Coaxial helicopter model identification based on differential evolution algorithm and accuracy analysis

The coaxial helicopter exists intense aerodynamic interaction between the upper and lower rotor, and it is difficult to establish the accurate dynamic model for flight control systems using the theory analysis and wind tunnel experiment. Frequency sweep flight experiment data was used to extract the non-parametric frequency responses that fully characterizes the coupled helicopter dynamics. A nonlinear search based on differential evolution algorithm for a linear state-space model which matches the frequency-response data set was conducted. Parameter insensitivity and Cramer-Rao bound analysis results have low values, indicating very good reliability of the identified model. The accuracy of the identified model is verified by comparing the model-predicted responses with the responses collected during flight experiments, and the model can be used for flight quality analysis and flight control system design.