The error in placement angle of the fiber Bragg grating(FBG)in fiber optic shape sensing can affect the accuracy of curvature calculation,thereby increasing the error of shape inversion.To achieve self-correction of the angle of the sensing rubber rod,a self-correction shape sensing structure was designed.Nine FBGs were deployed on the sensing cross-section of the sensing rubber rod,with equal angle intervals of 120° as the reference positions,and strains were extracted at±10° positions,thereby completing the functional mapping of the FBG response and angle deviation.A self-correction algorithm based on angle deviation is proposed,which optimizes the threshold of sensing parameters α and k through the fitness function to achieve self-correction of any angle deviation.A simulation analysis of the response relationship under different α and k conditions revealed that α had good linear variation characteristics,and k only fluctuated with the main sensitive FBG.In the single section experiment,the average response of the nine FBGs was between[-1.012 με/N,0.987 με/N]after loading 0～100 N stress changes.The positive or negative response characterized the bending direction,and the responses of adjacent FBGs had good linearity.In the composite cross-section experiment,the three-dimensional structure of the sensing rubber rod was reconstructed based on the inversion results,and the coordinates and stress values of each point were output.
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