System Identification Using Frequency Scanning and the Eigensystem Realization Algorithm

The application of the eigensystem realization algorithm to flexible structures excited with nonimpulse r type inputs is described. Sinusoidal pulses are a special subset of such inputs, and a discussion is given r. on their use to lock on to particular modes. The determination of impulse response functions from N) nonimpulse response functions is performed via a two step procedure. In the first step, free decay data is analyzed by the eigensystem realization algorithm to determine the structural frequencies and damping. "C:3 ammo Forced response data is analyzed in the second step, by solving an overdetermined set of linear equations - ,": for the modal 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.