Designing And Optimization Of Ship Straight-path Following Based On Slide Mode Control

The study on ship path following control has attracted much of experts and scholars’attention in recent years. The straight-path following control can ensure navigation safety, and is helpful to reduce the time consumption of the voyage, and contribute to energy savings at the same time. So it has significant meanings to design and optimize the straight-path following controller.In this paper the Sliding Mode Control method is used to design a robust ship straight-path following controller. The ship’s path is difficult to be directly regulated as the ship straight-path following control is very complex and the existing technical level is limited. The sliding mode method helps us turn the control objects to stabilization of intermediate variables by the rudder angel via decentralized sliding mode designing. In the designing of the controller, differential process is added in the integral sliding mode, so the overshoot can be avoided, as the result, the control performance becomes better.As the maneuverability of the ship is always changing, the environmental conditions are also time varying. Therefore, the controller can not meet the demand if the parameters don’t change as the condition changed. In this paper, a fixed relationship among the parameters is created, so the parameters can be optimized simultaneously without impeding the close loop system’s stability and performance. A mapping between ship’s maneuverability and control parameters is established to tune the parameters when the performance of the controller is not very good. So the ship can come back to the planned path as soon as possible, and the rudder angle will remain within a predetermined scope which can be tuned, by the user.MATLAB simulink toolbox is used for the simulation in this paper, the results of the simulation show that the designed controller is good enough to meet the demand of the ship straight-path following control. The controller can also work very well even when there are wind, wave and current flow. The results of the simulation also prove that the controller parameters can be optimized online very well.