Nonlinear Parameter Identification Base On Adaptive And Sparsest Time-Frequency Analysis Method

In civil engineering,non-linear behavior is widespread,and traditional methods forparameter identification of linear systems are not applicable and relatively difficult.In engineering practice,high-rise building structures often exhibit nonlinear behavior under wind load excitation,and structures also exhibit nonli-near behavior due to their own materials and cracks.Therefore,it is of great significance to identify the nonlinar parameters of the structure.In this paper,based on Adaptive Sparsest Time-Frequency Analysis method,parameter identification of nonlinear systems and vibration chrateistics of wind turbine tower foundations are analyzed.Firstly,the system prameter identification of two classic nonlinear systems,Duffing and Van der pol,is studied.Thenonlinear par-ameters are identified,and the reasons why Van der pol can be used to simul-ate the wind-induced nonlinear behavior of high-rise building strtures are explained.Taking the wind turbine tower foundation vibration monitoring test of a windfarm in Hunan as the background,the nonlinear parameter of the wind power foundationvibration data under the action of wind load is identified by using the Adaptive Sparsest Time-Frequency Analysis method.The main contents of the thesis include the following:1)The Adaptive Sparsest Time-Frequency Analysis method is compared with EEMD in terms of endpoint effects,modal aliasing and noise effects,and then the efect of parameter selection on the decomposition results is described,and a multcomponent non-stationary signal is carried out Decomposition illustrates the abiity of the method in processing non-stationary signals.The Adaptive Sparsest Time-Frequency Analysis method can directly extract the instantaneous amplitude and instantaneous frequency of the component signal,which provides a basis for nonlinear parameter identification.2)The approximate analytical solution of the nonlinear vibration system eqution is obtained by the average method,which is convenient to calculate and has small eror.Based on Adaptive Sparsest Time-Frequency Analysis method,two classical nonlinear system parameters are identified.Compared with HHT or wavelet transform recogntion results,the recognition accuracy is higher.And it can also identify the sytem parameters after processing the nonlinear equation by harmonic linearization.3)The nonlinear behavior of the structure under wind load can be roughly simu-lated by Van der pol nonlinear vibration system.Taking the foundation vibration of a wind power tower in a wind farm in Hunan as the background,the architecture of the monitoring system of the monitoring test and the arrangement of the measurement points of the sensors are introduced.TheAdaptive an-d Sparsest Time-Frequency Analysis method is used to analyze and identify thefundamental vibration data of the wind power tower The nonlinear parameters,damping coefficients and natural frquencies of the structure are given.