Accurate Planar Trajectory Tracking for a Class of Nonlinear Non-minimum Phase Marine Vehicles

The work presented addresses the tracking control problem for a class of marine vehicles characterized by the type of propulsion system used and resulting impact on dynamical behavior. Specifically, we consider movement in the horizontal plane of vehicles that use a rudder for steering (or, equivalently, vectored thrust), as opposed to differential thrust, or lateral thrusters. The corresponding system dynamics are underactuated, featuring fewer independent control inputs than degrees of freedom. They also typically display a non-minimal phase nature (in the nonlinear sense), where desirable equilibria of the internal (non-actuated) dynamics prove unstable. We present solutions to this problem, which rely on careful design of the set of errors tracked by the external dynamics, guaranteeing uniform ultimate boundedness of tracking errors.