Research On Shape Sensing Technology Of Submarine Power Cable Based On Fiber Strain

With the continuous development of marine resources,optical fiber composite submarine cables that integrate power transmission and communication are widely used in important places such as island power supply,offshore operation platforms,and offshore wind farm power transmission.The operating environment of the submarine cable is harsh,and it is often affected by human and natural factors,resulting in large deformation and large displacement of the submarine cable.The shape and displacement changes of the submarine cable can be monitored in time,which can make an important assessment of the operating state of the submarine cable and guarantee Safe operation of submarine cables.Aiming at the problem of large deformation and large displacement of submarine cables,this paper aims to design a three-dimensional shape reconstruction algorithm based on fiber strain,which can restore the deformed and displaced shape of submarine cables with high accuracy.The main research work is as follows:1.The basic principles of distributed optical fiber strain measurement based on OFDR(Optical Frequency Domain Reflectance Technology)and the basic principles of the Frenet framework were studied,and then on the basis of the Frenet framework,the optical fiber 3D shape reconstruction algorithm was designed,and the formula of fiber shape calculation based on the strain of each core of three-core fiber was derived.2.The shape reduction accuracy is an important indicator of the algorithm in this paper.In order to study the influence of the two methods of polynomial fitting and cubic interpolation on the reduction accuracy,the experiment took two typical curves,cylindrical spiral curve and conic curve as examples,and adopted polynomial fitting respectively.The curvature and torsion continuous functions were constructed by the combined and cubic spline interpolation,and the cubic spline interpolation algorithm was selected after comparison.3.The dynamic finite element model of the three-core optical fiber was established by ANSYS APDL.The simulation results of unidirectional bending and Sshaped deformation were obtained by applying mechanical load,and the strain data was extracted and substituted into the designed optical fiber shape reconstruction algorithm to realize the optical fiber the three-dimensional shape reconstruction was calculated and analyzed by the root mean square error(RMSE)and normalized accuracy(E).The results show that the algorithm has high reconstruction accuracy.4.Using ANSYS Maxwell and ANSYS Workbench,the dynamic finite element model of a single three-core fiber winding submarine cable was established,and the displacement and strain cloud diagrams were obtained by applying mechanical loads.Then,according to the simulation results,the axial strain was divided into two parts,respectively calculated and superimposed,and the fiber length-to-axial strain curve was drawn when the submarine cable was bent,and the axial strain change process of each fiber core was analyzed.Finally,the strain after superposition of each fiber core was substituted into the algorithm designed in this paper,the shape of the submarine cable was restored,and the error analysis was performed.The results show that the shape restoration effect of the algorithm in this paper is good,which provides technical support for practical engineering applications.