Cooperative positioning using range-only measurements between two AUVs

This paper presents a cooperative positioning system between two autonomous underwater vehicles (AUVs). Each AUV is equipped with some navigational sensors. However, AUVs with different tasks have different navigational capabilities. By introducing acoustic communication between AUVs, information from multiple AUVs can be fused to give a more accurate position estimates to AUVs with poorer navigational capabilities. We present results from a field trial where a lawnmower mission is executed by a survey AUV with poor navigational sensors while another AUV with higher positioning accuracy plays the role of a beacon AUV. The beacon AUV´s task is to help improve the survey AUV´s position accuracy by providing it regular range updates from various locations. An Extended Kalman Filter (EKF) was implemented to fuse the range information updates with the navigational sensor data on the survey AUV. We were able to avoid unbounded error growth in the position estimate of the survey AUV in our experiments through cooperative positioning between two AUVs using range-only measurements.