3-RRS机构是三自由度球面并联机构3-RRR的新构型之一,可作为人形机器人仿生肩关节的原型机构,因各支链的构件为球面上的曲杆,其刚度计算十分复杂。采用(杆件)变形法与小变形叠加原理,推得机构动平台的角位移、球心点线位移;利用机构静力学计算的结果,即各支链两构件上的力与动平台上外载荷的关系,建立了机构动平台上(球心点的)的位移与外载荷关系,进而求得机构的整体柔度、刚度矩阵;采用正交变换使刚度矩阵对角化,得到机构的6个主刚度指标及其所在的方向。研究结果为该机构的工程设计和应用提供了理论基础。
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.