Study On Modal Parameters Identification Of Time-varying System

In this paper, how to identify modal parameters of the time-varying system is analyzed. We focus on the time series analysis methods used to identify modal parameters of the time-varying system, and try a series of enhancements based on the study of the methods.First of all, we start from the finite element simulation, establish a finite element model of the cantilever beam, and construct a time-varying beam system by changing the mass matrix continuously. Secondly, the natural vibration frequencies of the beam at different time points are calculated with the finite element method as the standard values of the analog comparator. We use white noise to excite the beam model, and calculate the beam response in the time-varying process with the finite element method in order to lay the foundation for the time series model.The auto regressive moving average model (ARMA model) and auto regression model (AR model) are introduced, and the model theory and modal identification principle are discussed specifically. The time series model order determining methods with singular value decomposition is analyzed as the key and the method of difference between singular values is proposed and improved. An idea of changing order to determine the order of AR model and ARMA model is proposed based on the law of order. Then we discuss the sub-AR model algorithm applied to the time-varying system, based on the idea of sub-AR model algorithm, sub-ARMA model algorithm is proposed. Sub-AR model algorithm and sub-ARMA model algorithm are applied to the time-varying beam system in modal parameter identification. It is concluded that the first three natural frequencies are identified better.Finally, in the laboratory, the test of an adding-mass cantilever beam is used to verify the actual capacity of the studied algorithms. The experimental results show the effectiveness of the methods of this paper.