Module combination based configuration synthesis and kinematic analysis of generalized spherical parallel mechanism for ankle rehabilitation

In the previous rehabilitation robot research, the proposed ankle models for rehabilitation robot design have distinctions with the ankle bone structure. It leads to the unsatisfactory human-machine compatibility of the robots constructed based on the fitting onto the motion of these models. For this problem, 6 motion fitting models having higher similarities with ankle bone structure are proposed. For constructing a generalized spherical parallel mechanism (GSPM) with the same kinematic characteristics with these models, a module combination configuration synthesis method is presented. This method establishes the GSPM with partially decoupled characteristics by combining position and orientation modules. Firstly, this method constructs basic limbs/groups of 2 modules based on enumeration and screw theory. Secondly, a class of compact equivalent limbs and groups are constructed by equivalent replacement method based on basic limbs and groups. Thirdly, with the equivalent group being an example, the kinematics of 2 modules are analyzed based on the D-H method and their geometric characteristics, a module combination kinematic analysis method is summarized. Finally, 6 suitable GSPMs are established based on these methods.