| Operational modal analysis is to research the working structure’s dynamic characteristics.The results are more practical and instructive for solving the vibration and noise problems ofworking structure. The limitation and excitation of an automobile’s structure or componentare both extremely complex when the automobile is running on the road. For this reason, it isimpossible to measure the excitation or analyze the operational modal by using theinput-output test modal analysis method. It is only necessary to measure the response signalof the vibrating structure by using the output-only modal analysis method. This new way ofthinking and method makes it possible to study the operational modal of working vehicle forthe reason that the excitation signal is not needed.First of all, an method named steady sine excitation was used to get the modalparameters of a certain type of frame under the free limited situation in this paper. The resultfrom this method is considered as the reliable reference value. Secondly, to simulate theworking excitation condition of the road roughness, the frame was excited by a stationarystochastic signal under the same free limited situation. The output-only modal analysismethod was taken to obtain the modal parameters. The data processing and parameter settingsof the method was discussed, and a process consisting of both test and analysis was confirmed.Thirdly, the principles, the processes and the results of the two identification method werecompared respectively. The comparison results showed that the output-only modal analysismethod can identify the operational modal parameters of the frame effectively. And afoundation was settled to use this method on a real working car to study its operational modal.Finally, the mass versus eigenvalue sensitivity analysis was done based on the availablemodal parameters. The results of the sensitivity analysis was applied to commit a dynamicmodification, and the lightweight of the frame was achieved. |
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