We address the problem of navigation for underwater vehicles in harbor surveillance tasks including ship hull inspection. Maintaining accurate localization is important for navigation and ensuring coverage, but is difficult in cluttered environments such as harbors, where acoustic-based localization systems are difficult to employ.
For the open and locally flat areas of large ships, our approach uses onboard sensors in a simultaneous localization and mapping setting. We extract dense features from a forward looking imaging sonar and apply pair-wise registration between sonar frames. The registrations are combined with onboard velocity, attitude and acceleration sensors to obtain an improved estimate of the vehicle trajectory. We have successfully demonstrated hull search as well as closed-loop waypoint navigation on large Navy ships.
We handle the complex areas of a ship differently by using profiling sonar.
3D model of rudder and screw of a 180m long ship. Note the size of the ship in comparison to the HAUV (shown in yellow)