Wavelet analysis of F/A-18 aeroelastic and aeroservoelastic flight test data

摘要

Time-frequency signal representations combined with subspace identification methods were used to analyze aeroelastic flight data from the F/A-18 Systems Research Aircraft (SRA) and aeroservoelastic data from the F/A-18 High Alpha Research Vehicle (HARV). ^The F/A-18 SRA data were produced from a wingtip excitation system that generated linear frequency chirps and logarithmic sweeps. ^HARV data were acquired from digital Schroeder-phased and sinc pulse excitation signals to actuator commands. ^Nondilated continuous Morlet wavelets implemented as a filter bank were chosen for the time-frequency analysis to eliminate phase distortion as it occurs with sliding window discrete Fourier transform techniques. ^Wavelet coefficients were filtered to reduce effects of noise and nonlinear distortions identically in all inputs and outputs. ^Cleaned reconstructed time domain signals were used to compute improved transfer functions. ^Time and frequency domain subspace identification methods were applied to enhanced reconstructed time domain data and improved transfer functions, respectively. ^Time domain subspace performed poorly, even with the enhanced data, compared with frequency domain techniques. ^A frequency domain subspace method is shown to produce better results with the data processed using the Morlet time-frequency technique. ^(Author)