Method for improving low-frequency vibration performance of complex structure

The invention discloses a method for improving the low-frequency vibration performance of a complex structure. Firstly, a test modal analysis method is adopted to obtain a test modal and vibration frequency response function of the automobile structure, and the test system comprises a vibration exciter, a test system, a test computer, a three-way acceleration sensor and the like. Then, a finite element analysis model of the vehicle body structure is built through a finite element modeling technology, the accuracy and reliability of the model are determined through modal benchmarking analysis,and the modal and vibration frequency response function of the finite element model is calculated. For the frequency with abnormal vibration frequency response function peak value, sensitivity analysis based on the plate thickness is carried out, and the plate with the local rigidity not matched with the overall rigidity of the vehicle body design is found. According to the concentrated distribution area of the modal strain energy on the plate under the frequency, a structure optimization method is adopted, so that the problem frequency vibration peak amplitude is greatly reduced, a good effect is obtained, the product performance is improved, the research and development and manufacturing period is shortened, and the cost is reduced.