Figure 2
From: On the role of tail in stability and energetic cost of bird flapping flight
(a) Front view of the bird model. The wingbeat amplitude \(A_{s,x}\) about the \(x'\)-axis is the main kinematic parameter governing the wing amplitude of movement. (b) Top view of the bird model. The shoulder sweep offset \(\psi _{s,z}\) captures the average angle of the arm bone with respect to \(x'_{w}\) over the period. The angle \(\beta\) captures the magnitude of tail opening. (c) Section of the wing. It highlights the wing rotation angle governed by the wrist degree of freedom \(q_{w,y}\).
