Non-linear controller for non-linear model of hovering autonomous underwater vehicles

Non-linear controllers for attitude, altitude, and position of a Hovering Autonomous Underwater Vehicle (HAUV) non-linear model are presented The controllers allow the vehicle to reach any desired point in the horizontal and vertical planes. The controllers were applied to a small-sized, torpedo-shaped HAUV with six degrees of freedom The coupling between attitude and position makes the trajectory tracking control problem particularly hard. However, at least in the case of set-point control, it is possible to adopt a two decouple control strategy. A non-linear controller is applied for achieving attitude regulation, while a non-linear control strategy is used for achieving smooth motion back to the desired position coordinates. The performance of the proposed control scheme is evaluated numerically.