EXPERIMENTAL MODAL ANALYSIS OF A STRUCTURE EXCITED BY A RANDOM FORCE

A multivariate maximum likelihood procedure for the estimation of modal parameters is presented. The vibrating system is excited by a random force and only output sensors are used to estimate the natural frequencies and damping factors of the system. The method works in time domain and a vector autoregressive moving-average (VARMA) process is used. The information about modal parameters is contained in the multivariate AR part, which is estimated using an iterative maximum likelihood algorithm. This algorithm uses a score technique and output data only. The order of the AR part is obtained via the minimum description length associated with an instrumental variable procedure. Experimental results show the effectiveness of the method for model order selection and modal parameters estimation.