一種以圓管脊緣撓性波周向驅動之超音波馬達

Abstract

本文發展出一個以壓電圓管脊緣撓性波驅動的新型轉動式超音波馬達，採用高階的周向模態，增加馬達定子與轉子接觸點，改善傳統圓柱形超音波馬達採用梁共振模態，造成轉子晃動、扭矩小的缺點。馬達定子由一徑向極化之壓電陶瓷圓管與不鏽鋼基座黏結而成，以網版印刷在壓電圓管外側佈置兩組電極，兩組電極的間距為(n+1/4)，以相位差90度之兩組等強度弦波激發兩組周向匝數為整數的駐波，兩者建設性干涉成一行進波。藉著定子與轉子間的摩擦力，驅動轉子順時針或反時針方向轉動。本研究應用雙維有限元素法與ANSYS套裝軟體，數值計算馬達定子脊緣撓性波的頻散曲線及共振模態，並模擬雙相致動之馬達定子的行進波響應。由馬達定子基座高度的調整，有效達成良好的模態隔離設計，經都卜勒干涉儀及模態感測器量測阻抗實驗，驗證其確實可行。 超音波馬達性能測試結果顯示，壓電圓管軸對稱佈置電極者較兩側佈置電極者的性能優異。依據前者製作高階脊緣撓性波(1,3)與(1,4)模態的超音波馬達原型，最大扭矩可達6.9與22.6 mN-m，最大轉速為200與334 rpm。

This thesis develops a novel rotary ultrasonic motor (USM) driven by circumferential ridge waves around a piezoelectric tube which is polarized in radial direction. The proposed motor utilizes higher order circumferential modes to increase the number of contact points between motor stator and rotor. The wobble motion and poor torque output that frequently happen at those USM’s driven by the so-called beam mode are prevented and improved. The traveling ridge wave is generated by constructive interference of two equal-intensity standing waves of integer number circumferential modes induced by two sets of transducers. Both are located on the wall of the piezoelectric tube with an interval (n+1/4)□ apart and excited by two sinusoidal signals in 90o phase difference. A bi-dimensional finite element method and the commercial finite element code ANSYS are used to determine the dispersion curves of circumferential ridge waves. Response of traveling wave around the stator is simulated by using harmonic analysis of ANSYS. The change of the height of stator base has significant influence on the modal separation. Very good modal separation was achieved and verified by using laser Doppler vibrometer (LDV) and impedance measurement by modal sensors on the outer border of stator with network analyzer. Performance test results show that the prototype USM’s with axisymmetrically distributed electrodes have better performance than those with electrodes located on opposite sides of the piezoelectric tube. The motors based on resonant modes (1, 3) and (1, 4) achieve the maximum torque up to 6.9 and 22.6 mN-m and the maximum revolution speed at 200 and 334 rpm.