Modal Parameter Identification Of Objects Exiting Water Based On Time-varying PRONY Method

Modal parameters identification of objects exiting water need to solve two problems: the first is the time-varying feature, this is because the added mass of water decreasing, the system frequency is time-varying, and the second is the sampling signal is very short. Therefore this paper main studies the varying parameter identification method based on short-time signals. The main research work and conclusions are as follows:Firstly, the process of the classical Prony method base on the line time-invariant system has been discussed. It has been studied about relation of the sampling time, noise and modal parameter identification accuracy by some numerical simulations at different noise level and sampling time.Secondly, since the Prony identification method just need a small quantity of sample, So that segmented Prony method is establish to identify the linear time-varying structural parameters, the method was also simulated, and compared with the segmented AR method, results show that the identification accuracy of segmented Prony method is superior to segmented AR method, But also found that method is not satisfactory for identifying the fast varying parameters.Finally, The model coefficients are fitted by a set of basic functions, and a time-varying Prony method is establish, This method can fast track the time-varying parameters, Can not only identify good for parameters change slowly, also has good identification accuracy on rapidly changing parameters, but its more sensitive to noise, need to substantially improve the model order to reduce the impact of noise. Then through analysis the time-varying Prony method identification accuracy with six commonly used basic function, found that the method with DCT basic function, not only need little calculation, require small data length, but also have a higher identification accuracy than the time-varying Prony method with other basic functions. The time-varying Prony method with DCT basic function is proved to be effective for time-varying parameters identification by simulate a linear time-varying system, and convincible for short-time signal's identification by analyze the test data of the experiment facility of cantilever beam.