Advanced FRF Based Determination of Structural Inertia Properties

Accurate estimation of inertia properties is crucial in the design and development cycle of mechanical structures. When modeling complex structures and subassemblies, or simulating the dynamics of mechanisms, the rigid body characteristics of a subassembly might be too complex or inaccurate to calculate. Traditionally, inertia properties are obtained by a laborious pendulum test, a very time consuming procedure. A highly accurate alternative is to perform a typical modal test, inertia properties are than achieved based on frequency response function and its mass line characteristic. This paper explains, first of all, how to extract inertia properties such as center of gravity, moments and principal axes of inertia based on frequency response functions (FRF's), and then how to synthesize rigid body characteristics such as rigid body modes with respect to the geometry and the resulted inertia properties. Both an academic case and real-life applications are used to validate the approach. Moreover, different aspects such as measurement setup, influence of number of responses and references on the accuracy are also discussed in this paper.