A 6 DOF nonlinear observer for auvs with experimental results

In this paper we propose an observer system for underwater vehicles. Two separate control plant models are employed; a three DOF model accounting for the main current loads acting on the vehicle and a live DOF model describing the vehicle dynamics. By explicitly utilizing an estimation of the current velocity in the observer, this paper shows that a high degree of robustness related to environmental disturbance and measurement noise is achieved. This is related to the estimation of the destabilizing Coriolis forces and moments. UGES is proven for the observer error dynamics. Experimental results from full scale testing of the Minesniper Mkll demonstrate the proposed observer system.