One of the most apparent and often most objectionable characteristics of brake system performance during race track usage is the increase in pedal travel caused by lining taper wear, lining compression, and knockback. However, it is difficult to measure compliance on individual brake corners during race track usage, and complex apply profiles make it challenging to even quantify the overall change in pedal feel of the brake system.
This paper proposes a methodology by which the measured hydraulic pressure profiles of each brake corner during a brake apply are related to overall brake pedal travel. Using regressed parameters describing these relationships, a Mahalanobis-Taguchi ‘Normal Space’ is constructed for a set of brake applies with known ‘good’ pedal feel. This provides a basis for computing the Mahalanobis Distance for brake applies in a data set under evaluation. Brake applies with a high Mahalanobis Distance can be ‘flagged’ for further evaluation.
A brake system model, with a hydraulic model for each brake corner circuit, and an apply system model, is correlated to data measured on the test vehicle. This model can then be used to show how the rate of pressure rise at each brake corner versus pedal travel changes with various combinations of brake corner compliance issues.
The resultant data can be used to determine if one or more brake corners incurred a change in compliance, to estimate the severity of the change in compliance, and to identify extreme cases such as knockback.