“…To be more specific, the fault diagnosis methods based on feature extraction, feature selection, and feature fusion have been studied in [ 9 , 10 , 11 , 12 , 13 ], and the accuracies of fault diagnosis are improved greatly by these methods. The intermittent fault detection, isolation, and diagnosis of train multi-axis speed sensors are addressed in [ 14 , 15 , 16 ], and the composite fault diagnosis of rolling equipment such as train bearings has been proposed in [ 17 , 18 , 19 ]. These above technologies have greatly improved the level of intelligence in ensuring the safe and reliable operation of trains.…”