Coordinated Navigation of Multiple Underwater Vehicles

For a group of underwater vehicles, the relative positioning problem is considered. That is, the mutual relative positions of the individual vehicles and hence the group formation is determined. The observations to be used are the relative ranges between the vehicles and the dead reckoning estimates of the individual navigation systems of the single vehicles. These data are to be distributed via an acoustic underwater communication system. The solution to the relative positioning problem is a prerequisite for implementing algorithms for coordinated behaviours of multiple underwater vehicles. A crucial condition is the limited communication capability in the underwater communication network. This is due to the comparably small bandwidth of the underwater acoustic channel and the lack of reliability of those connections, caused by multipath, diffraction and other acoustic wave propagation related effects. This paper introduces a simple concept for the solution to this problem, which avoids the usage of an acoustic positioning system such as LBL or USBL. This is achieved by implementing a variant of a trilateration technique in an extended Kalman filter.