低深寬比楔形波壓電馬達的研發

Abstract

研究研發一低深寬比之楔形波壓電馬達，圓柱狀楔形體定子的直徑大，高度低，壓電制動元件距離轉子與楔形定子的接觸點近，能有效驅動壓電馬達。楔形定子下方黏貼厚度極化之壓電陶瓷圓環，表面電極分成偶數個扇形區塊，中心間距為1/4波長，兩組相同電壓與頻率惟時間相位差90度之交流電壓施於間隔排列之A、B相電極，生成兩組F(4, 1)模態駐波，彼此建設性干涉產生一周向行進波，定子接觸點行橢圓形運動，藉摩擦力推動轉子轉動。改變相位的領先與落後，可控制轉子旋轉方向。 本文以有限元素法計算楔形定子自然共振模態，調整頂角角度、樞紐連接厚度等幾何尺寸獲得適當的模態隔離。良好定子應具有足夠的扭轉剛性，比較定子的接觸點位移響應與扭轉剛度性，決定定子製作尺寸。壓電馬達定子原型機以表面陽極硬化處理之鋁合金製作，具耐磨特性。轉子為鋁合金環，不設轉軸連接器。實驗量測在250Vp-p驅動電壓及操作頻率21.25 kHz條件下。最大轉速約30 rpm，最大扭矩可達32 N-cm，本研究設計之楔形波壓電馬達在連續及步進旋轉運動上都具有穩定輸出特性。

This thesis developed low aspect ratio wedge-wave piezoelectric motors. This motor features large diameter and shallow profile. The piezoelectric ring actuating element closes the contact points between rotor and stator such that it can efficiently drive the piezoelectric motor. The bottom of the stator is attached a piezoelectric ring, whose surface electrodes have been segmented among several sector electrodes with interval of one fourth wavelength. Two orthogonal sinusoidal voltages of the same voltages and frequency are applied to two sets of alternating electrodes. The A and B phases each generates the flexural mode F(4,1), and both construct a circumferentially traveling wave. The contact points of stator undergo an out-of-plane elliptical trajectory to drive the rotor via friction forces produced at the interface between stator and rotor. Switching phase lead or leg will change revolution direction of the rotor. Based on finite element analysis, an appropriate modal separation has been achieved by adjusting the apex angle, hub connection thickness of the stator. A fine stator must have enough torsion rigidity. Dimension design is based on a compromise between wedge tip displacement and torsion rigidity of the stator. A prototype stator was made of surface anodized aluminum alloy for great abrasion resistance and a PZT-4 like piezoelectric circular ring. The aluminum alloy made rotor does not have coupling. Performance tests show that the present piezoelectric motor can achieve the highest rotating speed of 30 rpm and the maximum output torque of 32 N-cm at driving frequency 21.25 kHz and alternating voltage 250 Vp-p . The wedge-wave piezoelectric motors have good performance in both continuous and stepping revolution.