MULTIPHASE-STEP-SINE METHOD FOR EXPERIMENTAL MODAL ANALYSIS.

This article presents an approach to large-scale modal tests that combine the multishaker methodologies of sinusoidal and random excitation. The first phase of this method consists of verifying a single exciter location with either stepped sine or random excitation. Then, using closed-loop force control, a series of multishaker stepped-sine surveys are performed, alternating polarity patterns between the surveys (multiphase step sine). The responses in each such survey may be considered frequency-response functions with respect to a generalized force, since force amplitudes and polarities are controlled to be constant within each survey. Mode-indicator functions may hence be calculated and modal parameters can be extracted from these individual surveys, just as for standard single-point excitation methods.