A time-scale separation approach for time-varying model identification of a flapping-wing micro aerial vehicle

A time-varying model for the forward flight dynamics of a flapping-wing micro aerial vehicle is determined from free-flight optical tracking data using system identification. Based on time-scale separation, the aerodynamic forces and moments are each formulated as a linear addition of decoupled time-averaged and time-varying sub-models. The aerodynamic models are incorporated in linearised equations of motion, resulting in an accurate and simulation-capable dynamic model. The time-averaged component is assumed to be linear; the time-varying component is represented as a third-order Fourier series, which effectively approximates the flapping dynamics. Combining both components yields a more complete and realistic simulation. The model is used to assess the validity of the widely-applied timescale separation assumption and results suggest that while in steady flight the assumption applies well, during manoeuvres the time-varying dynamics are not fully captured. More accurate modelling of flapping-wing flight during manoeuvres may require more advanced models that consider coupling between the time scales.