Fault Failure Diagnosis for Compliant Assembly Structures Using Statistical Modal Analysis

This paper develops a new diagnostics methodology for N-2-1 fixtures used in assembly processes with compliant parts. The developed methodology includes: (i) the predetermined CAD-based dimensional variation fault patterns model; (ii) data-based dimensional variation fault model; and (iii) the fault mapping procedure isolating the unknown fault. The CAD-based variation fault pattern model is based on the piece-wise linear bi-partitioning of compliant part into deformed (faulty) and un-deformed regions. Data-based dimensional variation fault models are based on the statistical modal analysis (SMA) which allow to model part deformation with varying number of deformation modes. It is proved in the paper that these independent deformation modes are equivalent to the CAD-based faults models obtained in (i). The fault mapping procedure allows to diagnose the unknown fault by comparing the unknown fault variation pattern obtained from the SMA model with one of the predetermined CAD-based fault patterns. One industrial case study from an automotive roof framing assembly illustrates the proposed method.