Experimental modal analysis using undamped control for high damping system

This study proposes a methodology to identify the modal damping ratio of a highly damped structure. Specifically, we explain the change in the modal damping ratio of the object itself by using an existing novel multiple excitation testing method with velocity feedback (FB) control to counteract the damping force, and we propose a methodology to identify the original modal damping ratio of the object based on the methodology of modal analysis. In this methodology, the relation equation between the modal damping ratio and control gain is derived. In the numerical and experimental validations, the modal damping ratio is identified by applying velocity FB excitation to a multi-degree-of-freedom system, and it is confirmed that the original modal damping ratio of the target structure can be identified from the frequency response function after damping reduction. Therefore, the proposed method is expected to improve experimental modal analysis by facilitating the accurate identification of the modal damping ratios of the vibration mode wherein the resonance peak does not appear clearly.