A study on AGV-induced floor micro-vibration in TFT-LCD high-technology fabs

Abstract

SUMMARY This study explores vertical floor micro‐vibration induced by the automated guided vehicles (AGVs) in thin‐film‐transistor liquid‐crystal‐display (TFT‐LCD) fabs. The state‐space procedure is adopted to compute the AGV‐induced floor vibration as it preserves the desired numerical stability and accuracy in high‐frequency responses. The dynamic analysis of an 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 the AGV moving 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 dampers is also examined. In comparison with span‐reduction, application of energy‐dissipation devices is more effective in vibration suppression as they enhance the damping characteristics of the multi‐span floor system whose natural frequencies are potentially in resonance with the excitation frequencies of the AGV moving loads ranging in a broad bandwidth. Copyright © 2011 John Wiley & Sons, Ltd.

Investigation of vibration induced by moving cranes in high-tech factories

“…There are a number of investigations in the literature to study this topic. [1][2][3][4][5] Park et al 1 studied the motion of a Bernoulli-Euler cantilever beam clamped on a moving cart, and the results matched well with physical phenomena. Ngo and Hong 2 discussed a sliding-mode control for a crane, and the proposed mechanism can suppress lateral sway.…”

“…They indicated that energy dissipation devices can be effective in vibration-mitigations. Lee et al 5 explored vertical floor micro-vibration induced by the automated guided vehicles. They indicated that the energydissipation device is effective in vibration suppression.…”

Assessment of vibrations induced in factories by automated guided vehicles

“…The equation defining the motion of an undamped Bernoulli-Euler beam with (Q þ 1) supports subjected to N moving loads can be presented as (Zheng et al, 1998) Figure 2. Illustration of AGV moving loads on an equivalent three-span beam model (Lee et al, 2012) in which x ps (t) is the location of the moving loads (P s ), t 0 and t e are the time instants when the moving loads come onto and leave the beam, respectively, u(t ) is the unit step function defined as…”

“…It supports a RC cheese slab of thickness 0 . 55 m, giving a mass per unit length of rA ¼ 9 : 1505 3 10 3 kg/m (with air circulation holes) and an equivalent flexural rigidity of EI ¼ 2 : 3097 3 10 11 Nm 2 (Lee et al, 2012), so that the fundamental frequency of the three-span continuous beam is around 6 . 1 Hz.…”

“…However, adverse vibrations that are directly induced by moving vehicles on the production floor in industrial factories have rarely been considered in the design phase. As a consequence, most TFT-LCD factories encounter interior vehicle-induced floor vibration problems (Lee et al, 2012) when they begin operations. Figure 1 illustrates a typical TFT-LCD building with two clean rooms.…”