A Baseline-Normalized Suspension Degradation Index for Shock Absorber Health Monitoring

Shock absorber degradation develops gradually and is difficult to identify before significant damping loss occurs. Most existing diagnostic methods depend on multiple sensors, accurate system models, or supervised learning trained on labelled fault data. A baseline-normalized Suspension Degradation Index (SDI) is proposed for single-sensor suspension health monitoring. The SDI tracks resonance-band chassis vibration and quantifies damper degradation relative to a healthy baseline established using the median and median absolute deviation. False alarms caused by transient road disturbances are suppressed through a persistence criterion, while a wear-dependent thermal model provides an independent indication of progressive damper degradation. The two indicators are combined into one health index. The method is evaluated using a quarter-car model excited by an ISO 8608 Class-C road profile containing a transient pothole and progressive damping degradation from 1500 to 450 N·s/m. The persistence criterion rejects the pothole response without producing a false alarm, whereas the thermal indicator detects progressive wear. Across 25 independent road realizations, the combined framework achieved a 100% overall detection rate, and the thermal indicator became active only when damping degradation exceeded approximately 40%. The approach requires only one chassis-mounted accelerometer and simple statistical processing, which suits practical monitoring and future experimental implementation.