Application of Bayesian Inference to the Flutter Margin Method: New Developments

Zimmerman and Weissenburger flutter margin method is extended to account for modal parameter uncertainties by applying a Bayesian estimation technique to obtain the probability distribution function of the flutter speed. In previous work, a least-squares estimation technique was applied to obtain the posterior pdf of the flutter speed. The limitation of this technique is the assumption that the flutter margin at each airspeed is strictly Gaussian. In this paper, the joint distribution of the modal parameters (and consequently the flutter margin) is obtained from preflutter measured system responses using a full Bayesian analysis utilizing Markov Chain Monte Carlo sampling technique. The flutter margin pdfs are then utilized to obtain the posterior probability density function of the flutter speed. Results are presented for a two-degrees-of-freedom numerical model, for which the true flutter speed is known.