In noise and vibration engineering, a structure’s passive dynamic properties are often quantified by frequency response functions (FRFs). This paper focuses on acquiring FRFs from experimental tests, considering both, translational (x, y, z) and rotational (e.g. moments around these axes) terms. In practical applications, test structures may not allow FRFs to be measured directly due to the impracticality of applying a controlled excitation in a particular direction (e.g. in-plane), the inability to measure rotational dynamics (e.g. moment excitation), insufficient signal-to-noise ratio (SNR) between excitation and response degrees of freedom, or simply due to restricted access. Methods exist to resolve some of the mentioned issues using indirect experimental techniques, such as the round-trip identity. However, these methods are limited to cases in which the driving-point FRFs are sought-after. The present paper extends previous work into a more generalised formulation of the round-trip identity feasible for reconstructing driving-point and transfer mobilities from in-situ measurements conducted in coupled assemblies. By using the round-trip identity, the excitation of moments and/or inaccessible points is avoided altogether and instead replaced by a number of applied forces remote to the points of interest. Manipulation of this round-trip identity yields a formulation for long distance transfer FRFs, expressed in terms of multiple shorter transfer path elements, which are less prone to insufficient SNR. These practical applications of the generalised round-trip concept are experimentally validated for multi-input multi-output assemblies.

在噪声和振动工程中，结构的被动动态特性通常通过频率响应函数 (FRF) 进行量化。本文侧重于从实验测试中获取 FRF，同时考虑平移（x、y、z）和旋转（例如围绕这些轴的力矩）项。在实际应用中，由于在特定方向（例如平面内）施加受控激励不切实际，无法测量旋转动力学（例如力矩激励），信号不足，因此测试结构可能不允许直接测量 FRF。 - 激励和响应自由度之间的噪声比 (SNR)，或者仅仅是由于访问受限。存在使用间接实验技术（例如往返身份）来解决某些上述问题的方法。然而，这些方法仅限于寻求驱动点 FRF 的情况。本论文将先前的工作扩展到更通用的往返身份公式，该公式适用于从耦合组件中进行的原位测量重建驱动点和转移迁移率。通过使用往返标识，可以完全避免力矩和/或不可访问点的激发，而是由远离感兴趣点的许多施加力代替。对这种往返身份的操纵产生了长距离传输 FRF 的公式，以多个较短的传输路径元素表示，这些元素不太容易出现 SNR 不足的情况。广义往返概念的这些实际应用已针对多输入多输出组件进行了实验验证。