Research On Several Key Problems Of Dynamic Positioning Model Of Surface Ship

With the continuous exploration and development of marine resources,the demand for marine equipment is increasing.China’s ship dynamic positioning products are relatively low on the international market and mainly rely on importing.At present Dynamic Positioning system(DPS)products are basically monopolized by the three companies including Norwegian Kongsberg Simard,France’s Alstom and Australia’s Nautronix company.For improving the research capacity of the property rights of autonomous knowledge and the development of the high-end product,Chinese government has given first priority to strengthen independent inventive capability in all work of science and technology and strives to create an internationally competitive enterprise to enhance the national competitiveness.The coastline of Guangdong province is 8,500 kilometers long,accounting for more than one third of the national coastline.Its processes the longest coastline and the most extensive shore in China.The marine resources are abundant and the marine equipment market is in great demand in this district.Therefore,it is urgent to develop marine automation equipment and break the foreign technological monopoly.DPS is a system integrating navigation technology,automation technology,power technology and reliability technology.Ship dynamic positioning technology not only includes position and attitude maintenance under power plant,but also includes automatic navigation,course maintenance,automatic docking,avoiding,heading back,turning around,etc.As the power supplier of ship dynamic positioning,thrust system is usually a redundant system with multiple solutions for specific longitudinal force,transverse force and rotary torque.How to realize the fast and efficient thrust allocation is a key technologies of dynamic positioning system.During the voyage,the ship not only needs to overcome external disturbances(such as wind,wave,flow,etc.)to maintain a certain speed,course,and sometimes to change course,track and speed as needed.At this point,it is necessary to know the mathematical model of the ship’s environmental load force and the ship’s maneuvering motion performance for the positioning controller to realize the flexible operation of the ship.Main research contents:1.Modeling of wind load force for dynamic positioning ship.In accordance with the certain ability of dynamic positioning ship to keep working in a certain environment disturbance such as wind,wave and flow,the paper conducted ship model constraints test by the wind tunnel experiment,to obtain the wind load force and moment characteristics.Due to the limited experimental conditions,experiment data has a much poorer smoothness.In comparing this wind tunnel test results with the results of other strict tunnel test,the effectiveness of this wind tunnel experimental results was verified.Using support vector machine(SVM)regression algorithm,the 360° wind load force mathematical model was obtain.The mathematical model of wave and flow load force was also presented in this paper.2.Researches on thrust distribution of dynamic positioning ship.For the redundancy thrust system of dynamic positioning ship,a fast thrust allocation strategy was proposed to the realize energy save and low wear of propellers.This strategy not only considered the limited thrust magnitude and thrust zone,but also considered the change rate of thrust force and angle,moreover singular configuration was avoided.As thrust allocation algorithm directly affects ship’s positioning capability inculding position keeping ability and accuracy and rapidity of the control system,under the environmental interference.In this paper,its positioning capability was analyzed through positioning capability curve,under fully-actuated and underactuated.3.Based on support vector machine,noises polluted tracks of ship model was regressed.The GPS positioning system is usually used to record ship’s real time positon when actual ship tracks is to establish the maneuvering motion equation.In this case,the track is generally accurate enough to meet the demand.However,the maneuvering motion tests of the actual ship is very expensive and the human cost is relatively large.So the scaled ship model is usually applied to study its maneuvering properties.In this method,the accuracy of GPS positioning system is hardly guaranteed owing to the affect of ground construction circumstance.When we use other positioning system,the noise signal cannot be avoid in the sampling tracks,which could cause adverse effect in the identification of ship hydrodynamic model.In this paper,the regression support vector machine is used to depose the noise problem in the samping track.In this method,the satisfactory regression results were achieved both in the variant Gaussian noise polluted Mariner ship model tracks and the actual ship model tracks sampled by ultrasonic positioning system.4.Modeling of maneuvering motion based on free-running model tests.Generally,a good motion controller of dynamic positioning ship can be hardly achieved without regarding to its maneuvering motion function.Moreover,ship maneuvering movement characteristics have been listed as the key indicators of assessment of ship maneuver performance by the International Maritime Organisation(IMO).In this thesis,identifiability of viscous hydrodynamic model is researched and analyzed through the designed decoupling experiment.Based on free-running model tests,general viscous hydrodynamic model and viscous hydrodynamic model of a scaled ship model was identified.For the inertial hydrodynamic model,system identification was applied based on the viscous hydrodynamic model.Finally ship maneuvering motion model and corresponding hydrodynamics were obtained.The experiment shows the medeled ship maneuvering motion model can forecast the model speed and track exactly,it also inllustrated the modeling method is feasibility.This work fills the current domestic gap in modeling ship maneuvering motion based on free-running model tests in our country.