Program LINEARID for Identification of Linear Structural Dynamic Systems
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In this report, LINEARID, a computer program developed for the identification of the coefficient matrices in the equation of motion for a linear multi-degree-of-freedom structure, is documented. The equation of motion is obtained in the form of a conventional differential equation. However, it is transformed into an auto-regressive and moving-average with auxiliary input (ARMAX) model for the purpose of system identification. Methods of parameter identification are then applied to estimate the parameters of the ARMAX model, while the parameters of the original differential equations are recovered therefrom. Four different methods of parameter estimation are available in the program. They are the ordinary least squares method, instrumental variable method, maximum likelihood method and limited information maximum likelihood method. The theoretical background, program descriptions and user's guide are given. Numerical example analyses are given for two different structural systems. A FORTRAN listing of Program LINEARID is given in an appendix. Example input and output data files are also listed in the appendices.