Transient Dynamic Analysis of Vehicle Brake Creep Groan

Abstract

Brake creep groan is getting more and more attention in vehicle brake design and development. However, many complex motions of brake creep groan have not been comprehensively, which are critical for the understanding and prevention of the problem. In this paper, brake creep groan dynamics are studied and analysed to research the mechanisms of creep groan. Vehicle road experiments on a slope road are performed to record creep groans using two tri-axial accelerometers, which are install at the caliper and suspension strut. History curves of oil pressure and caliper accelerations, time–frequency spectrogram of the vibrations, and largest Lyapunov exponent are calculated using Hilbert–Huang transform and empirical mode decomposition methods. This study reveals that the sources of the brake creep groan include unstable sliding in addition to transient and steady-state motions of stick–slip between disc and pad. It is found that one of the important sources of the creep groan is the unstable sliding, which has impulsive and discontinuous nature and has effects of hammering leading to strong excitation and wideband vibrations. It is also found that when creep groan occurs, multiple modes of the brake system and subsystems contribute to the complex vibrations. The existences and the properties of the stable, unstable, and chaotic vibrations associated with the creep groan are characterized, which depend on the system natures, excitations, and tribological conditions.