Method to Detect and Isolate Brake Rotor Thickness Variation and Corrosion

Abstract

Brake rotors are essential parts of the disc brake systems. Brake rotor thickness variation (RTV) and corrosion are among top failure modes for brake rotors, which may lead to brake judder and pulsation, steering wheel oscillations and chassis vibration. To improve customer satisfaction, vehicle serviceability and availability, it is necessary to develop an onboard fault detection and isolation solution. This study presents a methodology to monitor the state-of-health of brake rotor system to reduce costs associated with scheduled inspection for autonomous fleet or corrective maintenance. We converted the vehicle signals from time-domain to angle-domain and determined health indicators to estimate the RTV level of the rotors. Variance, envelope and order analysis of the brake circuit pressure, longitudinal acceleration and wheel speed sensor signals in angle-domain were promising health indicators to differentiate healthy and faulty rotors. A classification model was developed to fuse the health indicators and estimate the state-of-health of the rotors to report the most degraded rotor with corner isolation. Results showed that using this concept we were able to detect failure levels of 20 microns and larger and meet the customer requirement. Robustness analysis showed that the concept is robust to the noise factors of tire type, tire pressure and vehicle weight. The sensitivity analysis showed that the algorithm is sensitive to two of the calibration parameters (i.e., brake pedal position gradient (BPPG) threshold and the filter order used to derive BPPG) used to determine the brake event and enable the algorithm.