多連桿機構的振動研究

Abstract

四連桿式二維運動機構可以和二維光學尺搭配成高精度長行程的二維定位系統。本研究旨在探討此機構進行急進急停時發生的暫振問題。首先使用有限元素軟體ANSYS，建立參數式模型，包括滑軌、連桿和握爪平台，進行靜態和模態分析，獲得振動模態和自然頻率的分布，而所計算出的模態資料進一步匯入多體機械系統分析軟體DADS，進行急動和急停的撓性機構動態分析，觀察二維定位系統的各方向暫振，另外還設定不同的設計參數進行模擬，以及改變機構設計，比較其振動量。本研究根據分析的結果發現，此機構若欲達到nm的定位精度，其振動量似乎還是稍嫌大了一點，另外，其連接握爪的平台沿鉛直Y方向的角速度特別顯著，而這表示連接握爪的平台並不與滑軌保持平行，會危及精密量測；最後觀察每個作動的頻譜，可發現第8、18、19模態很容易會被激發。

A two-dimensionally positioning system capable of long traverse distance of motion is made up of a multilink mechanism and a two dimensional optical grating. The objective of this study is to investigate vibration of the multilink mechanism undergoing sudden moving and sudden stop. The finite element model in ANSYS contains a track, links, and a stage. Static analysis and modal analysis are carried out. Modal data is further used in a multibody dynamic analysis software DADS for flexible mechanism simulation. This study investigates vibration source and improve mechanism design to reduce vibration. Several conclusions can be deduced from the simulation results. Due to vibration nanometer precision is unattainable. The vertical angular velocity is found significantly faster than the horizontal angular velocity. Therefore, the stage and the track don’t remain parallel to each other. Frequency spectra exhibited the eighth, the eighteenth and the nineteenth resonance mode are always easily excited.