Improved nonlinear control for ship course-keeping based on Lyapunov stability

Abstract

[Objectives] Course-keeping for ships is the core of automatic navigation in marine transportation,and it cannot be achieved without the design of the nonlinear controller. In order to simplify the design process,improve the robustness of the system and save the energy output of the controller,this paper proposes a nonlinear feedback controller based on the Lyapunov function.[Methods] By constructing a simplified Lyapunov function,the design process of the nonlinear controller is shortened and the cancellation of the nonlinear term of the control law avoided. The design of the control system can be optimized by replacing the course error with a nonlinear function of itself in the feedback loop. This optimization reduces energy consumption and improves the robustness of the system.[Results] Taking the ship ‘Yu Peng’ as an example,the simulation results show that the improved nonlinear control algorithm possesses good performance and robustness,and reduces energy consumption.[Conclusions] The results of this paper show that the introduction of a nonlinear feedback term can optimize the control system,and the energy saving advantages of such a measure are of great significance for practical engineering application.

Keywords

• course-keeping for ships
• Lyapunov stability
• nonlinear feedback