velocity is an essential requirement for high-precision navigation performance and an important topic for oceanographic research. In the small ocean area where AUV works, the current velocity remains stable for a short time, and it can be considered a constant value. This paper proposes an optimization-based alignment (OBA) method for estimating the ocean-current velocity based on the GNSS (global navigation satellite system)/SINS/DVL integrated system. The simulation results show that the proposed method can estimate the current velocity accurately and does not depend on the initial value compared with the traditional KF method.