Research On Positioning Capability Of Mooring-assisted Dynamic Position System

With more and more attention to the development and utilization of marine resources,many kinds of marine engineering vessels put into use.The mooring-assisted dynamic positioning system is a kind of motion control system which can keep the ship's fixed-point operation and is a positioning system of joint mooring system and dynamic positioning system,combines the advantages of both,and has great prospects in practical application.Therefore,it is of great significance to study the mooring-assisted dynamic positioning system.In this paper,aiming at the evaluation of the positioning capability of the mooring-assisted dynamic positioning system with a 1000-ton emergency salvage crane is taken as the research object.1.On the one hand,the main environmental: loads in the ocean: wind,wave and ocean current are analyzed,and the calculation model of the environmental load is established on the following three dimensions: Surge,Sway,Yaw.On the other hand,based on the static analysis of mooring system,the catenary equation is derived,and the use of catenary analysis method for static analysis of mooring system,including the calculation model of pre tension and mooring line tension after changing mooring line and restoring force of mooring system.2.In order to optimize the allocation of dynamic thrust,a mathematical model for optimal allocation with nonlinear constraints is established.According to the defects of the standard particle swarm algorithm is easy to fall into local optimum,combined with it and comprehensive learning particle swarm algorithm,improved particle velocity updating strategy,the idea of a variety of swarm and particle variation and population restructuring thought,put forward a multi-population comprehensive learning particle swarm algorithm.The proposed algorithm is applied to the dynamic thrust allocation.It can be seen from the simulation that the proposed algorithm can effectively track the desired instruction.3.For the problem of the evaluation of the positioning capability of the mooring assisted dynamic position system,two aspects of no mooring system and join the mooring system of the system are studied.To no the mooring system,namely,the dynamic positioning system,the calculation results of the positioning capability are compared with those obtained by Kongsberg,the result shows that the positioning capability of dynamic positioning system calculated in this paper is reliable.To join the mooring system,according to the ship not changes positioning points and changes positioning points in thepositioning process,the positioning capability is evaluated under the mooring lines complete model and the single line failure mode respectively.The simulation results show that the positioning capability of the changes position point is better than that of the fixed position point and it is also better than the dynamic positioning system,in the mooring lines complete mode;In the single line failure mode,both the fixed position point and the variable position point,the positioning capability has changed,and even in some directions will affect the safety of the ship.