Analysis of Aircraft Longitudinal Long-Period Oscillation by Hilbert-Huang Transform

W-J. Ma, W. Tang, and F-R. Chang

Abstract:	This paper deals with the analysis of aircraft longitudinal long-period oscillation named phugoid phenomenon. Phugoid motion has been known for a long time, but there are no direct measurements of actual flight data. This research serves the purpose of analyzing the phugoid oscillation from kinematic GPS measured data. In addition, a Hilbert-Huang Transform (HHT) proposed by Norden E. Huang from NASA in 1998 is used here to analyze the physical measurements in the time domain. The HHT is applicable to non-stationary and nonlinear data analysis, and finding out the instantaneous characteristics including frequency of the data is its main part. It is based on the empirical mode decomposition (EMD), which generates a set of intrinsic mode functions (IMFs). The EMD is a procedure to make the data meet the IMF limitations. This decomposition process is a time domain algorithm, and is based on the local characteristics of the signal. Here it can be seen that EMD is similar to de-trend in signal processing, but there is no distortion during EMD. After EMD, the IMFs are processed by Hilbert transform to obtain the analytical signals. Then, the instantaneous frequency of the data can be accurately and correctly calculated. In the simulation, the comparison between the non-stationary signal analysis, HHT, and the conventional Fourier based method from the real-time flight test data measured by kinematic GPS is presented.
Published in:	Proceedings of the 2006 National Technical Meeting of The Institute of Navigation January 18 - 20, 2006 Hyatt Regency Hotel Monterey, CA
Pages:	543 - 553
Cite this article:	Ma, W-J., Tang, W., Chang, F-R., "Analysis of Aircraft Longitudinal Long-Period Oscillation by Hilbert-Huang Transform," Proceedings of the 2006 National Technical Meeting of The Institute of Navigation, Monterey, CA, January 2006, pp. 543-553.
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