关键词: 球面并联机构, 静刚度, 正交变换, 线位移, 角位移

Abstract:

The 3-RRS mechanism is one of the latest architectures of the spherical parallel mechanism 3-RRR families with 3 DOF and it will be used as a prototype mechanism of bionic shoulder joints of humanoid robot. It is quite complex to calculate the stiffness of 3-RRS mechanism which the bar in each branch is arc-shaped. The angle displacement of mobile platform and line displacement of spherical center of the mechanism were derived by mean of calculation deformation and superposition principle at small strain; the relationships between outer loads and the displacements of (spherical center) vertex of mobile platform were set up based on the results of static analysis-the relationship between external wrenches and forces acted on the members in each branch. Flexibility，stiffness matrix were finally obtained herein. The 6 principal stiffness and principal directions of the mechanism was achieved by orthogonal transformation. It provides the important theoretical foundation and support for engineering design and application of 3-RRS mechanism in practice.

Key words: spherical parallel mechanism;static stiffness;orthogonal transformation;line displacement;angle displacement