IDENTIFICATION OF NONLINEAR DERIVATIVE MODELS FROM BO-105 FLIGHT TESTDATA

This paper describes the results of a study focusing on the possibilit y of identifying nonlinear helicopter models in the time domain. In re cent years, identification techniques working mainly in the frequency domain were applied to estimate the parameters in helicopter models. R ecently, the time domain identification method of the DLR was improved to allow the identification of fully nonlinear models. To investigate the applicability of this method to helicopters, a nonlinear derivati ve model with explicit equations for the individual blade flapping ang les was formulated. In comparison to the linear derivative models nonl inear models are physically more realistic and are not restricted by s mall perturbation assumptions. Although a large number of unknowns had to be determined, a nonlinear model was successfully identified.