A study on floor micro-vibration in high technology factories

This study explores vertical floor micro-vibration induced by the automated guided vehicles (AGVs). AGVs move on multiple long-span production floors in TFT-LCD fabs, where many vibration-sensitive tools are installed. A simplified method is proposed here to assess AGVinduced floor vibration, which has rarely been taken into account in the design stage. The statespace procedure (SSP) is adopted to compute theAGV-induced floor vibration as it preserves the desired numerical stability and accuracy in high frequency responses. The dynamic analysis of a AGV moving on an equivalent three-span beam model of a TFT-LCD building is simulated by taking into account various AGV speeds and engine forces. Numerical simulations demonstrate that if proper engine forces and excitation frequency contents of theAGVmoving loads are used, the peak AGV-induced floor micro-vibration level can be predicted by the proposed method. Moreover, the effectiveness of vibration control by span-reduction as well as energy-dissipation by viscoelastic (VE) dampers is also examined. In comparison with span-reduction, application of energy dissipation devices is more effective in vibration suppression as they enhance the dampingcharacteristicsofthemulti-spanfloorsystemwhosenaturalfrequenciesarepotentiallyin resonancewiththe excitationfrequenciesof theAGVmovingloads rangingina broadbandwidth.