Significance Analysis Of Thrusters Based On Dynamic Positioning Capability Of Vessels

Dynamic positioning(DP)vessel uses its own thrusters to counteract the influence of sea states to maintain ship position,so as to guarantee the safety of ship operations.To cope with drift-off caused by complex sea sates and equipment failure,vessels have a high requirement of DP capability.Because,a vessel with high DP capability is crucial to the safe of crews,the protection of equipment,the efficiency of operations.However,since DP capability is influenced by sea states and thrusters’ interaction,it is hard to quantify the contribution of thruster to DP capability.On the purpose of investigating the influence of thrusters to DP capability,empirical cumulative distribution function-based sensitivity analysis(SA)is introduced to compute the contribution of each thruster.Compared with variance-based and density-based SA methods,it is able to achieve a high accuracy of computation with lower time cost.In this paper,SA and statistical analysis method are used to analyze the significance of thrusters based on a DP capability criterion.Analysis results are able to provide onboard support to improve DP capability,as well as guidance for power allocation system optimization and thrusters’ maintenance.The main contributions are as follows:1.Based on standards of international maritime organization,other researches about DP capability assessment and our own data characteristics,a synthesized DP capability criterion is proposed to quantify the vessel’s DP capability,which is made of ship position,heading and consumed total power.2.Owing to high dependency of SA on a model,in this paper,machine leaning(ML)is selected to build a surrogate model.Through using Sobol and Ishigami as benchmark functions to test the modelling accuracy of support vector machine(SVM),back propagation neural network(BP)and regularized extreme learning machine(RELM),an optimal ML is selected to combine with SA.3.SA and statistical analysis are used to analyze the significance of thrusters in different sea states and thruster failures,including: significance analysis in different thruster failures at a certain sea state;significance analysis in different sea sates for a certain thruster failure.Finally,analysis on statistics and SA indices of thrusters could provide significative guidance for DP operations in different scenarios.