97-1  Saturday, Jan. 6 13:30 – 13:45  Multi-element wings: How coordinated feather motion enables avian wing morphing MATLOFF, LY*; CHANG, E; STOWERS, AK; FEO, TJ; THOMSON, C; LENTINK, D; Stanford University ; Stanford University ; Stanford University ; Smithsonian Institution, Division of Birds; Stanford University ; Stanford University lmatloff@stanford.edu

Feathers allow birds to morph their wings through continuous shapes, enabling them to control their aerodynamic wing planforms to attain maximal flight performance and maneuver. Each unique feather moves in concert with its neighbors in an under-actuated system controlled by skeletal motion. By studying feather motion and friction forces, we gain further insight into the underlying mechanisms of feather-to-feather interactions. Kinematic measurements of pigeon wings, Columba livia, were obtained using a motion capture camera system, and feather friction was measured with a six-axis force and torque transducer. We then corroborated models to describe feather motion to explain how feathers shape the wing during morphing. Using the data and model, we subsequently develop a robotic mechanical model, which we test in outdoor free flight. Together, the measurements, theory, and mechanical models advance our understanding of how birds control their feathers via the skeleton, and how tendons and feather friction enable feather underactuation.