IDENTIFICATION OF SYSTEM PHYSICAL PARAMETERS FROM FORCE APPROPRIATION TECHNIQUE

摘要

In the area of harmonic excitation techniques for modal analysis, the analyst can use single or multi excitation forces to tune real or complex modes and to measure mobility readings from which modal parameter estimations can be derived. The accuracy of the results depends on the ability of the experimentalist to select the appropriate values of the damped natural frequencies which, in turn, depends on the basic assumptions of the damping mechanism. This paper proposes experimental and analytical procedures based on multi-harmonic excitation of the structure and does not impose any condition on damping. These procedures are based on tuning a sufficient number of forced modes by appropriating the amplitudes of the in-phase multi-harmonic forces at fixed excitation frequencies. When a forced mode is excited a phase angle exists between the in-phase forces and the in-phase displacements. The errors between the measured phase angles and their corresponding theoretical values are minimized in the least square sense by allowing the parameters to change until the optimal values are obtained.