In the measurement of inertia properties (mass, centre of gravity and inertia tensor), both the body under investigation and the test rig are commonly considered as rigid bodies. However, in case of heavy or large bodies, these assumptions may not be satisfied. The present paper deals with the consequences of the test rig structure deformations on the measured inertia parameters. In fact, if the forces exchanged by the structure of the test rig and the body are large, the structure may deform changing its geometry and dynamic behavior. These effects, in turn, affect the measured kinematic and dynamic quantities needed for the measurement of the inertia properties.

In the paper, by considering the InTenso+ Measuring System of the Politecnico di Milano, a special type of multi-filar pendulum, the effects of the deformation of the test rig on the measurement of the inertia properties is investigated both numerically and experimentally. A flexible multibody model is employed to understand the dynamic effects of the deformations on the mass properties measurement. Several bodies are measured to validate such analyses. A proper mathematical procedure is then derived to measure the inertia properties of bodies when the realization of a sufficiently stiff structure is impractical.

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