119.5 Saturday, Jan. 7 Flexible frames for flight DYHR, JP*; COWAN, NJ; HINTERWIRTH, AJ; MORGANSEN, KA; DANIEL, TL; Univ. Washington; Johns Hopkins Univ.; Univ. Washington; Univ. Washington; Univ. Washington email@example.com
Moving animals modulate myriad muscles in response to multimodal sensory inputs. Coordinating movement during flight is challenged by an animal’s inherent instability, additional degrees of freedom, and the need to produce constant lift forces. This difficulty is compounded by different levels of precision, delays and frequency responses of incoming sensory signals. Prior studies have focused on wings as the primary flight control structures, for which changes in angle of attack or shape are used to modulate lift and drag forces. Other actuators are reflexively activated during flight which do not directly modulate the wings but may nevertheless impact flight performance. We investigated the visual-abdominal reflex displayed by the hawkmoth Manduca sexta to determine the role of the abdomen in flight control. Moths were presented with vertically moving gratings during tethered flight to measure the open-loop transfer function between the visual stimulus and abdominal response. That transfer function reveals a delay of approximately 50 ms and a high pass filter behavior with a 3 dB cut off at approximately 0.5 Hz. We also developed a physical model of hovering flight wherein articulation of the thoracic-abdominal joint is used to redirect a constant lift force provided by the wings. We show that control of the joint, subject to a high-pass filter, is sufficient to maintain stable hovering at time scales on the order of 5 ms. Our results agree with the behaviorally measured visual-abdominal transfer function of the moth, indicating that they may use a similar control strategy. Taken together, our experiments and models suggest a novel mechanism by which articulation of the body or “airframe” of an animal can be used to redirect lift forces for effective flight control.