Pre-filtered sliding mode control for nonlinear ship steering associated with disturbances

Abstract

This paper proposes a pre-filter based sliding mode approach to control the steering system in ocean going vessels. The stability conditions of vessel steering in linear and nonlinear mathematical formations are analyzed. The linear vessel steering system is derived considering the second-order Nomoto model, modified to include nonlinear vessel steering conditions: the stable and unstable steering conditions. Then the stability conditions of the steady-state vessel steering system are analyzed by the Routh's stability criteria. The stability conditions of the closed-loop nonlinear vessel steering system including a sliding mode controller are analyzed by the Lyapunov stability theorem.The proposed pre-filter based sliding mode controller can be implemented in nonlinear vessel steering even under parameter uncertainties and un-modeled dynamics, and can quantify the system response and the performance tradeoffs. Furthermore, an under-actuated system with the dynamics that are indirectly actuated and nonlinearly coupled can also be globally stabilized by the sliding mode controller. In addition, a PID controller is also considered as a comparison mechanism in this study. Finally, the two control algorithms are simulated, successful results are reported and the superior performance of the sliding mode controller is illustrated in this study.