A novel condition indicator gearbox diagnosis: amplitude of probability density function (APDF)

摘要

In critical machines with gearbox transmissions there is a requirement for robust methods of condition monitoring. Helicopters, for example, need rapid on-the-spot condition assessment for clearance for flight. Condition Indicators (CIs) are used as part of Health and Usage Monitoring System (HUMS). Vibration methods often use kurtosis of the residual signal of the measured vibration data, computed as part of the "FM4" method and compared to thresholds, which is accepted as a good and reliable indicator. But it has been observed that FM4 may give misleading readings, because in some cases it does not show a continually increasing trend in close correlation with the damage. In this paper we report a new CI based on the amplitude of the normal Probability Density Function (PDF), which shows a significantly better robustness in the examples tested, for trending of the cracking in a gear.