title: Pitch perfect: how fruit flies control their body pitch angle.
abstract: Flapping insect flight is a complex and beautiful phenomenon that relies on fast, active control mechanisms to counter aerodynamic instability. To directly investigate how freely flying Drosophila melanogaster control their body pitch angle against such instability, we perturbed them using impulsive mechanical torques and filmed their corrective maneuvers with high-speed video. Combining experimental observations and numerical simulation, we found that flies correct for pitch deflections of up to 40 deg in 29±8 ms by bilaterally modulating their wings' front-most stroke angle in a manner well described by a linear proportional-integral (PI) controller. Flies initiate this corrective process only 10±2 ms after the perturbation onset, indicating that pitch stabilization involves a fast reflex response. Remarkably, flies can also correct for very large-amplitude pitch perturbations--greater than 150 deg--providing a regime in which to probe the limits of the linear-response framework. Together with previous studies regarding yaw and roll control, our results on pitch show that flies' stabilization of each of these body angles is consistent with PI control.
authors.affiliation: Department of Physics, Cornell University, Ithaca, NY 14853, USA scw97@cornell.edu.
authors.forename: Samuel C
authors.initials: SC
authors.lastname: Whitehead
authors.affiliation: Department of Physics, Cornell University, Ithaca, NY 14853, USA.
authors.forename: Tsevi
authors.initials: T
authors.lastname: Beatus
authors.affiliation: Département de Mécanique, École Polytechnique, Palaiseau 911128, France.
authors.forename: Luca
authors.initials: L
authors.lastname: Canale
authors.affiliation: Department of Physics, Cornell University, Ithaca, NY 14853, USA.
authors.forename: Itai
authors.initials: I
authors.lastname: Cohen
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D004331:Drosophila melanogaster / Q000502:physiology*; D005426:Flight, Animal / Q000502:physiology*; D019415:Torque; D014921:Wings, Animal / Q000502:physiology*
keywords: Bio-locomotion; Drosophila melanogaster; Flight control; Insect flight; Linear control