Observer-feedback control based acoustic homing beacon for autonomous underwater vehicles

Abstract

One of the visions for Acoustically enabled Autonomous Underwater Vehicles (AUVs) is a fleet of these vehicles to be held on a ship, deployed for a specific mission and then recovered by the ship. A component of this mission is finding the ship after deployment to be recovered, since both the ship and AUVs have probably drifted from their original locations and intended deployments. While many vehicles can surface, utilize radio and GPS to relocate the ship and navigate towards it, the method presented allows the ship to be found by deploying an acoustic beacon, while the AUVs utilize an observer system to navigate towards the ship. The spatial decay of spreading sound waves provides a spatially dependent variable for the AUV to measure. Then, utilizing a linear model of the dynamics, a linear observer is constructed. The absolute value of the sound pressure readings are fit to a spatial decay model, which is then linearized to form the observer equation. By tuning the observer gain, the AUV can directly feed its observations of the sound field into the observer algorithm and generate navigation controls which will allow it to find the beacon. [Sponsored by the Raytheon Advanced Studies Fellowship.]