M.S. Thesis Presentation by Mawuli Dzirasa
Wednesday, April 10, 2002

(Dr. Kenneth Cunefare, advisor)

"An Experimental Investigation of Dither Control for the Suppression of Automotive Brake Squeal"


This research was performed to determine the effectiveness of dither control applied to a disc brake with various control signals, for the purpose of suppressing brake squeal. Brake squeal is a phenomenon that occurs when automobiles decelerate at slow speeds. Squeal is an annoyance to automotive consumers, and costs the automotive industry millions of dollars due to the warranty claims of dissatisfied customers. It is desirable to determine an effective method of eliminating brake squeal. One recently developed method is to introduce dither control to the braking mechanism in order to suppress squeal. Dithering is a control method that has been shown to suppress limit cycle oscillations in systems that are subject to friction-induced nonlinearities. Dither control, when applied at 100% duty cycle, has been demonstrated to effectively suppress the generation of rotor mode squeal vibration, thus eliminating the audible brake squeal. The dither system made use of a single piston floating caliper brake mounted on a brake dynamometer, with a piezoelectric stack actuator placed in the brake piston, which was used to apply dither control to the inner brake pad.

The research considered in this thesis investigated the effectiveness of 1) applying dither control at duty cycles of less than 100%, 2) examined the dynamic forces present in the brake system during active control of the squeal, 3) explored the effectiveness of the dither actuator at a frequency range of 5kHz to 30 kHz, and 4) explored the use of non-sinusoidal dither control signals.