Research On Thrust Allocation Strategy Of Dynamic Positioning System

Dynamic Position System is a closed-loop system that does not rely on anchoring and relies on its own thruster output thrust to resist environmental interference to maintain a certain position and direction.More and more ships and offshore platform are equipped with the dynamic positioning system without considering the limitation of water depth.As a important part of the dynamic positioning system.A new science and technology and industrial revolutions have begun to emerge.As one of the major systems of the dynamic positioning system,the functions of the thrust allocation is allocating the command from the controller to each propeller based on the reducing the propeller energy consumption.A more ideal optimization scheme will have important significance in reducing the energy consumption of the propeller and reducing the allocate error and mechanical wear of the propeller.Based on the project contract of Jiangsu Provincial Natural Science Research Projects for Natural Science,Focus on the parameters identification of the propeller,give the program of thrust allocation,solve the non-convex problem of the thrust zone,the impact of other ship load sudden to the ship power system,The main work is as follows:The main task of this research is as follows:(1)Based on the type characteristics and quantity of the thrusters of the research object and the operational requirements,an objective function including the propellant energy consumption,distribution error,thruster angle change rate,singular configuration optimization,etc.was established.In addition,the mechanical limit of the propeller was established.Based on the conditions and requirements of ship operations,established equality and inequality constraints.(2)Based on the model of thrust allocation,the two scenarios of setting the thrust prohibit zone without the ideal condition of the thrust prohibit zone and the consideration of the thrust reduction of the thruster are adopted,and the sequential quadratic programming and the introduction of the supervisory switch control are respectively adopted.Sequential quadratic programming algorithm is used to calculate the thrust allocation..Based on the simulation results,the thrust energy consumption and error of thrust allocation are discussed.(3)According to the transient stability of the ship power system is easy to be affected by load fluctuation.When the power of other loads suddenly increases,a dynamic load control strategy is introduced into the thrust allocation to reduce the propeller power while controlling the speed and position deviation of the ship.When the load drops,the group thrust biasing strategy was introduced to the thrust allocation,and power consumption of propeller is appropriately increased to buffer other load drop.Archive the goal that thrust allocation assist the power management of the ship,according to the result of simulation,the strategy can reduce the load fluctuation,increase the stability of the ship grid system.