Longitudinal Flight Dynamic Analysis on Vertical Takeoff of a Tailless Flapping-Wing Micro Air Vehicle

This paper first analyzed the longitudinal dynamic behavior during vertical takeoff without control of a Flapping-Wing Micro Air Vehicle (FW-MAV). The standard linear flight dynamics based on small disturbances from trim condition was not applicable for our analysis because the initial flight condition, which was at rest on the ground, could be such a large disturbance from the trim condition that the linearization is invalid. Therefore, we derived linearized Equations of Motion (EoM) which can treat an untrimmed flight condition as a reference for disturbances. The Computational Fluid Dynamic (CFD) software ANSYS Fluent was used to compute the aerodynamic forces and pitching moments. Three flight modes were found: a fast subsidence mode, a slow subsidence mode and a divergence oscillatory mode. Due to divergence oscillatory mode, the deviation from the reference flight grew with time; the FW-MAV tumbled without control. The simulation showed for the first 0.5 second after leaving the ground (the time that is long enough for delay of feedback control), the FW-MAV flew up to a height of 6 cm with small horizontal and pitching motion, which is close to a vertical flight.