Research On Dynamic Positioning Control Method Of A Vessel Based On Nonlinear Model Predictive Control

With the increasing demand of resources, the traditional land resources can not satisfythe demands, so people expand the vision into the ocean. As a support system for ships,Dynamic Positioning(DP) System which gets more attentions has widely used in offshoreplatforms. As the core of Dynamic Positioning System, the performance of the controlsubsystem has a direct impact for the Dynamic Positioning System. Nonlinear ModelPredictive Control(NMPC) technology is a new control technology, and its applicaition was inindustrial process control early period, and now it has been widely used, because it can handlethe the problem with nonlinear and multi-constraints. The paper introduces the NMPCtechnology into the ship Dynamic Positioning System, and studies the algorithm of NMPC,and finally conbines the ship model and the NMPC technology to design the controller of theDynamic Positioning System. According to the GreenDP’s ideology of the Kongsberg ofNorway, the author has simplified the construction appropriately, and completes its basicfunction of GreenDP.Firstly, the mathematical model of ship Dynamic Positioning System is built. The shipmodel of three degrees of freedom is built which includes the model of ship, andmathematical model of wind, sea wave and sea current in the ocean environment were built.And the parameters of the supply ship are given for use.Secondly, Nonlinear Model Predictive Control algorithm is studied for the ship DynamicPositioning System. The development of the NMPC technology is introduced, and the basictheories of the NMPC technology are given. For the problems of the Dynamic PositioningSystem, the ship model is handled appropriately, and the corresponding constraints of the shipare given. According to the Analytic NMPC algorithm, the controller of the DynamicPositioning System is designed, its stability is proved, and the controller is effective by theway of simulation results.Finally, the paper researched the control system based on GreenDP. GreenDP consists ofthree parts, and they are estimation filter, environment compensator and the NMPC controller.The paper designed the three parts, and the function area of the controllers is illustrated.According to the simulation results, the Dynamic Positioning System based on the ideology ofGreenDP has the advantages in energy conservation.