Improved model updating method by adding given mass

The model updating algorithm by adding given masses is an approach to correct the mass matrix and stiffness matrix of the finite element analytical model by using measured vibration modes. But when the number of measured modes is insufficient, the accuracy of this algorithm can not meet the requirements of engineering applications. However, the insufficiency of available measured modes is unavoidable in engineering. To ensure the updating accuracy, some improving approaches are proposed. In the first approach, when the correcting matrix is full rank, an iterative algorithm is presented to improve the updating accuracy step by step, but extra experiment expense should be paid. The reason of deficient rank is also discussed, and a mode reduction method is suggested to ensure that the correcting matrix is full rank. Based on the fact that the distribution of structural modeling errors usually is localized. In the second approach, local updating algorithm is developed, which enforces additional constraints on the final updating equations according to the localization of errors, so that the least square solution is more reasonable to correct the initial mass matrix and stiffness matrix of the system. The updating of a straight wing model is performed as an example to verify the improved algorithm. The results show that the improved updating algorithm has sufficient accuracy.