Optimal tracking control of an underactuated container ship based on direct Gauss pseudospectral method

In this paper, the problem of optimal tracking control for a container shipis addressed. the multi-input-multi-output nonlinear model of the s175 container ship iswell established in the literature and represents a challenging problem for control design,where the design requirement is to follow a commanded maneuver at a desired speed. tosatisfy the constraints on the states and control inputs of the vessel nonlinear dynamicsand minimize the heading error, a nonlinear optimal controller is formed. to solve theresulted nonlinear constrained optimal control problem, the gauss pseudospectral method(gpm) is used to transcribe the optimal control problem into a nonlinear programmingproblem (nlp) by discretization of states and controls. the resulted nlp is then solved bya well-developed algorithm known as snopt. the results for course-keeping and coursechangingautopilots illustrate the eectiveness of the proposed approach in dealing withvessel tracking control.