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

研究摘要：0218668研究报告：PA ST U University PARK NSF计划：动力系统和控制研究人员：Trethewey，Martin W.TITLE：开发用于低频结构振动测试的力-频移试验民用和建筑系统的实验振动测试有助于解决许多问题，包括：评估结构健康(桥梁的退化)，以及减少建筑物中用于敏感设备(如医院的医疗磁共振成像和电子显微镜)的麻烦的振荡运动。这些系统的测试要求在很低的频率(0.1-10赫兹)下施加高幅值的力激励，这在本质上是很难实现的。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技术基于以空间时变方式(在频率fx)对结构施加高幅度、高频力(在频率fz)。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。对于低频振动测试，特别感兴趣的是差频分量(fz-fx)。这是FFS技术固有的能力来创建这种低频分量，这是该项目的重点。这项研究将开发一种带有计算机控制的变刚度执行器阵列的FFS激振器。这一发展将提高低频作用力的性能和控制，使FFS适合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.