Identification and Classification of Stick-Slip Nonlinear Phenomena on Complex Dynamic Systems

Disk brake creep groan is a noise and vibration phenomenon generated by stick-slip during braking at slow vehicle speeds and low brake pressures. These operational states are especially present with automatic transmissions, automated driving functions and quiet, electrified drivetrains, which favor occurrence and also perception of creep groan vibrations. Creep groan phenomena lower the impression of a vehicle’s quality and can even be mistaken for a damaged brake system. To investigate and tackle such problems, real time identification of creep groan phenomena is needed. Therefore, an approach based on Quasi Acoustic Emission measurements is presented. This approach utilizes the character of stick-slip transitions: Due to a stick-slip transition’s inherent abrupt force change, vibrations with energy distribution over a wide frequency range occur. By subsequently applying a high-pass filter, a squaring, an amplification and a low-pass filter, a vast number of measured creep groan vibration signals was transformed into new, refined signals. New features were extracted from these signals and analyzed by a k-means algorithm. Results show that these Quasi Acoustic Emission features provide promising information for the automatic identification of creep groan in real time.