Dual substructure decoupling for joint identification with unmeasurable interface: a comparative study

In mechanical joint identification through dual substructure decoupling, the joint is considered as a standalone subsystem and is identified by subtracting the measured dynamics of the connected subsystems from that of the assembled system. A notable challenge in this process is measuring translational and rotational FRFs at the interface between subsystems, which is often impractical due to space limitations for instrumentation. Different techniques in the literature address obtaining FRFs at the interface based on available measurements, each with different error propagation and accuracy. This paper compares the results of the joint identification through dual decoupling when two different techniques are used to obtain interface FRFs: Virtual Point Transformation (VPT) and System Equivalent Model Mixing (SEMM). VPT uses measurements at boundary DoFs near the interface, while SEMM employs measurements at internal DoFs away from the interface. The study is carried out using experimental data on a laboratory benchmark.