变宽度分割电极片状压电致动器的位移特性

DEFLECTION CHARACTERISTICS OF SPLIT ELECTRODE INPLANE BENDING PIEZOELECTRIC ACTUATORS WITH VARYING WIDTH 

针对硬磁盘驱动器中磁头定位两级伺服系统设计了一种新型压电致动器———悬臂梁式变宽度分割电极片状压电致动器．沿厚度方向极化的ＰＺＴ压电陶瓷薄长片，宽度沿长度方向变化且沿长轴对称，一端固定一端自由构成悬臂梁．其上下两表面的电极均沿长轴分割成对称的两部分．施加电场使其中一半在ｄ３１模式作用下伸长，而与其对称的另一半缩短，则压电片沿宽度方向产生弯曲，自由端便可产生致动位移．对该致动器的驱动电压端部致动位移特性进行了理论分析、有限元模拟及实验验证．致动器中的电场诱导应力远小于陶瓷的抗张强度．致动器端部位移的测试结果略大于理论计算值．与现有磁头悬浮臂尺寸相近的致动器，在２０—５０Ｖ的电压驱动下均可获得１—２μｍ的致动位移．对２５ｋＴＰＩ（ｔｒａｃｋｐｅｒｉｎｃｈ）的高道密度硬磁盘，该位移已能覆盖至少一个磁道宽度，满足磁头定位两级伺服系统对第二级致动器致动位移的基本要求．

Abstract The cantilever split morph, a new type of piezoelectric actuator, have been designed for dual stage head positioning servo system of high density hard disk drives. In this actuator configuration, a PZT ceramic plate, with one end mechanically clamped and the other free, was poled along its thickness and divided into two symmetric parts along length by splitting electrodes. Driving voltages are preferably so arranged that they make one of the two parts expand by the “31”action while the other part, i.e., the symmetric part, contracts. This will result in a bending motion of the actuator along the direction of its width. The driving voltage tip displacement characteristics of the actuator have been investigated by theoretical analysis, finite element modeling and experiment. Theoretical analysis indicated that the electric field induced stress is much smaller than stretch strength of piezoelectric ceramic. Tip displacement measured by Michelson interferometer is a little larger than the calculated result. This is mainly due to the increase of piezoelectric coefficient d 31 at high driving field. Tip displacement of 1 to 2μm can be achieved at 20 to 50V driving voltage for the split morph whose size is similar to that of the existing suspension. As to 25 kTPI (track per inch) high track density hard disk drives, this actuating stroke can cover at least one track width and meet the primary requirements of dual stage head positioning servo system for displacement of the secondary actuator.