Extraction of normal modes from experimental data

A technique is presented to extract normal modes from complex modes. The frequency response function relation of the complex and the normal modes are derived, then an algorithm is developed to calculated the normal modes from the complex modes. A numerical example and an experiment are used to illustrate the applicability of the technique. The results indicate that the technique can extract normal modes well only need fewer FRF vectors for structures with lightly viscous damping and structural damping. For heavily damping, the accuracy of extraction depends on how many FRF vectors are included in the calculation.