A New Procedure for Simultaneous Navigation of Multiple AUV's

Navigation by Underwater Autonomous Vehicles (AUV's) is a challenging problem because radio waves do not penetrate water, and acoustic waves must be used instead for determination of position. Current systems utilize round-trip time-of-flight between single vehicles and fixed transponders to determine position. While reliable, the drawback of this method is that there is an upper limit on the number of vehicles that can navigate at the same time. We describe a new procedure that allows simultaneous navigation of multiple vehicles using the acoustic navigation signals from only one vehicle in the group. One vehicle in the group is assigned to navigate conventionally with an acoustic Long BaseLine (LBL) system. The other vehicles in the group are equipped with a sensor that can determine the relative angular heading to the source of an intercepted acoustic signal, and a separate sensor that can determine angular inertial heading. As the chosen vehicle navigates conventionally, the other vehicles in the group intercept the return pings from the fixed transponders. From these signals, and the inertial heading, each vehicle is able to determine their inertial position. The sensor used to determine relative angular heading to the source of an intercepted signal consists of two hydrophones separated by an approximate distance of one meter. Relative angular heading is extracted from the difference-in-arrival time using correlation between the hydrophone signals. An error propagation analysis is performed that quantifies the accuracy of the inertial position fix as it depends upon vehicle-transponder geometry, and sensor precision.