MODE TRACKING AND LCO ANALYSIS BASED ON CONTINUATION METHOD

Abstract

In the first part of this thesis, a 3 degrees of freedom fixed-wing model and a 3D BAH fixed-wing model with a nonlinear free-play control surface are modelled and described mathematically in different forms. The parameter values from NACA0012 and MSC. NASTRAN have been used to simulate the LCO respectively. We also analyzed the nonlinearity of the control surface motion and quasi-linearized it by using the Fourier’s transformation on the restoring torque. In the second part, a numerical analysis method - continuation method -was introduced and described briefly. In the third part, we showed how to implement this method into our 2 models in two different situations 1) Mode Tracking 2) Parameter Variation for LCO and corresponding results were shown and discussed to prove its efficiency and robustness. Both advantages and drawbacks of the continuation method in these two situations have been discussed in the analysis part. We also examined carefully the phenomenon “Modes Jumping” occurring in the parameter variation and came up with a solution to avoid it. In the last part, harmonic balance method for the nonlinear LCO analysis was described and we showed how it can be applied for our model. The harmonic balance results obtained from Avinash’s and Dowell et al. have been shown to be in a good agreement with our results.