Localization of an Unmanned Underwater Vehicle Using a Tethered Cooperative Surface Vehicle and Hybrid EKF/Grid-Based Method

This paper presents an approach for the localization of an Unmanned Underwater Vehicle (UUV) in a cooperative team with a tethered Unmanned Surface Vehicle (USV). For the localization, the UUV and the USV carry a camera and a sonar respectively to observe each other. The vehicle states are split between Extended Kalman Filter and grid-based estimators based on which sensors provide Gaussian or non-Gaussian observations of each state. Specifically, the horizontal position of the UUV is estimated using a grid-based method because the camera and sonar that observe these states provide non-Gaussian observations when they cannot detect their target. Additionally, the tether to the USV is treated as a non-Gaussian observation that prevents unbounded error growth. Validation of the technique was performed in simulations using sensor models developed based on testing in a lake and pool.