Research On Approach Of Spatial Prediction For Ship Angular Deformation

Large ships are equipped with a large number of weapons and detection equipment,which are calibrated in the dock with ship coordinate to achieve information sharing between each other.However,the ship is not an absolute rigid body,and angular deformation will occur under the conditions of sunshine,load changes,wave impacts etc.,which will lead to coordinate reference misalignment,thus restricting the effectiveness of shipborne equipment.In this paper,the spatial prediction method of ship angular deformation is studied.The prediction principle,deformation prediction model and the influencing factors of prediction accuracy are analyzed to achieve the prediction of ship angular deformation.The main contents and achievements of this paper are as follows:(1)a spatial prediction model for ship hull angle deformation is established.Firstly,the mechanical model of ship angular deformation is deduced based on two-dimensional hydroelastic theory and modal analysis method.Then the prediction model of ship angular deformation is obtained by polynomial spline function fitting method,and the parameters of the model are estimated by the least square method in real time.Finally,the feasibility of this method is verified by simulation based on the deformation data of real ship measurement.(2)the selection of local reference number is studied.The theoretical results show that the number of local references needed for ship angular deformation prediction is consistent with the order of the highest order in the prediction model.Simulation and analysis are made from the second-order fitting to the fifth-order fitting method.Through the comparison,the fourth-order fitting method has a higher comprehensive prediction accuracy.The interpolation prediction error is less than 3?,and the extension prediction error is less than 15?.Therefore,selecting four sets of local reference and one set of main inertial navigation system(MINS)can satisfy the deformation prediction of any point of the whole ship.(3)the layout of local reference is studied.According to the mean modal kinetic energy method,the installation positions of four sets of local reference are re-selected,and the rationality of the layout is verified by the modal orthogonal independence.The optimized angle deformation prediction model can better reflect the modal deformation characteristics.The simulation results show that the local reference layout based on the average modal kinetic energy method can significantly improve the prediction accuracy,in which the interpolation prediction error is less than 2?,and the extension prediction error is less than 3?.(4)local reference work state monitoring and ship attitude prediction are realized.According to the layout of the MINS and the local reference,the whole ship is divided into several regions.Combining the attitude information of the MINS or the local reference with the angular deformation prediction value of the prediction point,the fault detection of the local reference is carried out by the pre-determined discriminant conditions,and the attitude angular prediction value of any point of the whole ship can be obtained.The fault response time of local reference is less than 5s,and the prediction error of the whole ship attitude is less than 10?.