Brake Groan Simulation for a McPherson Strut Type Suspension

Brake groan noise and vibration occurs in a stopped vehicle by the simultaneous application of torque to the wheel and the gradual release of brake pressure. Eventually the torque load breaks the friction between pad and rotor causing slippage and energy release. If the torque load is not large enough to maintain slippage, a sustained stick-slip vibration, called groan, can occur which transmits a low frequency noise to the vehicle interior. In some cases the noise levels caused by groan can be objectionable, thus procedures for developing remedial designs are needed. To this end, a project was performed to analytically simulate groan vibration in a vehicle with a McPherson strut type suspension. The goal was to demonstrate that analytical models could be used to simulate groan behavior and to identify suspension components that affect the groan behavior. The ADAMS software was used to model a brake/suspension system. A nonlinear friction force was used to couple the rotor with the caliper. The spectral content of the groan vibration shows response at multiples of a certain fundamental frequency. The stick-slip vibration typically occurs at the 1^st, 2^nd, or 3^rd, order of the fundamental frequency. The model predictions were found to agree qualitatively with groan operating test data.