Potential control inputs for aerial turning in the pigeon

Meeting Abstract

17.2  Friday, Jan. 4  Potential control inputs for aerial turning in the pigeon ROS, I.G.*; BIEWENER, A.A.; Harvard University; Harvard University ivo.ros@gmail.com

To investigate the role of head stabilization in flight control of aerial turning, we analyzed 3D head and body orientations during 90°, level turns in pigeons. Assuming the eyes maintain a fixed orientation within the head, the velocity and orientation of the head can be used to approximate the visual feedback. Specifically, the position of the focus of expansion (FOE) of a visual flow field on the retina can be approximated by the degree of head side slip (the offset between the head-fixed gaze and head bearing). During low speed aerial turns, all four pigeons displayed periods of head stabilization alternated with brief repositioning movements (saccades). Translational head saccades consisted of periodic fore-aft speed fluctuations of ~1 m/s for flight speeds of 3-4 m/s. Rotational head saccades occurred near the downstroke-upstroke transition, immediately following peaks in translational head speed. Rotational saccades were of fixed duration (17±3% of wingbeat-cycle period), but of varying magnitude (5-30°) and speed (400-1200 °/s). Rotational head saccades were directed away from the flight direction and into the turn. The degree of head side-slip immediately after a saccade predicted the change in flight trajectory during the subsequent wingbeat-cycle and the body rotation component underlying those flight trajectory changes. Additionally, when the head was not measurably side-slipping, the degree of neck bending or twisting predicted body rotations that re-acquired the forward flight orientation of the body, without substantially affecting flight trajectory. These correlative results indicate that in slow turning flight pigeons use visual information to control flight trajectory, complemented by head deviations relative to their body to control body orientation. (NSF IOS-0744056 & ONR N0014-10-1-0951)

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