Dynamic Properties Identification And Modeling Of A3-axis Shaking Table

This thesis focuses on the dynamic properties identification and modeling of a3-axiselectro-dynamic shaking table. The work of the thesis is the basis for simulation of structural vibrationtest, virtual experiment and prediction of experiment results under complicated working condition.Firstly, the operational principle of electro-dynamic shakers and the functions of theircomponents are set forth. The key performance characteristics of the shakers are analyzed, includingthrust, displacement amplitude, working frequency and waveform distortion, especially theamplitude-frequency characteristics under constant current and constant voltage. The principalperformance parameters that can be used to judge the capability of a shaker are listed. The multi-axialshaking tables are also introduced, involving its structures and specifications.Secondly, some methods for modal identification and physical identification, based on measuredstructural frequency response data, are introduced and derived in detail. The modal identificationmethods including orthogonal polynomial fitting (OPF) method, least square iteration (LSI) methodand vector fitting (VF) method are researched. The FRF direct method and the FRF fitting method forphysical parameters identification are also studied. The feasibilities of the modal identificationmethods are investigated by a three degree of freedom example. It turns out that the OPF and VFmethods are more accurate and reliable than the LSI method which introduces calculation errorsbecause of its defect. The feasibility and precision of the2kinds of physical identification methodsare examined by a two degrees of freedom example.In the end, a small3-axis shaking table is measured. Its working characteristics are analyzed bythe measured FRF data. The dynamical properties of the shaking table are identified by the proposedmethods in the thesis. The identified properties include the modal parameters and physical parametersfor the shaker’s x-axis and y-axis vibration directions, and the natural frequencies and modal shape forthe shaker’s z-axis vibration direction. Based on the obtained physical parameters, the dynamicmodels of the shaking table along x-axis and y-axis are established and another experiment is finishedto check the reliability of the model.