Research On Predictive Control Of Low Speed Trajectory For Dynamic Positioning Ships

With the development of marine resources and waterway transportation and transport industry, the demand for the dynamic positioning system of vessels is increasing gradually. In the dynamic positioning system, the control algorithm is used to make the ship sail stably and accurately, which is the primary goal of the track control. In order to solve the problem of the influence of sea wind, waves, currents and other environmental forces causing the engineering ship track deviating from the scheduled route, in the paper, the mathematical model of marine multi - functional operation ship "299" is picked as research object to be studied, and the research work is carried out from two aspects of the design of the ship's route guidance system and the controller of the ship.First, given the motion of a ship in space has a total of six degrees of freedom, but most of the ships can only control the surge, sway and yaw,and under the influence of not a particularly bad environment force is these motions have little effect on the ship track. So this paper established the mathematical model of ship motion level of three degrees of freedom.Secondly, aimed at the navigation of the ship track control, in this paper, the design of the according to bow to the deviation of implementation of track to track "LOS" guiding strategy and the guidance strategy according to the coordinate changes of locating point to achieve the localization have been worked out. The effect of both ways of guidance were compared in simulation experiment.Thirdly, on the control algorithm of ship, this paper according to the thought of model predictive control linear approximated the ship motion mathematical model, and accordingly designed linear model predictive controller of the ship.Then,a method of building a BP neural network fitting ship multi step movement so as to optimize the solution of the nonlinear predictive control algorithm of dynamic positioning ship track control had been put forward. The effects of the two control algorithm were compared in simulation experiment.Finally, the track control methods were simulated on the MATLAB platform, and the environmental impact of wind,wave and current was considered to verify the performance and application results of the designed guidance system and the ship controller. The simulation results show that the guidance strategy according to the coordinate changes of locating point and the nonlinear predictive control algorithm based on BP neural network are able to accomplish the task of trajectory control well. This paper describes the trajectory control process of dynamic positioning ship, and the thoughts of applying of other control algorithms in the dynamic positioning ship, paving the way for the further motion control research of dynamic positioning ship.