The high performance and small size of MEMS based scanners has allowed various optical imaging techniques to be realized in a small form factor. Many such devices are resonant scanners, and thus their linear and nonlinear dynamic behaviors have been studied in the past. Thin-film piezoelectric materials, in contrast, provide sufficient energy density to achieve both large static displacements and high-frequency resonance, but large deformation can in turn influence dynamic scanner behavior. This paper reports on the influence of very large stroke translation of a piezoelectric vertical actuator on its resonant behavior, which may not be otherwise explained fully by common causes of resonance shift such as beam stiffening or nonlinear forcing. To examine the change of structural compliance over the course of scanner motion, a model has been developed that includes internal forces from residual stress and the resultant additional multi-axis coupling among actuator leg structures. Like some preceding vertical scanning micro-actuators, the scanner of this work has four legs, with each leg featuring four serially connected thin-film PZT unimorphs that allow the scanner to generate larger than 400μm of vertical displacement at 14VDC. Using an excitation near one or more resonances, the input voltage can be lowered, and complementary multi-axis rotations can be also generated, but change of the resonant frequencies with scanner height needs to be understood to maximize scanner performance. The presented model well predicts the experimental observation of the decrease of the resonant frequencies of the scanner with the increase of a dc bias voltage. Also, the effects of the magnitude and uniformity of residual stress across the scanner structure on the natural frequencies have been studied.

中文翻译：

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受多轴耦合和制造不对称影响的大垂直行程薄膜压电微致动器的动力学

基于 MEMS 的扫描仪的高性能和小尺寸使各种光学成像技术能够以小尺寸实现。许多这样的设备是共振扫描仪，因此过去已经研究了它们的线性和非线性动态行为。相比之下，薄膜压电材料提供足够的能量密度来实现大静态位移和高频共振，但大变形会反过来影响动态扫描仪行为。本文报告了压电垂直致动器的非常大的行程平移对其共振行为的影响，这可能无法通过共振位移的常见原因（例如梁刚度或非线性强迫）完全解释。为了检查扫描仪运动过程中结构顺应性的变化，已经开发了一个模型，其中包括来自残余应力的内力和致动器腿结构之间由此产生的额外多轴耦合。像之前的一些垂直扫描微致动器一样，这项工作的扫描仪有四个支腿，每个支腿都有四个串联的薄膜 PZT 单压电晶片，允许扫描仪在 14VDC 下产生大于 400μm 的垂直位移。使用一个或多个谐振附近的激励，可以降低输入电压，也可以产生互补的多轴旋转，但需要了解谐振频率随扫描仪高度的变化，以最大限度地提高扫描仪性能。所提出的模型很好地预测了扫描仪谐振频率随着直流偏置电压的增加而降低的实验观察结果。还，