The Design of a Bionic Duck Foot Based on a 6R Deployable Polygonal Mechanism

Abstract In this article, a biomimetic 6R deployable polygonal mechanism (DGM) according to the morphological characteristics of a duck's webbed foot is presented. First, based on the biological morphology of a duck's foot, a composite mechanism consisting of two plane-symmetric 6R DGMs was designed. The lengths of the links in a single 6R DGM and the angles between adjacent links when fully expanded into a planar state were determined. Second, seven different axial configuration schemes were proposed to allow the 6R DGM to achieve the same fully expanded state. The corresponding coordinate system for each configuration scheme was established, and homogeneous coordinate transformation methods were utilized. This made it possible to design the torsion angle parameters at the joints of each link, enabling the assembly of the two symmetric 6R DGMs at specific dihedral angles. Third, to ensure that the physical model of the mechanism can fold and unfold smoothly, the cross section of each link was designed with an axisymmetric octagonal configuration. This design prevents any interference between the links during the folding and unfolding process. Additionally, appropriate constraints were introduced to make sure the mechanism is of a single degree of freedom, guaranteeing the uniqueness of motion under simple driving conditions. Finally, on the basis of the theoretical analysis and optimization design, a physical model was constructed, and its folding and unfolding performance was systematically tested through experiments.