Strategies for the stabilization of longitudinal forward
flapping flight revealed using a dynamically-scaled robotic fly
Abstract
The ability to regulate forward speed is an essential
requirement for flying animals. Here, we use a dynamically-scaled robot to
study how flapping insects adjust their wing kinematics to regulate and
stabilize forward flight. The results suggest that the steady-state lift and
thrust requirements at different speeds may be accomplished with quite subtle
changes in hovering kinematics, and that these adjustments act primarily by
altering the pitch moment. This finding is consistent with prior hypotheses
regarding the relationship between body pitch and flight speed in fruit flies.
Adjusting the mean stroke position of the wings is a likely mechanism for
trimming the pitch moment at all speeds, whereas changes in the mean angle of
attack may be required at higher speeds. To ensure stability, the flapping
system requires additional pitch damping that increases in magnitude with
flight speed. A compensatory reflex driven by fast feedback of pitch rate from
the halteres could provide such damping, and would automatically exhibit gain
scheduling with flight speed if pitch torque was regulated via changes in
stroke deviation. Such a control scheme would provide an elegant solution for
stabilization across a wide range of forward flight speeds.