單頻雙模態及雙頻雙模態行進波壓電聲波馬達之最佳化設計

超聲波馬達是利用壓電材料進行驅動，優點為低轉速高扭矩、有良好的可控性與構造簡單，在旋轉型結構中，完全不須考慮到邊界問題，可以藉由輸入兩個相位差90度的訊號於壓電致動器，以產生行進波來推動載體或產生位移，是目前商業化的超聲波馬達的主流，但改為線性型結構時，因為無法克服結構邊界所產生反射波與原本的行進波疊加後，形成駐波而降低行進波的波傳效率。本論文是利用線性超聲波馬達之設計原理，於不鏽鋼基板上黏貼兩個壓電致動器，研究線性位移平台的行進波傳遞情形。由於線性超聲波馬達須考慮波傳在邊界的反彈效應，使得行進波無法在有限結構中持續傳遞，為了能克服此邊界問題，在近年的研究中，提出下列兩種雙模態激發(Two-mode excitation)方式來解決，第一種是利用相鄰模態正交(orthogonal)，使兩個彎曲模態相互疊合產生行進波，稱之為單頻雙模態激發，此方式的操作頻率設在兩共振頻的中間頻率，且能透過切換輸入訊號的相位差改變方向。第二種方法則是驅在兩個相鄰的彎曲模態上來進行模態疊合，稱為雙頻雙模態激發，藉由將操作頻率設在共振頻上來提高行進波的傳送效率，我們利用這兩種驅動方式來進行線性聲波馬達的設計與製作。本研究透過有限元素法進行模擬及分析，先利用特徵頻率找出結構共振頻，再分別利用兩種激發方式驅動，並分析位移平台隨時間的運動情形，釐清改變線性聲波馬達的兩片壓電致動器在空間位置、尺寸與時間相位對產生的傳遞波之影響，搭配MATLAB程式畫出線性聲波馬達在不同時間下的波傳情形，探討所產生之傳遞波性質及區域，並提出電極位置與長度於此線性馬達中的最佳化設計。

關鍵字

壓電材料；線性超聲波馬達；單頻雙模態激發；雙頻雙模態激發

並列摘要

Piezoelectric ultrasonic motor is driven by piezoelectric actuators.It has the advantages of low speed, high torque, good controllability and simple structure.In a rotary type configuration, propagating waves can be generated to propagate continuously without interference by boundaries. This is the priminary commercialized ultrasonic motor. However, in the linear type configurations, boundary effect is considerable. The reflected waves from the boundaries can hinder the generating of propagating waves, and standing waves are easily toform and dominant structure vibrations. In this paper, two different design principles of linear ultrasonic motor are studied, where propagating waves could be generated on a 1-D plate by placing two piezoelectric actuators on two different locations. These two methods are single-frequency-two-mode and two-frequency-two-mode. The first method is to use the orthogonality of two adjacent recent modes. The two bending modes overlap each other to produce a traveling wave. This traveling wave can be generated by operating at a frequency in the middle of the two resonant frequencies, and can change the direction by switching the phase difference of the input signal. The second method is to operate at the two resonant frequencies by setting the two resonant frequencies to the two actuators. Since this method is operated at resonant frequencies, the efficiency to generate propagating waves can be much improved. In this study, we use finite element method to study the contributions of the size and locations of the two piezoelectric plates to the performance of a fixed-fixed linear motor driven by using a single-frequency-two-mode and two-frequency-two-mode excitation methods. By combining spatial and temporal orthogonality through two independent piezoelectric actuators on a one-dimensional fixed-fixed plate, a traveling wave can be created. Both fixed-fixed and free-free boundaries are studied, and the optimization of piezoelectric linear motor is proposed.

並列關鍵字

Piezoelectric material ； Linear ultrasonic motor ； One-frequency-two-mode excitation ； Two-frequency-two-mode excitation

參考文獻

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單頻雙模態及雙頻雙模態行進波壓電聲波馬達之最佳化設計

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