A Flight Strategy for Intelligent Aerial Vehicles Learned from Dragonfly

Dragonfly is one of the most maneuverable insects and one of the oldest flying species on earth. It is important for human beings to study their flight techniques if we intend to make an insect-like Micro Aerial Vehicle, because their flight performance far exceeds other insects. They can hover, cruise up to 54km/h, turn 180° in three wing beats, fly sideways, glide, and even fly backwards (Alexander, 1984; Appleton, 1974; Whitehouse, 1941). They intercept prey in the air with amazing speed and accuracy. Their thorax are equipped with wing muscles which accounts for 24% (Aeshna) of its body weight, compared to 13% of those of the honey bees (Appleton, 1974). Most dragonflies change their wing motion kinematics for different flight modes such as hovering, cruising and turning. Among these kinematic parameters, the most interesting one is the phase difference (γ) between forewing and hindwing. It is defined as the phase angle by which the hindwing leads the forewing. When hovering, dragonflies employ 180° phase difference (anti-phase) (Alexander, 1984; Norberg, 1975; Ruppell, 1989), while 54~100° are used for forward flight (Azuma and Watanabe, 1988; Wang et al., 2003). When accelerating or performing aggressive maneuvers, they use 0° (inphase) phase difference (Alexander, 1984; Ruppell, 1989; Thomas et al., 2004). Of various phase differences, 270° is rarely observed in dragonfly flight.