Design and experimental evaluation of an Autonomous Surface Craft to support AUV operations

Abstract

In recent years, there has been a large increase in the use of autonomous underwater vehicles (AUV) for numerous military, commercial, and scientific missions. These include mapping, oceanographic data collection, and search and recovery. The list of the key technologies for AUV research includes communications, power, navigation, design, vehicle tracking and sensor fusion. Despite rapid progress in some of these areas, a number of barriers exists. This thesis offers a novel approach to address these issues by utilizing an Autonomous Surface Craft (ASC) with a wetbay from which to launch an AUV, including a launch capability. This paper also discusses the fusion of sensors required by these two vehicles, including computer resources, sonar images, and power. A new method is described by which an ASC can be tracked through the use of a towed underwater modem increasing the communication range over two kilometers. This thesis describes how an ASC tracks an AUV by configuring two modems together in a short baseline acoustic array. Results of this tracking show less than four meters of error under difficult real-world test conditions.

(cont.) Discussed are the advantages of transmitting the information obtained in the AUV modem transmission via surface communications. A tracking ASC maintaining close proximity to the AUV allows a larger bandwidth of underwater communication, increasing the flow of information. Expanded flow enables multiple assets to communicate over long-ranges. The impact of these contributions will expand the capabilities of autonomous vehicles.