Disc Brake Rotor Squeal Suppression Using Dither Control 2001-01-1605

“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.