System identification using frequency scanning and the eigensystem realization algorithm

The application of the eigensystem realization algorithm to flexible structures excited with nonimpulse-type inputs is described. Sinusoidal pulses are a special subset of such inputs, and their use to lock on to particular modes is discussed. The determination of impulse response functions from nonimpulse response functions is performed via a two-step procedure. In the first step, free decay data are analyzed by the eigensystem realization algorithm to determine the structural frequencies and damping. Forced response data are analyzed in the second step by solving an overdetermined set of linear equations for the model coefficients of the impulse responses. It is shown that the number of impulse response coefficients is halved if displacement, velocity, and/or acceleration sensors are used in conjunction with force actuators. System identification is completed after the eigensystem realization algorithm is used on the impulse responses to produce a linear state space model of the structure. Numerical examples are given in which structural models are determined from simulated data corrupted with noise. (AIAA)