An Inverse Method for Selection of Fourier Coefficients for Flight Load Identification

‡This work seeks to identify in -flight loads based on real time data provided by strain gages. Flight loads are identified based on an inverse interpolation method that utilizes results from a Finite Element Model (FEM) developed in I -DEAS. The inverse interpolation is based on minimization of the error be tween calculated verses measured strains. Finite element strains are used as representative of measured strains for input into the analysis. Strains determined from surface loads of individual Fourier terms are also determined from the FE model. Strain data from the applied unknown load coupled with FEM data from the Fourier loads allow prediction of the Fourier coefficients of the actual load. Predicted Fourier coefficients are compared to sets of Fourier coefficients from a database based on historica l or theoretical loads and a “least squares” minimization performed to determine which set of coefficients are most probable. Successful load predictions are made for polynomial surface functions of one and two independent variables.