Mode and design sensitivity analyses for brake judder reduction

Abstract

Brake judder is a phenomenon that occurs when the steering wheel vibrates abnormally owing to braking at a high speed. It is classified into cold and hot judders. The former is generated because of an initial uneven disc surface and the latter results from uneven heat spots on the disc surface by braking repeatedly. There are two ways to reduce the judder. One is to reduce the excitation by modification of the disc shapes and pad ingredients. The other is to improve modal characteristics of the suspension system. The latter approach is used in this research. Real vehicle tests and computer simulation are utilized to analyse systematically the judder phenomenon of the vehicle. The Macpherson strut suspension is employed, and the judder sensitivity is calculated on the basis of a design sensitivity analysis. The bush stiffness is reworked and a braking test is carried out to verify the sensitivity result. Judder reduction by the mode control is verified.

Keywords

brake judder cold judder hot judder brake torque variation disc thickness variation longitudinal mode rotational mode judder sensitivity transfer system kingpin offset

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