Mechanism properties of a bird-neck bionic rigid-flexible structure.

By the biological construction of a bird neck, a bionic bird-neck multilevel rigid-flexible structure is proposed and some biometric properties are explained. The proposed structure can flexibly deform in six directions, which inspires the study of its mechanical properties for flexible deformations. First, the structural configuration and composition are determined based on the study of the anatomical characteristics of the woodpeckers. Since the skeletons and muscles have very different values for the elasticity modulus and the deformation is mostly dependent on the muscle tension, the bionic structure consists of rigid units and bio-syncretic components. For combined deformations, the mechanical model is established by the connectivity matrix to describe the connection of each level. Second, based on the principle of minimum potential energy, an integral form-finding method is proposed for flexible combination deformations. All of the integral forms obtained with the theoretical analysis are compared with the results with Finite Element Analysis. The structural parameters of the bionic structure were then tightly fixed to the actual shape of the bird's neck and the corresponding overall form took on an "S" shape, which perfectly matched the construction of the bird's neck. In addition, for the pre-deformation form, by analyzing the potential energy of the bionic structure, due to the adjustable dynamic stiffness property, an explanation is provided for the significant dynamic stability of the bird neck in bending. This study not only proposes a bionic rigid-flexible structure with high spatial accessibility but also explains biological properties of a bird neck based on the study of its mechanics characteristics. Based on the modeling and the mechanical properties of the bionic structure in flexible spatial combination deformations, the multi-steady state, and the variable dynamic stiffness, the bird-neck bionic rigid-flexible structure has significant applications such as aeronautical deployable systems, manipulator positioning, and dynamic stability fields.