Developing a sensor-based underwater navigation system

The development and verification of a sensor-based underwater navigation system are described. We form a basic vehicle model, which relies on few parameters. This model is fused with inclinometer, compass, triaxial gyroscope and sonar data to produce an estimate of the vehicle's orientation and position. A dedicated sonar unit has been developed, to track and produce continuous range information from a passive target. The unit uses the range differential between multiple sonar transducers to obtain target bearing information, and a pan-and-tilt unit to keep the transducers aligned with the target. In this paper, we compare sonar model predictions with experimental data. We also present sensor noise characteristics. We show the results of combining the localization system with a simple controller. the vehicle performs a 'stand-off' experiment and moves in a predetermined path relative to a sonar feature. finally, we discuss the problem of missing sensor data, which arises when the sonar is changing between targets.