A method to obtain the in-process FRF of a machine tool based on operational modal analysis and experiment modal analysis

The dynamic parameters of a machine tool under the operating state are different from those under the static state. It is more accurate to use the dynamic parameters in the operating state to simulate the machining process and predict the machining stability. Operational modal analysis is a powerful tool to estimate the dynamic parameters of the machine tool in the operating condition; however, it has the problem of missing the scaling factor of the mode shape. Hence, the frequency response function (FRF) cannot be identified directly. To address this issue, this paper proposed a new method to obtain the in-process FRF based on the operational modal analysis (OMA) and the experiment modal analysis (EMA). This method employs the natural frequencies and damping ratios from the OMA and the modal constants from the EMA to compose the FRF for the operating condition. The method is verified by simulation of a three-degree-of-freedom mass-spring-damper system and is applied to the identification of the FRF for the work table of a machine tool.