創新壓電致動器的設計、建模與實驗驗證

Abstract

手機與相機的傳統鏡頭致動器不外乎是使用音圈馬達或是步進馬達，隨著壓電致動器的性能提升，壓電致動器也被使用於手機與相機的鏡頭驅動。為了提高在手機和相機中的壓電致動器的性能，本論文開發了三種類型的創新性壓電致動器。一自由度壓電致動器使用兩個壓電蜂鳴器，可運行20mm的距離並快速移動。兩自由度壓電致動器，可在Z軸方向移動62mm和繞著Y軸旋轉270°。三自由度壓電致動器，不僅可以在Z軸方向上移動，也可以繞Y軸及Z軸的旋轉。在Z軸上的位移可以達到62 mm，在Y軸與Z軸上可分別達到270°和360°的旋轉角度。 在這個創新壓電致動器中，壓電蜂鳴器扮演著驅動源的角色，正電壓會導致壓電蜂鳴器產生收縮變形，負電壓會使得壓電蜂鳴器產生伸展變形。壓電蜂鳴器的變形速度藉著佔空比進行調整。如壓電蜂鳴器的變形波形所描繪，在鋸齒波信號的每個週期中，前段波形的斜率小於後段波形的斜率。因此，前段的靜摩擦存在於移動體和桿之間，而且在這兩者之間不會發生相對位移。然而，在後段波形上的斜率大於前段的斜率，所以在移動體和桿之間的動摩擦使得移動體移動一個短的距離，靜摩擦和動摩擦不斷地切換，導致移動體移動。 在理論推導上，利用壓電方程式推導出峰鳴器的壓電力，並且在非線性摩擦力與壓電力的交互作用下，來獲得壓電致動器的運動方程式。壓電致動器的模態分析採用有限元素分析軟體進行模擬。本研究提出的動態模型由力學特性和壓電特性組合，並經由實驗結果進行驗證。對於未來的數位產品，多自由度壓電致動器的使用將不受限於特定場合，並且可以擴大數位產品的功能。

A conventional lens actuator of the cell phone and the camera is used in either voice coil motor or stepping motor. With the performance improvement of piezoelectric actuator, there are currently many piezoelectric actuators driving lenses on cell phones and cameras. In order to enhance the performance of piezoelectric actuators in cell phones and cameras, this thesis developed three types of innovative piezoelectric actuators, among which the one-DOF piezoelectric actuator, using two piezoelectric buzzers, can travel 20 mm and move rapidly. The two-DOF piezoelectric actuator, can move 62mm in the Z-axis direction and rotate 270° about the Y-axis. The three-DOF piezoelectric actuator can not only move in the Z-axis direction but also rotate about the Y-axis and Z-axis. The Z-axis displacement can reach 62 mm and the rotation angle about the Y-axis and Z-axis can reach 270° and 360°, respectively. The piezoelectric buzzers play the role of a driving source in this innovative piezoelectric actuator. The positive voltage causes shrinking deformation in the piezoelectric buzzer, while the negative voltage results in expansion. The deformation speed of the piezoelectric buzzer is adjusted by duty ratios. According to deformation sawtooth waveforms of piezoelectric buzzer, in each period of the sawtooth signal, the slope of the first half is smaller than that of the second half. Therefore, in the first half, the static friction exists between the moving body and the rod, and no relative displacement occurs between both. In the second half, however, the slope is larger, and the dynamic friction between the moving body and rod allows the moving body to move for a short distance. As a consequence, persistent switching between static and dynamic friction causes the moving body to move. In the theoretical derivation, the piezoelectric force of buzzers is obtained from the piezoelectric equation. Under the interaction of nonlinear friction and piezoelectric force, the motion equation of the piezoelectric actuator is obtained. The modal analysis of actuator is simulated and discussed by using the finite element method. The proposed dynamic model that incorporates both mechanical and piezoelectric properties is validated by experimental results. For future digital products, the usage of multi-DOF piezoelectric actuators is not limited to specific occasions and can broaden functions of digital products.