Experimental study of flapping-wing aerodynamic coefficients and landing performance estimation

In this research, a typical flapping-wing air vehicle is fabricated and tested in a wind tunnel to explore the effect of kinematic parameters on the aerodynamic forces and moments. Moderate and high incidence angles are considered to estimate the hover and landing performance of the birds. Flapping kinematics consisting of frequency and amplitude, velocity, incidence angle, and body pitch rate are assumed as the state. The aerodynamic forces and moments are also measured in each state via a force balance. A comprehensive experimental parameter study of a flapping-wing micro air vehicle (FMAV) is depicted, and some new remarks are drawn. Increasing the angle of attack would make a higher lift while diminishing the axial force required in the perching maneuver. The force hysteresis study reveals that increasing flapping frequency and angular velocity may lead to dynamic instability due to lag and deficiency effects. A semi-analytical aerodynamic model is developed to further estimate the landing scenario based on the conducted experiments. Based on the smooth descending transition, a quasi-equilibrium trajectory is proposed by which the flapping robot could approach the landing configuration from the initial cruise condition. It is shown that by controlling both frequency and pitch angle, the bird's velocity and altitude would reach from 9 m/s and 12 m to 3 m/s and 1 m, respectively, which is suitable for the terminal landing maneuver.