Disc Brake Rotor Squeal Suppression Using Dither Control

“Dither” control recently has been experimentally demonstrated to be an effective means to suppress and prevent rotor mode disc brake squeal. Dither control employs a control effort at a frequency higher, oftentimes significantly higher, than the disturbance to be controlled. The control actuator used for the work presented in this paper is a piezoelectric stack actuator located within the piston of a floating caliper brake. The actuator is driven in open-loop control at a frequency greater than the squeal frequency. This actuator configuration and drive signal produces a small fluctuation about the mean clamping force of the brake. The control exhibits a threshold behavior, where complete suppression of brake squeal is achieved once the control effort exceeds a threshold value. This paper examines the dependency of the threshold effort upon the frequency of the dither control signal, applied to the suppression of a 5.6 kHz rotor squeal mode. Threshold performance will be evaluated at a number of discrete dither control frequencies ranging into the ultrasonic frequency regime. The tradeoff in the use of dither control is the generation of a rotor response at the dither control frequency. With ultrasonic control frequencies, the rotor response at the control frequency is inaudible.