An Explanation for Brake Groan Based on Coupled Brake-Driveline System Analysis

Brake creep-groan is studied via a friction coupled torsional model consisting of driveline and brake sub-systems. The model captures the main torsional modes of interest while a suitable reduction of higher degree-of-freedom models allows selection of appropriate parameters. Numerical simulations are programmed that capture groan response with stick-slip friction and transient brake pressure. The vehicle is initially at rest and the groan may build into a steady state limit cycle, depending on the brake force actuation. For automatic transmission (AT) the driving torque is at the torque converter. For manual transmission (MT) the vehicle is on a slope and the driving torque is due to weight of the vehicle. On-vehicle tests provide time and frequency domain measured accelerations for comparison.