Equivalent input synthesis for multi-axis vibration testing from arbitrary reference data

Deriving input specifications for multi-axis vibration testing based on arbitrary known structural responses is addressed in this paper. The nominal excitations can include any combination of local or distributed loads and base motion. Measured responses and finite element method (FEM)-derived reference data is acceptable. Mathematical formulations for the excitations to be applied to a desired set of degrees of freedom (DOFs) are given for the cases of harmonic and random analysis. Solution optimality is defined in a bounded-variable least-squares (BVLS) sense, accounting for the practical constraints of test facilities. The proposed method is validated with a spacecraft mass dummy. Rotation-dominant 6-DOF support random vibration is simulated in FEM, reduced to an equivalent 3-DOF translational excitation and executed on a triaxial shaker. Finally, the recorded correlation between FEM results and test measurements is discussed.