Three dimensional trajectory control of underactuated AUVs

This paper considers the design of a novel closed-loop trajectory tracking controller for an underactuated AUV having 6 degrees of freedom (DOF) and 3 controls, namely a thruster, a rudder and moving surfaces to control the forward, yaw and pitch motions respectively. A backstepping methodology is adopted as a design tool since it is suitable for the cascaded nature of the vehicle dynamics. It also offers flexibility and robustness against parametric uncertainties which are often encountered in hydrodynamic modeling. Indeed, in our simulations we assume a 10% error in hydrodynamic parameters and yet the controller performs the task of position, orientation and linear and angular velocity tracking successfully.