Quantifying bearing fault severity using time synchronous averaging jerk energy

Flight control surfaces have the crucial task of allowing the pilot to control the aircraft. Currently, these are generally controlled by hydraulic actuators. As a part of More Electric Aircraft (MAE) trend, some redundant hydraulic actuators are being partially replaced by Electromechanical Actuators (EMA). In order to ensure the ultimate safety of EMA, reliable vibration-based diagnosis capabilities are potentially needed to minimize the catastrophic risk of EMA failure initiated by critical sub-components such as rolling-element bearing. In this paper a new technique to estimate the fault severity of a defective bearing is presented. The technique is based on analyzing the jerk energy gradient of the synchronously averaged fault impact. The averaged signal is extracted by using time synchronous averaging TSA) triggered by the fault race frequency FRF) for the detection task and triggered by shaft speed for the quantifying task. FRF is defined, in this work, as the bearing fault frequency of interest divided by the number of rolling elements, which eventually denotes the cage frequency in the case of an outer race fault and the difference between the shaft speed and the cage frequency in the case of an inner race fault. Detailed monitoring of the TSA-based energy is developed for the EMA bearings noting in particular that this can be utilized in other lowspeed applications. The effectiveness of the proposed technique is demonstrated and discussed on several seeded faults.