巢狀式位移放大壓電致動器之設計與開發

Abstract

壓電式致動器是一種利用壓電效應將電能轉換為機械能的元件。壓電材料在受到電場作用時會產生形變，而這種形變可以用來驅動機械元件。壓電式致動器具有耐用度高、出力強、驅動頻率高等優勢，因此被廣泛應用於自動化工業、精密儀器等領域。然而，壓電材料的變形量較低，因此壓電式致動器的行程也較小。為了滿足某些應用場合的需求，需要對壓電式致動器的行程進行放大。壓電行程放大器是一種用於放大壓電式致動器行程的機構。現有的壓電行程放大器多為槓桿式。槓桿式放大器的原理是利用槓桿的力學原理，將壓電材料的微小形變放大為較大的行程。槓桿式放大器具有結構簡單的優點，但其垂直輸出位移方向上的尺寸較大，因此不適合安裝在空間狹小的場所。為了克服槓桿式放大器的缺點，本文提出了一撓性結構的壓電行程放大器設計。此設計使用尺寸為7736 mm3之積層式壓電元件，首先以壓電元件推動一菱形撓性放大機構，菱形機構再推動一對對稱之槓桿結構，槓桿結構再撐開一個半菱形結構，共可達到285 μm之致動行程，以及11.5倍之行程放大倍率。所提出之結構利用槓桿及菱形結構之特性互補，使得占用較大空間的槓桿式結構及積層式壓電元件能被配置在平行輸出位移之方向上，使得所設計之致動器尺寸可在604412 mm3以內。相較於同伸長量之其他致動器，所提出之致動器寬度尺寸可減少50%以上，並具有935 Hz之輸出方向共振頻率及0.16 N/μm之輸出剛性。

Through converting electrical energy into mechanical deformation, piezo-actuator can be used to actuate mechanical components. Piezoelectric actuators have advantages of high durability, large output force, and high bandwidth, which have been widely used in automatic manufacturing and precision instruments. Due to the small displacement of the piezoelectric actuator, amplification mechanism is necessary for many applications required long travel distance. The lever-type amplifier is a commonly used mechanism, which has simple structure. However, the lever-type amplifier usually has a larger dimension in the direction that paralleled to the output axis, making it difficult to fit in a narrow space. To overcome this limitation, this study proposed a nested-type amplified piezo actuator design using a compliant mechanism. This design employed a piezoelectric stack with dimensions of 7×7×36 mm3 to drive a rhombus-type amplifier. The displacement of the rhombus-type amplifier then actuated two symmetrical lever-type amplifiers. Finally, the two levers deformed a half rhombus-type amplifier to achieve a total displacement of 285 μm with an amplification ratio of 11.5. The proposed design integrated two types of the amplifiers to reduce the width, and the dimensions of the actuator were under 60×44×12 mm3, offering up to a 50% reduction in width compared to other actuator designs. The design also featured an output resonance frequency of 935 Hz and an output stiffness of 0.16 N/μm.