On Controllability of Structures with Closely Spaced Natural Frequencies Based on Perturbation Analysis.

His paper investigated the influence of frequency intensity parameters on the controllability of structures with closely-spaced natural frequencies. The perturbation equations were established for a closed-loop system to study the relationship between frequencies, mode damping ratios and perturbation parameters. The calculation results showed that the damping ratios of two modes are decreasing as the decreasing of intensity parameter values of the structure with closely spaced natural frequencies, indicating that the controllability of corresponding modes was losing. The uncertainties in mass and stiffness matrices were also discussed in this paper. [ABSTRACT FROM AUTHOR]