The Effect of Perturbation on the FRF Based Substructuring

Abstract

The substructuring method premised on the receptance functions of the subsystems is studied in order to determine the global dynamics behavior of a coupled transmission system. This approach is applied on a double reducer stage. The formulation of the lumped-parameter model and the resolution of the eigenvalue problem are determined. Measurements of FRFs produce noise, which can affect the efficiency of the studied system. In fact, the effect of perturbation due to the noise of measurement in the FRFs of subsystems (which can represent a fault in gears systems) is illustrated on the model studied. Two types of noise are artificially introduced to the exact FRFs, which are the pole shifting, and the perturbed FRFs. The theoretically FRFs are simulated by applying the method of modes superposition. The disturbed FRFs for the subsystems are generated and the results of these FRFs are compared to exact FRFs. The effect of perturbed FRF and the pole shifting on the FRF substructuring method were discussed. Simulation demonstrate that the noise on FRFs of reducer stage can be influence by the neighbor FRFs system. The perturbation in subsystem FRFs can be propagated due to the process of coupling and they affect especially the coupling frequency.