Computational simulation and free flight validation of body vibration of flapping-wing MAV in forward flight

FWMAVs (Flapping Wing Micro Air Vehicles) turn to be a flexible multi-body dynamic (FMBD) system when the inertia and flexibility of flapping wing are considered. The vibration caused by interaction of unsteady aerodynamics, structural dynamics and multi-body dynamics makes the analysis of aerodynamic and acquisition of equilibrium become full of challenge. In this study, a method coupled three-dimensional CFD (Computational Fluid Dynamics) and CSD (Computational Structural Dynamics) considering FMBD (flexible multi-body dynamics) between flexible wings and body is developed. And a trim algorithm is developed to satisfy three aspects of conditions including convergence of structural deformation and periodic condition of body's vibration in longitudinal direction and conditions of equilibrium. The computational results show that the trim conditions when body's vibration is taken into account are different from that when body's vibration is ignored. The vibration of body mainly increases the aerodynamic drag while having a little effect on lift. When the flight is trimmed, the corresponding flapping frequency increases and angle of attack decreases. In order to validate the method of simulation, the free flight data including the time course of oscillated plunging acceleration and pitch angle is collected based on the steady flight ability of “DOVE” FWMAV. Through comparison, though there is slight discrepancy between computational results and free flight data, it proves that CFD/FMBD method provides a sufficiently good accuracy for the simulation of body vibration of FWMAVs. Based on the proposed and validated model, the influence of various take-off mass on the vibration of body is studied and it indicates that a proper mass ratio between wing to body can suppress the maximum acceleration of vibration to protect the precise sensors and equipment.