A New Stabilization Controller of Asymmetric Underactuated Surface Ship Under Input Saturation

A stabilization controller is addressed for an asymmetric underactuated surface ship subject to input saturation in this work. Prior to control design, the considered ship system is converted into a cascade nonlinear system with a minimum phase by applying state and input transformations. And by introducing a circular trajectory, the investigated stabilization problem is successfully expressed into a tracking issue. Under these preparatory works, a saturated tracking control law is proposed by converting the equivalent subsystem of the cascade tracking error system into an augmented new system and applying Nussbaum function. It has been demonstrated in stability analysis that the designed controller can enable system states to converge to zero by choosing a sufficiently small radius of the circle, and meanwhile can also achieve the desired input saturation.