Frequency Response Function (FRF) Technique for the Diagnosis of Suspension System

Abstract

Some of the common faults associated with suspension components are damaged or leaking shock absorbers, spring weakness, wearing down of the pivot and bushing. To investigate these problems, a seven degree-of-freedom (7-DOF) model has been developed, for a full vehicle, using MATLAB. In the simulation, the suspension faults have been considered via the damage caused to the shock absorbers (dampers) and the faults were seeded by reducing the damper coefficient by 25%, 50% and 80%. Frequency Response Function (FRF) technique was used to develop conditioned monitoring tools for suspension faults and detects the level of damping coefficients. To validate the model and evaluate the FRF technique stated in this study, experimental investigation was carried out on 4-post-test rig at the University of Huddersfield in order to measure the FRFs of the suspension for different damping setting. The results demonstrate that, the shape of the frequency response depends on the damping coefficient ( ), since low damping coefficients lead to good isolation properties of the vehicle mass in the mid- to high frequency range, but also leads to high amplitudes of the acceleration in the range of the natural frequency of the vehicle body (sprung mass). Therefore, FRFs analyses provide an effective monitoring of the suspension and to detect the level of change in damping coefficients.