Research On The Thrust Allocation For Dynamic Positioning Systems With The Fault Of Thrust

The dynamic positioning system is an automatic control system that maintains a specified attitude under the command of the system controller by relying on the power generated by the propeller.Among them,the propulsion system is an important component of the dynamic positioning system,and most of the propulsion system failures are caused by the propeller failure.If there is a fault in the propulsion system,no timely treatment will be made at this time,which will affect the stability of the ship in operation,and even serious accidents will occur.The purpose of this research is to redistribute the thrust when the dynamic positioning of the ship propulsion system fails,so that the dynamic positioning ship continues to work under the premise of still meeting certain performance indicators.The specific research work of this paper is as follows:Firstly,the mathematical model of the dynamic positioning ship is established,including the three-degree-of-freedom kinematics and dynamics models of the ship moving in the water surface.The model of the ship propulsion system is introduced,and the thrust distribution process is analyzed,and the upstream and downstream full-slewing are considered.The hydrodynamic interference of the propeller establishes the angle of the forbidden zone of the full-turn propeller.Secondly,the faults of the ship propulsion system are classified.Based on the analysis of various fault characteristics,the thrust redistribution optimization model in the fault mode is established,the maximum thrust fault coefficient is established,and the propulsion fault use priority matrix is generated.The matrix adjusts the priority of use of the faulty thruster,using a criterion based on two norms for optimal allocation.Then,the genetic algorithm is used to optimize the thrust distribution.The genetic algorithm is improved for the problem that the genetic algorithm optimizes the amplitude and frequency of the output ripple.The improved method includes the selection of the real number,the initial value of the multi-group method,and the initial population with the propulsion parameter limitation in the early stage of evolution.The random traversal sampling selection strategy with low time complexity,dynamic adjustment of gene crossover rate and gene mutation rate,and the addition of immigration operators to dynamically adjust offspring individuals,and improved genetic algorithm improve the accuracy and stability of thrust distribution.Finally,the thrust distribution under different fault modes is verified by simulation.The thrust distribution algorithm under fault mode is studied in the path tracking process to verify the correctness and effectiveness of thrust distribution under thruster failure.The results show that the thrust distribution strategy of the ship dynamic positioning system thruster under the problem of this paper still makes the ship continue to maintain the performance indicators before the failure,and improves the safety and reliability of the ship.