In view of the experimental observation of the free takeoff process and the quasi free take-off process of dragonflies

two high-speed cameras were photographed with each other perpendicular to the optical axis. The motion parameters of the dragonfly body and wings during the two take-off processes were accurately captured by feature point matching and three-dimensional reconstruction

and the dynamic analysis and comparison were carried out. The experimental results showed that the dragonfly adopted synchronous vibration wing during the free take-off process and gradually transformed into asynchronous vibration wing (around 110 degrees)

the maximum instantaneous vertical acceleration could reach 20m/s2; with use of asynchronous vibration wing (phase difference of 180 degrees) in the course of quasi free take-off

the phase difference gradually decreased

and the maximum instantaneous vertical acceleration was 12m/s2. In addition

synchronous flap

large angle of attack and large flapping angle were favorable for lift.