Development of Force-Frequency Shifting for Low Frequency Structural Vibration Testing

研究摘要提案号。项目名称：Trethewey， Martin w .题目：用于低频结构振动测试的力频移技术的发展民用和建筑系统的振动实验测试有助于解决以下几个问题：结构健康评估（桥梁退化），以及减少建筑物中敏感装置（如医院的医疗核磁共振成像和电子显微镜）令人烦恼的振荡运动。这些系统的测试需要在非常低的频率（0.1 - 10赫兹）下施加高振幅的力激励，这本身是非常难以实现的。该研究计划的重点是开发一种新技术，称为力频移（FFS），以提供这种激励。FFS技术是基于将高振幅、高频力（频率为fz）以时空变化的方式（频率为fx）施加到结构上。系统的非线性动力学行为在力和空间运动频率的和和差（fz+fx和fz-fx）处产生激励。对低频振动测试特别感兴趣的是差频分量（fz-fx）。FFS技术创造这种低频成分的固有能力是该项目的重点。该研究将开发一种具有计算机控制的可变刚度执行器阵列的FFS励磁器。这一发展将提高低频力性能和控制，使FFS适用于目标系统的振动测试。

Research AbstractPROPOSAL NO.: 0218668INSTITUTION: PA St U University ParkNSF PROGRAM: DYNAMIC SYSTEMS AND CONTROLPRINCIPAL INVESTIGATOR: Trethewey, Martin W.TITLE: Development of Force-Frequency Shifting for Low Frequency Structural Vibration TestingExperimental vibration testing of civil and architectural systems is useful for addressing a number of issues including; assessment of structural health (degradation of bridges), and reduction of troublesome oscillatory motion in buildings for sensitive installations such as medical MRIs in hospitals and electron microscopes. The testing of these systems requires that a high amplitude force excitation be applied at very low frequencies (0.1 - 10 Hz), which is inherently very difficult to accomplish. The research program is focused on developing a new technique, referred to as Force Frequency Shifting (FFS), to provide such an excitation. The FFS technique is based on the application of a high amplitude, high frequency force (at frequency fz) to a structure in a spatially time variant fashion (at frequency fx). The nonlinear dynamic behavior of the system produces an excitation at a sum and difference (fz+fx, and fz-fx) of the force and spatial motion frequencies. Of particular interest for low frequency vibration testing, is the difference frequency component (fz-fx). It is the innate ability of the FFS technique to create this low frequency component that is the focus of the project. The research will develop an FFS exciter with a computer-controlled array of variable stiffness actuators. This development will increase the low frequency force performance and control making the FFS suitable for vibration testing of the targeted systems.