請用此 Handle URI 來引用此文件:
http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/49695
標題: | 雙頻雙模態行進波線性位移平台之研發 Research and development of two-frequency two-mode traveling wave based linear stages |
作者: | Chia-Chin Li 李佳縉 |
指導教授: | 李世光 |
關鍵字: | 直線型超音波馬達,雙模態激發,自由邊界振動分析, Linear ultrasonic motor,two modes excitation, |
出版年 : | 2016 |
學位: | 碩士 |
摘要: | 本論文之研究目標為研究並開發線性位移平台並提高它的效能,利用簡單的結構設計,搭配理論分析與模擬實驗,企圖利用結構與材料在共振時之特殊物理性質來提升位移平台之效能。超音波馬達為利用給予定子(stator)振動,帶動轉子(rotator)驅動馬達,而其工作振動之頻率可以達人耳無法分辨的超音波頻段,因此稱作超音波馬達。而本研究採用超音波馬達之概念,將兩片壓電片PZT(Lead Zirconate Titanate)膠合於一金屬基板上,利用給予壓電片不同頻率之電訊號,當作外力激盪源,激發出結構於自然頻率(nature frequency)時的模態(mode),並使原先為定子之結構邊界變為自由邊界,讓其可以在相對為轉子的支撐位移,進而順利完成位移平台設計與建造的功能需求。
於共振模態的裝置,其行為為駐波(standing wave)之形式,換言之,運用兩個駐波來建構一個行進波。本研究有別於傳統的駐波形式超音波馬達,將採用雙模態(two modes excitation)激發之形式來控制移動平台,因此這種新開發的操作形式,在本論文中就被稱之為雙模態(two modes excitation)激發模式。藉由行進波之操控,超音波馬達的運動可以被明確的控制。 自超音波馬達被發展至今約五十年之期間,行進波形的超音波馬達可以大致被分為旋型與直線型。而由於旋型結構之邊界條件,沒有反射波之問題,較容易達成行進波產生之結果,因此也大量被研究、生產並商業化。相較於旋型結構,直線型結構因為邊界反射波之問題,較難以有行進波之產生與操作,雖已有不同的研究在討論如何消除邊界反射波之效應,但仍有被發展的空間,也離商業化也還有一段距離。除了研究如何消除反射波干涉形成駐波的方式外,另有同時對直線型結構進行雙激發,讓結構中產生兩個時間與空間均相差90度的駐波,利用疊加原理,可得到行進波之驅動結果,而本團隊先前也成功的利用此種機制,製作應用此驅動方式所製成之微流道傳輸系統。 本論文之研究基礎在於將雙模態激發之激發原理驗證,於一般習知之雙模態激發為單一頻率之激發,此單一頻率選在兩自然頻率之正中間,因此一般認為可以視作此相鄰模態之疊合。但由振動理論量理論可知,若要以正交模態展開疊合成外力激盪下之振動行為,每個模態將會有各自的權重係於加權中,因此一般操作雙模態激發之操作頻率選在自然頻率之正中間不一定合適於此兩模態之疊加,可能會降低操作之效率。此外,因為非操作在共振頻率,結構反應出之增益值,沒有共振發生時來顯著。因此本研究想以直接操作在共振頻率上,利用共振行為下極大的反應值,來降低位移平台在行進時所需之供給能量,來提升直線型行進波位移平台之效能。 研究過程中,藉由理論分析,將建立位移平台振動反應詳細的數值模型,由此模型可得知結構共振發生頻率、模態型狀,並且可利用此數值模型,驗證雙模態疊合之結果,並利用此結果設計出較好的平台操作方式。除了數值模型外,本研究也用COMSOL來做三維真實時變模型,將藉由此模型驗證數值理論之結果,並預測位移平台之行為,避開不必要的模態干擾,使目標模態可進行較完美之疊合。而藉由理論計算與有限元素分析共振頻外,本研究也利用雙壓電複合結構之優勢,利用阻抗分析之方式,實驗確認系統極點發生頻率,再藉由克拉里尼圖形法(Chladni’s Pattern)測試極點頻率上之模態結果,以找出正確模態激發之頻率。 於本研究中,驗證了真實的雙模態激發之可能,且因共振頻上之非線性行為過大,本團隊行進波輸送系統中原先採用之鋁基材,經實驗後發現易產生塑性形變,因此於研究中改為使用勁度相對較高之不銹鋼基材,而在勁度較高的基板上,本研究仍達成了低電壓驅動裝置之結果,此乃驗證裡用共振頻的反應可大幅的提高位移平台之操作效率。本論文以真實模態疊合之角度切入,分析後發現一般雙模態激發所採用之結論”相鄰兩模態之疊和”之觀念應予以修正。而本論文突破性的將一般系統操作時會盡量避開之共振行為反過來應用,且成功的使裝置驅動。希望藉此可為直線型超音波馬達帶來不一樣了發展層面 In this thesis, we tried to pursue research and development of an ultrasonic traveling wave displacement stage with theoretical analysis and finite element simulation. Both of which were validated successfully with experimental results. We also tried to improve its efficiency with the amplification effect associated with structural resonance. Ultrasonic motor excites stator to drive rotor with the frequency higher than the audio range of human ears. In this thesis, we used the concept of ultrasonic motor to construct displacement stage with two piezo patches glued on metal thin plate. It was demonstrated that we can drive the piezo material at the nature frequency so as to excite the pre-specified mode. The boundary conditions of the stator were set to be free-free. The supporting material becomes the rotor relatively to the stator. The experimental results obtained verified the goal of controlling the moving direction and speed of the stage. For devices designed based on resonance modes, standing waves excitation set the foundation of the associated ultrasonic motor with its own design rule. Unlike traditional standing wave superposition type, i.e., superimpose two standing waves to create a traveling wave, this thesis adopted a new excitation modes by using two excitations to generate the traveling wave needed. For ease of identifications, this newly developed driving mode was termed “two mode excitation” in this thesis. “Two mode excitation” superpose different modes to generate traveling wave. By controlling the traveling wave, the motion of the ultrasonic motor can be specified. It has been fifty years or so since the ultrasonic motor was developed. The traveling wave type motor can be categorized into two kinds, one is linear structure and the other one is rotary structure. Because the boundary condition of rotary structure, there is no reflective wave in the structure. As the result, rotary structure traveling wave based ultrasonic motor can generate traveling wave easily, which even led to successful commercialization. Compare to the rotary structure, linear structure faces the reflective wave problem to generate traveling wave, except dealing with eliminating the reflective wave, there is a different solution for generating traveling wave. More specifically, traditional “two mode excitation” is to superpose two standing waves having different 90-degree phase in both space and time domain to get the traveling wave. In comparison, this thesis developed a new concept to design and to construct the traveling wave based micro-transportation. In the study, I tried to use the true modal function to validate the possibility of “two mode excitation”. Traditionally, people drive their device in a frequency located between two nature frequencies, and claim the response of their device can be seen as the superposition of the two modes. However, in vibration theory, once the driven frequency is not at the nature frequency, the gain of system would be small. That is the reason why I try to use two distinct resonant modes to generate the traveling wave needed with an attempt to improve the efficiency of linear ultrasonic displacement stage. In the study, I built a numerical model of the transverse displacement of the thin stage in detail for analyzing the nature frequency, mode shape and the result of modes superposition in order to search and to design the better operation condition. Besides, we also use the finite element simulation software, COMSOL, to model real 3-D time-dependent model to validate the numerical result and to predict the behavior of the stage. We also used the advantage of our dual piezo-system to measure the pole response of system for reference of doing Chladni’s pattern. After Chladni’s pattern test, we can get the precise frequency correspond to the different mode. In the study, we did drive the stage in two nature frequency successfully. Since the gain is high at the resonance condition, I chose a stiffer stainless steel to replace the softer aluminum foil based structure. With the new concept to operate the displacement stage, we can drive the stage with relative low voltage. It is expected that this innovative concept in operation can induce and to accelerate the advancement of the linear ultrasonic motor. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/49695 |
DOI: | 10.6342/NTU201602581 |
全文授權: | 有償授權 |
顯示於系所單位: | 應用力學研究所 |
文件中的檔案:
檔案 | 大小 | 格式 | |
---|---|---|---|
ntu-105-1.pdf 目前未授權公開取用 | 5.15 MB | Adobe PDF |
系統中的文件,除了特別指名其著作權條款之外,均受到著作權保護,並且保留所有的權利。