Event-Anchored Early Identification of Mechanical Degradation in ZYJ7 Turnout External Locking Mechanisms Using Phase Energy and Locking Rebound Features

Abstract

Early mechanical deterioration of ZYJ7 turnout external locking mechanisms is difficult to detect consistently through manual inspection of power curves. This study proposes a mechanism-interpretable method combining event-anchored operating-phase segmentation, relative excess phase energy (Early RAE), and locking-tail rebound loss (ReboundLoss). Three-phase drive-current dropout provides the terminal timing anchor; a local Valley–Rebound pattern and machine-/direction-specific healthy templates define comparable mechanical intervals. The method was evaluated using historical MSS power/current recordings, pre-event replay sequences, and maintenance findings from a Shanghai Metro line. Offline segmentation playback successfully parsed 221 screenshots from three machines; the median differences in dropout timing between two replay/detection results ranged from 0.0080 to 0.0159 s. Three representative histories illustrated distinct degradation patterns: turnout No. 16 showed an increasing 24 h Top-2 Early RAE envelope (Spearman ρ = 0.821, p = 0.023); turnout No. 1 showed a ReboundLoss shift from a healthy median of 0 to a 48 h pre-event median of 2.192; and turnout No. 7 showed intermittent, recurring multi-feature impulses. The proposed indicators provide phase-specific, auditable evidence for early risk screening and condition-based maintenance support. They are not yet validated as operational safety thresholds.