Analysis of Brake Judder by use of Amplitude Functions

Brake judder is a forced vibration occurring in different types of vehicles. The frequency of the vibration can be as high as 500 Hz, but usually remains below 100 Hz and often as low as 10-20 Hz. The driver experiences judder as vibrations in the steering wheel, brake pedal and floor. For high frequency brake judder, the structural vibrations are accompanied by a sound.

In the present paper the vibration amplitude (in terms of angular deflection, velocity or acceleration) of the caliper has been used as a quantitative measure of the vibration level.

Brake Torque Variation (BTV) is the primary excitation for the vibrations. The mechanical effects generating BTV are linked not only to manufacturing tolerances but also to tribological issues. Uneven disc wear as well as Thermo-Elastic Instabilities (TEI) can lead to judder. Especially the effect of the wheel suspension on the transfer of the vibrations to the driver has to be considered. The aim of this work has been to

1. 1
   describe the amplitude variation with a function including a small number of parameters.
2. 2
   analyze the dependence of the parameters on the maximum amplitude.
3. 3
   find a method for generating the actual amplitude function corresponding to a specific brake application.
4. 4
   compare the theoretical results with measurements.