A Framework to Rank Prognostics Health Indicators with Application to Brake Rotors

Abstract

This study presents a framework to assess the effectiveness of various health indicators (HIs) used to monitor the state of health (SOH) of a brake rotor health monitoring system. The following criteria were used to rank various health indicators: (i) Identifiability: Correlation of the HI with the Ground Truth (GT); (ii) Compactness: Mean of the standard deviation of the estimated SOHs; (iii) Robustness to Noise Factors: An HI is considered robust when it meets all functional and customer requirements under all operating conditions and its performance is not affected by the variations in the environment, operating conditions or other factors impacting the performance in an undesired way (noise factors); (iv) Monotonicity: To quantify the monotonic trend in HIs as the fault level increases from healthy baseline to the most severe faults. Monotone HIs are preferred as they will likely generalize better to data not used in development; and (v) Estimation Error: The average relative error between the GT and the prediction obtained from the regression analysis. Results showed that this framework can be applied to several HIs derived from performing time and frequency analysis on various sensor signals used to monitor the health of brake rotors. Top HIs selected based on this framework provided the best performance in detecting degraded brake rotors as evidenced by higher classification score.