Relative positioning of multiple underwater vehicles in the GREX project

This paper discusses the estimation of relative positions of a swarm of autonomous underwater or surface vehicles. The solution of this problem is crucial for performing a coordinated path following in a spatial formation. It forms a necessary prerequisite for establishing a coordinated control behavior of multiple vehicles which is the major goal of the European Project GREX. It is shown that the relative positioning problem is solvable when dead reckoning data are combined with the mutual range data measured via acoustic modems. Therefore, the limited capability of the acoustic communication channel has to be considered when developing a solution algorithm. A simple concept is achieved by implementing a recursive variant of a trilateration technique by means of an extended Kalman filter.