Validation of autopilot controller for marine surface vessels with six DoF model

A marine vessels at sea experiences rotational as well as translational motions under the influence of diverse nature of forces and moments originating due to external and internal nature of dynamics including uncertainties and disturbances. For the purpose of design of autopilot controller, use of these modeling becomes too tedious and complex and therefore, controllers are usually designed based on simplified models which depict complex nature of ship motion at sea. In this paper, Extended State Observer (ESO) based Input-Output Linearisation (IOL) controller and Generalised Extended State Observer (GESO) based Output tracking controllers, developed based on simplified Nomoto model have been implemented with six Degree of Freedom model for validating their efficacy. The notable features of the proposed controllers are they neither requires accurate plant model nor any information about the uncertainties and disturbances while achieving robustness and desired performances. It has been demonstrated with the help simulation results how these controllers are effective under various practical scenarios.