圓柱楔形超音波馬達之研發

Abstract

本文發展出一個以壓電圓管楔形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的梁模態驅動方式，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、不鏽鋼基座與15度楔角之圓柱楔形體黏結而成，以網版印刷在壓電圓管外側佈置兩組電極，兩組電極的間距為四分之一波長，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。兩駐波建設性干涉成一行進波，藉著定子與轉子間的摩擦力，驅動轉子順時針或逆時針方向轉動。本文應用數值雙維有限元素分析法，計算馬達定子楔形撓性波的頻散曲線及共振模態，並以ANSYS套裝軟體的模態分析、時諧分析與暫態分析，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(LDV)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，圓柱楔形超音波馬達的機械輸出具有彈性。只要改變轉子與定子接觸點的位置就可以改變輸出的轉速與扭距，並不需要改變馬達的本體架構。在驅動頻率36.605 kHz、驅動電壓400 Vpp與預負載0.98 N的條件之下，最快轉速可達225 rpm，最大輸出扭矩為15.735 mN-m，最大機電轉換效率為16.22%。

This thesis develops a novel rotary ultrasonic motor (USM) driven by circumferential wedge 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 wedge 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 1/4 wavelength apart and excited by two sinusoidal signals in 90o phase difference. A bi-dimensional finite element method is used to determine the dispersion curves and resonant mode shapes of circumferential wedge waves. Dual-phase driving response of traveling wave around the stator is simulated by using modal analysis, harmonic analysis and transient analysis of the commercial finite element code 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 impedance analyzer. The proposed motors have a flexible mechanical output. Varying the contact position of the rotor on the inclined surface of the stator can change the output torque and angular speed without changing the entire structure. The proposed wedge wave ultrasonic motor has a driving voltage of 400 Vpp, a driving frequency of 36.605 kHz, and a static preload of 0.98 N. The maximum angular speed is 225 rpm and the maximum output torque is 15.735 mN-m. The maximum electro-mechanical transformation efficiency is 16.22%.