Remaining useful life prediction of steer-by-wire system with intermittent faults and imperfect preventive maintenance

This paper develops a remaining useful life (RUL) prediction method for the steer-by-wire (SBW) system in the presence of intermittent faults and imperfect preventive maintenance (IPM). To extract the features of intermittent faults, the concept of variable-size window (VW) is proposed, by which the degradation properties of intermittent faults can be comprehensively reflected. Since the IPM is a common practice to improve the system health condition and the operation condition of the SBW system is variable, the operation condition dependent compound degradation models incorporating the IPM are developed. In these models, the piecewise functions divided by the VW subjected to IPM are proposed to capture the degradation behaviors of the extracted features, by which the varying degradation coefficients and the varying IPM effects can be accommodated. To aid the RUL prediction of intermittently faulty component, the unified health indicator is developed by which the extracted features are integrated. The comparative experiment demonstrates that the proposed method can achieve the relative accuracy of RUL prediction with 95.37% and 94.83% under two operation conditions for the feedback motor sensor fault. As for the steering motor sensor fault, the proposed method can achieve the relative accuracy of RUL prediction with 95.59% and 94.28% under two operation conditions.