Estimation of mass and modal mass in the identification of non-linear single and multi degree of freedom systems using the force-state mapping approach

Abstract The application of the force-state mapping approach to the identification of single degree of freedom non-linear systems requires the mass of the system to be known. In the case of multi degree of freedom systems both the modal mass and modal matrices need to be available for the necessary transformation into modal space. In this paper a method is presented in which an initial mass or modal mass estimate is refined by examining the sensitivity of identified parameters to the estimated mass using data from two or more excitation frequencies. This sensitivity method effectively compensates for errors in mode shapes by an implicit scaling of the physical equations and the final identified non-linear model has the correct response characteristics.