The influence of period variation on time/frequency analysis of the Westland helicopter data

We address the influence of period variation on the Westland CH-46E helicopter vibration data. The estimation of the time-varying shaft speed by using a newly developed constrained AR(2) estimator and the well-known EKF estimator are discussed. The influence that the period variation captured by these two estimators has on the periodic time/frequency analysis is illustrated via numerical simulation. This simulation clearly illustrates a potential spectral smearing if the period variation is not properly accommodated. A data resampling scheme is then be proposed to eliminate the spectral smearing effect. The potential of this scheme is demonstrated via the analysis of the helicopter vibration data