Studies On Inverse Problem Of Vehicle Structure Vibration

The inverse problem has been reseached in a long history. its field of application is also quite broad, such as scanning imaging, physical detection.it also have a important influence on flight vehicle design. And there exist many ways to reseach recognition of inverse problem, the frequency domain method, time domain method, wavelet analysis, simulation of evolution. However, due to the inverse problem is not qualitative, that is, the existence of solutions, the stability of the result and the uniqueness of result ,Can not be met at the same time .To solve these problems, Some methods are used to improve them in this paper.Embarks from the general vibration question, considered that the initial value and the boundary value of the differential equation , as well as the supplemental condition the differential equation simultaneous has been established, The Laplace transformation was used to transfor the time domain question to the frequency range to carries on the solution. The Anti-theoretical issue of differential equations main solution method: Pillips smooth method, regularization method, average nuclear method as well as regular homotopy method. The numerical simulation of the regular homotopy method has been carried on. The inverse problem is ill-posedness is showed and analysised. The related proof also be made.In order to recognize the subtle change in stiffness function, Anti-theoretical issue of differential equations will be used to identify areas of vibration parameters. Structural stiffness distribution function has been broken down into the original stiffness distribution functions and additional stiffness function. Decomposed the Green function.In addition,the Laplace transformation,and the additional conditions are applied to identify. The perturbation method and separation method are mainly introduced.Many structures in vehicle can simplify to cantilever. For a better description of the practical application of anti-value, crack cantilever with the location and depth parameters coefficient have been recognised in this paper. The differential equations of beams will be deducted, combined with the crack of the conditions can obtain the equation of crack cantilever with the location and depth parameters coefficient, calculated using Matlab programming data to draw the imaging relationship of the 1-5 band frequency and location of the dimensionless parameters (calculate according to the modulas value different method depth), and calculate with one-dimensional search method to the location of various non-dimensional frequency. Campared the formulas deduced in this paper with the ansys simulation, the error analysis is made to determine the location of craks .Then mixed identification method is used ,The first and second order dimensionless frequency will be got through ansys simulate method to identify cantilever's location and depth parameters coefficient at the same time. Finally, identify comparison of the numerical simulation and testing can prove the method is feasibility and correctness.it have some values on vehicle' failure diagnosis.