The Controller Design Of Marine Dynamic Positioning System

Dynamic Positioning(DP) system is an integral system that maintains floater in a fixed position,and resist disturbances from environment such as wind,wave,and current disturbance which can cause floater drift away from desired position and change floater's attitude,using its own power generated by propellers,rudders,and so on.As the society of people develops more and more rapidly,we,human being consume huge amount of resources,like crude oil and valuable mineral.The growing need of natural resources makes us expand our exploitation of sea,and now,the pace of people is reaching deep-sea.Therefore,we can see that DP system is increasingly important to operations in sea,such as sea floor exploitation,marine petroleum development,and mining marine mineral resources.DP system has been developed over fifty years.And as the advance of technology,new complex control methods continuously been formed and implemented in the DP system.Within them,the development of nonlinear theory makes the research of DP system shift from linear to nonlinear.In most control system applications,the existence of some sort of uncertain factors is unavoidable,therefore, DP system nonlinear adaptive control become the frontier of control system research.This paper set marine vessel's DP system as its subject to be studied and analyzed. About the controller design problem of marine vessel DP system,the paper has built a nonlinear 3 DOF mathematical model of DP system,after analyzing the feature of marine vessel's kinematics and dynamics.When a floater is floating in the surface of sea,it will be affected by force and moment generated by wind,wave,and currents of surrounding environment,and its position and attitude will be changed.To counteract the bias caused by environment disturbances,this paper introduced an integrator into backstepping controller,eliminate constant error while achieving stable.Moreover,because DP system have some uncertain factors,this paper aim to build up a nonlinear adaptive backstepping controller, based on backstepping design method,to against the uncertain variable of environment disturbances.