Aerodynamic model identification of a clap-and-fling flapping-wing MAV: A comparison between quasi-steady and black-box approaches

Valid models of flapping-wing aerodynamic forces would allow for the development of model-based control, necessary for active autonomous flight of flapping-wing micro aerial vehicles (FWMAVs). Two different models to describe the time-resolved aerodynamics of a clap-and-fling FWMAV are compared, with an outlook on control. The first is a quasi- steady model based on blade element theory; the second is a black-box model based on Fourier series expansion. The unknown parameters in the models are computed from wind tunnel force data using maximum likelihood estimation. The advantages and limitations of each model are discussed, including their ability to represent transient effects such as clap-and-fling. Additionally, we evaluate the changes in sub-flap aerodynamics with different steady flight conditions and investigate the possibilities of developing a global flight envelope model with the suggested approaches. We find that a quasi-steady model can capture a significant component of the aerodynamics of a clap-and-fling FWMAV, but that a black-box model provides higher accuracy and can also capture unsteady effects. While the black-box models are more precise for single test conditions, the quasi-steady model adapts to different flight conditions and is hence more adequate for global modeling. Changes with forward flight velocity are found to be small for the force component perpendicular to the wing stroke plane, the predominant contributor to lift for the considered FWMAV, and an averaged quasi-steady model is shown to be a good approximation for a basic full flight envelope sub-flap model of this force.