Energy transfer model for squeeze-film air damping in low vacuum
Energy transfer model for squeeze-film air damping in low vacuum
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DOI：
10.1088/0960-1317/12/3/322
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发表时间：
2002-05-01
影响因子：
2.3
通讯作者：
Sun, YC
中科院分区：
文献类型：
--
作者：
Bao, MH;Yang, H;Sun, YC
高质量的因素是必不可少的振动微传感器。因此，传感器的振动结构通常封装在一个外壳中，其中空气被抽走以减少空气阻尼。然而，真空度通常很低，质量因子仍然主要取决于对周围空气分子的能量损失。通常使用Christian提出的自由分子模型来估计低真空下的空气阻尼（Christian R 1966 vacuum 16 175-8）。该模型的主要缺点是不能考虑附近物体（例如用于静电驱动的电极）的影响和板的尺寸。因此，实际结构的阻尼效应往往被严重低估。本文提出了一种新的低真空微结构空气阻尼模型。在这个模型中，用能量传递机制代替Christian模型中的动量传递机制来计算阻尼效应。对于孤立振动板，该模型计算的质量因子与Christian模型计算的质量因子相同。然而，对于有邻近物体的振动板，新模型的阻尼效果与振动板的尺寸和板与附近物体之间的间隙有关。计算出的质量因子与实验数据的一致性比克里斯蒂安的模型好一个数量级。
High quality factors are essential for vibratory microsensors. Therefore, the vibrating structure of the sensors is often encapsulated in a housing where the air is evacuated for reduced air damping. However, the vacuum is usually low and the quality factor is still mainly determined by the energy losses to the surrounding air molecules. Air damping in low vacuum is usually estimated using the free molecular model proposed by Christian (Christian R 1966 Vacuum 16 175-8). The major drawback of the model is that the effect of the nearby objects (e.g. the electrodes for electrostatic driving) and the dimensions of the plate cannot be considered. Therefore, the damping effect is often significantly underestimated for real structures.This paper proposes a new model for air damping of microstructures in low vacuum. In this model, the damping effect is calculated by using an energy transfer mechanism instead of the momentum transfer mechanism in Christian's model. For an isolated oscillating plate, the calculated quality factor by the model is the same as that by Christian's model. However, for an oscillating plate with a neighboring object, the damping effect by the new model is related to the dimensions of the vibrating plate and the gap between the plate and the nearby object. The quality factors calculated agree with experimental data better than with Christian's model by about an order of magnitude.