Abstract:In this paper, a conventional surface vessel is selected as the research object. It is pointed out that under specific control requirements, the system has an under-actuated characteristic and the problem of under-actuated ship stabilization control is studied. The dynamic mathematical model of ship motion is established and a simplified three-DOF under-actuated ship mathematical model is deduced. The non-complete characteristics of the system, the characteristic of balance point and the controllability of small time are analyzed.