Stabilization of asymmetric underactuated ships with input saturation: From underactuated to nonholonomic configuration

Abstract

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, finite-time and saturated tracking control laws are proposed by converting the obtained tracking error system into an augmented new system and applying Nussbaum function. It has been demonstrated in stability analysis that the designed controllers 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. The simulation results illustrate the validity of the presented control algorithm.