Fault Detection and Lubricant Health Monitoring for Slow Bearings in Extreme Operating Conditions

Slow rotating bearings are an integral part of aerospace and turbomachinery actuation systems. These actuation systems may be driven by electric, hydraulic or fueldraulic power and often operate under high loads and extreme temperatures. This makes these actuation systems and their slow rotating bearings highly susceptible to degradation and failure. Vibration monitoring techniques are not applicable to the PHM of these bearings, because their slow speeds are unable to produce a measureable vibration signature. Furthermore, the slow bearings are sealed and use grease lubrication, thus eliminating traditional oil debris monitoring. To address these problems, Impact Technologies, LLC has developed a PHM system that relies on system identification and uses available control system data and sensor measurements. This PHM system consists of algorithms and models that perform fault detection and identification for the bearings and its actuation train components like valves, pumps, motors, gears and bearings. The PHM process is divided into two stages — diagnostics and prognostics. Diagnostics is the process of detecting and isolating faults, while prognostics is the process of predicting remaining useful life (RUL) or time to failure. The authors demonstrate the PHM system through simulation on a dynamic model that is representative of hydraulic-mechanical actuation systems used in new and existing manned aircrafts, UAVs and Short Take-off and Vertical Landing aircrafts.