Control of slender body underactuated AUVs with current estimation

In this paper we present a controller for under-actuated underwater vehicles with current estimation. A new approach is proposed where the complete model of the vehicle is split into two separate control plant models. The main design objective behind this strategy is to reduce the effect of the destabilizing Coriolis and centripetal forces and moments, which represent a significant challenge for automatic control when the forward speed is sufficiently high. However, by explicitly utilizing an estimation of the current velocity in the controller, this paper shows that a high degree of robustness related to environmental disturbances and unmodelled dynamics is achieved. This is related to the computation of the destabilizing Coriolis and centripetal forces and moments. The cascaded system consisting of the controller and the current observer error dynamics is proved to be globally asymptotically stable. Moreover, it is proved that the unactuated states converge to a bounded set by analyzing the inherent dynamics of the controller. Simulations demonstrate the performance of the proposed controller