Reduction of the Effect of the Creep Groan Brake Excitation in a Comercial Vehicle

One of the results generated by the stick-slip intermittent motion of a brake at the friction interface is the Creep Groan Noise which is a low frequency self-excited vibration, normally less than 220 Hz. This local vibration generated between the brake couple, is transmitted through the suspension system until the passengers of the vehicle in form of vibration and noise. This paper presents a methodology that combines testing and numerical models in order to 1) detect the source of the Creep Groan, 2) create a correlated numerical model and 3) produce countermeasures that reduce the amplitude of the noise at occupant positions. The vehicle under investigation was a commercial vehicle employing air-actuated brake drums. From testing, global vehicles modes and displacements under operational conditions were respectively investigated by means of Operational Deflection Shapes and Real Time Animation. These techniques allowed to prove the existence of a feedback loop with a positive gain that excites a suspension resonance mode, creating an unstable shaking effect in the whole vehicle. In-service data suggest that the brake actuation system has a great influence in the generation of the feedback loop. The numerical model succeeded in reproducing the vibration response of the brake actuation system. Thereafter, countermeasures were implemented in order to break the feedback loop that amplifies the creep groan phenomenon. This work presents an alternative methodology to understand and restrict the creep groan being suffered by the vehicle under study. Even thought the low-level stick-slip effect is maintained, the overall creep groan annoyance is dismissed.