Research On Thrust Distribution Of Dynamic Positioning System Based On Power Management

With the rapid progress of the times and the vigorous development of society,the demand for resources continues to increase.The development and utilization of land resources can no longer meet people’s needs,and humans have begun to conduct in-depth research on ocean resources.In this process,dynamic positioning vessels have been widely used as important ocean tools.Thrust allocation is an important component of the ship’s dynamic positioning system.The thrust allocation unit calculates the thrust and azimuth angle of each thruster according to the ship’s controller instructions,using thrust allocation optimization algorithms,so that the force and torque generated by the thrusters can meet the controller’s expected control force command,which is important for the accuracy and flexibility of ship positioning.Supported by the Ministry of Industry and Information Technology’s project "Development of an Intelligent Dredging Vessel Operation System," this thesis selects the large self-propelled hopper suction dredger "Xin Hai Hu 8" as the research object to study the thrust allocation problem of ship configuration rudder-propeller combinations.The aim is to reduce the energy consumption of thrusters,thrust allocation errors,and wear of propulsion equipment,while considering the impact of power fluctuations from other high-power loads on the ship’s power grid.The study adjusts the power consumption of the propulsion system to assist the power management system in reducing power grid consumption fluctuations and maintaining the stability of the ship’s power system.The specific work contents are as follows:(1)Mathematical modeling of dynamic positioning system.The working principle,components,and functions of the dynamic positioning system are introduced.A mathematical model of the ship is constructed,including two commonly used coordinate systems,ship kinematics model,and ship dynamics model.In addition,disturbance models for wind,waves,and currents are established to address environmental interference.(2)Research on ship thrusters and thrust allocation optimization model.In view of the types and characteristics of ship thruster configurations studied in this thesis,the mathematical models of propellers and rudder-propeller combination thrusters are introduced,focusing on the characteristics of the thrust area of rudder-propeller combination thrusters and the solution to non-convex regions.The basic principles and construction methods of the thrust allocation model are introduced.The objective function in the model includes optimization items such as the minimum thruster energy consumption,the minimum thrust allocation error,the minimum thruster wear,and the optimal thrust of the bow thrusters.The constraints include that the force and moment after thrust allocation should be equal to the controller instructions,and the limitations on the size,direction,and thrust feasible range of the thrusters.(3)Research and implementation of thrust allocation strategy for dynamic positioning system.With regard to the research on thrust allocation strategy,the sequential quadratic programming algorithm and the adaptive particle swarm optimization algorithm are used to solve the thrust allocation problem.The optimization principles and steps are analyzed,and experiments are conducted based on the thrust allocation model.Simulation results show that the adaptive particle swarm optimization algorithm can effectively balance global and local optimization capabilities,improve the speed and accuracy of optimization,not only can complete the thrust allocation task reasonably and stably,but also can reduce system energy consumption and thrust allocation error.The low energy consumption of the system effectively solves the problem of thrust allocation for ships.(4)Research on Power Management-Based Thrust Allocation.Analyzed the power system configuration and main equipment loads of the self-propelled hopper suction dredger.To address the issue that the stability of a ship’s electrical system is easily affected by the fluctuation of other large loads,this study adopts two control modes,biased control and unbiased control based on load dynamic control mode,to control the thrust allocation and verify it through simulation.The simulation results show that both control modes based on the load dynamic control method can adjust the power consumption of the propulsion system to compensate for the fluctuation of power consumption of other high-power equipment,thereby stabilizing the overall power consumption of the ship’s electrical network.