Avoiding stick-slip limit cycle vibration in electric vehicle brake system via brake force distribution

Brake creep groan, a friction-induced nonlinear vibration in the brake system, has significantly contributed to the reduction of ride comfort. In order to mitigate brake creep groan, a brake force distribution strategy based on the stick-slip curve is proposed and examined. The critical boundary of the stick-slip limit cycle is determined and established as the constraint condition. Focusing on avoiding stick-slip limit cycle vibration, an adaptive particle swarm optimization method is employed to study the distribution of brake force between regenerative brake and friction brake, with energy recovery efficiency serving as the objective function. Four distinct operational conditions-NEDC, UDDS, WLTP, and FTP-are simulated. The results demonstrate that under these conditions, vibrations associated with the stick-slip limit cycle can be reduced by up to 23.596%, 15.368%, 15.342%, and 17.557%, respectively. Considering the peak power and peak torque of the drive motor, three regions can be identified: the region where stick-slip limit cycle vibration cannot be avoided, the region where avoidance efficiency increases with the rise in the drive motor's peak torque and peak power, and the region where avoidance efficiency remains constant despite increases in the drive motor's peak torque and peak power.