Robust nonlinear ship course-keeping control under the influence of high wind and large wave disturbances

Ship course-keeping control is a complicated problem because the ship dynamics are nonlinear and nonminimum-phase. In this paper, the robust nonlinear control design approach employs two feedback loops: the H
_∞
approximate input/output (I/O) linearization in the inner-loop and μ-synthesis in the outer-loop to address tracking, regulation, and robustness issues. Computer simulations clearly show that the performance of the proposed robust nonlinear controller design is better than the linear robust controller in handling high wind and large wave disturbances.