Dynamic Modeling and Performance Evaluation of a Novel Humanoid Ankle Joint

Aimed at the problems of design difficulty and weak kinematic performance caused by spherical joint, a novel PRC+PRCR+RR humanoid ankle joint based on the partially decoupled spherical parallel mechanism is proposed. According to screw theory, the degree of freedom and decoupling characteristics of this mechanism are analyzed. Based on Klein formula and virtual work principle, the kinematic expressions of each link and dynamic model are established. The correctness of the dynamic model is verified by combining the virtual prototype software and the ankle pose function obtained by gait planning and Fourier fitting. The workspace of this mechanism is mapped into a two-dimensional polar coordinate system with the azimuth and elevation angles of the spherical coordinate system as parameters. The motion/force transmission index and constraint index of this mechanism are evaluated and expressed in the workspace, showing this mechanism with excellent kinematic characteristics.