An Experimental Investigation of State-Variable Modal Decomposition for Modal Analysis

Abstract

This work presents the experimental evaluation of the state-variable modal decomposition method for a modal parameter estimation of multidegree-of-freedom and continuous vibration systems. Using output response ensembles only, the generalized eigenvalue problem is formed to estimate eigenfrequencies and modal vectors for a lightly damped linear clamped-free experimental beam. The estimated frequencies and modal vectors are compared against the theoretical system frequencies and modal vectors. Satisfactory results are obtained for estimating both system frequencies and modal vectors for the first five modes. To validate the actual modes from the spurious ones, modal coordinates are employed, which, together with frequency and vector estimates, substantiate the true modes. This paper also addresses the error associated with estimation when the number of sensors is less than the active/dominant modes of the system shown via a numerical example.