Research On Thrust Allocation Algorithms And Strategies Of Dynamic Positioning System

Dynamic positioning system is the key support system to the deep sea resources development,which is also the important part of marine engineering equipment.With the increase of its range of application,the requirements on ability of dynamic positioning system haven been improved.The thrust allocation module plays an important role in the dynamic positioning system.In this paper,the algorithms and strategies applied in the thrust allocation module are studied.The summary about domestic and foreign research status of the thrust allocation in the dynamic positioning system is made in this paper.The still existing problems in optimal thrust allocation have been put forward.The current applications of mainstream propeller type and mathematical model of optimal thrust allocation in the thrust allocation are presented.Iterative algorithm can solve the constrained optimization problem effectively,but the high real time requirement is often hard to meet.Under this condition,the quadratic programming active set method is used to solve the thrust optimal allocation problem in this paper.And the real-time problem of iterative algorithm is solved by improving processes.Besides,the generalized inverse method has been implemented to solve the fixed angle optimal thrust allocation problem.The sequential quadratic programming algorithm is also implemented for comparison.For azimuth thruster,the hydrodynamic interaction between propellers has great influence on the efficiency.The interaction issues need to be fully considered.Different strategies are adopted to handle the interaction areas,and related convexification processing of the mathematical model need to be done,such as regional cutting,etc.When there are multiple interaction areas on one propeller,setting the thrust forbidden zones often leads to great loss of thrust feasible region.Study the influence of thrust weight matrix and change the weight ratio or the minimum thrust to achieve the purpose of avoiding staying in the interaction areas.The vessels or platforms equipped with dynamic positioning system have to face more and more complex sea condition,the requirement of ability of the thrust allocation module is raised accordingly.In this paper,based on quadratic programming effective set method and generalized inverse method,combined with the four thrust allocation model,according to the working condition of sea state switching standards,establish a smooth and effective form of adaptive thrust allocation optimization module.In the simulation platform the controller combines with thrust allocation to verify the effectiveness of the switching strategies.