Manoeuvring flight of a model insect—Saccadic yaw and sideslip

Abstract

Insects are well known for their agility in flight. This may be attributed to the large but highly transient forces that are generated in every stroke of their rapidly flapping wings. In recent times, with advances in scientific videography, many agile manoeuvres of insects, especially small ones such as fruit flies, have been documented and studied by zoologists – these include body saccades, sharp banking turns and evasive take-offs etc. The typical manoeuvres in 3D space frequently involve simultaneous and coordinated rolling, yawing and pitching of the flyer, produced by small subtle changes in the kinematics of the flapping wings. In this paper, we numerically simulated the saccadic yawing and sideslip manoeuvres of a model fruit fly. The numerical model integrated the Navier-Stokes equations for fluid with the 6-DoF Newtonian dynamics of the model fly and a PID-based motion controller. Saccadic body yaw ranging from 45° to 180° were obtained through small asymmetric adjustments in the twist of the contralateral wing pair, while sideslip flight was motivated by body roll induced via the asymmetry of the stroke angles. The dynamic coupling between body roll and yaw implied that these rotational modes had to be concurrently controlled to produce the desired manoeuvring outcomes. The roll and yaw rates of the model fly obtained in these simulated manoeuvres were comparable to values observed for the body saccades of fruit flies in experiments.