| Summary: | 碩士 === 國立臺灣海洋大學 === 機械與機電工程學系 === 95 === This study applies the techniques of experimental modal Analysis (EMA), finite element analysis (FEA), structural dynamics modification (SDM), and system identification techniques for dynamic analysis and vibration control of a base/cantilever structure. Experimental modal analysis was first performed for an unconstrained cantilever structure and the natural frequencies and mode shapes of the structure, which includes the base/cantilever beam and the piezoelectricity inertia actuator, were determined. The experimental results were compared with those obtained from the FEA. The model was further revised to enhance its rigidity and both the theoretical and experimental modal analyses were performed to determine the modal parameters. Different boundary or support conditions can have decisive influence on the structure’s dynamic characteristics. Experimental structural dynamics modification was performed on the revised model by fixing four positions on the bottom of the base to mimic the actual service condition. Both the FEA and the EMA were performed on the modified structure for confirmation. The first three modes in the vertical direction were targeted for vibration control. Direct feedback control was first considered in this work. The frequency response was measured afterwards from the input of the piezoelectricity inertia actuator and the output of the system response. The transfer function of the system was determined using the system identification method based on the frequency response measurement. Subsequently, the transfer function of the vibration controller was then obtained. Finally, the controller transfer function was realized by electric circuits. This study shows that the vibration controller performs satisfactory, with the original vibration being reduced by 8.95 dB approximately.
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