Modal Identification of Aircraft Wing Coupled Heave-Pitch Modes Using Wavelet Packet Decomposition and Logarithmic Decrement

Low frequency bending mode (heave) and high frequency twisting mode (pitch) are the two typical modes of motion that exist in an aircraft wing. Coupling of these modes produce flutter effect, which can severely distort the wing without warning. To avoid such distortions, flutter speed must be identified accurately by using modal parameters, so that necessary decision could be taken. This paper focuses on using an effective method for the modal testing of an aircraft wing to estimate the modal parameters of coupled heave-pitch modes. The method includes Wavelet Packet Decomposition (WPD) to uncouple a complex signal, followed by Logarithmic Decrement Method to estimate the modal parameters. Simulation is done to validate the effectiveness of the method. Finally the method is applied on the 2-DOF model (NACA 0012 aerofoil wing model) under free vibration test to estimate coupled heave-pitch modal parameters.