Research On Structural Modal Parameter Identification Under Non-White Noise Environment

Aerospace vehicles and other structures are often in complex vibration environment in the working process.This paper studies modal parameter identification under non-white noise environment,which has important engineering significance and theoretical value.The main work of this paper is as follows:(1)Several time-domain methods of conventional operational modal analysis are studied.The Natural Excitation Technique,Autoregressive Moving-Average Model,Eigensystem Realization Algorithm and Stochastic Subspace Identification method are theoretically deduced and programmed by MATLAB.Through the numerical simulation and experiment of the foundation excitation beam,the recognition effect of the above methods is compared and verified.(2)The applicability of conventional operational modal analysis under non-uniform spectrum environment is studied,and the phenomenon of modal omission is found and the reasons are analyzed.It is pointed out that under the excitation of non-uniform spectrum environment,due to the uneven distribution of excitation energy in the frequency domain,the main reason for modal omission is that a certain order modal of the structure can not be fully excited or even not.(3)Based on NExT-ERA method,an enhanced modal analysis method is proposed,which combines filtering technology,stability diagram method and fuzzy clustering method.It solves the modal omission problem of the conventional operational modal analysis method under the excitation of non-uniform spectrum environment.The validity of this method is verified by several typical experiments of beam and control surface structures under non-uniform spectrum excitation.(4)The Fast Approximated Power Iteration Subspace Tracking(FAPI)and the NExT-ERA method based on short-term steady-state assumption(TERA)are studied,and the parameters of these methods are optimized.The validity of the method is verified by numerical simulation and experiment of time-varying beam.Based on MATLAB,an application software for operation modal analysis under non-stationary state is developed.