P. Liu and Z. Wu (PR China)
coaxial helicopter; state-space model; frequency response identification; K-means clustering algorithm
A frequency identification method for a six-DoF state space model of coaxial helicopter is presented. This method combines the advantages of mechanism modeling and system identification. A complete set of non parametric input-to-output frequency responses that fully characterizes the coupled helicopter dynamics are extracted from the frequency sweep test data. With the help of small perturbation theory, a linearized dynamic model for the stability and control derivative is extracted from linearization of a non-linear mathematical model in hover. A well-suited time-history database is collected by a frequency sweep test that is properly designed and executed. Then, a nonlinear search based on K-means clustering algorithm is conducted for a six-DoF linear state-space model that matches the frequency-response data set. The accuracy of the identified model is verified by comparing the model-predicted responses with the responses collected during flight experiments.
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