Nonlinear Vibration-Interaction Metric for Health Assessment of Helicopter Drivetrain Systems

摘要

in this paper, concept of cross-bispectrum is used torninvestigate and model vibration interaction due to nonlinearitiesrnin faulted drive shafts in an AH-64 helicopter. Most of therncurrently available vibration-monitoring tools are built aroundrnauto- and cross-power spectral analyses which have limited valuernin detecting frequency correlations higher than first order.rnStudying higher order correlations provides more informationrnabout the mechanical system which helps in building morernaccurate diagnostic model using the same collected vibrationrndata. Based on cross-bispectrum as higher order spectralrnanalysis, health conditions of rotating shafts are assessed byrnstudying quadratic nonlinear correlation between two vibrationrnsignals collected at the bearing supporting the shafts. Vibrationrndata are gathered from dedicated condition based maintenancernexperimental helicopter drive-train simulating different shaftrnconditions, namely; baseline case, shaft misalignment, shaftrnimbalance, and combination of misalignment and imbalance. Forrneach of these settings, the experiment is repeated three timesrnusing different hanger bearing articles, making a grand total ofrntwelve experiment runs. This work is targeting the developmentrnof health indicators based on higher order spectra (HOS) forrnmore effective condition based maintenance (CBM) programs.