Research On Dynamic Positioning Ship Motion Prediction After Typically Single Failure

With the development of ocean exploitation, many large ocean projects appeared, so weneeded more and more vessels working on ocean, and the request was higher. Large DP vessel,such as deepwater pipe-laying crane vessel, semi-submersible drilling platform and so on,haddeveloped from DP1to DP3. In the DP2class and above, there were some related regulationsabout motion prediction analysis of DP ship. In any weather condition, the analysis andprediction of the movement trend of the ship is requested when typically single failurehappened in DP control system. Therefore,the paper had he meaning of theoretical researchand engineering applications.A general linear mathematical model of surface-ship was established using mechanismmodeling method in this paper. Duing to the inaccuracy of waves online calculation,uncertains of wave disturbance were included in motion prediction model of DP ship.Toresearch the motion prediction model, For the establishment of ship motion prediction model,the three aspects of the study had done as follow:Firstly, hydrodynamic coefficients inadditional inertia matrix and the damping force and moment matrix which need to beidentified were introduced. A kind of observer based on Kalman filter identification algorithm(OKID) was introduced to implement the identification on hydrodynamic coefficients.Additional inertia matrix, the damping force and moment matrix were obtained after theonline identification.Sencondly,more accurate empirical formula for the calculation of theforce of wind disturbance,and in order to calculate ocean currents and their effect on vessalmotion, the ship parameters in the equation of motion was processed into the relative motionparameters assuming that the current velocity vecoter was slowly-varying. Thirdly, inprocessing of the Marine environment disturbance acting on the DP ship, uncertainties ofwaves disturbance was considered. To predict the uncertainties of waves disturbance acting onthe DP ship, this paper established a kind of prediction method based on the grey neuralnetwork.A model named GNNM(3,1) which can predict uncertain problem wasestablished,and it was trained to improve precision of prediction.The influence of theuncertainties of waves-disturbance acting on ship motion was predicted using this method.The pseudo inverse method used in thrust allocation algorithm was expounded.According to functional requirements for the dynamic positioning ship motion prediction,typically single failure happened in dynamic positioning control system was analyzed,and thethrusters’ configuration matrix was used to set the failure.Considering the mode of failure mode, force calculated by controller was allocated to the remaining propeller using thethrusters’ configuration matrix when typically single failure happened.At last, the motion prediction simulation system was established,and the experiment ofmotion prediction of the DP ship was designed when when typically single failurehappened.In different marine environment, the motion trend of dynamic positioning ship waspredicted and analyzed successfully.