大行程微機電靜電式垂直致動器之設計、分析、製作與應用

Abstract

本論文提出一個具有大致動範圍的創新靜電式微機電致動器（PCA）。他是利用雙金屬薄膜間，因為殘餘應力的不平衡效益，使得一懸臂樑結構於非固定端產生一垂直方向的大角度翹曲與位移，以達到具有大致動範圍的設計目的。此外，經由設計一梳狀致動器於翹曲懸臂樑邊緣的方式，使得此致動器獲得不會有不穩定的驅動現象（pull-in）。經由對靜電力與懸臂樑彈性回復力的分析，不穩定現象初步獲得證實。經由數學模式的推導與模擬，不穩定現象也未曾發現。因此本文便以標準的表面微機電製程技術（PolyMUMPS）實現了此一新穎的靜電式微致動器。經過微機電後製程的處理與封裝後，此致動器的靜態與動態特性已經被完整量測，其結果與模擬結果相符合。因此，為了進一步的驗證精良特性，本文設計與製作了一適用於光通訊應用的微光學切換器元件，此光切換元件的驅動器便是本文所設計的PCA。為了量測與分析光切換元件的動態特性，本文利用一雷射光點偵測器元件（PSD）、氦氖雷射、多工資料擷取卡、功率放大器與個人電腦完成了一動態光點監控系統。在未加控制器的狀況下，光切換元件表現出低阻尼系統的劇烈震盪現象，且其步階響應穩定時間達到8 msec，但是在經由一常見PID控制器的迴授控制下，除了可完全抑制震盪現象，其步階響應穩定時間更加快至1.1 msec。可見本文所提出的新穎微機店靜電致動器具有極高的穩定性與可控性，對於微機電系統領域的研究提供了一絕佳的致動器範例。

This dissertation proposes a novel large vertical displacement electrostatic actuator, called pre-stress comb-drive actuator (PCA), which exhibits no pull-in and no hysteresis characteristics. The proposed PCA consists of a set of comb fingers fabricated along the composite beam and substrate. One end of the composite beam is clamped to the anchor, whereas the other end is elevated vertically by the residual stress. The actuation occurs when the electrostatic force, induced by the fringe effect, pulls the composite beam downward to the substrate. A post-heat treatment process was employed to increase the initial lift height of the PCA to obtain a large actuation stroke. A mathematical model, based on a newly developed modeling approach, is introduced to estimate the static characteristic of the PCA. A PCA was fabricated using the PolyMUMPs process based on the proposed design concept. Following packaging and applying a post-heat treatment process, a 110 μm initial tip height and a 90 μm vertical motion range were achieved. Neither pull-in nor hysteresis was observed. The simulation results were closely matched with the observations. This work also studies the dynamic/frequency response and measurement of the maximum vibration magnitude of the PCA. A half mode phenomenon due to the nonlinear characteristics of electrostatic actuator is also discussed. Finally, a servo control of optical switch that is driven by PCA is used to demonstrate the controllability and stability of PCA.